1 /* Callgraph based analysis of static variables.
2 Copyright (C) 2004, 2005, 2007, 2008, 2009, 2010
3 Free Software Foundation, Inc.
4 Contributed by Kenneth Zadeck <zadeck@naturalbridge.com>
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/>. */
22 /* This file marks functions as being either const (TREE_READONLY) or
23 pure (DECL_PURE_P). It can also set a variant of these that
24 are allowed to loop indefinitely (DECL_LOOPING_CONST_PURE_P).
26 This must be run after inlining decisions have been made since
27 otherwise, the local sets will not contain information that is
28 consistent with post inlined state. The global sets are not prone
29 to this problem since they are by definition transitive. */
31 /* The code in this module is called by the ipa pass manager. It
32 should be one of the later passes since it's information is used by
33 the rest of the compilation. */
37 #include "coretypes.h"
40 #include "tree-flow.h"
41 #include "tree-inline.h"
42 #include "tree-pass.h"
43 #include "langhooks.h"
44 #include "pointer-set.h"
46 #include "ipa-utils.h"
52 #include "diagnostic.h"
53 #include "gimple-pretty-print.h"
54 #include "langhooks.h"
56 #include "lto-streamer.h"
58 #include "tree-scalar-evolution.h"
62 static struct pointer_set_t
*visited_nodes
;
64 /* Lattice values for const and pure functions. Everything starts out
65 being const, then may drop to pure and then neither depending on
67 enum pure_const_state_e
74 const char *pure_const_names
[3] = {"const", "pure", "neither"};
76 /* Holder for the const_state. There is one of these per function
81 enum pure_const_state_e pure_const_state
;
82 /* What user set here; we can be always sure about this. */
83 enum pure_const_state_e state_previously_known
;
84 bool looping_previously_known
;
86 /* True if the function could possibly infinite loop. There are a
87 lot of ways that this could be determined. We are pretty
88 conservative here. While it is possible to cse pure and const
89 calls, it is not legal to have dce get rid of the call if there
90 is a possibility that the call could infinite loop since this is
91 a behavioral change. */
97 /* State used when we know nothing about function. */
98 static struct funct_state_d varying_state
99 = { IPA_NEITHER
, IPA_NEITHER
, true, true, true };
102 typedef struct funct_state_d
* funct_state
;
104 /* The storage of the funct_state is abstracted because there is the
105 possibility that it may be desirable to move this to the cgraph
108 /* Array, indexed by cgraph node uid, of function states. */
110 DEF_VEC_P (funct_state
);
111 DEF_VEC_ALLOC_P (funct_state
, heap
);
112 static VEC (funct_state
, heap
) *funct_state_vec
;
114 /* Holders of ipa cgraph hooks: */
115 static struct cgraph_node_hook_list
*function_insertion_hook_holder
;
116 static struct cgraph_2node_hook_list
*node_duplication_hook_holder
;
117 static struct cgraph_node_hook_list
*node_removal_hook_holder
;
119 /* Try to guess if function body will always be visible to compiler
120 when compiling the call and whether compiler will be able
121 to propagate the information by itself. */
124 function_always_visible_to_compiler_p (tree decl
)
126 return (!TREE_PUBLIC (decl
) || DECL_DECLARED_INLINE_P (decl
));
129 /* Emit suggestion about attribute ATTRIB_NAME for DECL. KNOWN_FINITE
130 is true if the function is known to be finite. The diagnostic is
131 controlled by OPTION. WARNED_ABOUT is a pointer_set unique for
132 OPTION, this function may initialize it and it is always returned
135 static struct pointer_set_t
*
136 suggest_attribute (int option
, tree decl
, bool known_finite
,
137 struct pointer_set_t
*warned_about
,
138 const char * attrib_name
)
140 if (!option_enabled (option
, &global_options
))
142 if (TREE_THIS_VOLATILE (decl
)
143 || (known_finite
&& function_always_visible_to_compiler_p (decl
)))
147 warned_about
= pointer_set_create ();
148 if (pointer_set_contains (warned_about
, decl
))
150 pointer_set_insert (warned_about
, decl
);
151 warning_at (DECL_SOURCE_LOCATION (decl
),
154 ? _("function might be candidate for attribute %<%s%>")
155 : _("function might be candidate for attribute %<%s%>"
156 " if it is known to return normally"), attrib_name
);
160 /* Emit suggestion about __attribute_((pure)) for DECL. KNOWN_FINITE
161 is true if the function is known to be finite. */
164 warn_function_pure (tree decl
, bool known_finite
)
166 static struct pointer_set_t
*warned_about
;
169 = suggest_attribute (OPT_Wsuggest_attribute_pure
, decl
,
170 known_finite
, warned_about
, "pure");
173 /* Emit suggestion about __attribute_((const)) for DECL. KNOWN_FINITE
174 is true if the function is known to be finite. */
177 warn_function_const (tree decl
, bool known_finite
)
179 static struct pointer_set_t
*warned_about
;
181 = suggest_attribute (OPT_Wsuggest_attribute_const
, decl
,
182 known_finite
, warned_about
, "const");
186 warn_function_noreturn (tree decl
)
188 static struct pointer_set_t
*warned_about
;
189 if (!lang_hooks
.missing_noreturn_ok_p (decl
))
191 = suggest_attribute (OPT_Wsuggest_attribute_noreturn
