1 /* Global common subexpression elimination/Partial redundancy elimination
2 and global constant/copy propagation for GNU compiler.
3 Copyright (C) 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005,
4 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
6 This file is part of GCC.
8 GCC is free software; you can redistribute it and/or modify it under
9 the terms of the GNU General Public License as published by the Free
10 Software Foundation; either version 3, or (at your option) any later
13 GCC is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
18 You should have received a copy of the GNU General Public License
19 along with GCC; see the file COPYING3. If not see
20 <http://www.gnu.org/licenses/>. */
23 - reordering of memory allocation and freeing to be more space efficient
24 - do rough calc of how many regs are needed in each block, and a rough
25 calc of how many regs are available in each class and use that to
26 throttle back the code in cases where RTX_COST is minimal.
27 - a store to the same address as a load does not kill the load if the
28 source of the store is also the destination of the load. Handling this
29 allows more load motion, particularly out of loops.
33 /* References searched while implementing this.
35 Compilers Principles, Techniques and Tools
39 Global Optimization by Suppression of Partial Redundancies
41 communications of the acm, Vol. 22, Num. 2, Feb. 1979
43 A Portable Machine-Independent Global Optimizer - Design and Measurements
45 Stanford Ph.D. thesis, Dec. 1983
47 A Fast Algorithm for Code Movement Optimization
49 SIGPLAN Notices, Vol. 23, Num. 10, Oct. 1988
51 A Solution to a Problem with Morel and Renvoise's
52 Global Optimization by Suppression of Partial Redundancies
53 K-H Drechsler, M.P. Stadel
54 ACM TOPLAS, Vol. 10, Num. 4, Oct. 1988
56 Practical Adaptation of the Global Optimization
57 Algorithm of Morel and Renvoise
59 ACM TOPLAS, Vol. 13, Num. 2. Apr. 1991
61 Efficiently Computing Static Single Assignment Form and the Control
63 R. Cytron, J. Ferrante, B.K. Rosen, M.N. Wegman, and F.K. Zadeck
64 ACM TOPLAS, Vol. 13, Num. 4, Oct. 1991
67 J. Knoop, O. Ruthing, B. Steffen
68 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
70 What's In a Region? Or Computing Control Dependence Regions in Near-Linear
71 Time for Reducible Flow Control
73 ACM Letters on Programming Languages and Systems,
74 Vol. 2, Num. 1-4, Mar-Dec 1993
76 An Efficient Representation for Sparse Sets
77 Preston Briggs, Linda Torczon
78 ACM Letters on Programming Languages and Systems,
79 Vol. 2, Num. 1-4, Mar-Dec 1993
81 A Variation of Knoop, Ruthing, and Steffen's Lazy Code Motion
82 K-H Drechsler, M.P. Stadel
83 ACM SIGPLAN Notices, Vol. 28, Num. 5, May 1993
85 Partial Dead Code Elimination
86 J. Knoop, O. Ruthing, B. Steffen
87 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
89 Effective Partial Redundancy Elimination
90 P. Briggs, K.D. Cooper
91 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
93 The Program Structure Tree: Computing Control Regions in Linear Time
94 R. Johnson, D. Pearson, K. Pingali
95 ACM SIGPLAN Notices, Vol. 29, Num. 6, Jun. 1994
97 Optimal Code Motion: Theory and Practice
98 J. Knoop, O. Ruthing, B. Steffen
99 ACM TOPLAS, Vol. 16, Num. 4, Jul. 1994
101 The power of assignment motion
102 J. Knoop, O. Ruthing, B. Steffen
103 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
105 Global code motion / global value numbering
107 ACM SIGPLAN Notices Vol. 30, Num. 6, Jun. 1995, '95 Conference on PLDI
109 Value Driven Redundancy Elimination
111 Rice University Ph.D. thesis, Apr. 1996
115 Massively Scalar Compiler Project, Rice University, Sep. 1996
117 High Performance Compilers for Parallel Computing
121 Advanced Compiler Design and Implementation
123 Morgan Kaufmann, 1997
125 Building an Optimizing Compiler
129 People wishing to speed up the code here should read:
130 Elimination Algorithms for Data Flow Analysis
131 B.G. Ryder, M.C. Paull
132 ACM Computing Surveys, Vol. 18, Num. 3, Sep. 1986
134 How to Analyze Large Programs Efficiently and Informatively
135 D.M. Dhamdhere, B.K. Rosen, F.K. Zadeck
136 ACM SIGPLAN Notices Vol. 27, Num. 7, Jul. 1992, '92 Conference on PLDI
138 People wishing to do something different can find various possibilities
139 in the above papers and elsewhere.
144 #include "coretypes.h"
152 #include "hard-reg-set.h"
155 #include "insn-config.h"
157 #include "basic-block.h"
159 #include "function.h"
168 #include "tree-pass.h"
173 /* Propagate flow information through back edges and thus enable PRE's
174 moving loop invariant calculations out of loops.
176 Originally this tended to create worse overall code, but several
177 improvements during the development of PRE seem to have made following
178 back edges generally a win.
180 Note much of the loop invariant code motion done here would normally
181 be done by loop.c, which has more heuristics for when to move invariants
182 out of loops. At some point we might need to move some of those
183 heuristics into gcse.c. */
185 /* We support GCSE via Partial Redundancy Elimination. PRE optimizations
186 are a superset of those done by GCSE.
188 We perform the following steps:
190 1) Compute table of places where registers are set.
192 2) Perform copy/constant propagation.
194 3) Perform global cse using lazy code motion if not optimizing
195 for size, or code hoisting if we are.
197 4) Perform another pass of copy/constant propagation. Try to bypass
198 conditional jumps if the condition can be computed from a value of
201 5) Perform store motion.
203 Two passes of copy/constant propagation are done because the first one
204 enables more GCSE and the second one helps to clean up the copies that
205 GCSE creates. This is needed more for PRE than for Classic because Classic
206 GCSE will try to use an existing register containing the common
207 subexpression rather than create a new one. This is harder to do for PRE
208 because of the code motion (which Classic GCSE doesn't do).
210 Expressions we are interested in GCSE-ing are of the form
211 (set (pseudo-reg) (expression)).
212 Function want_to_gcse_p says what these are.
214 In addition, expressions in REG_EQUAL notes are candidates for GXSE-ing.
215 This allows PRE to hoist expressions that are expressed in multiple insns,
216 such as comprex address calculations (e.g. for PIC code, or loads with a
217 high part and as lowe part).
219 PRE handles moving invariant expressions out of loops (by treating them as
220 partially redundant).
222 Eventually it would be nice to replace cse.c/gcse.c with SSA (static single
223 assignment) based GVN (global value numbering). L. T. Simpson's paper
224 (Rice University) on value numbering is a useful reference for this.
226 **********************
228 We used to support multiple passes but there are diminishing returns in
229 doing so. The first pass usually makes 90% of the changes that are doable.
230 A second pass can make a few more changes made possible by the first pass.
231 Experiments show any further passes don't make enough changes to justify
234 A study of spec92 using an unlimited number of passes:
235 [1 pass] = 1208 substitutions, [2] = 577, [3] = 202, [4] = 192, [5] = 83,
236 [6] = 34, [7] = 17, [8] = 9, [9] = 4, [10] = 4, [11] = 2,
237 [12] = 2, [13] = 1, [15] = 1, [16] = 2, [41] = 1
239 It was found doing copy propagation between each pass enables further
242 This study was done before expressions in REG_EQUAL notes were added as
243 candidate expressions for optimization, and before the GIMPLE optimizers
244 were added. Probably, multiple passes is even less efficient now than
245 at the time when the study was conducted.
247 PRE is quite expensive in complicated functions because the DFA can take
248 a while to converge. Hence we only perform one pass.
250 **********************
252 The steps for PRE are:
254 1) Build the hash table of expressions we wish to GCSE (expr_hash_table).
256 2) Perform the data flow analysis for PRE.
258 3) Delete the redundant instructions
260 4) Insert the required copies [if any] that make the partially
261 redundant instructions fully redundant.
263 5) For other reaching expressions, insert an instruction to copy the value
264 to a newly created pseudo that will reach the redundant instruction.
266 The deletion is done first so that when we do insertions we
267 know which pseudo reg to use.
269 Various papers have argued that PRE DFA is expensive (O(n^2)) and others
270 argue it is not. The number of iterations for the algorithm to converge
271 is typically 2-4 so I don't view it as that expensive (relatively speaking).
273 PRE GCSE depends heavily on the second CSE pass to clean up the copies
274 we create. To make an expression reach the place where it's redundant,
275 the result of the expression is copied to a new register, and the redundant
276 expression is deleted by replacing it with this new register. Classic GCSE
277 doesn't have this problem as much as it computes the reaching defs of
278 each register in each block and thus can try to use an existing
281 /* GCSE global vars. */
283 /* Set to non-zero if CSE should run after all GCSE optimizations are done. */
284 int flag_rerun_cse_after_global_opts
;
286 /* An obstack for our working variables. */
287 static struct obstack gcse_obstack
;
289 struct reg_use
{rtx reg_rtx
; };
291 /* Hash table of expressions. */
295 /* The expression (SET_SRC for expressions, PATTERN for assignments). */
297 /* Index in the available expression bitmaps. */
299 /* Next entry with the same hash. */
300 struct expr
*next_same_hash
;
301 /* List of anticipatable occurrences in basic blocks in the function.
302 An "anticipatable occurrence" is one that is the first occurrence in the
303 basic block, the operands are not modified in the basic block prior
304 to the occurrence and the output is not used between the start of
305 the block and the occurrence. */
306 struct occr
*antic_occr
;
307 /* List of available occurrence in basic blocks in the function.
308 An "available occurrence" is one that is the last occurrence in the
309 basic block and the operands are not modified by following statements in
310 the basic block [including this insn]. */
311 struct occr
*avail_occr
;
312 /* Non-null if the computation is PRE redundant.
313 The value is the newly created pseudo-reg to record a copy of the
314 expression in all the places that reach the redundant copy. */
318 /* Occurrence of an expression.
319 There is one per basic block. If a pattern appears more than once the
320 last appearance is used [or first for anticipatable expressions]. */
324 /* Next occurrence of this expression. */
326 /* The insn that computes the expression. */
328 /* Nonzero if this [anticipatable] occurrence has been deleted. */
330 /* Nonzero if this [available] occurrence has been copied to
332 /* ??? This is mutually exclusive with deleted_p, so they could share
337 /* Expression and copy propagation hash tables.
338 Each hash table is an array of buckets.
339 ??? It is known that if it were an array of entries, structure elements
340 `next_same_hash' and `bitmap_index' wouldn't be necessary. However, it is
341 not clear whether in the final analysis a sufficient amount of memory would
342 be saved as the size of the available expression bitmaps would be larger
343 [one could build a mapping table without holes afterwards though].
344 Someday I'll perform the computation and figure it out. */
349 This is an array of `expr_hash_table_size' elements. */
352 /* Size of the hash table, in elements. */
355 /* Number of hash table elements. */
356 unsigned int n_elems
;
358 /* Whether the table is expression of copy propagation one. */
362 /* Expression hash table. */
363 static struct hash_table expr_hash_table
;
365 /* Copy propagation hash table. */
366 static struct hash_table set_hash_table
;
368 /* This is a list of expressions which are MEMs and will be used by load
370 Load motion tracks MEMs which aren't killed by
371 anything except itself. (i.e., loads and stores to a single location).
372 We can then allow movement of these MEM refs with a little special
373 allowance. (all stores copy the same value to the reaching reg used
374 for the loads). This means all values used to store into memory must have
375 no side effects so we can re-issue the setter value.
376 Store Motion uses this structure as an expression table to track stores
377 which look interesting, and might be moveable towards the exit block. */
381 struct expr
* expr
; /* Gcse expression reference for LM. */
382 rtx pattern
; /* Pattern of this mem. */
383 rtx pattern_regs
; /* List of registers mentioned by the mem. */
384 rtx loads
; /* INSN list of loads seen. */
385 rtx stores
; /* INSN list of stores seen. */
386 struct ls_expr
* next
; /* Next in the list. */
387 int invalid
; /* Invalid for some reason. */
388 int index
; /* If it maps to a bitmap index. */
389 unsigned int hash_index
; /* Index when in a hash table. */
390 rtx reaching_reg
; /* Register to use when re-writing. */
393 /* Array of implicit set patterns indexed by basic block index. */
394 static rtx
*implicit_sets
;
396 /* Head of the list of load/store memory refs. */
397 static struct ls_expr
* pre_ldst_mems
= NULL
;
399 /* Hashtable for the load/store memory refs. */
400 static htab_t pre_ldst_table
= NULL
;
402 /* Bitmap containing one bit for each register in the program.
403 Used when performing GCSE to track which registers have been set since
404 the start of the basic block. */
405 static regset reg_set_bitmap
;
407 /* Array, indexed by basic block number for a list of insns which modify
408 memory within that block. */
409 static rtx
* modify_mem_list
;
410 static bitmap modify_mem_list_set
;
412 /* This array parallels modify_mem_list, but is kept canonicalized. */
413 static rtx
* canon_modify_mem_list
;
415 /* Bitmap indexed by block numbers to record which blocks contain
417 static bitmap blocks_with_calls
;
419 /* Various variables for statistics gathering. */
421 /* Memory used in a pass.
422 This isn't intended to be absolutely precise. Its intent is only
423 to keep an eye on memory usage. */
424 static int bytes_used
;
426 /* GCSE substitutions made. */
427 static int gcse_subst_count
;
428 /* Number of copy instructions created. */
429 static int gcse_create_count
;
430 /* Number of local constants propagated. */
431 static int local_const_prop_count
;
432 /* Number of local copies propagated. */
433 static int local_copy_prop_count
;
434 /* Number of global constants propagated. */
435 static int global_const_prop_count
;
436 /* Number of global copies propagated. */
437 static int global_copy_prop_count
;
439 /* For available exprs */
440 static sbitmap
*ae_kill
;
442 static void compute_can_copy (void);
443 static void *gmalloc (size_t) ATTRIBUTE_MALLOC
;
444 static void *gcalloc (size_t, size_t) ATTRIBUTE_MALLOC
;
445 static void *gcse_alloc (unsigned long);
446 static void alloc_gcse_mem (void);
447 static void free_gcse_mem (void);
448 static void hash_scan_insn (rtx
, struct hash_table
*);
449 static void hash_scan_set (rtx
, rtx
, struct hash_table
*);
450 static void hash_scan_clobber (rtx
, rtx
, struct hash_table
*);
451 static void hash_scan_call (rtx
, rtx
, struct hash_table
*);
452 static int want_to_gcse_p (rtx
);
453 static bool gcse_constant_p (const_rtx
);
454 static int oprs_unchanged_p (const_rtx
, const_rtx
, int);
455 static int oprs_anticipatable_p (const_rtx
, const_rtx
);
456 static int oprs_available_p (const_rtx
, const_rtx
);
457 static void insert_expr_in_table (rtx
, enum machine_mode
, rtx
, int, int,
458 struct hash_table
*);
459 static void insert_set_in_table (rtx
, rtx
, struct hash_table
*);
460 static unsigned int hash_expr (const_rtx
, enum machine_mode
, int *, int);
461 static unsigned int hash_set (int, int);
462 static int expr_equiv_p (const_rtx
, const_rtx
);
463 static void record_last_reg_set_info (rtx
, int);
464 static void record_last_mem_set_info (rtx
);
465 static void record_last_set_info (rtx
, const_rtx
, void *);
466 static void compute_hash_table (struct hash_table
*);
467 static void alloc_hash_table (int, struct hash_table
*, int);
468 static void free_hash_table (struct hash_table
*);
469 static void compute_hash_table_work (struct hash_table
*);
470 static void dump_hash_table (FILE *, const char *, struct hash_table
*);
471 static struct expr
*lookup_set (unsigned int, struct hash_table
*);
472 static struct expr
*next_set (unsigned int, struct expr
*);
473 static void reset_opr_set_tables (void);
474 static int oprs_not_set_p (const_rtx
, const_rtx
);
475 static void mark_call (rtx
);
476 static void mark_set (rtx
, rtx
);
477 static void mark_clobber (rtx
, rtx
);
478 static void mark_oprs_set (rtx
);
479 static void alloc_cprop_mem (int, int);
480 static void free_cprop_mem (void);
481 static void compute_transp (const_rtx
, int, sbitmap
*, int);
482 static void compute_transpout (void);
483 static void compute_local_properties (sbitmap
*, sbitmap
*, sbitmap
*,
484 struct hash_table
*);
485 static void compute_cprop_data (void);
486 static void find_used_regs (rtx
*, void *);
487 static int try_replace_reg (rtx
, rtx
, rtx
);
488 static struct expr
*find_avail_set (int, rtx
);
489 static int cprop_jump (basic_block
, rtx
, rtx
, rtx
, rtx
);
490 static void mems_conflict_for_gcse_p (rtx
, const_rtx
, void *);
491 static int load_killed_in_block_p (const_basic_block
, int, const_rtx
, int);
492 static void canon_list_insert (rtx
, const_rtx
, void *);
493 static int cprop_insn (rtx
);
494 static void find_implicit_sets (void);
495 static int one_cprop_pass (void);
496 static bool constprop_register (rtx
, rtx
, rtx
);
497 static struct expr
*find_bypass_set (int, int);
498 static bool reg_killed_on_edge (const_rtx
, const_edge
);
499 static int bypass_block (basic_block
, rtx
, rtx
);
500 static int bypass_conditional_jumps (void);
501 static void alloc_pre_mem (int, int);
502 static void free_pre_mem (void);
503 static void compute_pre_data (void);
504 static int pre_expr_reaches_here_p (basic_block
, struct expr
*,
506 static void insert_insn_end_basic_block (struct expr
*, basic_block
, int);
507 static void pre_insert_copy_insn (struct expr
*, rtx
);
508 static void pre_insert_copies (void);
509 static int pre_delete (void);
510 static int pre_gcse (void);
511 static int one_pre_gcse_pass (void);
512 static void add_label_notes (rtx
, rtx
);
513 static void alloc_code_hoist_mem (int, int);
514 static void free_code_hoist_mem (void);
515 static void compute_code_hoist_vbeinout (void);
516 static void compute_code_hoist_data (void);
517 static int hoist_expr_reaches_here_p (basic_block
, int, basic_block
, char *);
518 static int hoist_code (void);
519 static int one_code_hoisting_pass (void);
520 static rtx
process_insert_insn (struct expr
*);
521 static int pre_edge_insert (struct edge_list
*, struct expr
**);
522 static int pre_expr_reaches_here_p_work (basic_block
, struct expr
*,
523 basic_block
, char *);
524 static struct ls_expr
* ldst_entry (rtx
);
525 static void free_ldst_entry (struct ls_expr
*);
526 static void free_ldst_mems (void);
527 static void print_ldst_list (FILE *);
528 static struct ls_expr
* find_rtx_in_ldst (rtx
);
529 static inline struct ls_expr
* first_ls_expr (void);
530 static inline struct ls_expr
* next_ls_expr (struct ls_expr
*);
531 static int simple_mem (const_rtx
);
532 static void invalidate_any_buried_refs (rtx
);
533 static void compute_ld_motion_mems (void);
534 static void trim_ld_motion_mems (void);
535 static void update_ld_motion_stores (struct expr
*);
536 static void free_insn_expr_list_list (rtx
*);
537 static void clear_modify_mem_tables (void);
538 static void free_modify_mem_tables (void);
539 static rtx
gcse_emit_move_after (rtx
, rtx
, rtx
);
540 static void local_cprop_find_used_regs (rtx
*, void *);
541 static bool do_local_cprop (rtx
, rtx
);
542 static int local_cprop_pass (void);
543 static bool is_too_expensive (const char *);
545 #define GNEW(T) ((T *) gmalloc (sizeof (T)))
546 #define GCNEW(T) ((T *) gcalloc (1, sizeof (T)))
548 #define GNEWVEC(T, N) ((T *) gmalloc (sizeof (T) * (N)))
549 #define GCNEWVEC(T, N) ((T *) gcalloc ((N), sizeof (T)))
551 #define GNEWVAR(T, S) ((T *) gmalloc ((S)))
552 #define GCNEWVAR(T, S) ((T *) gcalloc (1, (S)))
554 #define GOBNEW(T) ((T *) gcse_alloc (sizeof (T)))
555 #define GOBNEWVAR(T, S) ((T *) gcse_alloc ((S)))
557 /* Misc. utilities. */
559 /* Nonzero for each mode that supports (set (reg) (reg)).