, decl
,
192 true, warned_about
, "noreturn");
194 /* Init the function state. */
199 free (funct_state_vec
);
203 /* Return true if we have a function state for NODE. */
206 has_function_state (struct cgraph_node
*node
)
209 || VEC_length (funct_state
, funct_state_vec
) <= (unsigned int)node
->uid
)
211 return VEC_index (funct_state
, funct_state_vec
, node
->uid
) != NULL
;
214 /* Return the function state from NODE. */
216 static inline funct_state
217 get_function_state (struct cgraph_node
*node
)
220 || VEC_length (funct_state
, funct_state_vec
) <= (unsigned int)node
->uid
221 || !VEC_index (funct_state
, funct_state_vec
, node
->uid
))
222 /* We might want to put correct previously_known state into varying. */
223 return &varying_state
;
224 return VEC_index (funct_state
, funct_state_vec
, node
->uid
);
227 /* Set the function state S for NODE. */
230 set_function_state (struct cgraph_node
*node
, funct_state s
)
233 || VEC_length (funct_state
, funct_state_vec
) <= (unsigned int)node
->uid
)
234 VEC_safe_grow_cleared (funct_state
, heap
, funct_state_vec
, node
->uid
+ 1);
235 VEC_replace (funct_state
, funct_state_vec
, node
->uid
, s
);
238 /* Check to see if the use (or definition when CHECKING_WRITE is true)
239 variable T is legal in a function that is either pure or const. */
242 check_decl (funct_state local
,
243 tree t
, bool checking_write
, bool ipa
)
245 /* Do not want to do anything with volatile except mark any
246 function that uses one to be not const or pure. */
247 if (TREE_THIS_VOLATILE (t
))
249 local
->pure_const_state
= IPA_NEITHER
;
251 fprintf (dump_file
, " Volatile operand is not const/pure");
255 /* Do not care about a local automatic that is not static. */
256 if (!TREE_STATIC (t
) && !DECL_EXTERNAL (t
))
259 /* If the variable has the "used" attribute, treat it as if it had a
260 been touched by the devil. */
261 if (DECL_PRESERVE_P (t
))
263 local
->pure_const_state
= IPA_NEITHER
;
265 fprintf (dump_file
, " Used static/global variable is not const/pure\n");
269 /* In IPA mode we are not interested in checking actual loads and stores;
270 they will be processed at propagation time using ipa_ref. */
274 /* Since we have dealt with the locals and params cases above, if we
275 are CHECKING_WRITE, this cannot be a pure or constant
279 local
->pure_const_state
= IPA_NEITHER
;
281 fprintf (dump_file
, " static/global memory write is not const/pure\n");
285 if (DECL_EXTERNAL (t
) || TREE_PUBLIC (t
))
287 /* Readonly reads are safe. */
288 if (TREE_READONLY (t
) && !TYPE_NEEDS_CONSTRUCTING (TREE_TYPE (t
)))
289 return; /* Read of a constant, do not change the function state. */
293 fprintf (dump_file
, " global memory read is not const\n");
294 /* Just a regular read. */
295 if (local
->pure_const_state
== IPA_CONST
)
296 local
->pure_const_state
= IPA_PURE
;
301 /* Compilation level statics can be read if they are readonly
303 if (TREE_READONLY (t
))
307 fprintf (dump_file
, " static memory read is not const\n");
308 /* Just a regular read. */
309 if (local
->pure_const_state
== IPA_CONST
)
310 local
->pure_const_state
= IPA_PURE
;
315 /* Check to see if the use (or definition when CHECKING_WRITE is true)
316 variable T is legal in a function that is either pure or const. */
319 check_op (funct_state local
, tree t
, bool checking_write
)
321 t
= get_base_address (t
);
322 if (t
&& TREE_THIS_VOLATILE (t
))
324 local
->pure_const_state
= IPA_NEITHER
;
326 fprintf (dump_file
, " Volatile indirect ref is not const/pure\n");
330 && (INDIRECT_REF_P (t
) || TREE_CODE (t
) == MEM_REF
)
331 && TREE_CODE (TREE_OPERAND (t
, 0)) == SSA_NAME
332 && !ptr_deref_may_alias_global_p (TREE_OPERAND (t
, 0)))
335 fprintf (dump_file
, " Indirect ref to local memory is OK\n");
338 else if (checking_write
)
340 local
->pure_const_state
= IPA_NEITHER
;
342 fprintf (dump_file
, " Indirect ref write is not const/pure\n");
348 fprintf (dump_file
, " Indirect ref read is not const\n");
349 if (local
->pure_const_state
== IPA_CONST
)
350 local
->pure_const_state
= IPA_PURE
;
354 /* compute state based on ECF FLAGS and store to STATE and LOOPING. */
357 state_from_flags (enum pure_const_state_e
*state
, bool *looping
,
358 int flags
, bool cannot_lead_to_return
)
361 if (flags
& ECF_LOOPING_CONST_OR_PURE
)
364 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
365 fprintf (dump_file
, " looping");
367 if (flags
& ECF_CONST
)
370 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
371 fprintf (dump_file
, " const\n");
373 else if (flags
& ECF_PURE
)
376 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
377 fprintf (dump_file
, " pure\n");
379 else if (cannot_lead_to_return
)
383 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
384 fprintf (dump_file
, " ignoring side effects->pure looping\n");
388 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
389 fprintf (dump_file
, " neihter\n");
390 *state
= IPA_NEITHER
;
395 /* Merge STATE and STATE2 and LOOPING and LOOPING2 and store
396 into STATE and LOOPING better of the two variants.