560 This is trivially true for integer and floating point values.
561 It may or may not be true for condition codes. */
562 static char can_copy
[(int) NUM_MACHINE_MODES
];
564 /* Compute which modes support reg/reg copy operations. */
567 compute_can_copy (void)
570 #ifndef AVOID_CCMODE_COPIES
573 memset (can_copy
, 0, NUM_MACHINE_MODES
);
576 for (i
= 0; i
< NUM_MACHINE_MODES
; i
++)
577 if (GET_MODE_CLASS (i
) == MODE_CC
)
579 #ifdef AVOID_CCMODE_COPIES
582 reg
= gen_rtx_REG ((enum machine_mode
) i
, LAST_VIRTUAL_REGISTER
+ 1);
583 insn
= emit_insn (gen_rtx_SET (VOIDmode
, reg
, reg
));
584 if (recog (PATTERN (insn
), insn
, NULL
) >= 0)
594 /* Returns whether the mode supports reg/reg copy operations. */
597 can_copy_p (enum machine_mode mode
)
599 static bool can_copy_init_p
= false;
601 if (! can_copy_init_p
)
604 can_copy_init_p
= true;
607 return can_copy
[mode
] != 0;
611 /* Cover function to xmalloc to record bytes allocated. */
614 gmalloc (size_t size
)
617 return xmalloc (size
);
620 /* Cover function to xcalloc to record bytes allocated. */
623 gcalloc (size_t nelem
, size_t elsize
)
625 bytes_used
+= nelem
* elsize
;
626 return xcalloc (nelem
, elsize
);
629 /* Cover function to obstack_alloc. */
632 gcse_alloc (unsigned long size
)
635 return obstack_alloc (&gcse_obstack
, size
);
638 /* Allocate memory for the reg/memory set tracking tables.
639 This is called at the start of each pass. */
642 alloc_gcse_mem (void)
644 /* Allocate vars to track sets of regs. */
645 reg_set_bitmap
= BITMAP_ALLOC (NULL
);
647 /* Allocate array to keep a list of insns which modify memory in each
649 modify_mem_list
= GCNEWVEC (rtx
, last_basic_block
);
650 canon_modify_mem_list
= GCNEWVEC (rtx
, last_basic_block
);
651 modify_mem_list_set
= BITMAP_ALLOC (NULL
);
652 blocks_with_calls
= BITMAP_ALLOC (NULL
);
655 /* Free memory allocated by alloc_gcse_mem. */
660 free_modify_mem_tables ();
661 BITMAP_FREE (modify_mem_list_set
);
662 BITMAP_FREE (blocks_with_calls
);
665 /* Compute the local properties of each recorded expression.
667 Local properties are those that are defined by the block, irrespective of
670 An expression is transparent in a block if its operands are not modified
673 An expression is computed (locally available) in a block if it is computed
674 at least once and expression would contain the same value if the
675 computation was moved to the end of the block.
677 An expression is locally anticipatable in a block if it is computed at
678 least once and expression would contain the same value if the computation
679 was moved to the beginning of the block.
681 We call this routine for cprop, pre and code hoisting. They all compute
682 basically the same information and thus can easily share this code.
684 TRANSP, COMP, and ANTLOC are destination sbitmaps for recording local
685 properties. If NULL, then it is not necessary to compute or record that
688 TABLE controls which hash table to look at. If it is set hash table,
689 additionally, TRANSP is computed as ~TRANSP, since this is really cprop's
693 compute_local_properties (sbitmap
*transp
, sbitmap
*comp
, sbitmap
*antloc
,
694 struct hash_table
*table
)
698 /* Initialize any bitmaps that were passed in. */
702 sbitmap_vector_zero (transp
, last_basic_block
);
704 sbitmap_vector_ones (transp
, last_basic_block
);
708 sbitmap_vector_zero (comp
, last_basic_block
);
710 sbitmap_vector_zero (antloc
, last_basic_block
);
712 for (i
= 0; i
< table
->size
; i
++)
716 for (expr
= table
->table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
718 int indx
= expr
->bitmap_index
;
721 /* The expression is transparent in this block if it is not killed.
722 We start by assuming all are transparent [none are killed], and
723 then reset the bits for those that are. */
725 compute_transp (expr
->expr
, indx
, transp
, table
->set_p
);
727 /* The occurrences recorded in antic_occr are exactly those that
728 we want to set to nonzero in ANTLOC. */
730 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
732 SET_BIT (antloc
[BLOCK_NUM (occr
->insn
)], indx
);
734 /* While we're scanning the table, this is a good place to
739 /* The occurrences recorded in avail_occr are exactly those that
740 we want to set to nonzero in COMP. */
742 for (occr
= expr
->avail_occr
; occr
!= NULL
; occr
= occr
->next
)
744 SET_BIT (comp
[BLOCK_NUM (occr
->insn
)], indx
);
746 /* While we're scanning the table, this is a good place to
751 /* While we're scanning the table, this is a good place to
753 expr
->reaching_reg
= 0;
758 /* Hash table support. */
760 struct reg_avail_info
767 static struct reg_avail_info
*reg_avail_info
;
768 static basic_block current_bb
;
771 /* See whether X, the source of a set, is something we want to consider for
775 want_to_gcse_p (rtx x
)
778 /* On register stack architectures, don't GCSE constants from the
779 constant pool, as the benefits are often swamped by the overhead
780 of shuffling the register stack between basic blocks. */
781 if (IS_STACK_MODE (GET_MODE (x
)))
782 x
= avoid_constant_pool_reference (x
);
785 switch (GET_CODE (x
))
797 return can_assign_to_reg_without_clobbers_p (x
);
801 /* Used internally by can_assign_to_reg_without_clobbers_p. */
803 static GTY(()) rtx test_insn
;
805 /* Return true if we can assign X to a pseudo register such that the
806 resulting insn does not result in clobbering a hard register as a
808 This function is typically used by code motion passes, to verify
809 that it is safe to insert an insn without worrying about clobbering
810 maybe live hard regs. */
813 can_assign_to_reg_without_clobbers_p (rtx x
)
815 int num_clobbers
= 0;
818 /* If this is a valid operand, we are OK. If it's VOIDmode, we aren't. */
819 if (general_operand (x
, GET_MODE (x
)))
821 else if (GET_MODE (x
) == VOIDmode
)
824 /* Otherwise, check if we can make a valid insn from it. First initialize
825 our test insn if we haven't already. */
829 = make_insn_raw (gen_rtx_SET (VOIDmode
,
830 gen_rtx_REG (word_mode
,
831 FIRST_PSEUDO_REGISTER
* 2),
833 NEXT_INSN (test_insn
) = PREV_INSN (test_insn
) = 0;
836 /* Now make an insn like the one we would make when GCSE'ing and see if
838 PUT_MODE (SET_DEST (PATTERN (test_insn
)), GET_MODE (x
));
839 SET_SRC (PATTERN (test_insn
)) = x
;
840 return ((icode
= recog (PATTERN (test_insn
), test_insn
, &num_clobbers
)) >= 0
841 && (num_clobbers
== 0 || ! added_clobbers_hard_reg_p (icode
)));
844 /* Return nonzero if the operands of expression X are unchanged from the
845 start of INSN's basic block up to but not including INSN (if AVAIL_P == 0),
846 or from INSN to the end of INSN's basic block (if AVAIL_P != 0). */
849 oprs_unchanged_p (const_rtx x
, const_rtx insn
, int avail_p
)
863 struct reg_avail_info
*info
= ®_avail_info
[REGNO (x
)];
865 if (info
->last_bb
!= current_bb
)
868 return info
->last_set
< DF_INSN_LUID (insn
);
870 return info
->first_set
>= DF_INSN_LUID (insn
);
874 if (load_killed_in_block_p (current_bb
, DF_INSN_LUID (insn
),
878 return oprs_unchanged_p (XEXP (x
, 0), insn
, avail_p
);
905 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
909 /* If we are about to do the last recursive call needed at this
910 level, change it into iteration. This function is called enough
913 return oprs_unchanged_p (XEXP (x
, i
), insn
, avail_p
);
915 else if (! oprs_unchanged_p (XEXP (x
, i
), insn
, avail_p
))
918 else if (fmt
[i
] == 'E')
919 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
920 if (! oprs_unchanged_p (XVECEXP (x
, i
, j
), insn
, avail_p
))
927 /* Used for communication between mems_conflict_for_gcse_p and
928 load_killed_in_block_p. Nonzero if mems_conflict_for_gcse_p finds a
929 conflict between two memory references. */
930 static int gcse_mems_conflict_p
;
932 /* Used for communication between mems_conflict_for_gcse_p and
933 load_killed_in_block_p. A memory reference for a load instruction,
934 mems_conflict_for_gcse_p will see if a memory store conflicts with
936 static const_rtx gcse_mem_operand
;
938 /* DEST is the output of an instruction. If it is a memory reference, and
939 possibly conflicts with the load found in gcse_mem_operand, then set
940 gcse_mems_conflict_p to a nonzero value. */
943 mems_conflict_for_gcse_p (rtx dest
, const_rtx setter ATTRIBUTE_UNUSED
,
944 void *data ATTRIBUTE_UNUSED
)
946 while (GET_CODE (dest
) == SUBREG
947 || GET_CODE (dest
) == ZERO_EXTRACT
948 || GET_CODE (dest
) == STRICT_LOW_PART
)
949 dest
= XEXP (dest
, 0);
951 /* If DEST is not a MEM, then it will not conflict with the load. Note
952 that function calls are assumed to clobber memory, but are handled
957 /* If we are setting a MEM in our list of specially recognized MEMs,
958 don't mark as killed this time. */
960 if (expr_equiv_p (dest
, gcse_mem_operand
) && pre_ldst_mems
!= NULL
)
962 if (!find_rtx_in_ldst (dest
))
963 gcse_mems_conflict_p
= 1;
967 if (true_dependence (dest
, GET_MODE (dest
), gcse_mem_operand
,
969 gcse_mems_conflict_p
= 1;
972 /* Return nonzero if the expression in X (a memory reference) is killed
973 in block BB before or after the insn with the LUID in UID_LIMIT.
974 AVAIL_P is nonzero for kills after UID_LIMIT, and zero for kills
977 To check the entire block, set UID_LIMIT to max_uid + 1 and
981 load_killed_in_block_p (const_basic_block bb
, int uid_limit
, const_rtx x
, int avail_p
)
983 rtx list_entry
= modify_mem_list
[bb
->index
];
985 /* If this is a readonly then we aren't going to be changing it. */
986 if (MEM_READONLY_P (x
))
992 /* Ignore entries in the list that do not apply. */
994 && DF_INSN_LUID (XEXP (list_entry
, 0)) < uid_limit
)
996 && DF_INSN_LUID (XEXP (list_entry
, 0)) > uid_limit
))
998 list_entry
= XEXP (list_entry
, 1);
1002 setter
= XEXP (list_entry
, 0);
1004 /* If SETTER is a call everything is clobbered. Note that calls
1005 to pure functions are never put on the list, so we need not
1006 worry about them. */
1007 if (CALL_P (setter
))
1010 /* SETTER must be an INSN of some kind that sets memory. Call
1011 note_stores to examine each hunk of memory that is modified.
1013 The note_stores interface is pretty limited, so we have to
1014 communicate via global variables. Yuk. */
1015 gcse_mem_operand
= x
;
1016 gcse_mems_conflict_p
= 0;
1017 note_stores (PATTERN (setter
), mems_conflict_for_gcse_p
, NULL
);
1018 if (gcse_mems_conflict_p
)
1020 list_entry
= XEXP (list_entry
, 1);
1025 /* Return nonzero if the operands of expression X are unchanged from
1026 the start of INSN's basic block up to but not including INSN. */
1029 oprs_anticipatable_p (const_rtx x
, const_rtx insn
)
1031 return oprs_unchanged_p (x
, insn
, 0);
1034 /* Return nonzero if the operands of expression X are unchanged from
1035 INSN to the end of INSN's basic block. */
1038 oprs_available_p (const_rtx x
, const_rtx insn
)
1040 return oprs_unchanged_p (x
, insn
, 1);
1043 /* Hash expression X.
1045 MODE is only used if X is a CONST_INT. DO_NOT_RECORD_P is a boolean
1046 indicating if a volatile operand is found or if the expression contains
1047 something we don't want to insert in the table. HASH_TABLE_SIZE is
1048 the current size of the hash table to be probed. */
1051 hash_expr (const_rtx x
, enum machine_mode mode
, int *do_not_record_p
,
1052 int hash_table_size
)
1056 *do_not_record_p
= 0;
1058 hash
= hash_rtx (x
, mode
, do_not_record_p
,
1059 NULL
, /*have_reg_qty=*/false);
1060 return hash
% hash_table_size
;
1063 /* Hash a set of register REGNO.
1065 Sets are hashed on the register that is set. This simplifies the PRE copy
1068 ??? May need to make things more elaborate. Later, as necessary. */
1071 hash_set (int regno
, int hash_table_size
)
1076 return hash
% hash_table_size
;
1079 /* Return nonzero if exp1 is equivalent to exp2. */
1082 expr_equiv_p (const_rtx x
, const_rtx y
)
1084 return exp_equiv_p (x
, y
, 0, true);
1087 /* Insert expression X in INSN in the hash TABLE.
1088 If it is already present, record it as the last occurrence in INSN's
1091 MODE is the mode of the value X is being stored into.
1092 It is only used if X is a CONST_INT.
1094 ANTIC_P is nonzero if X is an anticipatable expression.
1095 AVAIL_P is nonzero if X is an available expression. */
1098 insert_expr_in_table (rtx x
, enum machine_mode mode
, rtx insn
, int antic_p
,
1099 int avail_p
, struct hash_table
*table
)
1101 int found
, do_not_record_p
;
1103 struct expr
*cur_expr
, *last_expr
= NULL
;
1104 struct occr
*antic_occr
, *avail_occr
;
1106 hash
= hash_expr (x
, mode
, &do_not_record_p
, table
->size
);
1108 /* Do not insert expression in table if it contains volatile operands,
1109 or if hash_expr determines the expression is something we don't want
1110 to or can't handle. */
1111 if (do_not_record_p
)
1114 cur_expr
= table
->table
[hash
];
1117 while (cur_expr
&& 0 == (found
= expr_equiv_p (cur_expr
->expr
, x
)))
1119 /* If the expression isn't found, save a pointer to the end of
1121 last_expr
= cur_expr
;
1122 cur_expr
= cur_expr
->next_same_hash
;
1127 cur_expr
= GOBNEW (struct expr
);
1128 bytes_used
+= sizeof (struct expr
);
1129 if (table
->table
[hash
] == NULL
)
1130 /* This is the first pattern that hashed to this index. */
1131 table
->table
[hash
] = cur_expr
;
1133 /* Add EXPR to end of this hash chain. */
1134 last_expr
->next_same_hash
= cur_expr
;
1136 /* Set the fields of the expr element. */
1138 cur_expr
->bitmap_index
= table
->n_elems
++;
1139 cur_expr
->next_same_hash
= NULL
;
1140 cur_expr
->antic_occr
= NULL
;
1141 cur_expr
->avail_occr
= NULL
;
1144 /* Now record the occurrence(s). */
1147 antic_occr
= cur_expr
->antic_occr
;
1149 if (antic_occr
&& BLOCK_NUM (antic_occr
->insn
) != BLOCK_NUM (insn
))
1153 /* Found another instance of the expression in the same basic block.
1154 Prefer the currently recorded one. We want the first one in the
1155 block and the block is scanned from start to end. */
1156 ; /* nothing to do */
1159 /* First occurrence of this expression in this basic block. */
1160 antic_occr
= GOBNEW (struct occr
);
1161 bytes_used
+= sizeof (struct occr
);
1162 antic_occr
->insn
= insn
;
1163 antic_occr
->next
= cur_expr
->antic_occr
;
1164 antic_occr
->deleted_p
= 0;
1165 cur_expr
->antic_occr
= antic_occr
;
1171 avail_occr
= cur_expr
->avail_occr
;
1173 if (avail_occr
&& BLOCK_NUM (avail_occr
->insn
) == BLOCK_NUM (insn
))
1175 /* Found another instance of the expression in the same basic block.
1176 Prefer this occurrence to the currently recorded one. We want
1177 the last one in the block and the block is scanned from start
1179 avail_occr
->insn
= insn
;
1183 /* First occurrence of this expression in this basic block. */
1184 avail_occr
= GOBNEW (struct occr
);
1185 bytes_used
+= sizeof (struct occr
);
1186 avail_occr
->insn
= insn
;
1187 avail_occr
->next
= cur_expr
->avail_occr
;
1188 avail_occr
->deleted_p
= 0;
1189 cur_expr
->avail_occr
= avail_occr
;
1194 /* Insert pattern X in INSN in the hash table.
1195 X is a SET of a reg to either another reg or a constant.
1196 If it is already present, record it as the last occurrence in INSN's
1200 insert_set_in_table (rtx x
, rtx insn
, struct hash_table
*table
)
1204 struct expr
*cur_expr
, *last_expr
= NULL
;
1205 struct occr
*cur_occr
;
1207 gcc_assert (GET_CODE (x
) == SET
&& REG_P (SET_DEST (x
)));
1209 hash
= hash_set (REGNO (SET_DEST (x
)), table
->size
);
1211 cur_expr
= table
->table
[hash
];
1214 while (cur_expr
&& 0 == (found
= expr_equiv_p (cur_expr
->expr
, x
)))
1216 /* If the expression isn't found, save a pointer to the end of
1218 last_expr
= cur_expr
;
1219 cur_expr
= cur_expr
->next_same_hash
;
1224 cur_expr
= GOBNEW (struct expr
);
1225 bytes_used
+= sizeof (struct expr
);
1226 if (table
->table
[hash
] == NULL
)
1227 /* This is the first pattern that hashed to this index. */
1228 table
->table
[hash
] = cur_expr
;
1230 /* Add EXPR to end of this hash chain. */
1231 last_expr
->next_same_hash
= cur_expr
;
1233 /* Set the fields of the expr element.
1234 We must copy X because it can be modified when copy propagation is
1235 performed on its operands. */
1236 cur_expr
->expr
= copy_rtx (x
);
1237 cur_expr
->bitmap_index
= table
->n_elems
++;
1238 cur_expr
->next_same_hash
= NULL
;
1239 cur_expr
->antic_occr
= NULL
;
1240 cur_expr
->avail_occr
= NULL
;
1243 /* Now record the occurrence. */
1244 cur_occr
= cur_expr
->avail_occr
;
1246 if (cur_occr
&& BLOCK_NUM (cur_occr
->insn
) == BLOCK_NUM (insn
))
1248 /* Found another instance of the expression in the same basic block.
1249 Prefer this occurrence to the currently recorded one. We want
1250 the last one in the block and the block is scanned from start
1252 cur_occr
->insn
= insn
;
1256 /* First occurrence of this expression in this basic block. */
1257 cur_occr
= GOBNEW (struct occr
);
1258 bytes_used
+= sizeof (struct occr
);
1259 cur_occr
->insn
= insn
;
1260 cur_occr
->next
= cur_expr
->avail_occr
;
1261 cur_occr
->deleted_p
= 0;
1262 cur_expr
->avail_occr
= cur_occr
;
1266 /* Determine whether the rtx X should be treated as a constant for
1267 the purposes of GCSE's constant propagation. */
1270 gcse_constant_p (const_rtx x
)
1272 /* Consider a COMPARE of two integers constant. */
1273 if (GET_CODE (x
) == COMPARE
1274 && GET_CODE (XEXP (x
, 0)) == CONST_INT
1275 && GET_CODE (XEXP (x
, 1)) == CONST_INT
)
1278 /* Consider a COMPARE of the same registers is a constant
1279 if they are not floating point registers. */
1280 if (GET_CODE(x
) == COMPARE
1281 && REG_P (XEXP (x
, 0)) && REG_P (XEXP (x
, 1))
1282 && REGNO (XEXP (x
, 0)) == REGNO (XEXP (x
, 1))
1283 && ! FLOAT_MODE_P (GET_MODE (XEXP (x
, 0)))
1284 && ! FLOAT_MODE_P (GET_MODE (XEXP (x
, 1))))
1287 /* Since X might be inserted more than once we have to take care that it
1289 return CONSTANT_P (x
) && (GET_CODE (x
) != CONST
|| shared_const_p (x
));
1292 /* Scan pattern PAT of INSN and add an entry to the hash TABLE (set or
1296 hash_scan_set (rtx pat
, rtx insn
, struct hash_table
*table
)
1298 rtx src
= SET_SRC (pat
);
1299 rtx dest
= SET_DEST (pat
);
1302 if (GET_CODE (src
) == CALL
)
1303 hash_scan_call (src
, insn
, table
);
1305 else if (REG_P (dest
))
1307 unsigned int regno
= REGNO (dest
);
1310 /* See if a REG_EQUAL note shows this equivalent to a simpler expression.
1312 This allows us to do a single GCSE pass and still eliminate
1313 redundant constants, addresses or other expressions that are
1314 constructed with multiple instructions.
1316 However, keep the original SRC if INSN is a simple reg-reg move. In
1317 In this case, there will almost always be a REG_EQUAL note on the
1318 insn that sets SRC. By recording the REG_EQUAL value here as SRC
1319 for INSN, we miss copy propagation opportunities and we perform the
1320 same PRE GCSE operation repeatedly on the same REG_EQUAL value if we
1321 do more than one PRE GCSE pass.
1323 Note that this does not impede profitable constant propagations. We
1324 "look through" reg-reg sets in lookup_avail_set. */
1325 note
= find_reg_equal_equiv_note (insn
);
1327 && REG_NOTE_KIND (note
) == REG_EQUAL
1330 ? gcse_constant_p (XEXP (note
, 0))
1331 : want_to_gcse_p (XEXP (note
, 0))))
1332 src
= XEXP (note
, 0), pat
= gen_rtx_SET (VOIDmode
, dest
, src
);
1334 /* Only record sets of pseudo-regs in the hash table. */
1336 && regno
>= FIRST_PSEUDO_REGISTER
1337 /* Don't GCSE something if we can't do a reg/reg copy. */
1338 && can_copy_p (GET_MODE (dest
))
1339 /* GCSE commonly inserts instruction after the insn. We can't
1340 do that easily for EH_REGION notes so disable GCSE on these
1342 && !find_reg_note (insn
, REG_EH_REGION
, NULL_RTX
)
1343 /* Is SET_SRC something we want to gcse? */
1344 && want_to_gcse_p (src
)
1345 /* Don't CSE a nop. */
1346 && ! set_noop_p (pat
)
1347 /* Don't GCSE if it has attached REG_EQUIV note.
1348 At this point this only function parameters should have
1349 REG_EQUIV notes and if the argument slot is used somewhere
1350 explicitly, it means address of parameter has been taken,
1351 so we should not extend the lifetime of the pseudo. */
1352 && (note
== NULL_RTX
|| ! MEM_P (XEXP (note
, 0))))
1354 /* An expression is not anticipatable if its operands are
1355 modified before this insn or if this is not the only SET in
1356 this insn. The latter condition does not have to mean that
1357 SRC itself is not anticipatable, but we just will not be
1358 able to handle code motion of insns with multiple sets. */
1359 int antic_p
= oprs_anticipatable_p (src
, insn
)
1360 && !multiple_sets (insn
);
1361 /* An expression is not available if its operands are
1362 subsequently modified, including this insn. It's also not
1363 available if this is a branch, because we can't insert
1364 a set after the branch. */
1365 int avail_p
= (oprs_available_p (src
, insn
)
1366 && ! JUMP_P (insn
));
1368 insert_expr_in_table (src
, GET_MODE (dest
), insn
, antic_p
, avail_p
, table
);
1371 /* Record sets for constant/copy propagation. */
1372 else if (table
->set_p
1373 && regno
>= FIRST_PSEUDO_REGISTER
1375 && REGNO (src
) >= FIRST_PSEUDO_REGISTER
1376 && can_copy_p (GET_MODE (dest
))
1377 && REGNO (src
) != regno
)
1378 || gcse_constant_p (src
))
1379 /* A copy is not available if its src or dest is subsequently
1380 modified. Here we want to search from INSN+1 on, but
1381 oprs_available_p searches from INSN on. */
1382 && (insn
== BB_END (BLOCK_FOR_INSN (insn
))
1383 || (tmp
= next_nonnote_insn (insn
)) == NULL_RTX
1384 || BLOCK_FOR_INSN (tmp
) != BLOCK_FOR_INSN (insn
)
1385 || oprs_available_p (pat
, tmp
)))
1386 insert_set_in_table (pat
, insn
, table
);
1388 /* In case of store we want to consider the memory value as available in
1389 the REG stored in that memory. This makes it possible to remove
1390 redundant loads from due to stores to the same location. */
1391 else if (flag_gcse_las
&& REG_P (src
) && MEM_P (dest
))
1393 unsigned int regno
= REGNO (src
);
1395 /* Do not do this for constant/copy propagation. */
1397 /* Only record sets of pseudo-regs in the hash table. */
1398 && regno
>= FIRST_PSEUDO_REGISTER
1399 /* Don't GCSE something if we can't do a reg/reg copy. */
1400 && can_copy_p (GET_MODE (src
))
1401 /* GCSE commonly inserts instruction after the insn. We can't
1402 do that easily for EH_REGION notes so disable GCSE on these
1404 && ! find_reg_note (insn
, REG_EH_REGION
, NULL_RTX
)
1405 /* Is SET_DEST something we want to gcse? */
1406 && want_to_gcse_p (dest
)
1407 /* Don't CSE a nop. */
1408 && ! set_noop_p (pat
)
1409 /* Don't GCSE if it has attached REG_EQUIV note.
1410 At this point this only function parameters should have
1411 REG_EQUIV notes and if the argument slot is used somewhere
1412 explicitly, it means address of parameter has been taken,
1413 so we should not extend the lifetime of the pseudo. */
1414 && ((note
= find_reg_note (insn
, REG_EQUIV
, NULL_RTX
)) == 0
1415 || ! MEM_P (XEXP (note
, 0))))
1417 /* Stores are never anticipatable. */
1419 /* An expression is not available if its operands are
1420 subsequently modified, including this insn. It's also not
1421 available if this is a branch, because we can't insert
1422 a set after the branch. */
1423 int avail_p
= oprs_available_p (dest
, insn
)
1426 /* Record the memory expression (DEST) in the hash table. */
1427 insert_expr_in_table (dest
, GET_MODE (dest
), insn
,
1428 antic_p
, avail_p
, table
);
1434 hash_scan_clobber (rtx x ATTRIBUTE_UNUSED
, rtx insn ATTRIBUTE_UNUSED
,
1435 struct hash_table
*table ATTRIBUTE_UNUSED
)
1437 /* Currently nothing to do. */
1441 hash_scan_call (rtx x ATTRIBUTE_UNUSED
, rtx insn ATTRIBUTE_UNUSED
,
1442 struct hash_table
*table ATTRIBUTE_UNUSED
)
1444 /* Currently nothing to do. */
1447 /* Process INSN and add hash table entries as appropriate.
1449 Only available expressions that set a single pseudo-reg are recorded.
1451 Single sets in a PARALLEL could be handled, but it's an extra complication
1452 that isn't dealt with right now. The trick is handling the CLOBBERs that
1453 are also in the PARALLEL. Later.
1455 If SET_P is nonzero, this is for the assignment hash table,
1456 otherwise it is for the expression hash table. */
1459 hash_scan_insn (rtx insn
, struct hash_table
*table
)
1461 rtx pat
= PATTERN (insn
);
1464 /* Pick out the sets of INSN and for other forms of instructions record
1465 what's been modified. */
1467 if (GET_CODE (pat
) == SET
)
1468 hash_scan_set (pat
, insn
, table
);
1469 else if (GET_CODE (pat
) == PARALLEL
)
1470 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
1472 rtx x
= XVECEXP (pat
, 0, i
);
1474 if (GET_CODE (x
) == SET
)
1475 hash_scan_set (x
, insn
, table
);
1476 else if (GET_CODE (x
) == CLOBBER
)
1477 hash_scan_clobber (x
, insn
, table
);
1478 else if (GET_CODE (x
) == CALL
)
1479 hash_scan_call (x
, insn
, table
);
1482 else if (GET_CODE (pat
) == CLOBBER
)
1483 hash_scan_clobber (pat
, insn
, table
);
1484 else if (GET_CODE (pat
) == CALL
)
1485 hash_scan_call (pat
, insn
, table
);
1489 dump_hash_table (FILE *file
, const char *name
, struct hash_table
*table
)
1492 /* Flattened out table, so it's printed in proper order. */
1493 struct expr
**flat_table
;
1494 unsigned int *hash_val
;
1497 flat_table
= XCNEWVEC (struct expr
*, table
->n_elems
);
1498 hash_val
= XNEWVEC (unsigned int, table
->n_elems
);
1500 for (i
= 0; i
< (int) table
->size
; i
++)
1501 for (expr
= table
->table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
1503 flat_table
[expr
->bitmap_index
] = expr
;
1504 hash_val
[expr
->bitmap_index
] = i
;
1507 fprintf (file
, "%s hash table (%d buckets, %d entries)\n",
1508 name
, table
->size
, table
->n_elems
);
1510 for (i
= 0; i
< (int) table
->n_elems
; i
++)
1511 if (flat_table
[i
] != 0)
1513 expr
= flat_table
[i
];
1514 fprintf (file
, "Index %d (hash value %d)\n ",
1515 expr
->bitmap_index
, hash_val
[i
]);
1516 print_rtl (file
, expr
->expr
);
1517 fprintf (file
, "\n");
1520 fprintf (file
, "\n");
1526 /* Record register first/last/block set information for REGNO in INSN.
1528 first_set records the first place in the block where the register
1529 is set and is used to compute "anticipatability".
1531 last_set records the last place in the block where the register
1532 is set and is used to compute "availability".
1534 last_bb records the block for which first_set and last_set are
1535 valid, as a quick test to invalidate them. */
1538 record_last_reg_set_info (rtx insn
, int regno
)
1540 struct reg_avail_info
*info
= ®_avail_info
[regno
];
1541 int luid
= DF_INSN_LUID (insn
);
1543 info
->last_set
= luid
;
1544 if (info
->last_bb
!= current_bb
)
1546 info
->last_bb
= current_bb
;
1547 info
->first_set
= luid
;
1552 /* Record all of the canonicalized MEMs of record_last_mem_set_info's insn.
1553 Note we store a pair of elements in the list, so they have to be
1554 taken off pairwise. */
1557 canon_list_insert (rtx dest ATTRIBUTE_UNUSED
, const_rtx unused1 ATTRIBUTE_UNUSED
,
1560 rtx dest_addr
, insn
;
1563 while (GET_CODE (dest
) == SUBREG
1564 || GET_CODE (dest
) == ZERO_EXTRACT
1565 || GET_CODE (dest
) == STRICT_LOW_PART
)
1566 dest
= XEXP (dest
, 0);
1568 /* If DEST is not a MEM, then it will not conflict with a load. Note
1569 that function calls are assumed to clobber memory, but are handled
1575 dest_addr
= get_addr (XEXP (dest
, 0));
1576 dest_addr
= canon_rtx (dest_addr
);
1577 insn
= (rtx
) v_insn
;
1578 bb
= BLOCK_NUM (insn
);
1580 canon_modify_mem_list
[bb
] =
1581 alloc_EXPR_LIST (VOIDmode
, dest_addr
, canon_modify_mem_list
[bb
]);
1582 canon_modify_mem_list
[bb
] =
1583 alloc_EXPR_LIST (VOIDmode
, dest
, canon_modify_mem_list
[bb
]);
1586 /* Record memory modification information for INSN. We do not actually care
1587 about the memory location(s) that are set, or even how they are set (consider
1588 a CALL_INSN). We merely need to record which insns modify memory. */
1591 record_last_mem_set_info (rtx insn
)
1593 int bb
= BLOCK_NUM (insn
);
1595 /* load_killed_in_block_p will handle the case of calls clobbering
1597 modify_mem_list
[bb
] = alloc_INSN_LIST (insn
, modify_mem_list
[bb
]);
1598 bitmap_set_bit (modify_mem_list_set
, bb
);
1602 /* Note that traversals of this loop (other than for free-ing)
1603 will break after encountering a CALL_INSN. So, there's no
1604 need to insert a pair of items, as canon_list_insert does. */
1605 canon_modify_mem_list
[bb
] =
1606 alloc_INSN_LIST (insn
, canon_modify_mem_list
[bb
]);
1607 bitmap_set_bit (blocks_with_calls
, bb
);
1610 note_stores (PATTERN (insn
), canon_list_insert
, (void*) insn
);
1613 /* Called from compute_hash_table via note_stores to handle one
1614 SET or CLOBBER in an insn. DATA is really the instruction in which
1615 the SET is taking place. */
1618 record_last_set_info (rtx dest
, const_rtx setter ATTRIBUTE_UNUSED
, void *data
)
1620 rtx last_set_insn
= (rtx
) data
;
1622 if (GET_CODE (dest
) == SUBREG
)
1623 dest
= SUBREG_REG (dest
);
1626 record_last_reg_set_info (last_set_insn
, REGNO (dest
));
1627 else if (MEM_P (dest
)
1628 /* Ignore pushes, they clobber nothing. */
1629 && ! push_operand (dest
, GET_MODE (dest
)))
1630 record_last_mem_set_info (last_set_insn
);
1633 /* Top level function to create an expression or assignment hash table.
1635 Expression entries are placed in the hash table if
1636 - they are of the form (set (pseudo-reg) src),
1637 - src is something we want to perform GCSE on,
1638 - none of the operands are subsequently modified in the block
1640 Assignment entries are placed in the hash table if
1641 - they are of the form (set (pseudo-reg) src),
1642 - src is something we want to perform const/copy propagation on,
1643 - none of the operands or target are subsequently modified in the block
1645 Currently src must be a pseudo-reg or a const_int.
1647 TABLE is the table computed. */
1650 compute_hash_table_work (struct hash_table
*table
)
1654 /* re-Cache any INSN_LIST nodes we have allocated. */
1655 clear_modify_mem_tables ();
1656 /* Some working arrays used to track first and last set in each block. */
1657 reg_avail_info
= GNEWVEC (struct reg_avail_info
, max_reg_num ());
1659 for (i
= 0; i
< max_reg_num (); ++i
)
1660 reg_avail_info
[i
].last_bb
= NULL
;
1662 FOR_EACH_BB (current_bb
)
1667 /* First pass over the instructions records information used to
1668 determine when registers and memory are first and last set. */
1669 FOR_BB_INSNS (current_bb
, insn
)
1671 if (! INSN_P (insn
))
1676 for (regno
= 0; regno
< FIRST_PSEUDO_REGISTER
; regno
++)
1677 if (TEST_HARD_REG_BIT (regs_invalidated_by_call
, regno
))
1678 record_last_reg_set_info (insn
, regno
);
1683 note_stores (PATTERN (insn
), record_last_set_info
, insn
);
1686 /* Insert implicit sets in the hash table. */
1688 && implicit_sets
[current_bb
->index
] != NULL_RTX
)
1689 hash_scan_set (implicit_sets
[current_bb
->index
],
1690 BB_HEAD (current_bb
), table
);
1692 /* The next pass builds the hash table. */
1693 FOR_BB_INSNS (current_bb
, insn
)
1695 hash_scan_insn (insn
, table
);
1698 free (reg_avail_info
);
1699 reg_avail_info
= NULL
;
1702 /* Allocate space for the set/expr hash TABLE.
1703 N_INSNS is the number of instructions in the function.
1704 It is used to determine the number of buckets to use.
1705 SET_P determines whether set or expression table will
1709 alloc_hash_table (int n_insns
, struct hash_table
*table
, int set_p
)
1713 table
->size
= n_insns
/ 4;
1714 if (table
->size
< 11)
1717 /* Attempt to maintain efficient use of hash table.
1718 Making it an odd number is simplest for now.
1719 ??? Later take some measurements. */
1721 n
= table
->size
* sizeof (struct expr
*);
1722 table
->table
= GNEWVAR (struct expr
*, n
);
1723 table
->set_p
= set_p
;
1726 /* Free things allocated by alloc_hash_table. */
1729 free_hash_table (struct hash_table
*table
)
1731 free (table
->table
);
1734 /* Compute the hash TABLE for doing copy/const propagation or
1735 expression hash table. */
1738 compute_hash_table (struct hash_table
*table
)
1740 /* Initialize count of number of entries in hash table. */
1742 memset (table
->table
, 0, table
->size
* sizeof (struct expr
*));
1744 compute_hash_table_work (table
);
1747 /* Expression tracking support. */
1749 /* Lookup REGNO in the set TABLE. The result is a pointer to the
1750 table entry, or NULL if not found. */
1752 static struct expr
*
1753 lookup_set (unsigned int regno
, struct hash_table
*table
)
1755 unsigned int hash
= hash_set (regno
, table
->size
);
1758 expr
= table
->table
[hash
];
1760 while (expr
&& REGNO (SET_DEST (expr
->expr
)) != regno
)
1761 expr
= expr
->next_same_hash
;
1766 /* Return the next entry for REGNO in list EXPR. */
1768 static struct expr
*
1769 next_set (unsigned int regno
, struct expr
*expr
)
1772 expr
= expr
->next_same_hash
;
1773 while (expr
&& REGNO (SET_DEST (expr
->expr
)) != regno
);
1778 /* Like free_INSN_LIST_list or free_EXPR_LIST_list, except that the node
1779 types may be mixed. */
1782 free_insn_expr_list_list (rtx
*listp
)
1786 for (list
= *listp
; list
; list
= next
)
1788 next
= XEXP (list
, 1);
1789 if (GET_CODE (list
) == EXPR_LIST
)
1790 free_EXPR_LIST_node (list
);
1792 free_INSN_LIST_node (list
);
1798 /* Clear canon_modify_mem_list and modify_mem_list tables. */
1800 clear_modify_mem_tables (void)
1805 EXECUTE_IF_SET_IN_BITMAP (modify_mem_list_set
, 0, i
, bi
)
1807 free_INSN_LIST_list (modify_mem_list
+ i
);
1808 free_insn_expr_list_list (canon_modify_mem_list
+ i
);
1810 bitmap_clear (modify_mem_list_set
);
1811 bitmap_clear (blocks_with_calls
);
1814 /* Release memory used by modify_mem_list_set. */
1817 free_modify_mem_tables (void)
1819 clear_modify_mem_tables ();
1820 free (modify_mem_list
);
1821 free (canon_modify_mem_list
);
1822 modify_mem_list
= 0;
1823 canon_modify_mem_list
= 0;
1826 /* Reset tables used to keep track of what's still available [since the
1827 start of the block]. */
1830 reset_opr_set_tables (void)
1832 /* Maintain a bitmap of which regs have been set since beginning of
1834 CLEAR_REG_SET (reg_set_bitmap
);
1836 /* Also keep a record of the last instruction to modify memory.