397 Be sure to merge looping correctly. IPA_NEITHER functions
398 have looping 0 even if they don't have to return. */
401 better_state (enum pure_const_state_e
*state
, bool *looping
,
402 enum pure_const_state_e state2
, bool looping2
)
406 if (*state
== IPA_NEITHER
)
409 *looping
= MIN (*looping
, looping2
);
411 else if (state2
!= IPA_NEITHER
)
412 *looping
= MIN (*looping
, looping2
);
415 /* Merge STATE and STATE2 and LOOPING and LOOPING2 and store
416 into STATE and LOOPING worse of the two variants. */
419 worse_state (enum pure_const_state_e
*state
, bool *looping
,
420 enum pure_const_state_e state2
, bool looping2
)
422 *state
= MAX (*state
, state2
);
423 *looping
= MAX (*looping
, looping2
);
426 /* Recognize special cases of builtins that are by themselves not pure or const
427 but function using them is. */
429 special_builtin_state (enum pure_const_state_e
*state
, bool *looping
,
432 if (DECL_BUILT_IN_CLASS (callee
) == BUILT_IN_NORMAL
)
433 switch (DECL_FUNCTION_CODE (callee
))
435 case BUILT_IN_RETURN
:
436 case BUILT_IN_UNREACHABLE
:
437 case BUILT_IN_ALLOCA
:
438 case BUILT_IN_STACK_SAVE
:
439 case BUILT_IN_STACK_RESTORE
:
440 case BUILT_IN_EH_POINTER
:
441 case BUILT_IN_EH_FILTER
:
442 case BUILT_IN_UNWIND_RESUME
:
443 case BUILT_IN_CXA_END_CLEANUP
:
444 case BUILT_IN_EH_COPY_VALUES
:
445 case BUILT_IN_FRAME_ADDRESS
:
447 case BUILT_IN_APPLY_ARGS
:
451 case BUILT_IN_PREFETCH
:
459 /* Check the parameters of a function call to CALL_EXPR to see if
460 there are any references in the parameters that are not allowed for
461 pure or const functions. Also check to see if this is either an
462 indirect call, a call outside the compilation unit, or has special
463 attributes that may also effect the purity. The CALL_EXPR node for
464 the entire call expression. */
467 check_call (funct_state local
, gimple call
, bool ipa
)
469 int flags
= gimple_call_flags (call
);
470 tree callee_t
= gimple_call_fndecl (call
);
471 bool possibly_throws
= stmt_could_throw_p (call
);
472 bool possibly_throws_externally
= (possibly_throws
473 && stmt_can_throw_external (call
));
478 for (i
= 0; i
< gimple_num_ops (call
); i
++)
479 if (gimple_op (call
, i
)
480 && tree_could_throw_p (gimple_op (call
, i
)))
482 if (possibly_throws
&& cfun
->can_throw_non_call_exceptions
)
485 fprintf (dump_file
, " operand can throw; looping\n");
486 local
->looping
= true;
488 if (possibly_throws_externally
)
491 fprintf (dump_file
, " operand can throw externally\n");
492 local
->can_throw
= true;
497 /* The const and pure flags are set by a variety of places in the
498 compiler (including here). If someone has already set the flags
499 for the callee, (such as for some of the builtins) we will use
500 them, otherwise we will compute our own information.