1837 For now this is very trivial, we only record whether any memory
1838 location has been modified. */
1839 clear_modify_mem_tables ();
1842 /* Return nonzero if the operands of X are not set before INSN in
1843 INSN's basic block. */
1846 oprs_not_set_p (const_rtx x
, const_rtx insn
)
1855 code
= GET_CODE (x
);
1872 if (load_killed_in_block_p (BLOCK_FOR_INSN (insn
),
1873 DF_INSN_LUID (insn
), x
, 0))
1876 return oprs_not_set_p (XEXP (x
, 0), insn
);
1879 return ! REGNO_REG_SET_P (reg_set_bitmap
, REGNO (x
));
1885 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
1889 /* If we are about to do the last recursive call
1890 needed at this level, change it into iteration.
1891 This function is called enough to be worth it. */
1893 return oprs_not_set_p (XEXP (x
, i
), insn
);
1895 if (! oprs_not_set_p (XEXP (x
, i
), insn
))
1898 else if (fmt
[i
] == 'E')
1899 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
1900 if (! oprs_not_set_p (XVECEXP (x
, i
, j
), insn
))
1907 /* Mark things set by a CALL. */
1910 mark_call (rtx insn
)
1912 if (! RTL_CONST_OR_PURE_CALL_P (insn
))
1913 record_last_mem_set_info (insn
);
1916 /* Mark things set by a SET. */
1919 mark_set (rtx pat
, rtx insn
)
1921 rtx dest
= SET_DEST (pat
);
1923 while (GET_CODE (dest
) == SUBREG
1924 || GET_CODE (dest
) == ZERO_EXTRACT
1925 || GET_CODE (dest
) == STRICT_LOW_PART
)
1926 dest
= XEXP (dest
, 0);
1929 SET_REGNO_REG_SET (reg_set_bitmap
, REGNO (dest
));
1930 else if (MEM_P (dest
))
1931 record_last_mem_set_info (insn
);
1933 if (GET_CODE (SET_SRC (pat
)) == CALL
)
1937 /* Record things set by a CLOBBER. */
1940 mark_clobber (rtx pat
, rtx insn
)
1942 rtx clob
= XEXP (pat
, 0);
1944 while (GET_CODE (clob
) == SUBREG
|| GET_CODE (clob
) == STRICT_LOW_PART
)
1945 clob
= XEXP (clob
, 0);
1948 SET_REGNO_REG_SET (reg_set_bitmap
, REGNO (clob
));
1950 record_last_mem_set_info (insn
);
1953 /* Record things set by INSN.
1954 This data is used by oprs_not_set_p. */
1957 mark_oprs_set (rtx insn
)
1959 rtx pat
= PATTERN (insn
);
1962 if (GET_CODE (pat
) == SET
)
1963 mark_set (pat
, insn
);
1964 else if (GET_CODE (pat
) == PARALLEL
)
1965 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
1967 rtx x
= XVECEXP (pat
, 0, i
);
1969 if (GET_CODE (x
) == SET
)
1971 else if (GET_CODE (x
) == CLOBBER
)
1972 mark_clobber (x
, insn
);
1973 else if (GET_CODE (x
) == CALL
)
1977 else if (GET_CODE (pat
) == CLOBBER
)
1978 mark_clobber (pat
, insn
);
1979 else if (GET_CODE (pat
) == CALL
)
1984 /* Compute copy/constant propagation working variables. */
1986 /* Local properties of assignments. */
1987 static sbitmap
*cprop_pavloc
;
1988 static sbitmap
*cprop_absaltered
;
1990 /* Global properties of assignments (computed from the local properties). */
1991 static sbitmap
*cprop_avin
;
1992 static sbitmap
*cprop_avout
;
1994 /* Allocate vars used for copy/const propagation. N_BLOCKS is the number of
1995 basic blocks. N_SETS is the number of sets. */
1998 alloc_cprop_mem (int n_blocks
, int n_sets
)
2000 cprop_pavloc
= sbitmap_vector_alloc (n_blocks
, n_sets
);
2001 cprop_absaltered
= sbitmap_vector_alloc (n_blocks
, n_sets
);
2003 cprop_avin
= sbitmap_vector_alloc (n_blocks
, n_sets
);
2004 cprop_avout
= sbitmap_vector_alloc (n_blocks
, n_sets
);
2007 /* Free vars used by copy/const propagation. */
2010 free_cprop_mem (void)
2012 sbitmap_vector_free (cprop_pavloc
);
2013 sbitmap_vector_free (cprop_absaltered
);
2014 sbitmap_vector_free (cprop_avin
);
2015 sbitmap_vector_free (cprop_avout
);
2018 /* For each block, compute whether X is transparent. X is either an
2019 expression or an assignment [though we don't care which, for this context
2020 an assignment is treated as an expression]. For each block where an
2021 element of X is modified, set (SET_P == 1) or reset (SET_P == 0) the INDX
2025 compute_transp (const_rtx x
, int indx
, sbitmap
*bmap
, int set_p
)
2031 /* repeat is used to turn tail-recursion into iteration since GCC
2032 can't do it when there's no return value. */
2038 code
= GET_CODE (x
);
2045 for (def
= DF_REG_DEF_CHAIN (REGNO (x
));
2047 def
= DF_REF_NEXT_REG (def
))
2048 SET_BIT (bmap
[DF_REF_BB (def
)->index
], indx
);
2053 for (def
= DF_REG_DEF_CHAIN (REGNO (x
));
2055 def
= DF_REF_NEXT_REG (def
))
2056 RESET_BIT (bmap
[DF_REF_BB (def
)->index
], indx
);
2062 if (! MEM_READONLY_P (x
))
2067 /* First handle all the blocks with calls. We don't need to
2068 do any list walking for them. */
2069 EXECUTE_IF_SET_IN_BITMAP (blocks_with_calls
, 0, bb_index
, bi
)
2072 SET_BIT (bmap
[bb_index
], indx
);
2074 RESET_BIT (bmap
[bb_index
], indx
);
2077 /* Now iterate over the blocks which have memory modifications
2078 but which do not have any calls. */
2079 EXECUTE_IF_AND_COMPL_IN_BITMAP (modify_mem_list_set
,
2083 rtx list_entry
= canon_modify_mem_list
[bb_index
];
2087 rtx dest
, dest_addr
;
2089 /* LIST_ENTRY must be an INSN of some kind that sets memory.
2090 Examine each hunk of memory that is modified. */
2092 dest
= XEXP (list_entry
, 0);
2093 list_entry
= XEXP (list_entry
, 1);
2094 dest_addr
= XEXP (list_entry
, 0);
2096 if (canon_true_dependence (dest
, GET_MODE (dest
), dest_addr
,
2097 x
, NULL_RTX
, rtx_addr_varies_p
))
2100 SET_BIT (bmap
[bb_index
], indx
);
2102 RESET_BIT (bmap
[bb_index
], indx
);
2105 list_entry
= XEXP (list_entry
, 1);
2130 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
2134 /* If we are about to do the last recursive call
2135 needed at this level, change it into iteration.
2136 This function is called enough to be worth it. */
2143 compute_transp (XEXP (x
, i
), indx
, bmap
, set_p
);
2145 else if (fmt
[i
] == 'E')
2146 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
2147 compute_transp (XVECEXP (x
, i
, j
), indx
, bmap
, set_p
);
2151 /* Top level routine to do the dataflow analysis needed by copy/const
2155 compute_cprop_data (void)
2157 compute_local_properties (cprop_absaltered
, cprop_pavloc
, NULL
, &set_hash_table
);
2158 compute_available (cprop_pavloc
, cprop_absaltered
,
2159 cprop_avout
, cprop_avin
);
2162 /* Copy/constant propagation. */
2164 /* Maximum number of register uses in an insn that we handle. */
2167 /* Table of uses found in an insn.
2168 Allocated statically to avoid alloc/free complexity and overhead. */
2169 static struct reg_use reg_use_table
[MAX_USES
];
2171 /* Index into `reg_use_table' while building it. */
2172 static int reg_use_count
;
2174 /* Set up a list of register numbers used in INSN. The found uses are stored
2175 in `reg_use_table'. `reg_use_count' is initialized to zero before entry,
2176 and contains the number of uses in the table upon exit.
2178 ??? If a register appears multiple times we will record it multiple times.
2179 This doesn't hurt anything but it will slow things down. */
2182 find_used_regs (rtx
*xptr
, void *data ATTRIBUTE_UNUSED
)
2189 /* repeat is used to turn tail-recursion into iteration since GCC
2190 can't do it when there's no return value. */
2195 code
= GET_CODE (x
);
2198 if (reg_use_count
== MAX_USES
)
2201 reg_use_table
[reg_use_count
].reg_rtx
= x
;
2205 /* Recursively scan the operands of this expression. */
2207 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
2211 /* If we are about to do the last recursive call
2212 needed at this level, change it into iteration.
2213 This function is called enough to be worth it. */
2220 find_used_regs (&XEXP (x
, i
), data
);
2222 else if (fmt
[i
] == 'E')
2223 for (j
= 0; j
< XVECLEN (x
, i
); j
++)
2224 find_used_regs (&XVECEXP (x
, i
, j
), data
);
2228 /* Try to replace all non-SET_DEST occurrences of FROM in INSN with TO.
2229 Returns nonzero is successful. */
2232 try_replace_reg (rtx from
, rtx to
, rtx insn
)
2234 rtx note
= find_reg_equal_equiv_note (insn
);
2237 rtx set
= single_set (insn
);
2239 /* Usually we substitute easy stuff, so we won't copy everything.
2240 We however need to take care to not duplicate non-trivial CONST
2244 validate_replace_src_group (from
, to
, insn
);
2245 if (num_changes_pending () && apply_change_group ())
2248 /* Try to simplify SET_SRC if we have substituted a constant. */
2249 if (success
&& set
&& CONSTANT_P (to
))
2251 src
= simplify_rtx (SET_SRC (set
));
2254 validate_change (insn
, &SET_SRC (set
), src
, 0);
2257 /* If there is already a REG_EQUAL note, update the expression in it
2258 with our replacement. */
2259 if (note
!= 0 && REG_NOTE_KIND (note
) == REG_EQUAL
)
2260 set_unique_reg_note (insn
, REG_EQUAL
,
2261 simplify_replace_rtx (XEXP (note
, 0), from
,
2263 if (!success
&& set
&& reg_mentioned_p (from
, SET_SRC (set
)))
2265 /* If above failed and this is a single set, try to simplify the source of
2266 the set given our substitution. We could perhaps try this for multiple
2267 SETs, but it probably won't buy us anything. */
2268 src
= simplify_replace_rtx (SET_SRC (set
), from
, to
);
2270 if (!rtx_equal_p (src
, SET_SRC (set
))
2271 && validate_change (insn
, &SET_SRC (set
), src
, 0))
2274 /* If we've failed to do replacement, have a single SET, don't already
2275 have a note, and have no special SET, add a REG_EQUAL note to not
2276 lose information. */
2277 if (!success
&& note
== 0 && set
!= 0
2278 && GET_CODE (SET_DEST (set
)) != ZERO_EXTRACT
2279 && GET_CODE (SET_DEST (set
)) != STRICT_LOW_PART
)
2280 note
= set_unique_reg_note (insn
, REG_EQUAL
, copy_rtx (src
));
2283 /* REG_EQUAL may get simplified into register.
2284 We don't allow that. Remove that note. This code ought
2285 not to happen, because previous code ought to synthesize
2286 reg-reg move, but be on the safe side. */
2287 if (note
&& REG_NOTE_KIND (note
) == REG_EQUAL
&& REG_P (XEXP (note
, 0)))
2288 remove_note (insn
, note
);
2293 /* Find a set of REGNOs that are available on entry to INSN's block. Returns
2294 NULL no such set is found. */
2296 static struct expr
*
2297 find_avail_set (int regno
, rtx insn
)
2299 /* SET1 contains the last set found that can be returned to the caller for
2300 use in a substitution. */
2301 struct expr
*set1
= 0;
2303 /* Loops are not possible here. To get a loop we would need two sets
2304 available at the start of the block containing INSN. i.e. we would
2305 need two sets like this available at the start of the block:
2307 (set (reg X) (reg Y))
2308 (set (reg Y) (reg X))
2310 This can not happen since the set of (reg Y) would have killed the
2311 set of (reg X) making it unavailable at the start of this block. */
2315 struct expr
*set
= lookup_set (regno
, &set_hash_table
);
2317 /* Find a set that is available at the start of the block
2318 which contains INSN. */
2321 if (TEST_BIT (cprop_avin
[BLOCK_NUM (insn
)], set
->bitmap_index
))
2323 set
= next_set (regno
, set
);
2326 /* If no available set was found we've reached the end of the
2327 (possibly empty) copy chain. */
2331 gcc_assert (GET_CODE (set
->expr
) == SET
);
2333 src
= SET_SRC (set
->expr
);
2335 /* We know the set is available.
2336 Now check that SRC is ANTLOC (i.e. none of the source operands
2337 have changed since the start of the block).
2339 If the source operand changed, we may still use it for the next
2340 iteration of this loop, but we may not use it for substitutions. */
2342 if (gcse_constant_p (src
) || oprs_not_set_p (src
, insn
))
2345 /* If the source of the set is anything except a register, then
2346 we have reached the end of the copy chain. */
2350 /* Follow the copy chain, i.e. start another iteration of the loop
2351 and see if we have an available copy into SRC. */
2352 regno
= REGNO (src
);
2355 /* SET1 holds the last set that was available and anticipatable at
2360 /* Subroutine of cprop_insn that tries to propagate constants into
2361 JUMP_INSNS. JUMP must be a conditional jump. If SETCC is non-NULL
2362 it is the instruction that immediately precedes JUMP, and must be a
2363 single SET of a register. FROM is what we will try to replace,
2364 SRC is the constant we will try to substitute for it. Returns nonzero
2365 if a change was made. */
2368 cprop_jump (basic_block bb
, rtx setcc
, rtx jump
, rtx from
, rtx src
)
2370 rtx new_rtx
, set_src
, note_src
;
2371 rtx set
= pc_set (jump
);
2372 rtx note
= find_reg_equal_equiv_note (jump
);
2376 note_src
= XEXP (note
, 0);
2377 if (GET_CODE (note_src
) == EXPR_LIST
)
2378 note_src
= NULL_RTX
;
2380 else note_src
= NULL_RTX
;
2382 /* Prefer REG_EQUAL notes except those containing EXPR_LISTs. */
2383 set_src
= note_src
? note_src
: SET_SRC (set
);
2385 /* First substitute the SETCC condition into the JUMP instruction,
2386 then substitute that given values into this expanded JUMP. */
2387 if (setcc
!= NULL_RTX
2388 && !modified_between_p (from
, setcc
, jump
)
2389 && !modified_between_p (src
, setcc
, jump
))
2392 rtx setcc_set
= single_set (setcc
);
2393 rtx setcc_note
= find_reg_equal_equiv_note (setcc
);
2394 setcc_src
= (setcc_note
&& GET_CODE (XEXP (setcc_note
, 0)) != EXPR_LIST
)
2395 ? XEXP (setcc_note
, 0) : SET_SRC (setcc_set
);
2396 set_src
= simplify_replace_rtx (set_src
, SET_DEST (setcc_set
),
2402 new_rtx
= simplify_replace_rtx (set_src
, from
, src
);
2404 /* If no simplification can be made, then try the next register. */
2405 if (rtx_equal_p (new_rtx
, SET_SRC (set
)))
2408 /* If this is now a no-op delete it, otherwise this must be a valid insn. */
2409 if (new_rtx
== pc_rtx
)
2413 /* Ensure the value computed inside the jump insn to be equivalent
2414 to one computed by setcc. */
2415 if (setcc
&& modified_in_p (new_rtx
, setcc
))
2417 if (! validate_unshare_change (jump
, &SET_SRC (set
), new_rtx
, 0))
2419 /* When (some) constants are not valid in a comparison, and there
2420 are two registers to be replaced by constants before the entire
2421 comparison can be folded into a constant, we need to keep
2422 intermediate information in REG_EQUAL notes. For targets with
2423 separate compare insns, such notes are added by try_replace_reg.
2424 When we have a combined compare-and-branch instruction, however,
2425 we need to attach a note to the branch itself to make this
2426 optimization work. */
2428 if (!rtx_equal_p (new_rtx
, note_src
))
2429 set_unique_reg_note (jump
, REG_EQUAL
, copy_rtx (new_rtx
));
2433 /* Remove REG_EQUAL note after simplification. */
2435 remove_note (jump
, note
);
2439 /* Delete the cc0 setter. */
2440 if (setcc
!= NULL
&& CC0_P (SET_DEST (single_set (setcc
))))
2441 delete_insn (setcc
);
2444 global_const_prop_count
++;
2445 if (dump_file
!= NULL
)
2448 "GLOBAL CONST-PROP: Replacing reg %d in jump_insn %d with constant ",
2449 REGNO (from
), INSN_UID (jump
));
2450 print_rtl (dump_file
, src
);
2451 fprintf (dump_file
, "\n");
2453 purge_dead_edges (bb
);
2455 /* If a conditional jump has been changed into unconditional jump, remove
2456 the jump and make the edge fallthru - this is always called in
2458 if (new_rtx
!= pc_rtx
&& simplejump_p (jump
))
2463 for (ei
= ei_start (bb
->succs
); (e
= ei_safe_edge (ei
)); ei_next (&ei
))
2464 if (e
->dest
!= EXIT_BLOCK_PTR
2465 && BB_HEAD (e
->dest
) == JUMP_LABEL (jump
))
2467 e
->flags
|= EDGE_FALLTHRU
;
2477 constprop_register (rtx insn
, rtx from
, rtx to
)
2481 /* Check for reg or cc0 setting instructions followed by
2482 conditional branch instructions first. */
2483 if ((sset
= single_set (insn
)) != NULL
2485 && any_condjump_p (NEXT_INSN (insn
)) && onlyjump_p (NEXT_INSN (insn
)))
2487 rtx dest
= SET_DEST (sset
);
2488 if ((REG_P (dest
) || CC0_P (dest
))
2489 && cprop_jump (BLOCK_FOR_INSN (insn
), insn
, NEXT_INSN (insn
), from
, to
))
2493 /* Handle normal insns next. */
2494 if (NONJUMP_INSN_P (insn
)
2495 && try_replace_reg (from
, to
, insn
))
2498 /* Try to propagate a CONST_INT into a conditional jump.
2499 We're pretty specific about what we will handle in this
2500 code, we can extend this as necessary over time.
2502 Right now the insn in question must look like
2503 (set (pc) (if_then_else ...)) */
2504 else if (any_condjump_p (insn
) && onlyjump_p (insn
))
2505 return cprop_jump (BLOCK_FOR_INSN (insn
), NULL
, insn
, from
, to
);
2509 /* Perform constant and copy propagation on INSN.
2510 The result is nonzero if a change was made. */
2513 cprop_insn (rtx insn
)
2515 struct reg_use
*reg_used
;
2523 note_uses (&PATTERN (insn
), find_used_regs
, NULL
);
2525 note
= find_reg_equal_equiv_note (insn
);
2527 /* We may win even when propagating constants into notes. */
2529 find_used_regs (&XEXP (note
, 0), NULL
);
2531 for (reg_used
= ®_use_table
[0]; reg_use_count
> 0;
2532 reg_used
++, reg_use_count
--)
2534 unsigned int regno
= REGNO (reg_used
->reg_rtx
);
2538 /* If the register has already been set in this block, there's
2539 nothing we can do. */
2540 if (! oprs_not_set_p (reg_used
->reg_rtx
, insn
))
2543 /* Find an assignment that sets reg_used and is available
2544 at the start of the block. */
2545 set
= find_avail_set (regno
, insn
);
2550 /* ??? We might be able to handle PARALLELs. Later. */
2551 gcc_assert (GET_CODE (pat
) == SET
);
2553 src
= SET_SRC (pat
);
2555 /* Constant propagation. */
2556 if (gcse_constant_p (src
))
2558 if (constprop_register (insn
, reg_used
->reg_rtx
, src
))
2561 global_const_prop_count
++;
2562 if (dump_file
!= NULL
)
2564 fprintf (dump_file
, "GLOBAL CONST-PROP: Replacing reg %d in ", regno
);
2565 fprintf (dump_file
, "insn %d with constant ", INSN_UID (insn
));
2566 print_rtl (dump_file
, src
);
2567 fprintf (dump_file
, "\n");
2569 if (INSN_DELETED_P (insn
))
2573 else if (REG_P (src
)
2574 && REGNO (src
) >= FIRST_PSEUDO_REGISTER
2575 && REGNO (src
) != regno
)
2577 if (try_replace_reg (reg_used
->reg_rtx
, src
, insn
))
2580 global_copy_prop_count
++;
2581 if (dump_file
!= NULL
)
2583 fprintf (dump_file
, "GLOBAL COPY-PROP: Replacing reg %d in insn %d",
2584 regno
, INSN_UID (insn
));
2585 fprintf (dump_file
, " with reg %d\n", REGNO (src
));
2588 /* The original insn setting reg_used may or may not now be
2589 deletable. We leave the deletion to flow. */
2590 /* FIXME: If it turns out that the insn isn't deletable,
2591 then we may have unnecessarily extended register lifetimes
2592 and made things worse. */
2600 /* Like find_used_regs, but avoid recording uses that appear in
2601 input-output contexts such as zero_extract or pre_dec. This
2602 restricts the cases we consider to those for which local cprop
2603 can legitimately make replacements. */
2606 local_cprop_find_used_regs (rtx
*xptr
, void *data
)
2613 switch (GET_CODE (x
))
2617 case STRICT_LOW_PART
:
2626 /* Can only legitimately appear this early in the context of
2627 stack pushes for function arguments, but handle all of the
2628 codes nonetheless. */
2632 /* Setting a subreg of a register larger than word_mode leaves
2633 the non-written words unchanged. */
2634 if (GET_MODE_BITSIZE (GET_MODE (SUBREG_REG (x
))) > BITS_PER_WORD
)
2642 find_used_regs (xptr
, data
);
2645 /* Try to perform local const/copy propagation on X in INSN. */
2648 do_local_cprop (rtx x
, rtx insn
)
2650 rtx newreg
= NULL
, newcnst
= NULL
;
2652 /* Rule out USE instructions and ASM statements as we don't want to
2653 change the hard registers mentioned. */
2655 && (REGNO (x
) >= FIRST_PSEUDO_REGISTER
2656 || (GET_CODE (PATTERN (insn
)) != USE
2657 && asm_noperands (PATTERN (insn
)) < 0)))
2659 cselib_val
*val
= cselib_lookup (x
, GET_MODE (x
), 0);
2660 struct elt_loc_list
*l
;
2664 for (l
= val
->locs
; l
; l
= l
->next
)
2666 rtx this_rtx
= l
->loc
;
2669 if (gcse_constant_p (this_rtx
))
2671 if (REG_P (this_rtx
) && REGNO (this_rtx
) >= FIRST_PSEUDO_REGISTER
2672 /* Don't copy propagate if it has attached REG_EQUIV note.
2673 At this point this only function parameters should have
2674 REG_EQUIV notes and if the argument slot is used somewhere
2675 explicitly, it means address of parameter has been taken,
2676 so we should not extend the lifetime of the pseudo. */
2677 && (!(note
= find_reg_note (l
->setting_insn
, REG_EQUIV
, NULL_RTX
))
2678 || ! MEM_P (XEXP (note
, 0))))
2681 if (newcnst
&& constprop_register (insn
, x
, newcnst
))
2683 if (dump_file
!= NULL
)
2685 fprintf (dump_file
, "LOCAL CONST-PROP: Replacing reg %d in ",
2687 fprintf (dump_file
, "insn %d with constant ",
2689 print_rtl (dump_file
, newcnst
);
2690 fprintf (dump_file
, "\n");
2692 local_const_prop_count
++;
2695 else if (newreg
&& newreg
!= x
&& try_replace_reg (x
, newreg
, insn
))
2697 if (dump_file
!= NULL
)
2700 "LOCAL COPY-PROP: Replacing reg %d in insn %d",
2701 REGNO (x
), INSN_UID (insn
));
2702 fprintf (dump_file
, " with reg %d\n", REGNO (newreg
));
2704 local_copy_prop_count
++;
2711 /* Do local const/copy propagation (i.e. within each basic block). */
2714 local_cprop_pass (void)
2718 struct reg_use
*reg_used
;
2719 bool changed
= false;
2721 cselib_init (false);
2724 FOR_BB_INSNS (bb
, insn
)
2728 rtx note
= find_reg_equal_equiv_note (insn
);
2732 note_uses (&PATTERN (insn
), local_cprop_find_used_regs
,
2735 local_cprop_find_used_regs (&XEXP (note
, 0), NULL
);
2737 for (reg_used
= ®_use_table
[0]; reg_use_count
> 0;
2738 reg_used
++, reg_use_count
--)
2740 if (do_local_cprop (reg_used
->reg_rtx
, insn
))
2746 if (INSN_DELETED_P (insn
))
2749 while (reg_use_count
);
2751 cselib_process_insn (insn
);
2754 /* Forget everything at the end of a basic block. */
2755 cselib_clear_table ();
2763 /* Similar to get_condition, only the resulting condition must be
2764 valid at JUMP, instead of at EARLIEST.
2766 This differs from noce_get_condition in ifcvt.c in that we prefer not to
2767 settle for the condition variable in the jump instruction being integral.
2768 We prefer to be able to record the value of a user variable, rather than
2769 the value of a temporary used in a condition. This could be solved by
2770 recording the value of *every* register scanned by canonicalize_condition,
2771 but this would require some code reorganization. */
2774 fis_get_condition (rtx jump
)
2776 return get_condition (jump
, NULL
, false, true);
2779 /* Check the comparison COND to see if we can safely form an implicit set from
2780 it. COND is either an EQ or NE comparison. */
2783 implicit_set_cond_p (const_rtx cond
)
2785 const enum machine_mode mode
= GET_MODE (XEXP (cond
, 0));
2786 const_rtx cst
= XEXP (cond
, 1);
2788 /* We can't perform this optimization if either operand might be or might
2789 contain a signed zero. */
2790 if (HONOR_SIGNED_ZEROS (mode
))
2792 /* It is sufficient to check if CST is or contains a zero. We must
2793 handle float, complex, and vector. If any subpart is a zero, then
2794 the optimization can't be performed. */
2795 /* ??? The complex and vector checks are not implemented yet. We just
2796 always return zero for them. */
2797 if (GET_CODE (cst
) == CONST_DOUBLE
)
2800 REAL_VALUE_FROM_CONST_DOUBLE (d
, cst
);
2801 if (REAL_VALUES_EQUAL (d
, dconst0
))
2808 return gcse_constant_p (cst
);
2811 /* Find the implicit sets of a function. An "implicit set" is a constraint
2812 on the value of a variable, implied by a conditional jump. For example,
2813 following "if (x == 2)", the then branch may be optimized as though the
2814 conditional performed an "explicit set", in this example, "x = 2". This
2815 function records the set patterns that are implicit at the start of each
2818 FIXME: This would be more effective if critical edges are pre-split. As
2819 it is now, we can't record implicit sets for blocks that have
2820 critical successor edges. This results in missed optimizations
2821 and in more (unnecessary) work in cfgcleanup.c:thread_jump(). */
2824 find_implicit_sets (void)
2826 basic_block bb
, dest
;
2832 /* Check for more than one successor. */
2833 if (EDGE_COUNT (bb
->succs
) > 1)
2835 cond
= fis_get_condition (BB_END (bb
));
2838 && (GET_CODE (cond
) == EQ
|| GET_CODE (cond
) == NE
)
2839 && REG_P (XEXP (cond
, 0))
2840 && REGNO (XEXP (cond
, 0)) >= FIRST_PSEUDO_REGISTER
2841 && implicit_set_cond_p (cond
))
2843 dest
= GET_CODE (cond
) == EQ
? BRANCH_EDGE (bb
)->dest
2844 : FALLTHRU_EDGE (bb
)->dest
;
2847 /* Record nothing for a critical edge. */
2848 && single_pred_p (dest
)
2849 && dest
!= EXIT_BLOCK_PTR
)
2851 new_rtx
= gen_rtx_SET (VOIDmode
, XEXP (cond
, 0),
2853 implicit_sets
[dest
->index
] = new_rtx
;
2856 fprintf(dump_file
, "Implicit set of reg %d in ",
2857 REGNO (XEXP (cond
, 0)));
2858 fprintf(dump_file
, "basic block %d\n", dest
->index
);
2866 fprintf (dump_file
, "Found %d implicit sets\n", count
);
2869 /* Bypass conditional jumps. */
2871 /* The value of last_basic_block at the beginning of the jump_bypass
2872 pass. The use of redirect_edge_and_branch_force may introduce new
2873 basic blocks, but the data flow analysis is only valid for basic
2874 block indices less than bypass_last_basic_block. */
2876 static int bypass_last_basic_block
;
2878 /* Find a set of REGNO to a constant that is available at the end of basic
2879 block BB. Returns NULL if no such set is found. Based heavily upon
2882 static struct expr
*
2883 find_bypass_set (int regno
, int bb
)
2885 struct expr
*result
= 0;
2890 struct expr
*set
= lookup_set (regno
, &set_hash_table
);
2894 if (TEST_BIT (cprop_avout
[bb
], set
->bitmap_index
))
2896 set
= next_set (regno
, set
);
2902 gcc_assert (GET_CODE (set
->expr
) == SET
);
2904 src
= SET_SRC (set
->expr
);
2905 if (gcse_constant_p (src
))
2911 regno
= REGNO (src
);
2917 /* Subroutine of bypass_block that checks whether a pseudo is killed by
2918 any of the instructions inserted on an edge. Jump bypassing places
2919 condition code setters on CFG edges using insert_insn_on_edge. This
2920 function is required to check that our data flow analysis is still
2921 valid prior to commit_edge_insertions. */
2924 reg_killed_on_edge (const_rtx reg
, const_edge e
)
2928 for (insn
= e
->insns
.r
; insn
; insn
= NEXT_INSN (insn
))
2929 if (INSN_P (insn
) && reg_set_p (reg
, insn
))
2935 /* Subroutine of bypass_conditional_jumps that attempts to bypass the given
2936 basic block BB which has more than one predecessor. If not NULL, SETCC
2937 is the first instruction of BB, which is immediately followed by JUMP_INSN
2938 JUMP. Otherwise, SETCC is NULL, and JUMP is the first insn of BB.
2939 Returns nonzero if a change was made.
2941 During the jump bypassing pass, we may place copies of SETCC instructions
2942 on CFG edges. The following routine must be careful to pay attention to
2943 these inserted insns when performing its transformations. */
2946 bypass_block (basic_block bb
, rtx setcc
, rtx jump
)
2951 int may_be_loop_header
;
2955 insn
= (setcc
!= NULL
) ? setcc
: jump
;
2957 /* Determine set of register uses in INSN. */
2959 note_uses (&PATTERN (insn
), find_used_regs
, NULL
);
2960 note
= find_reg_equal_equiv_note (insn
);
2962 find_used_regs (&XEXP (note
, 0), NULL
);
2964 may_be_loop_header
= false;
2965 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
2966 if (e
->flags
& EDGE_DFS_BACK
)
2968 may_be_loop_header
= true;
2973 for (ei
= ei_start (bb
->preds
); (e
= ei_safe_edge (ei
)); )
2977 if (e
->flags
& EDGE_COMPLEX
)
2983 /* We can't redirect edges from new basic blocks. */
2984 if (e
->src
->index
>= bypass_last_basic_block
)
2990 /* The irreducible loops created by redirecting of edges entering the
2991 loop from outside would decrease effectiveness of some of the following
2992 optimizations, so prevent this. */
2993 if (may_be_loop_header
2994 && !(e
->flags
& EDGE_DFS_BACK
))
3000 for (i
= 0; i
< reg_use_count
; i
++)
3002 struct reg_use
*reg_used
= ®_use_table
[i
];
3003 unsigned int regno
= REGNO (reg_used
->reg_rtx
);
3004 basic_block dest
, old_dest
;
3008 set
= find_bypass_set (regno
, e
->src
->index
);
3013 /* Check the data flow is valid after edge insertions. */
3014 if (e
->insns
.r
&& reg_killed_on_edge (reg_used
->reg_rtx
, e
))
3017 src
= SET_SRC (pc_set (jump
));
3020 src
= simplify_replace_rtx (src
,
3021 SET_DEST (PATTERN (setcc
)),
3022 SET_SRC (PATTERN (setcc
)));
3024 new_rtx
= simplify_replace_rtx (src
, reg_used
->reg_rtx
,
3025 SET_SRC (set
->expr
));
3027 /* Jump bypassing may have already placed instructions on
3028 edges of the CFG. We can't bypass an outgoing edge that
3029 has instructions associated with it, as these insns won't
3030 get executed if the incoming edge is redirected. */
3032 if (new_rtx
== pc_rtx
)
3034 edest
= FALLTHRU_EDGE (bb
);
3035 dest
= edest
->insns
.r
? NULL
: edest
->dest
;
3037 else if (GET_CODE (new_rtx
) == LABEL_REF
)
3039 dest
= BLOCK_FOR_INSN (XEXP (new_rtx
, 0));
3040 /* Don't bypass edges containing instructions. */
3041 edest
= find_edge (bb
, dest
);
3042 if (edest
&& edest
->insns
.r
)
3048 /* Avoid unification of the edge with other edges from original
3049 branch. We would end up emitting the instruction on "both"
3052 if (dest
&& setcc
&& !CC0_P (SET_DEST (PATTERN (setcc
)))
3053 && find_edge (e
->src
, dest
))
3059 && dest
!= EXIT_BLOCK_PTR
)
3061 redirect_edge_and_branch_force (e
, dest
);
3063 /* Copy the register setter to the redirected edge.
3064 Don't copy CC0 setters, as CC0 is dead after jump. */
3067 rtx pat
= PATTERN (setcc
);
3068 if (!CC0_P (SET_DEST (pat
)))
3069 insert_insn_on_edge (copy_insn (pat
), e
);
3072 if (dump_file
!= NULL
)
3074 fprintf (dump_file
, "JUMP-BYPASS: Proved reg %d "
3075 "in jump_insn %d equals constant ",
3076 regno
, INSN_UID (jump
));
3077 print_rtl (dump_file
, SET_SRC (set
->expr
));
3078 fprintf (dump_file
, "\nBypass edge from %d->%d to %d\n",
3079 e
->src
->index
, old_dest
->index
, dest
->index
);
3092 /* Find basic blocks with more than one predecessor that only contain a
3093 single conditional jump. If the result of the comparison is known at
3094 compile-time from any incoming edge, redirect that edge to the
3095 appropriate target. Returns nonzero if a change was made.
3097 This function is now mis-named, because we also handle indirect jumps. */
3100 bypass_conditional_jumps (void)
3108 /* Note we start at block 1. */
3109 if (ENTRY_BLOCK_PTR
->next_bb
== EXIT_BLOCK_PTR
)
3112 bypass_last_basic_block
= last_basic_block
;
3113 mark_dfs_back_edges ();
3116 FOR_BB_BETWEEN (bb
, ENTRY_BLOCK_PTR
->next_bb
->next_bb
,
3117 EXIT_BLOCK_PTR
, next_bb
)
3119 /* Check for more than one predecessor. */
3120 if (!single_pred_p (bb
))
3123 FOR_BB_INSNS (bb
, insn
)
3124 if (NONJUMP_INSN_P (insn
))
3128 if (GET_CODE (PATTERN (insn
)) != SET
)
3131 dest
= SET_DEST (PATTERN (insn
));
3132 if (REG_P (dest
) || CC0_P (dest
))
3137 else if (JUMP_P (insn
))
3139 if ((any_condjump_p (insn
) || computed_jump_p (insn
))
3140 && onlyjump_p (insn
))
3141 changed
|= bypass_block (bb
, setcc
, insn
);
3144 else if (INSN_P (insn
))
3149 /* If we bypassed any register setting insns, we inserted a
3150 copy on the redirected edge. These need to be committed. */
3152 commit_edge_insertions ();
3157 /* Compute PRE+LCM working variables. */
3159 /* Local properties of expressions. */
3160 /* Nonzero for expressions that are transparent in the block. */
3161 static sbitmap
*transp
;
3163 /* Nonzero for expressions that are transparent at the end of the block.