502 Const and pure functions have less clobber effects than other
503 functions so we process these first. Otherwise if it is a call
504 outside the compilation unit or an indirect call we punt. This
505 leaves local calls which will be processed by following the call
509 enum pure_const_state_e call_state
;
512 if (special_builtin_state (&call_state
, &call_looping
, callee_t
))
514 worse_state (&local
->pure_const_state
, &local
->looping
,
515 call_state
, call_looping
);
518 /* When bad things happen to bad functions, they cannot be const
520 if (setjmp_call_p (callee_t
))
523 fprintf (dump_file
, " setjmp is not const/pure\n");
524 local
->looping
= true;
525 local
->pure_const_state
= IPA_NEITHER
;
528 if (DECL_BUILT_IN_CLASS (callee_t
) == BUILT_IN_NORMAL
)
529 switch (DECL_FUNCTION_CODE (callee_t
))
531 case BUILT_IN_LONGJMP
:
532 case BUILT_IN_NONLOCAL_GOTO
:
534 fprintf (dump_file
, " longjmp and nonlocal goto is not const/pure\n");
535 local
->pure_const_state
= IPA_NEITHER
;
536 local
->looping
= true;
543 /* When not in IPA mode, we can still handle self recursion. */
544 if (!ipa
&& callee_t
== current_function_decl
)
547 fprintf (dump_file
, " Recursive call can loop.\n");
548 local
->looping
= true;
550 /* Either callee is unknown or we are doing local analysis.
551 Look to see if there are any bits available for the callee (such as by
552 declaration or because it is builtin) and process solely on the basis of
556 enum pure_const_state_e call_state
;
558 if (possibly_throws
&& cfun
->can_throw_non_call_exceptions
)
561 fprintf (dump_file
, " can throw; looping\n");
562 local
->looping
= true;
564 if (possibly_throws_externally
)
568 fprintf (dump_file
, " can throw externally to lp %i\n",
569 lookup_stmt_eh_lp (call
));
571 fprintf (dump_file
, " callee:%s\n",
572 IDENTIFIER_POINTER (DECL_ASSEMBLER_NAME (callee_t
)));
574 local
->can_throw
= true;
576 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
577 fprintf (dump_file
, " checking flags for call:");
578 state_from_flags (&call_state
, &call_looping
, flags
,
579 ((flags
& (ECF_NORETURN
| ECF_NOTHROW
))
580 == (ECF_NORETURN
| ECF_NOTHROW
))
581 || (!flag_exceptions
&& (flags
& ECF_NORETURN
)));
582 worse_state (&local
->pure_const_state
, &local
->looping
,
583 call_state
, call_looping
);
585 /* Direct functions calls are handled by IPA propagation. */
588 /* Wrapper around check_decl for loads in local more. */
591 check_load (gimple stmt ATTRIBUTE_UNUSED
, tree op
, void *data
)
594 check_decl ((funct_state
)data
, op
, false, false);
596 check_op ((funct_state
)data
, op
, false);
600 /* Wrapper around check_decl for stores in local more. */
603 check_store (gimple stmt ATTRIBUTE_UNUSED
, tree op
, void *data
)
606 check_decl ((funct_state
)data
, op
, true, false);
608 check_op ((funct_state
)data
, op
, true);
612 /* Wrapper around check_decl for loads in ipa mode. */
615 check_ipa_load (gimple stmt ATTRIBUTE_UNUSED
, tree op
, void *data
)
618 check_decl ((funct_state
)data
, op
, false, true);
620 check_op ((funct_state
)data
, op
, false);
624 /* Wrapper around check_decl for stores in ipa mode. */
627 check_ipa_store (gimple stmt ATTRIBUTE_UNUSED
, tree op
, void *data
)
630 check_decl ((funct_state
)data
, op
, true, true);
632 check_op ((funct_state
)data
, op
, true);
636 /* Look into pointer pointed to by GSIP and figure out what interesting side
639 check_stmt (gimple_stmt_iterator
*gsip
, funct_state local
, bool ipa
)
641 gimple stmt
= gsi_stmt (*gsip
);
643 if (is_gimple_debug (stmt
))
648 fprintf (dump_file
, " scanning: ");
649 print_gimple_stmt (dump_file
, stmt
, 0, 0);
652 if (gimple_has_volatile_ops (stmt
))
654 local
->pure_const_state
= IPA_NEITHER
;
656 fprintf (dump_file
, " Volatile stmt is not const/pure\n");
659 /* Look for loads and stores. */
660 walk_stmt_load_store_ops (stmt
, local
,
661 ipa
? check_ipa_load
: check_load
,
662 ipa
? check_ipa_store
: check_store
);
664 if (gimple_code (stmt
) != GIMPLE_CALL
665 && stmt_could_throw_p (stmt
))
667 if (cfun
->can_throw_non_call_exceptions
)
670 fprintf (dump_file
, " can throw; looping");
671 local
->looping
= true;
673 if (stmt_can_throw_external (stmt
))
676 fprintf (dump_file
, " can throw externally");
677 local
->can_throw
= true;
680 switch (gimple_code (stmt
))
683 check_call (local
, stmt
, ipa
);
686 if (DECL_NONLOCAL (gimple_label_label (stmt
)))
687 /* Target of long jump. */
690 fprintf (dump_file
, " nonlocal label is not const/pure");
691 local
->pure_const_state
= IPA_NEITHER
;
695 if (gimple_asm_clobbers_memory_p (stmt
))
698 fprintf (dump_file
, " memory asm clobber is not const/pure");
699 /* Abandon all hope, ye who enter here. */
700 local
->pure_const_state
= IPA_NEITHER
;
702 if (gimple_asm_volatile_p (stmt
))
705 fprintf (dump_file