3164 This is only zero for expressions killed by abnormal critical edge
3165 created by a calls. */
3166 static sbitmap
*transpout
;
3168 /* Nonzero for expressions that are computed (available) in the block. */
3169 static sbitmap
*comp
;
3171 /* Nonzero for expressions that are locally anticipatable in the block. */
3172 static sbitmap
*antloc
;
3174 /* Nonzero for expressions where this block is an optimal computation
3176 static sbitmap
*pre_optimal
;
3178 /* Nonzero for expressions which are redundant in a particular block. */
3179 static sbitmap
*pre_redundant
;
3181 /* Nonzero for expressions which should be inserted on a specific edge. */
3182 static sbitmap
*pre_insert_map
;
3184 /* Nonzero for expressions which should be deleted in a specific block. */
3185 static sbitmap
*pre_delete_map
;
3187 /* Contains the edge_list returned by pre_edge_lcm. */
3188 static struct edge_list
*edge_list
;
3190 /* Allocate vars used for PRE analysis. */
3193 alloc_pre_mem (int n_blocks
, int n_exprs
)
3195 transp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
3196 comp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
3197 antloc
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
3200 pre_redundant
= NULL
;
3201 pre_insert_map
= NULL
;
3202 pre_delete_map
= NULL
;
3203 ae_kill
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
3205 /* pre_insert and pre_delete are allocated later. */
3208 /* Free vars used for PRE analysis. */
3213 sbitmap_vector_free (transp
);
3214 sbitmap_vector_free (comp
);
3216 /* ANTLOC and AE_KILL are freed just after pre_lcm finishes. */
3219 sbitmap_vector_free (pre_optimal
);
3221 sbitmap_vector_free (pre_redundant
);
3223 sbitmap_vector_free (pre_insert_map
);
3225 sbitmap_vector_free (pre_delete_map
);
3227 transp
= comp
= NULL
;
3228 pre_optimal
= pre_redundant
= pre_insert_map
= pre_delete_map
= NULL
;
3231 /* Top level routine to do the dataflow analysis needed by PRE. */
3234 compute_pre_data (void)
3236 sbitmap trapping_expr
;
3240 compute_local_properties (transp
, comp
, antloc
, &expr_hash_table
);
3241 sbitmap_vector_zero (ae_kill
, last_basic_block
);
3243 /* Collect expressions which might trap. */
3244 trapping_expr
= sbitmap_alloc (expr_hash_table
.n_elems
);
3245 sbitmap_zero (trapping_expr
);
3246 for (ui
= 0; ui
< expr_hash_table
.size
; ui
++)
3249 for (e
= expr_hash_table
.table
[ui
]; e
!= NULL
; e
= e
->next_same_hash
)
3250 if (may_trap_p (e
->expr
))
3251 SET_BIT (trapping_expr
, e
->bitmap_index
);
3254 /* Compute ae_kill for each basic block using:
3264 /* If the current block is the destination of an abnormal edge, we
3265 kill all trapping expressions because we won't be able to properly
3266 place the instruction on the edge. So make them neither
3267 anticipatable nor transparent. This is fairly conservative. */
3268 FOR_EACH_EDGE (e
, ei
, bb
->preds
)
3269 if (e
->flags
& EDGE_ABNORMAL
)
3271 sbitmap_difference (antloc
[bb
->index
], antloc
[bb
->index
], trapping_expr
);
3272 sbitmap_difference (transp
[bb
->index
], transp
[bb
->index
], trapping_expr
);
3276 sbitmap_a_or_b (ae_kill
[bb
->index
], transp
[bb
->index
], comp
[bb
->index
]);
3277 sbitmap_not (ae_kill
[bb
->index
], ae_kill
[bb
->index
]);
3280 edge_list
= pre_edge_lcm (expr_hash_table
.n_elems
, transp
, comp
, antloc
,
3281 ae_kill
, &pre_insert_map
, &pre_delete_map
);
3282 sbitmap_vector_free (antloc
);
3284 sbitmap_vector_free (ae_kill
);
3286 sbitmap_free (trapping_expr
);
3291 /* Return nonzero if an occurrence of expression EXPR in OCCR_BB would reach
3294 VISITED is a pointer to a working buffer for tracking which BB's have
3295 been visited. It is NULL for the top-level call.
3297 We treat reaching expressions that go through blocks containing the same
3298 reaching expression as "not reaching". E.g. if EXPR is generated in blocks
3299 2 and 3, INSN is in block 4, and 2->3->4, we treat the expression in block
3300 2 as not reaching. The intent is to improve the probability of finding
3301 only one reaching expression and to reduce register lifetimes by picking
3302 the closest such expression. */
3305 pre_expr_reaches_here_p_work (basic_block occr_bb
, struct expr
*expr
, basic_block bb
, char *visited
)
3310 FOR_EACH_EDGE (pred
, ei
, bb
->preds
)
3312 basic_block pred_bb
= pred
->src
;
3314 if (pred
->src
== ENTRY_BLOCK_PTR
3315 /* Has predecessor has already been visited? */
3316 || visited
[pred_bb
->index
])
3317 ;/* Nothing to do. */
3319 /* Does this predecessor generate this expression? */
3320 else if (TEST_BIT (comp
[pred_bb
->index
], expr
->bitmap_index
))
3322 /* Is this the occurrence we're looking for?
3323 Note that there's only one generating occurrence per block
3324 so we just need to check the block number. */
3325 if (occr_bb
== pred_bb
)
3328 visited
[pred_bb
->index
] = 1;
3330 /* Ignore this predecessor if it kills the expression. */
3331 else if (! TEST_BIT (transp
[pred_bb
->index
], expr
->bitmap_index
))
3332 visited
[pred_bb
->index
] = 1;
3334 /* Neither gen nor kill. */
3337 visited
[pred_bb
->index
] = 1;
3338 if (pre_expr_reaches_here_p_work (occr_bb
, expr
, pred_bb
, visited
))
3343 /* All paths have been checked. */
3347 /* The wrapper for pre_expr_reaches_here_work that ensures that any
3348 memory allocated for that function is returned. */
3351 pre_expr_reaches_here_p (basic_block occr_bb
, struct expr
*expr
, basic_block bb
)
3354 char *visited
= XCNEWVEC (char, last_basic_block
);
3356 rval
= pre_expr_reaches_here_p_work (occr_bb
, expr
, bb
, visited
);
3363 /* Given an expr, generate RTL which we can insert at the end of a BB,
3364 or on an edge. Set the block number of any insns generated to
3368 process_insert_insn (struct expr
*expr
)
3370 rtx reg
= expr
->reaching_reg
;
3371 rtx exp
= copy_rtx (expr
->expr
);
3376 /* If the expression is something that's an operand, like a constant,
3377 just copy it to a register. */
3378 if (general_operand (exp
, GET_MODE (reg
)))
3379 emit_move_insn (reg
, exp
);
3381 /* Otherwise, make a new insn to compute this expression and make sure the
3382 insn will be recognized (this also adds any needed CLOBBERs). Copy the
3383 expression to make sure we don't have any sharing issues. */
3386 rtx insn
= emit_insn (gen_rtx_SET (VOIDmode
, reg
, exp
));
3388 if (insn_invalid_p (insn
))
3399 /* Add EXPR to the end of basic block BB.
3401 This is used by both the PRE and code hoisting.
3403 For PRE, we want to verify that the expr is either transparent
3404 or locally anticipatable in the target block. This check makes
3405 no sense for code hoisting. */
3408 insert_insn_end_basic_block (struct expr
*expr
, basic_block bb
, int pre
)
3410 rtx insn
= BB_END (bb
);
3412 rtx reg
= expr
->reaching_reg
;
3413 int regno
= REGNO (reg
);
3416 pat
= process_insert_insn (expr
);
3417 gcc_assert (pat
&& INSN_P (pat
));
3420 while (NEXT_INSN (pat_end
) != NULL_RTX
)
3421 pat_end
= NEXT_INSN (pat_end
);
3423 /* If the last insn is a jump, insert EXPR in front [taking care to
3424 handle cc0, etc. properly]. Similarly we need to care trapping
3425 instructions in presence of non-call exceptions. */
3428 || (NONJUMP_INSN_P (insn
)
3429 && (!single_succ_p (bb
)
3430 || single_succ_edge (bb
)->flags
& EDGE_ABNORMAL
)))
3435 /* It should always be the case that we can put these instructions
3436 anywhere in the basic block with performing PRE optimizations.
3438 gcc_assert (!NONJUMP_INSN_P (insn
) || !pre
3439 || TEST_BIT (antloc
[bb
->index
], expr
->bitmap_index
)
3440 || TEST_BIT (transp
[bb
->index
], expr
->bitmap_index
));
3442 /* If this is a jump table, then we can't insert stuff here. Since
3443 we know the previous real insn must be the tablejump, we insert
3444 the new instruction just before the tablejump. */
3445 if (GET_CODE (PATTERN (insn
)) == ADDR_VEC
3446 || GET_CODE (PATTERN (insn
)) == ADDR_DIFF_VEC
)
3447 insn
= prev_real_insn (insn
);
3450 /* FIXME: 'twould be nice to call prev_cc0_setter here but it aborts
3451 if cc0 isn't set. */
3452 note
= find_reg_note (insn
, REG_CC_SETTER
, NULL_RTX
);
3454 insn
= XEXP (note
, 0);
3457 rtx maybe_cc0_setter
= prev_nonnote_insn (insn
);
3458 if (maybe_cc0_setter
3459 && INSN_P (maybe_cc0_setter
)
3460 && sets_cc0_p (PATTERN (maybe_cc0_setter
)))
3461 insn
= maybe_cc0_setter
;
3464 /* FIXME: What if something in cc0/jump uses value set in new insn? */
3465 new_insn
= emit_insn_before_noloc (pat
, insn
, bb
);
3468 /* Likewise if the last insn is a call, as will happen in the presence
3469 of exception handling. */
3470 else if (CALL_P (insn
)
3471 && (!single_succ_p (bb
)
3472 || single_succ_edge (bb
)->flags
& EDGE_ABNORMAL
))
3474 /* Keeping in mind SMALL_REGISTER_CLASSES and parameters in registers,
3475 we search backward and place the instructions before the first
3476 parameter is loaded. Do this for everyone for consistency and a
3477 presumption that we'll get better code elsewhere as well.
3479 It should always be the case that we can put these instructions
3480 anywhere in the basic block with performing PRE optimizations.
3484 || TEST_BIT (antloc
[bb
->index
], expr
->bitmap_index
)
3485 || TEST_BIT (transp
[bb
->index
], expr
->bitmap_index
));
3487 /* Since different machines initialize their parameter registers
3488 in different orders, assume nothing. Collect the set of all
3489 parameter registers. */
3490 insn
= find_first_parameter_load (insn
, BB_HEAD (bb
));
3492 /* If we found all the parameter loads, then we want to insert
3493 before the first parameter load.
3495 If we did not find all the parameter loads, then we might have
3496 stopped on the head of the block, which could be a CODE_LABEL.
3497 If we inserted before the CODE_LABEL, then we would be putting
3498 the insn in the wrong basic block. In that case, put the insn
3499 after the CODE_LABEL. Also, respect NOTE_INSN_BASIC_BLOCK. */
3500 while (LABEL_P (insn
)
3501 || NOTE_INSN_BASIC_BLOCK_P (insn
))
3502 insn
= NEXT_INSN (insn
);
3504 new_insn
= emit_insn_before_noloc (pat
, insn
, bb
);
3507 new_insn
= emit_insn_after_noloc (pat
, insn
, bb
);
3512 add_label_notes (PATTERN (pat
), new_insn
);
3515 pat
= NEXT_INSN (pat
);
3518 gcse_create_count
++;
3522 fprintf (dump_file
, "PRE/HOIST: end of bb %d, insn %d, ",
3523 bb
->index
, INSN_UID (new_insn
));
3524 fprintf (dump_file
, "copying expression %d to reg %d\n",
3525 expr
->bitmap_index
, regno
);
3529 /* Insert partially redundant expressions on edges in the CFG to make
3530 the expressions fully redundant. */
3533 pre_edge_insert (struct edge_list
*edge_list
, struct expr
**index_map
)
3535 int e
, i
, j
, num_edges
, set_size
, did_insert
= 0;
3538 /* Where PRE_INSERT_MAP is nonzero, we add the expression on that edge
3539 if it reaches any of the deleted expressions. */
3541 set_size
= pre_insert_map
[0]->size
;
3542 num_edges
= NUM_EDGES (edge_list
);
3543 inserted
= sbitmap_vector_alloc (num_edges
, expr_hash_table
.n_elems
);
3544 sbitmap_vector_zero (inserted
, num_edges
);
3546 for (e
= 0; e
< num_edges
; e
++)
3549 basic_block bb
= INDEX_EDGE_PRED_BB (edge_list
, e
);
3551 for (i
= indx
= 0; i
< set_size
; i
++, indx
+= SBITMAP_ELT_BITS
)
3553 SBITMAP_ELT_TYPE insert
= pre_insert_map
[e
]->elms
[i
];
3555 for (j
= indx
; insert
&& j
< (int) expr_hash_table
.n_elems
; j
++, insert
>>= 1)
3556 if ((insert
& 1) != 0 && index_map
[j
]->reaching_reg
!= NULL_RTX
)
3558 struct expr
*expr
= index_map
[j
];
3561 /* Now look at each deleted occurrence of this expression. */
3562 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
3564 if (! occr
->deleted_p
)
3567 /* Insert this expression on this edge if it would
3568 reach the deleted occurrence in BB. */
3569 if (!TEST_BIT (inserted
[e
], j
))
3572 edge eg
= INDEX_EDGE (edge_list
, e
);
3574 /* We can't insert anything on an abnormal and
3575 critical edge, so we insert the insn at the end of
3576 the previous block. There are several alternatives
3577 detailed in Morgans book P277 (sec 10.5) for
3578 handling this situation. This one is easiest for
3581 if (eg
->flags
& EDGE_ABNORMAL
)
3582 insert_insn_end_basic_block (index_map
[j
], bb
, 0);
3585 insn
= process_insert_insn (index_map
[j
]);
3586 insert_insn_on_edge (insn
, eg
);
3591 fprintf (dump_file
, "PRE: edge (%d,%d), ",
3593 INDEX_EDGE_SUCC_BB (edge_list
, e
)->index
);
3594 fprintf (dump_file
, "copy expression %d\n",
3595 expr
->bitmap_index
);
3598 update_ld_motion_stores (expr
);
3599 SET_BIT (inserted
[e
], j
);
3601 gcse_create_count
++;
3608 sbitmap_vector_free (inserted
);
3612 /* Copy the result of EXPR->EXPR generated by INSN to EXPR->REACHING_REG.
3613 Given "old_reg <- expr" (INSN), instead of adding after it
3614 reaching_reg <- old_reg
3615 it's better to do the following:
3616 reaching_reg <- expr
3617 old_reg <- reaching_reg
3618 because this way copy propagation can discover additional PRE
3619 opportunities. But if this fails, we try the old way.
3620 When "expr" is a store, i.e.
3621 given "MEM <- old_reg", instead of adding after it
3622 reaching_reg <- old_reg
3623 it's better to add it before as follows:
3624 reaching_reg <- old_reg
3625 MEM <- reaching_reg. */
3628 pre_insert_copy_insn (struct expr
*expr
, rtx insn
)
3630 rtx reg
= expr
->reaching_reg
;
3631 int regno
= REGNO (reg
);
3632 int indx
= expr
->bitmap_index
;
3633 rtx pat
= PATTERN (insn
);
3634 rtx set
, first_set
, new_insn
;
3638 /* This block matches the logic in hash_scan_insn. */
3639 switch (GET_CODE (pat
))
3646 /* Search through the parallel looking for the set whose
3647 source was the expression that we're interested in. */
3648 first_set
= NULL_RTX
;
3650 for (i
= 0; i
< XVECLEN (pat
, 0); i
++)
3652 rtx x
= XVECEXP (pat
, 0, i
);
3653 if (GET_CODE (x
) == SET
)
3655 /* If the source was a REG_EQUAL or REG_EQUIV note, we
3656 may not find an equivalent expression, but in this
3657 case the PARALLEL will have a single set. */
3658 if (first_set
== NULL_RTX
)
3660 if (expr_equiv_p (SET_SRC (x
), expr
->expr
))
3668 gcc_assert (first_set
);
3669 if (set
== NULL_RTX
)
3677 if (REG_P (SET_DEST (set
)))
3679 old_reg
= SET_DEST (set
);
3680 /* Check if we can modify the set destination in the original insn. */
3681 if (validate_change (insn
, &SET_DEST (set
), reg
, 0))
3683 new_insn
= gen_move_insn (old_reg
, reg
);
3684 new_insn
= emit_insn_after (new_insn
, insn
);
3688 new_insn
= gen_move_insn (reg
, old_reg
);
3689 new_insn
= emit_insn_after (new_insn
, insn
);
3692 else /* This is possible only in case of a store to memory. */
3694 old_reg
= SET_SRC (set
);
3695 new_insn
= gen_move_insn (reg
, old_reg
);
3697 /* Check if we can modify the set source in the original insn. */
3698 if (validate_change (insn
, &SET_SRC (set
), reg
, 0))
3699 new_insn
= emit_insn_before (new_insn
, insn
);
3701 new_insn
= emit_insn_after (new_insn
, insn
);
3704 gcse_create_count
++;
3708 "PRE: bb %d, insn %d, copy expression %d in insn %d to reg %d\n",
3709 BLOCK_NUM (insn
), INSN_UID (new_insn
), indx
,
3710 INSN_UID (insn
), regno
);
3713 /* Copy available expressions that reach the redundant expression
3714 to `reaching_reg'. */
3717 pre_insert_copies (void)
3719 unsigned int i
, added_copy
;
3724 /* For each available expression in the table, copy the result to
3725 `reaching_reg' if the expression reaches a deleted one.
3727 ??? The current algorithm is rather brute force.
3728 Need to do some profiling. */
3730 for (i
= 0; i
< expr_hash_table
.size
; i
++)
3731 for (expr
= expr_hash_table
.table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
3733 /* If the basic block isn't reachable, PPOUT will be TRUE. However,
3734 we don't want to insert a copy here because the expression may not
3735 really be redundant. So only insert an insn if the expression was
3736 deleted. This test also avoids further processing if the
3737 expression wasn't deleted anywhere. */
3738 if (expr
->reaching_reg
== NULL
)
3741 /* Set when we add a copy for that expression. */
3744 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
3746 if (! occr
->deleted_p
)
3749 for (avail
= expr
->avail_occr
; avail
!= NULL
; avail
= avail
->next
)
3751 rtx insn
= avail
->insn
;
3753 /* No need to handle this one if handled already. */
3754 if (avail
->copied_p
)
3757 /* Don't handle this one if it's a redundant one. */
3758 if (INSN_DELETED_P (insn
))
3761 /* Or if the expression doesn't reach the deleted one. */
3762 if (! pre_expr_reaches_here_p (BLOCK_FOR_INSN (avail
->insn
),
3764 BLOCK_FOR_INSN (occr
->insn
)))
3769 /* Copy the result of avail to reaching_reg. */
3770 pre_insert_copy_insn (expr
, insn
);
3771 avail
->copied_p
= 1;
3776 update_ld_motion_stores (expr
);
3780 /* Emit move from SRC to DEST noting the equivalence with expression computed
3783 gcse_emit_move_after (rtx src
, rtx dest
, rtx insn
)
3786 rtx set
= single_set (insn
), set2
;
3790 /* This should never fail since we're creating a reg->reg copy
3791 we've verified to be valid. */
3793 new_rtx
= emit_insn_after (gen_move_insn (dest
, src
), insn
);
3795 /* Note the equivalence for local CSE pass. */
3796 set2
= single_set (new_rtx
);
3797 if (!set2
|| !rtx_equal_p (SET_DEST (set2
), dest
))
3799 if ((note
= find_reg_equal_equiv_note (insn
)))
3800 eqv
= XEXP (note
, 0);
3802 eqv
= SET_SRC (set
);
3804 set_unique_reg_note (new_rtx
, REG_EQUAL
, copy_insn_1 (eqv
));
3809 /* Delete redundant computations.
3810 Deletion is done by changing the insn to copy the `reaching_reg' of
3811 the expression into the result of the SET. It is left to later passes
3812 (cprop, cse2, flow, combine, regmove) to propagate the copy or eliminate it.
3814 Returns nonzero if a change is made. */
3825 for (i
= 0; i
< expr_hash_table
.size
; i
++)
3826 for (expr
= expr_hash_table
.table
[i
];
3828 expr
= expr
->next_same_hash
)
3830 int indx
= expr
->bitmap_index
;
3832 /* We only need to search antic_occr since we require
3835 for (occr
= expr
->antic_occr
; occr
!= NULL
; occr
= occr
->next
)
3837 rtx insn
= occr
->insn
;
3839 basic_block bb
= BLOCK_FOR_INSN (insn
);
3841 /* We only delete insns that have a single_set. */
3842 if (TEST_BIT (pre_delete_map
[bb
->index
], indx
)
3843 && (set
= single_set (insn
)) != 0
3844 && dbg_cnt (pre_insn
))
3846 /* Create a pseudo-reg to store the result of reaching
3847 expressions into. Get the mode for the new pseudo from
3848 the mode of the original destination pseudo. */
3849 if (expr
->reaching_reg
== NULL
)
3850 expr
->reaching_reg
= gen_reg_rtx_and_attrs (SET_DEST (set
));
3852 gcse_emit_move_after (expr
->reaching_reg
, SET_DEST (set
), insn
);
3854 occr
->deleted_p
= 1;
3861 "PRE: redundant insn %d (expression %d) in ",
3862 INSN_UID (insn
), indx
);
3863 fprintf (dump_file
, "bb %d, reaching reg is %d\n",
3864 bb
->index
, REGNO (expr
->reaching_reg
));
3873 /* Perform GCSE optimizations using PRE.
3874 This is called by one_pre_gcse_pass after all the dataflow analysis
3877 This is based on the original Morel-Renvoise paper Fred Chow's thesis, and
3878 lazy code motion from Knoop, Ruthing and Steffen as described in Advanced
3879 Compiler Design and Implementation.
3881 ??? A new pseudo reg is created to hold the reaching expression. The nice
3882 thing about the classical approach is that it would try to use an existing
3883 reg. If the register can't be adequately optimized [i.e. we introduce
3884 reload problems], one could add a pass here to propagate the new register
3887 ??? We don't handle single sets in PARALLELs because we're [currently] not
3888 able to copy the rest of the parallel when we insert copies to create full
3889 redundancies from partial redundancies. However, there's no reason why we
3890 can't handle PARALLELs in the cases where there are no partial
3897 int did_insert
, changed
;
3898 struct expr
**index_map
;
3901 /* Compute a mapping from expression number (`bitmap_index') to
3902 hash table entry. */
3904 index_map
= XCNEWVEC (struct expr
*, expr_hash_table
.n_elems
);
3905 for (i
= 0; i
< expr_hash_table
.size
; i
++)
3906 for (expr
= expr_hash_table
.table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
3907 index_map
[expr
->bitmap_index
] = expr
;
3909 /* Delete the redundant insns first so that
3910 - we know what register to use for the new insns and for the other
3911 ones with reaching expressions
3912 - we know which insns are redundant when we go to create copies */
3914 changed
= pre_delete ();
3915 did_insert
= pre_edge_insert (edge_list
, index_map
);
3917 /* In other places with reaching expressions, copy the expression to the
3918 specially allocated pseudo-reg that reaches the redundant expr. */
3919 pre_insert_copies ();
3922 commit_edge_insertions ();
3930 /* Top level routine to perform one PRE GCSE pass.
3932 Return nonzero if a change was made. */
3935 one_pre_gcse_pass (void)
3939 gcse_subst_count
= 0;
3940 gcse_create_count
= 0;
3942 /* Return if there's nothing to do, or it is too expensive. */
3943 if (n_basic_blocks
<= NUM_FIXED_BLOCKS
+ 1
3944 || is_too_expensive (_("PRE disabled")))
3947 /* We need alias. */
3948 init_alias_analysis ();
3951 gcc_obstack_init (&gcse_obstack
);
3954 alloc_hash_table (get_max_uid (), &expr_hash_table
, 0);
3955 add_noreturn_fake_exit_edges ();
3957 compute_ld_motion_mems ();
3959 compute_hash_table (&expr_hash_table
);
3960 trim_ld_motion_mems ();
3962 dump_hash_table (dump_file
, "Expression", &expr_hash_table
);
3964 if (expr_hash_table
.n_elems
> 0)
3966 alloc_pre_mem (last_basic_block
, expr_hash_table
.n_elems
);
3967 compute_pre_data ();
3968 changed
|= pre_gcse ();
3969 free_edge_list (edge_list
);
3974 remove_fake_exit_edges ();
3975 free_hash_table (&expr_hash_table
);
3978 obstack_free (&gcse_obstack
, NULL
);
3980 /* We are finished with alias. */
3981 end_alias_analysis ();
3985 fprintf (dump_file
, "PRE GCSE of %s, %d basic blocks, %d bytes needed, ",
3986 current_function_name (), n_basic_blocks
, bytes_used
);
3987 fprintf (dump_file
, "%d substs, %d insns created\n",
3988 gcse_subst_count
, gcse_create_count
);
3994 /* If X contains any LABEL_REF's, add REG_LABEL_OPERAND notes for them
3995 to INSN. If such notes are added to an insn which references a
3996 CODE_LABEL, the LABEL_NUSES count is incremented. We have to add
3997 that note, because the following loop optimization pass requires
4000 /* ??? If there was a jump optimization pass after gcse and before loop,
4001 then we would not need to do this here, because jump would add the
4002 necessary REG_LABEL_OPERAND and REG_LABEL_TARGET notes. */
4005 add_label_notes (rtx x
, rtx insn
)
4007 enum rtx_code code
= GET_CODE (x
);
4011 if (code
== LABEL_REF
&& !LABEL_REF_NONLOCAL_P (x
))
4013 /* This code used to ignore labels that referred to dispatch tables to
4014 avoid flow generating (slightly) worse code.
4016 We no longer ignore such label references (see LABEL_REF handling in
4017 mark_jump_label for additional information). */
4019 /* There's no reason for current users to emit jump-insns with
4020 such a LABEL_REF, so we don't have to handle REG_LABEL_TARGET
4022 gcc_assert (!JUMP_P (insn
));
4023 add_reg_note (insn
, REG_LABEL_OPERAND
, XEXP (x
, 0));
4025 if (LABEL_P (XEXP (x
, 0)))
4026 LABEL_NUSES (XEXP (x
, 0))++;
4031 for (i
= GET_RTX_LENGTH (code
) - 1, fmt
= GET_RTX_FORMAT (code
); i
>= 0; i
--)
4034 add_label_notes (XEXP (x
, i
), insn
);
4035 else if (fmt
[i
] == 'E')
4036 for (j
= XVECLEN (x
, i
) - 1; j
>= 0; j
--)
4037 add_label_notes (XVECEXP (x
, i
, j
), insn
);
4041 /* Compute transparent outgoing information for each block.
4043 An expression is transparent to an edge unless it is killed by
4044 the edge itself. This can only happen with abnormal control flow,
4045 when the edge is traversed through a call. This happens with
4046 non-local labels and exceptions.
4048 This would not be necessary if we split the edge. While this is
4049 normally impossible for abnormal critical edges, with some effort
4050 it should be possible with exception handling, since we still have
4051 control over which handler should be invoked. But due to increased
4052 EH table sizes, this may not be worthwhile. */
4055 compute_transpout (void)
4061 sbitmap_vector_ones (transpout
, last_basic_block
);
4065 /* Note that flow inserted a nop at the end of basic blocks that
4066 end in call instructions for reasons other than abnormal
4068 if (! CALL_P (BB_END (bb
)))
4071 for (i
= 0; i
< expr_hash_table
.size
; i
++)
4072 for (expr
= expr_hash_table
.table
[i
]; expr
; expr
= expr
->next_same_hash
)
4073 if (MEM_P (expr
->expr
))
4075 if (GET_CODE (XEXP (expr
->expr
, 0)) == SYMBOL_REF
4076 && CONSTANT_POOL_ADDRESS_P (XEXP (expr
->expr
, 0)))
4079 /* ??? Optimally, we would use interprocedural alias
4080 analysis to determine if this mem is actually killed
4082 RESET_BIT (transpout
[bb
->index
], expr
->bitmap_index
);
4087 /* Code Hoisting variables and subroutines. */
4089 /* Very busy expressions. */
4090 static sbitmap
*hoist_vbein
;
4091 static sbitmap
*hoist_vbeout
;
4093 /* Hoistable expressions. */
4094 static sbitmap
*hoist_exprs
;
4096 /* ??? We could compute post dominators and run this algorithm in
4097 reverse to perform tail merging, doing so would probably be
4098 more effective than the tail merging code in jump.c.
4100 It's unclear if tail merging could be run in parallel with
4101 code hoisting. It would be nice. */
4103 /* Allocate vars used for code hoisting analysis. */
4106 alloc_code_hoist_mem (int n_blocks
, int n_exprs
)
4108 antloc
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4109 transp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4110 comp
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4112 hoist_vbein
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4113 hoist_vbeout
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4114 hoist_exprs
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4115 transpout
= sbitmap_vector_alloc (n_blocks
, n_exprs
);
4118 /* Free vars used for code hoisting analysis. */
4121 free_code_hoist_mem (void)
4123 sbitmap_vector_free (antloc
);
4124 sbitmap_vector_free (transp
);
4125 sbitmap_vector_free (comp
);
4127 sbitmap_vector_free (hoist_vbein
);
4128 sbitmap_vector_free (hoist_vbeout
);
4129 sbitmap_vector_free (hoist_exprs
);
4130 sbitmap_vector_free (transpout
);
4132 free_dominance_info (CDI_DOMINATORS
);
4135 /* Compute the very busy expressions at entry/exit from each block.
4137 An expression is very busy if all paths from a given point
4138 compute the expression. */
4141 compute_code_hoist_vbeinout (void)
4143 int changed
, passes
;
4146 sbitmap_vector_zero (hoist_vbeout
, last_basic_block
);
4147 sbitmap_vector_zero (hoist_vbein
, last_basic_block
);
4156 /* We scan the blocks in the reverse order to speed up
4158 FOR_EACH_BB_REVERSE (bb
)
4160 if (bb
->next_bb
!= EXIT_BLOCK_PTR
)
4161 sbitmap_intersection_of_succs (hoist_vbeout
[bb
->index
],
4162 hoist_vbein
, bb
->index
);
4164 changed
|= sbitmap_a_or_b_and_c_cg (hoist_vbein
[bb
->index
],
4166 hoist_vbeout
[bb
->index
],
4174 fprintf (dump_file
, "hoisting vbeinout computation: %d passes\n", passes
);
4177 /* Top level routine to do the dataflow analysis needed by code hoisting. */
4180 compute_code_hoist_data (void)
4182 compute_local_properties (transp
, comp
, antloc
, &expr_hash_table
);
4183 compute_transpout ();
4184 compute_code_hoist_vbeinout ();
4185 calculate_dominance_info (CDI_DOMINATORS
);
4187 fprintf (dump_file
, "\n");
4190 /* Determine if the expression identified by EXPR_INDEX would
4191 reach BB unimpared if it was placed at the end of EXPR_BB.
4193 It's unclear exactly what Muchnick meant by "unimpared". It seems
4194 to me that the expression must either be computed or transparent in
4195 *every* block in the path(s) from EXPR_BB to BB. Any other definition
4196 would allow the expression to be hoisted out of loops, even if
4197 the expression wasn't a loop invariant.
4199 Contrast this to reachability for PRE where an expression is
4200 considered reachable if *any* path reaches instead of *all*
4204 hoist_expr_reaches_here_p (basic_block expr_bb
, int expr_index
, basic_block bb
, char *visited
)
4208 int visited_allocated_locally
= 0;
4211 if (visited
== NULL
)
4213 visited_allocated_locally
= 1;
4214 visited
= XCNEWVEC (char, last_basic_block
);
4217 FOR_EACH_EDGE (pred
, ei
, bb
->preds
)
4219 basic_block pred_bb
= pred
->src
;
4221 if (pred
->src
== ENTRY_BLOCK_PTR
)
4223 else if (pred_bb
== expr_bb
)
4225 else if (visited
[pred_bb
->index
])
4228 /* Does this predecessor generate this expression? */
4229 else if (TEST_BIT (comp
[pred_bb
->index
], expr_index
))
4231 else if (! TEST_BIT (transp
[pred_bb
->index
], expr_index
))
4237 visited
[pred_bb
->index
] = 1;
4238 if (! hoist_expr_reaches_here_p (expr_bb
, expr_index
,
4243 if (visited_allocated_locally
)
4246 return (pred
== NULL
);
4249 /* Actually perform code hoisting. */
4254 basic_block bb
, dominated
;
4255 VEC (basic_block
, heap
) *domby
;
4257 struct expr
**index_map
;
4261 sbitmap_vector_zero (hoist_exprs
, last_basic_block
);
4263 /* Compute a mapping from expression number (`bitmap_index') to
4264 hash table entry. */
4266 index_map
= XCNEWVEC (struct expr
*, expr_hash_table
.n_elems
);
4267 for (i
= 0; i
< expr_hash_table
.size
; i
++)
4268 for (expr
= expr_hash_table
.table
[i
]; expr
!= NULL
; expr
= expr
->next_same_hash
)
4269 index_map
[expr
->bitmap_index
] = expr
;
4271 /* Walk over each basic block looking for potentially hoistable
4272 expressions, nothing gets hoisted from the entry block. */
4276 int insn_inserted_p
;
4278 domby
= get_dominated_by (CDI_DOMINATORS
, bb
);
4279 /* Examine each expression that is very busy at the exit of this
4280 block. These are the potentially hoistable expressions. */
4281 for (i
= 0; i
< hoist_vbeout
[bb
->index
]->n_bits
; i
++)
4285 if (TEST_BIT (hoist_vbeout
[bb
->index
], i
)
4286 && TEST_BIT (transpout
[bb
->index
], i
))
4288 /* We've found a potentially hoistable expression, now
4289 we look at every block BB dominates to see if it
4290 computes the expression. */
4291 for (j
= 0; VEC_iterate (basic_block
, domby
, j
, dominated
); j
++)
4293 /* Ignore self dominance. */
4294 if (bb
== dominated
)
4296 /* We've found a dominated block, now see if it computes
4297 the busy expression and whether or not moving that
4298 expression to the "beginning" of that block is safe. */
4299 if (!TEST_BIT (antloc
[dominated
->index
], i
))
4302 /* Note if the expression would reach the dominated block
4303 unimpared if it was placed at the end of BB.
4305 Keep track of how many times this expression is hoistable
4306 from a dominated block into BB. */
4307 if (hoist_expr_reaches_here_p (bb
, i
, dominated
, NULL
))
4311 /* If we found more than one hoistable occurrence of this
4312 expression, then note it in the bitmap of expressions to
4313 hoist. It makes no sense to hoist things which are computed
4314 in only one BB, and doing so tends to pessimize register
4315 allocation. One could increase this value to try harder
4316 to avoid any possible code expansion due to register
4317 allocation issues; however experiments have shown that
4318 the vast majority of hoistable expressions are only movable
4319 from two successors, so raising this threshold is likely
4320 to nullify any benefit we get from code hoisting. */
4323 SET_BIT (hoist_exprs
[bb
->index
], i
);
4328 /* If we found nothing to hoist, then quit now. */
4331 VEC_free (basic_block
, heap
, domby
);
4335 /* Loop over all the hoistable expressions. */
4336 for (i
= 0; i
< hoist_exprs
[bb
->index
]->n_bits
; i
++)
4338 /* We want to insert the expression into BB only once, so
4339 note when we've inserted it. */
4340 insn_inserted_p
= 0;
4342 /* These tests should be the same as the tests above. */
4343 if (TEST_BIT (hoist_exprs
[bb
->index
], i
))
4345 /* We've found a potentially hoistable expression, now
4346 we look at every block BB dominates to see if it
4347 computes the expression. */
4348 for (j
= 0; VEC_iterate (basic_block
, domby
, j
, dominated
); j
++)
4350 /* Ignore self dominance. */
4351 if (bb
== dominated
)
4354 /* We've found a dominated block, now see if it computes
4355 the busy expression and whether or not moving that
4356 expression to the "beginning" of that block is safe. */
4357 if (!TEST_BIT (antloc
[dominated
->index
], i
))
4360 /* The expression is computed in the dominated block and
4361 it would be safe to compute it at the start of the
4362 dominated block. Now we have to determine if the
4363 expression would reach the dominated block if it was
4364 placed at the end of BB. */
4365 if (hoist_expr_reaches_here_p (bb
, i
, dominated
, NULL
))
4367 struct expr
*expr
= index_map
[i
];
4368 struct occr
*occr
= expr
->antic_occr
;
4372 /* Find the right occurrence of this expression. */
4373 while (BLOCK_FOR_INSN (occr
->insn
) != dominated
&& occr
)
4378 set
= single_set (insn
);
4381 /* Create a pseudo-reg to store the result of reaching
4382 expressions into. Get the mode for the new pseudo
4383 from the mode of the original destination pseudo. */
4384 if (expr
->reaching_reg
== NULL
)
4386 = gen_reg_rtx_and_attrs (SET_DEST (set
));
4388 gcse_emit_move_after (expr
->reaching_reg
, SET_DEST (set
), insn
);
4390 occr
->deleted_p
= 1;
4394 if (!insn_inserted_p
)
4396 insert_insn_end_basic_block (index_map
[i
], bb
, 0);
4397 insn_inserted_p
= 1;
4403 VEC_free (basic_block
, heap
, domby
);
4411 /* Top level routine to perform one code hoisting (aka unification) pass
4413 Return nonzero if a change was made. */
4416 one_code_hoisting_pass (void)
4420 gcse_subst_count
= 0;
4421 gcse_create_count
= 0;
4423 /* Return if there's nothing to do, or it is too expensive. */
4424 if (n_basic_blocks
<= NUM_FIXED_BLOCKS
+ 1
4425 || is_too_expensive (_("GCSE disabled")))
4428 /* We need alias. */
4429 init_alias_analysis ();
4432 gcc_obstack_init (&gcse_obstack
);
4435 alloc_hash_table (get_max_uid (), &expr_hash_table
, 0);
4436 compute_hash_table (&expr_hash_table
);
4438 dump_hash_table (dump_file
, "Code Hosting Expressions", &expr_hash_table
);
4440 if (expr_hash_table
.n_elems
> 0)
4442 alloc_code_hoist_mem (last_basic_block
, expr_hash_table
.n_elems
);
4443 compute_code_hoist_data ();
4444 changed
= hoist_code ();
4445 free_code_hoist_mem ();
4448 free_hash_table (&expr_hash_table
);
4450 obstack_free (&gcse_obstack
, NULL
);
4452 /* We are finished with alias. */
4453 end_alias_analysis ();
4457 fprintf (dump_file
, "HOIST of %s, %d basic blocks, %d bytes needed, ",
4458 current_function_name (), n_basic_blocks
, bytes_used
);
4459 fprintf (dump_file
, "%d substs, %d insns created\n",
4460 gcse_subst_count
, gcse_create_count
);
4466 /* Here we provide the things required to do store motion towards
4467 the exit. In order for this to be effective, gcse also needed to
4468 be taught how to move a load when it is kill only by a store to itself.