, " volatile is not const/pure");
706 /* Abandon all hope, ye who enter here. */
707 local
->pure_const_state
= IPA_NEITHER
;
708 local
->looping
= true;
717 /* This is the main routine for finding the reference patterns for
718 global variables within a function FN. */
721 analyze_function (struct cgraph_node
*fn
, bool ipa
)
723 tree decl
= fn
->decl
;
724 tree old_decl
= current_function_decl
;
726 basic_block this_block
;
728 l
= XCNEW (struct funct_state_d
);
729 l
->pure_const_state
= IPA_CONST
;
730 l
->state_previously_known
= IPA_NEITHER
;
731 l
->looping_previously_known
= true;
733 l
->can_throw
= false;
737 fprintf (dump_file
, "\n\n local analysis of %s\n ",
738 cgraph_node_name (fn
));
741 push_cfun (DECL_STRUCT_FUNCTION (decl
));
742 current_function_decl
= decl
;
744 FOR_EACH_BB (this_block
)
746 gimple_stmt_iterator gsi
;
747 struct walk_stmt_info wi
;
749 memset (&wi
, 0, sizeof(wi
));
750 for (gsi
= gsi_start_bb (this_block
);
754 check_stmt (&gsi
, l
, ipa
);
755 if (l
->pure_const_state
== IPA_NEITHER
&& l
->looping
&& l
->can_throw
)
761 if (l
->pure_const_state
!= IPA_NEITHER
)
763 /* Const functions cannot have back edges (an
764 indication of possible infinite loop side
766 if (mark_dfs_back_edges ())
768 /* Preheaders are needed for SCEV to work.
769 Simple latches and recorded exits improve chances that loop will
770 proved to be finite in testcases such as in loop-15.c and loop-24.c */
771 loop_optimizer_init (LOOPS_NORMAL
772 | LOOPS_HAVE_RECORDED_EXITS
);
773 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
774 flow_loops_dump (dump_file
, NULL
, 0);
775 if (mark_irreducible_loops ())
778 fprintf (dump_file
, " has irreducible loops\n");
786 FOR_EACH_LOOP (li
, loop
, 0)
787 if (!finite_loop_p (loop
))
790 fprintf (dump_file
, " can not prove finiteness of loop %i\n", loop
->num
);
796 loop_optimizer_finalize ();
800 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
801 fprintf (dump_file
, " checking previously known:");
802 state_from_flags (&l
->state_previously_known
, &l
->looping_previously_known
,
803 flags_from_decl_or_type (fn
->decl
),
804 cgraph_node_cannot_return (fn
));
806 better_state (&l
->pure_const_state
, &l
->looping
,
807 l
->state_previously_known
,
808 l
->looping_previously_known
);
809 if (TREE_NOTHROW (decl
))
810 l
->can_throw
= false;
813 current_function_decl
= old_decl
;
817 fprintf (dump_file
, "Function is locally looping.\n");
819 fprintf (dump_file
, "Function is locally throwing.\n");
820 if (l
->pure_const_state
== IPA_CONST
)
821 fprintf (dump_file
, "Function is locally const.\n");
822 if (l
->pure_const_state
== IPA_PURE
)
823 fprintf (dump_file
, "Function is locally pure.\n");
828 /* Called when new function is inserted to callgraph late. */
830 add_new_function (struct cgraph_node
*node
, void *data ATTRIBUTE_UNUSED
)
832 if (cgraph_function_body_availability (node
) < AVAIL_OVERWRITABLE
)
834 /* There are some shared nodes, in particular the initializers on
835 static declarations. We do not need to scan them more than once
836 since all we would be interested in are the addressof
838 visited_nodes
= pointer_set_create ();
839 if (cgraph_function_body_availability (node
) > AVAIL_OVERWRITABLE
)
840 set_function_state (node
, analyze_function (node
, true));
841 pointer_set_destroy (visited_nodes
);
842 visited_nodes
= NULL
;
845 /* Called when new clone is inserted to callgraph late. */
848 duplicate_node_data (struct cgraph_node
*src
, struct cgraph_node
*dst
,
849 void *data ATTRIBUTE_UNUSED
)
851 if (has_function_state (src
))
853 funct_state l
= XNEW (struct funct_state_d
);
854 gcc_assert (!has_function_state (dst
));
855 memcpy (l
, get_function_state (src
), sizeof (*l
));
856 set_function_state (dst
, l
);
860 /* Called when new clone is inserted to callgraph late. */
863 remove_node_data (struct cgraph_node
*node
, void *data ATTRIBUTE_UNUSED
)
865 if (has_function_state (node
))
867 funct_state l
= get_function_state (node
);
868 if (l
!= &varying_state
)
870 set_function_state (node
, NULL
);
876 register_hooks (void)
878 static bool init_p
= false;
885 node_removal_hook_holder
=
886 cgraph_add_node_removal_hook (&remove_node_data
, NULL
);
887 node_duplication_hook_holder
=
888 cgraph_add_node_duplication_hook (&duplicate_node_data
, NULL
);
889 function_insertion_hook_holder
=
890 cgraph_add_function_insertion_hook (&add_new_function
, NULL
);
894 /* Analyze each function in the cgraph to see if it is locally PURE or
898 generate_summary (void)
900 struct cgraph_node
*node
;
904 /* There are some shared nodes, in particular the initializers on
905 static declarations. We do not need to scan them more than once
906 since all we would be interested in are the addressof
908 visited_nodes
= pointer_set_create ();
910 /* Process all of the functions.