4473 void foo(float scale)
4475 for (i=0; i<10; i++)
4479 'i' is both loaded and stored to in the loop. Normally, gcse cannot move
4480 the load out since its live around the loop, and stored at the bottom
4483 The 'Load Motion' referred to and implemented in this file is
4484 an enhancement to gcse which when using edge based lcm, recognizes
4485 this situation and allows gcse to move the load out of the loop.
4487 Once gcse has hoisted the load, store motion can then push this
4488 load towards the exit, and we end up with no loads or stores of 'i'
4492 pre_ldst_expr_hash (const void *p
)
4494 int do_not_record_p
= 0;
4495 const struct ls_expr
*const x
= (const struct ls_expr
*) p
;
4496 return hash_rtx (x
->pattern
, GET_MODE (x
->pattern
), &do_not_record_p
, NULL
, false);
4500 pre_ldst_expr_eq (const void *p1
, const void *p2
)
4502 const struct ls_expr
*const ptr1
= (const struct ls_expr
*) p1
,
4503 *const ptr2
= (const struct ls_expr
*) p2
;
4504 return expr_equiv_p (ptr1
->pattern
, ptr2
->pattern
);
4507 /* This will search the ldst list for a matching expression. If it
4508 doesn't find one, we create one and initialize it. */
4510 static struct ls_expr
*
4513 int do_not_record_p
= 0;
4514 struct ls_expr
* ptr
;
4519 hash
= hash_rtx (x
, GET_MODE (x
), &do_not_record_p
,
4520 NULL
, /*have_reg_qty=*/false);
4523 slot
= htab_find_slot_with_hash (pre_ldst_table
, &e
, hash
, INSERT
);
4525 return (struct ls_expr
*)*slot
;
4527 ptr
= XNEW (struct ls_expr
);
4529 ptr
->next
= pre_ldst_mems
;
4532 ptr
->pattern_regs
= NULL_RTX
;
4533 ptr
->loads
= NULL_RTX
;
4534 ptr
->stores
= NULL_RTX
;
4535 ptr
->reaching_reg
= NULL_RTX
;
4538 ptr
->hash_index
= hash
;
4539 pre_ldst_mems
= ptr
;
4545 /* Free up an individual ldst entry. */
4548 free_ldst_entry (struct ls_expr
* ptr
)
4550 free_INSN_LIST_list (& ptr
->loads
);
4551 free_INSN_LIST_list (& ptr
->stores
);
4556 /* Free up all memory associated with the ldst list. */
4559 free_ldst_mems (void)
4562 htab_delete (pre_ldst_table
);
4563 pre_ldst_table
= NULL
;
4565 while (pre_ldst_mems
)
4567 struct ls_expr
* tmp
= pre_ldst_mems
;
4569 pre_ldst_mems
= pre_ldst_mems
->next
;
4571 free_ldst_entry (tmp
);
4574 pre_ldst_mems
= NULL
;
4577 /* Dump debugging info about the ldst list. */
4580 print_ldst_list (FILE * file
)
4582 struct ls_expr
* ptr
;
4584 fprintf (file
, "LDST list: \n");
4586 for (ptr
= first_ls_expr (); ptr
!= NULL
; ptr
= next_ls_expr (ptr
))
4588 fprintf (file
, " Pattern (%3d): ", ptr
->index
);
4590 print_rtl (file
, ptr
->pattern
);
4592 fprintf (file
, "\n Loads : ");
4595 print_rtl (file
, ptr
->loads
);
4597 fprintf (file
, "(nil)");
4599 fprintf (file
, "\n Stores : ");
4602 print_rtl (file
, ptr
->stores
);
4604 fprintf (file
, "(nil)");
4606 fprintf (file
, "\n\n");
4609 fprintf (file
, "\n");
4612 /* Returns 1 if X is in the list of ldst only expressions. */
4614 static struct ls_expr
*
4615 find_rtx_in_ldst (rtx x
)
4619 if (!pre_ldst_table
)
4622 slot
= htab_find_slot (pre_ldst_table
, &e
, NO_INSERT
);
4623 if (!slot
|| ((struct ls_expr
*)*slot
)->invalid
)
4625 return (struct ls_expr
*) *slot
;
4628 /* Return first item in the list. */
4630 static inline struct ls_expr
*
4631 first_ls_expr (void)
4633 return pre_ldst_mems
;
4636 /* Return the next item in the list after the specified one. */
4638 static inline struct ls_expr
*
4639 next_ls_expr (struct ls_expr
* ptr
)
4644 /* Load Motion for loads which only kill themselves. */
4646 /* Return true if x is a simple MEM operation, with no registers or
4647 side effects. These are the types of loads we consider for the
4648 ld_motion list, otherwise we let the usual aliasing take care of it. */
4651 simple_mem (const_rtx x
)
4656 if (MEM_VOLATILE_P (x
))
4659 if (GET_MODE (x
) == BLKmode
)
4662 /* If we are handling exceptions, we must be careful with memory references
4663 that may trap. If we are not, the behavior is undefined, so we may just
4665 if (flag_non_call_exceptions
&& may_trap_p (x
))
4668 if (side_effects_p (x
))
4671 /* Do not consider function arguments passed on stack. */
4672 if (reg_mentioned_p (stack_pointer_rtx
, x
))
4675 if (flag_float_store
&& FLOAT_MODE_P (GET_MODE (x
)))
4681 /* Make sure there isn't a buried reference in this pattern anywhere.
4682 If there is, invalidate the entry for it since we're not capable
4683 of fixing it up just yet.. We have to be sure we know about ALL
4684 loads since the aliasing code will allow all entries in the
4685 ld_motion list to not-alias itself. If we miss a load, we will get
4686 the wrong value since gcse might common it and we won't know to
4690 invalidate_any_buried_refs (rtx x
)
4694 struct ls_expr
* ptr
;
4696 /* Invalidate it in the list. */
4697 if (MEM_P (x
) && simple_mem (x
))
4699 ptr
= ldst_entry (x
);
4703 /* Recursively process the insn. */
4704 fmt
= GET_RTX_FORMAT (GET_CODE (x
));
4706 for (i
= GET_RTX_LENGTH (GET_CODE (x
)) - 1; i
>= 0; i
--)
4709 invalidate_any_buried_refs (XEXP (x
, i
));
4710 else if (fmt
[i
] == 'E')
4711 for (j
= XVECLEN (x
, i
) - 1; j
>= 0; j
--)
4712 invalidate_any_buried_refs (XVECEXP (x
, i
, j
));
4716 /* Find all the 'simple' MEMs which are used in LOADs and STORES. Simple
4717 being defined as MEM loads and stores to symbols, with no side effects
4718 and no registers in the expression. For a MEM destination, we also
4719 check that the insn is still valid if we replace the destination with a
4720 REG, as is done in update_ld_motion_stores. If there are any uses/defs
4721 which don't match this criteria, they are invalidated and trimmed out
4725 compute_ld_motion_mems (void)
4727 struct ls_expr
* ptr
;
4731 pre_ldst_mems
= NULL
;
4732 pre_ldst_table
= htab_create (13, pre_ldst_expr_hash
,
4733 pre_ldst_expr_eq
, NULL
);
4737 FOR_BB_INSNS (bb
, insn
)
4741 if (GET_CODE (PATTERN (insn
)) == SET
)
4743 rtx src
= SET_SRC (PATTERN (insn
));
4744 rtx dest
= SET_DEST (PATTERN (insn
));
4746 /* Check for a simple LOAD... */
4747 if (MEM_P (src
) && simple_mem (src
))
4749 ptr
= ldst_entry (src
);
4751 ptr
->loads
= alloc_INSN_LIST (insn
, ptr
->loads
);
4757 /* Make sure there isn't a buried load somewhere. */
4758 invalidate_any_buried_refs (src
);
4761 /* Check for stores. Don't worry about aliased ones, they
4762 will block any movement we might do later. We only care
4763 about this exact pattern since those are the only
4764 circumstance that we will ignore the aliasing info. */
4765 if (MEM_P (dest
) && simple_mem (dest
))
4767 ptr
= ldst_entry (dest
);
4770 && GET_CODE (src
) != ASM_OPERANDS
4771 /* Check for REG manually since want_to_gcse_p
4772 returns 0 for all REGs. */
4773 && can_assign_to_reg_without_clobbers_p (src
))
4774 ptr
->stores
= alloc_INSN_LIST (insn
, ptr
->stores
);
4780 invalidate_any_buried_refs (PATTERN (insn
));
4786 /* Remove any references that have been either invalidated or are not in the
4787 expression list for pre gcse. */
4790 trim_ld_motion_mems (void)
4792 struct ls_expr
* * last
= & pre_ldst_mems
;
4793 struct ls_expr
* ptr
= pre_ldst_mems
;
4799 /* Delete if entry has been made invalid. */
4802 /* Delete if we cannot find this mem in the expression list. */
4803 unsigned int hash
= ptr
->hash_index
% expr_hash_table
.size
;
4805 for (expr
= expr_hash_table
.table
[hash
];
4807 expr
= expr
->next_same_hash
)
4808 if (expr_equiv_p (expr
->expr
, ptr
->pattern
))
4812 expr
= (struct expr
*) 0;
4816 /* Set the expression field if we are keeping it. */
4824 htab_remove_elt_with_hash (pre_ldst_table
, ptr
, ptr
->hash_index
);
4825 free_ldst_entry (ptr
);
4830 /* Show the world what we've found. */
4831 if (dump_file
&& pre_ldst_mems
!= NULL
)
4832 print_ldst_list (dump_file
);
4835 /* This routine will take an expression which we are replacing with
4836 a reaching register, and update any stores that are needed if
4837 that expression is in the ld_motion list. Stores are updated by
4838 copying their SRC to the reaching register, and then storing
4839 the reaching register into the store location. These keeps the
4840 correct value in the reaching register for the loads. */
4843 update_ld_motion_stores (struct expr
* expr
)
4845 struct ls_expr
* mem_ptr
;
4847 if ((mem_ptr
= find_rtx_in_ldst (expr
->expr
)))
4849 /* We can try to find just the REACHED stores, but is shouldn't
4850 matter to set the reaching reg everywhere... some might be
4851 dead and should be eliminated later. */
4853 /* We replace (set mem expr) with (set reg expr) (set mem reg)
4854 where reg is the reaching reg used in the load. We checked in
4855 compute_ld_motion_mems that we can replace (set mem expr) with
4856 (set reg expr) in that insn. */
4857 rtx list
= mem_ptr
->stores
;
4859 for ( ; list
!= NULL_RTX
; list
= XEXP (list
, 1))
4861 rtx insn
= XEXP (list
, 0);
4862 rtx pat
= PATTERN (insn
);
4863 rtx src
= SET_SRC (pat
);
4864 rtx reg
= expr
->reaching_reg
;
4867 /* If we've already copied it, continue. */
4868 if (expr
->reaching_reg
== src
)
4873 fprintf (dump_file
, "PRE: store updated with reaching reg ");
4874 print_rtl (dump_file
, expr
->reaching_reg
);
4875 fprintf (dump_file
, ":\n ");
4876 print_inline_rtx (dump_file
, insn
, 8);
4877 fprintf (dump_file
, "\n");
4880 copy
= gen_move_insn (reg
, copy_rtx (SET_SRC (pat
)));
4881 new_rtx
= emit_insn_before (copy
, insn
);
4882 SET_SRC (pat
) = reg
;
4883 df_insn_rescan (insn
);
4885 /* un-recognize this pattern since it's probably different now. */
4886 INSN_CODE (insn
) = -1;
4887 gcse_create_count
++;
4892 /* Return true if the graph is too expensive to optimize. PASS is the
4893 optimization about to be performed. */
4896 is_too_expensive (const char *pass
)
4898 /* Trying to perform global optimizations on flow graphs which have
4899 a high connectivity will take a long time and is unlikely to be
4900 particularly useful.
4902 In normal circumstances a cfg should have about twice as many
4903 edges as blocks. But we do not want to punish small functions
4904 which have a couple switch statements. Rather than simply
4905 threshold the number of blocks, uses something with a more
4906 graceful degradation. */
4907 if (n_edges
> 20000 + n_basic_blocks
* 4)
4909 warning (OPT_Wdisabled_optimization
,
4910 "%s: %d basic blocks and %d edges/basic block",
4911 pass
, n_basic_blocks
, n_edges
/ n_basic_blocks
);
4916 /* If allocating memory for the cprop bitmap would take up too much
4917 storage it's better just to disable the optimization. */
4919 * SBITMAP_SET_SIZE (max_reg_num ())
4920 * sizeof (SBITMAP_ELT_TYPE
)) > MAX_GCSE_MEMORY
)
4922 warning (OPT_Wdisabled_optimization
,
4923 "%s: %d basic blocks and %d registers",
4924 pass
, n_basic_blocks
, max_reg_num ());
4933 /* Main function for the CPROP pass. */
4936 one_cprop_pass (void)
4940 /* Return if there's nothing to do, or it is too expensive. */
4941 if (n_basic_blocks
<= NUM_FIXED_BLOCKS
+ 1
4942 || is_too_expensive (_ ("const/copy propagation disabled")))
4945 global_const_prop_count
= local_const_prop_count
= 0;
4946 global_copy_prop_count
= local_copy_prop_count
= 0;
4949 gcc_obstack_init (&gcse_obstack
);
4952 /* Do a local const/copy propagation pass first. The global pass
4953 only handles global opportunities.
4954 If the local pass changes something, remove any unreachable blocks
4955 because the CPROP global dataflow analysis may get into infinite
4956 loops for CFGs with unreachable blocks.
4958 FIXME: This local pass should not be necessary after CSE (but for
4959 some reason it still is). It is also (proven) not necessary
4960 to run the local pass right after FWPWOP.
4962 FIXME: The global analysis would not get into infinite loops if it
4963 would use the DF solver (via df_simple_dataflow) instead of
4964 the solver implemented in this file. */
4965 if (local_cprop_pass ())
4967 delete_unreachable_blocks ();
4971 /* Determine implicit sets. */
4972 implicit_sets
= XCNEWVEC (rtx
, last_basic_block
);
4973 find_implicit_sets ();
4975 alloc_hash_table (get_max_uid (), &set_hash_table
, 1);
4976 compute_hash_table (&set_hash_table
);
4978 /* Free implicit_sets before peak usage. */
4979 free (implicit_sets
);
4980 implicit_sets
= NULL
;
4983 dump_hash_table (dump_file
, "SET", &set_hash_table
);
4984 if (set_hash_table
.n_elems
> 0)
4989 alloc_cprop_mem (last_basic_block
, set_hash_table
.n_elems
);
4990 compute_cprop_data ();
4992 FOR_BB_BETWEEN (bb
, ENTRY_BLOCK_PTR
->next_bb
->next_bb
, EXIT_BLOCK_PTR
, next_bb
)
4994 /* Reset tables used to keep track of what's still valid [since
4995 the start of the block]. */
4996 reset_opr_set_tables ();
4998 FOR_BB_INSNS (bb
, insn
)
5001 changed
|= cprop_insn (insn
);
5003 /* Keep track of everything modified by this insn. */
5004 /* ??? Need to be careful w.r.t. mods done to INSN.
5005 Don't call mark_oprs_set if we turned the
5006 insn into a NOTE. */
5007 if (! NOTE_P (insn
))
5008 mark_oprs_set (insn
);
5012 changed
|= bypass_conditional_jumps ();
5016 free_hash_table (&set_hash_table
);
5018 obstack_free (&gcse_obstack
, NULL
);
5022 fprintf (dump_file
, "CPROP of %s, %d basic blocks, %d bytes needed, ",
5023 current_function_name (), n_basic_blocks
, bytes_used
);
5024 fprintf (dump_file
, "%d local const props, %d local copy props, ",
5025 local_const_prop_count
, local_copy_prop_count
);
5026 fprintf (dump_file
, "%d global const props, %d global copy props\n\n",
5027 global_const_prop_count
, global_copy_prop_count
);
5034 /* All the passes implemented in this file. Each pass has its
5035 own gate and execute function, and at the end of the file a
5036 pass definition for passes.c.
5038 We do not construct an accurate cfg in functions which call
5039 setjmp, so none of these passes runs if the function calls
5041 FIXME: Should just handle setjmp via REG_SETJMP notes. */
5044 gate_rtl_cprop (void)
5046 return optimize
> 0 && flag_gcse
5047 && !cfun
->calls_setjmp
5052 execute_rtl_cprop (void)
5054 delete_unreachable_blocks ();
5055 df_note_add_problem ();
5056 df_set_flags (DF_LR_RUN_DCE
);
5058 flag_rerun_cse_after_global_opts
|= one_cprop_pass ();
5065 return optimize
> 0 && flag_gcse
5066 && !cfun
->calls_setjmp
5067 && optimize_function_for_speed_p (cfun
)
5072 execute_rtl_pre (void)
5074 delete_unreachable_blocks ();
5075 df_note_add_problem ();
5077 flag_rerun_cse_after_global_opts
|= one_pre_gcse_pass ();
5082 gate_rtl_hoist (void)
5084 return optimize
> 0 && flag_gcse
5085 && !cfun
->calls_setjmp
5086 /* It does not make sense to run code hoisting unless we are optimizing
5087 for code size -- it rarely makes programs faster, and can make then
5088 bigger if we did PRE (when optimizing for space, we don't run PRE). */
5089 && optimize_function_for_size_p (cfun
)
5094 execute_rtl_hoist (void)
5096 delete_unreachable_blocks ();
5097 df_note_add_problem ();
5099 flag_rerun_cse_after_global_opts
|= one_code_hoisting_pass ();
5103 struct rtl_opt_pass pass_rtl_cprop
=
5108 gate_rtl_cprop
, /* gate */
5109 execute_rtl_cprop
, /* execute */
5112 0, /* static_pass_number */
5113 TV_CPROP
, /* tv_id */
5114 PROP_cfglayout
, /* properties_required */
5115 0, /* properties_provided */
5116 0, /* properties_destroyed */
5117 0, /* todo_flags_start */
5118 TODO_df_finish
| TODO_verify_rtl_sharing
|
5120 TODO_verify_flow
| TODO_ggc_collect
/* todo_flags_finish */
5124 struct rtl_opt_pass pass_rtl_pre
=
5129 gate_rtl_pre
, /* gate */
5130 execute_rtl_pre
, /* execute */
5133 0, /* static_pass_number */
5135 PROP_cfglayout
, /* properties_required */
5136 0, /* properties_provided */
5137 0, /* properties_destroyed */
5138 0, /* todo_flags_start */
5139 TODO_df_finish
| TODO_verify_rtl_sharing
|
5141 TODO_verify_flow
| TODO_ggc_collect
/* todo_flags_finish */
5145 struct rtl_opt_pass pass_rtl_hoist
=
5150 gate_rtl_hoist
, /* gate */
5151 execute_rtl_hoist
, /* execute */
5154 0, /* static_pass_number */
5155 TV_HOIST
, /* tv_id */
5156 PROP_cfglayout
, /* properties_required */
5157 0, /* properties_provided */
5158 0, /* properties_destroyed */
5159 0, /* todo_flags_start */
5160 TODO_df_finish
| TODO_verify_rtl_sharing
|
5162 TODO_verify_flow
| TODO_ggc_collect
/* todo_flags_finish */
5166 #include "gt-gcse.h"