912 We process AVAIL_OVERWRITABLE functions. We can not use the results
913 by default, but the info can be used at LTO with -fwhole-program or
914 when function got cloned and the clone is AVAILABLE. */
916 for (node
= cgraph_nodes
; node
; node
= node
->next
)
917 if (cgraph_function_body_availability (node
) >= AVAIL_OVERWRITABLE
)
918 set_function_state (node
, analyze_function (node
, true));
920 pointer_set_destroy (visited_nodes
);
921 visited_nodes
= NULL
;
925 /* Serialize the ipa info for lto. */
928 pure_const_write_summary (cgraph_node_set set
,
929 varpool_node_set vset ATTRIBUTE_UNUSED
)
931 struct cgraph_node
*node
;
932 struct lto_simple_output_block
*ob
933 = lto_create_simple_output_block (LTO_section_ipa_pure_const
);
934 unsigned int count
= 0;
935 cgraph_node_set_iterator csi
;
937 for (csi
= csi_start (set
); !csi_end_p (csi
); csi_next (&csi
))
939 node
= csi_node (csi
);
940 if (node
->analyzed
&& has_function_state (node
))
944 lto_output_uleb128_stream (ob
->main_stream
, count
);
946 /* Process all of the functions. */
947 for (csi
= csi_start (set
); !csi_end_p (csi
); csi_next (&csi
))
949 node
= csi_node (csi
);
950 if (node
->analyzed
&& has_function_state (node
))
955 lto_cgraph_encoder_t encoder
;
957 fs
= get_function_state (node
);
959 encoder
= ob
->decl_state
->cgraph_node_encoder
;
960 node_ref
= lto_cgraph_encoder_encode (encoder
, node
);
961 lto_output_uleb128_stream (ob
->main_stream
, node_ref
);
963 /* Note that flags will need to be read in the opposite
964 order as we are pushing the bitflags into FLAGS. */
965 bp
= bitpack_create (ob
->main_stream
);
966 bp_pack_value (&bp
, fs
->pure_const_state
, 2);
967 bp_pack_value (&bp
, fs
->state_previously_known
, 2);
968 bp_pack_value (&bp
, fs
->looping_previously_known
, 1);
969 bp_pack_value (&bp
, fs
->looping
, 1);
970 bp_pack_value (&bp
, fs
->can_throw
, 1);
971 lto_output_bitpack (&bp
);
975 lto_destroy_simple_output_block (ob
);
979 /* Deserialize the ipa info for lto. */
982 pure_const_read_summary (void)
984 struct lto_file_decl_data
**file_data_vec
= lto_get_file_decl_data ();
985 struct lto_file_decl_data
*file_data
;
989 while ((file_data
= file_data_vec
[j
++]))
993 struct lto_input_block
*ib
994 = lto_create_simple_input_block (file_data
,
995 LTO_section_ipa_pure_const
,
1000 unsigned int count
= lto_input_uleb128 (ib
);
1002 for (i
= 0; i
< count
; i
++)
1005 struct cgraph_node
*node
;
1006 struct bitpack_d bp
;
1008 lto_cgraph_encoder_t encoder
;
1010 fs
= XCNEW (struct funct_state_d
);
1011 index
= lto_input_uleb128 (ib
);
1012 encoder
= file_data
->cgraph_node_encoder
;
1013 node
= lto_cgraph_encoder_deref (encoder
, index
);
1014 set_function_state (node
, fs
);
1016 /* Note that the flags must be read in the opposite
1017 order in which they were written (the bitflags were
1018 pushed into FLAGS). */
1019 bp
= lto_input_bitpack (ib
);
1020 fs
->pure_const_state
1021 = (enum pure_const_state_e
) bp_unpack_value (&bp
, 2);
1022 fs
->state_previously_known
1023 = (enum pure_const_state_e
) bp_unpack_value (&bp
, 2);
1024 fs
->looping_previously_known
= bp_unpack_value (&bp
, 1);
1025 fs
->looping
= bp_unpack_value (&bp
, 1);
1026 fs
->can_throw
= bp_unpack_value (&bp
, 1);
1029 int flags
= flags_from_decl_or_type (node
->decl
);
1030 fprintf (dump_file
, "Read info for %s/%i ",
1031 cgraph_node_name (node
),
1033 if (flags
& ECF_CONST
)
1034 fprintf (dump_file
, " const");
1035 if (flags
& ECF_PURE
)
1036 fprintf (dump_file
, " pure");
1037 if (flags
& ECF_NOTHROW
)
1038 fprintf (dump_file
, " nothrow");
1039 fprintf (dump_file
, "\n pure const state: %s\n",
1040 pure_const_names
[fs
->pure_const_state
]);
1041 fprintf (dump_file
, " previously known state: %s\n",
1042 pure_const_names
[fs
->looping_previously_known
]);
1044 fprintf (dump_file
," function is locally looping\n");
1045 if (fs
->looping_previously_known
)
1046 fprintf (dump_file
," function is previously known looping\n");
1048 fprintf (dump_file
," function is locally throwing\n");
1052 lto_destroy_simple_input_block (file_data
,
1053 LTO_section_ipa_pure_const
,
1061 ignore_edge (struct cgraph_edge
*e
)
1063 return (!e
->can_throw_external
);
1066 /* Return true if NODE is self recursive function. */
1069 self_recursive_p (struct cgraph_node
*node
)
1071 struct cgraph_edge
*e
;
1072 for (e
= node
->callees
; e
; e
= e
->next_callee
)
1073 if (e
->callee
== node
)
1078 /* Produce transitive closure over the callgraph and compute pure/const
1082 propagate_pure_const (void)
1084 struct cgraph_node
*node
;
1085 struct cgraph_node
*w
;
1086 struct cgraph_node
**order
=
1087 XCNEWVEC (struct cgraph_node
*, cgraph_n_nodes
);
1090 struct ipa_dfs_info
* w_info
;
1092 order_pos
= ipa_reduced_postorder (order
, true, false, NULL
);
1095 dump_cgraph (dump_file
);
1096 ipa_print_order(dump_file
, "reduced", order
, order_pos
);
1099 /* Propagate the local information thru the call graph to produce
1100 the global information. All the nodes within a cycle will have
1101 the same info so we collapse cycles first. Then we can do the
1102 propagation in one pass from the leaves to the roots. */
1103 for (i
= 0; i
< order_pos
; i
++ )
1105 enum pure_const_state_e pure_const_state
= IPA_CONST
;
1106 bool looping
= false;
1110 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1111 fprintf (dump_file
, "Starting cycle\n");
1113 /* Find the worst state for any node in the cycle. */
1115 while (w
&& pure_const_state
!= IPA_NEITHER
)
1117 struct cgraph_edge
*e
;
1118 struct cgraph_edge
*ie
;
1120 struct ipa_ref
*ref
;
1122 funct_state w_l
= get_function_state (w
);
1123 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1124 fprintf (dump_file
, " Visiting %s/%i state:%s looping %i\n",
1125 cgraph_node_name (w
),
1127 pure_const_names
[w_l
->pure_const_state
],
1130 /* First merge in function body properties. */
1131 worse_state (&pure_const_state
, &looping
,
1132 w_l
->pure_const_state
, w_l
->looping
);
1133 if (pure_const_state
== IPA_NEITHER
)
1136 /* For overwritable nodes we can not assume anything. */
1137 if (cgraph_function_body_availability (w
) == AVAIL_OVERWRITABLE
)
1139 worse_state (&pure_const_state
, &looping
,
1140 w_l
->state_previously_known
,
1141 w_l
->looping_previously_known
);
1142 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1145 " Overwritable. state %s looping %i\n",
1146 pure_const_names
[w_l
->state_previously_known
],
1147 w_l
->looping_previously_known
);
1154 /* We consider recursive cycles as possibly infinite.
1155 This might be relaxed since infinite recursion leads to stack
1160 /* Now walk the edges and merge in callee properties. */
1161 for (e
= w
->callees
; e
; e
= e
->next_callee
)
1163 struct cgraph_node
*y
= e
->callee
;
1164 enum pure_const_state_e edge_state
= IPA_CONST
;
1165 bool edge_looping
= false;
1167 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1171 cgraph_node_name (e
->callee
),
1174 if (cgraph_function_body_availability (y
) > AVAIL_OVERWRITABLE
)
1176 funct_state y_l
= get_function_state (y
);
1177 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1180 " state:%s looping:%i\n",
1181 pure_const_names
[y_l
->pure_const_state
],
1184 if (y_l
->pure_const_state
> IPA_PURE
1185 && cgraph_edge_cannot_lead_to_return (e
))
1187 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1189 " Ignoring side effects"
1190 " -> pure, looping\n");
1191 edge_state
= IPA_PURE
;
1192 edge_looping
= true;
1196 edge_state
= y_l
->pure_const_state
;
1197 edge_looping
= y_l
->looping
;
1200 else if (special_builtin_state (&edge_state
, &edge_looping
,
1204 state_from_flags (&edge_state
, &edge_looping
,
1205 flags_from_decl_or_type (y
->decl
),
1206 cgraph_edge_cannot_lead_to_return (e
));
1208 /* Merge the results with what we already know. */
1209 better_state (&edge_state
, &edge_looping
,
1210 w_l
->state_previously_known
,
1211 w_l
->looping_previously_known
);
1212 worse_state (&pure_const_state
, &looping
,
1213 edge_state
, edge_looping
);
1214 if (pure_const_state
== IPA_NEITHER
)
1217 if (pure_const_state
== IPA_NEITHER
)
1220 /* Now process the indirect call. */
1221 for (ie
= node
->indirect_calls
; ie
; ie
= ie
->next_callee
)
1223 enum pure_const_state_e edge_state
= IPA_CONST
;
1224 bool edge_looping
= false;
1226 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1227 fprintf (dump_file
, " Indirect call");
1228 state_from_flags (&edge_state
, &edge_looping
,
1229 ie
->indirect_info
->ecf_flags
,
1230 cgraph_edge_cannot_lead_to_return (ie
));
1231 /* Merge the results with what we already know. */
1232 better_state (&edge_state
, &edge_looping
,
1233 w_l
->state_previously_known
,
1234 w_l
->looping_previously_known
);
1235 worse_state (&pure_const_state
, &looping
,
1236 edge_state
, edge_looping
);
1237 if (pure_const_state
== IPA_NEITHER
)
1240 if (pure_const_state
== IPA_NEITHER
)
1243 /* And finally all loads and stores. */
1244 for (i
= 0; ipa_ref_list_reference_iterate (&node
->ref_list
, i
, ref
); i
++)
1246 enum pure_const_state_e ref_state
= IPA_CONST
;
1247 bool ref_looping
= false;
1251 /* readonly reads are safe. */
1252 if (TREE_READONLY (ipa_ref_varpool_node (ref
)->decl
))
1254 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1255 fprintf (dump_file
, " nonreadonly global var read\n");
1256 ref_state
= IPA_PURE
;
1259 if (ipa_ref_cannot_lead_to_return (ref
))
1261 ref_state
= IPA_NEITHER
;
1262 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1263 fprintf (dump_file
, " global var write\n");
1268 better_state (&ref_state
, &ref_looping
,
1269 w_l
->state_previously_known
,
1270 w_l
->looping_previously_known
);
1271 worse_state (&pure_const_state
, &looping
,
1272 ref_state
, ref_looping
);
1273 if (pure_const_state
== IPA_NEITHER
)
1276 w_info
= (struct ipa_dfs_info
*) w
->aux
;
1277 w
= w_info
->next_cycle
;
1279 if (dump_file
&& (dump_flags
& TDF_DETAILS
))
1280 fprintf (dump_file
, "Result %s looping %i\n",
1281 pure_const_names
[pure_const_state
],
1284 /* Copy back the region's pure_const_state which is shared by
1285 all nodes in the region. */
1289 funct_state w_l
= get_function_state (w
);
1290 enum pure_const_state_e this_state
= pure_const_state
;
1291 bool this_looping
= looping
;
1293 if (w_l
->state_previously_known
!= IPA_NEITHER
1294 && this_state
> w_l
->state_previously_known
)
1296 this_state
= w_l
->state_previously_known
;
1297 this_looping
|= w_l
->looping_previously_known
;
1299 if (!this_looping
&& self_recursive_p (w
))
1300 this_looping
= true;
1301 if (!w_l
->looping_previously_known
)
1302 this_looping
= false;
1304 /* All nodes within a cycle share the same info. */
1305 w_l
->pure_const_state
= this_state
;
1306 w_l
->looping
= this_looping
;
1311 if (!TREE_READONLY (w
->decl
))
1313 warn_function_const (w
->decl
, !this_looping
);
1315 fprintf (dump_file
, "Function found to be %sconst: %s\n",
1316 this_looping
? "looping " : "",
1317 cgraph_node_name (w
));
1319 cgraph_set_const_flag (w
, true, this_looping
);
1323 if (!DECL_PURE_P (w
->decl
))
1325 warn_function_pure (w
->decl
, !this_looping
);
1327 fprintf (dump_file
, "Function found to be %spure: %s\n",
1328 this_looping
? "looping " : "",
1329 cgraph_node_name (w
));
1331 cgraph_set_pure_flag (w
, true, this_looping
);
1337 w_info
= (struct ipa_dfs_info
*) w
->aux
;
1338 w
= w_info
->next_cycle
;
1342 ipa_free_postorder_info ();
1346 /* Produce transitive closure over the callgraph and compute nothrow
1350 propagate_nothrow (void)
1352 struct cgraph_node
*node
;
1353 struct cgraph_node
*w
;
1354 struct cgraph_node
**order
=
1355 XCNEWVEC (struct cgraph_node
*, cgraph_n_nodes
);
1358 struct ipa_dfs_info
* w_info
;
1360 order_pos
= ipa_reduced_postorder (order
, true, false, ignore_edge
);
1363 dump_cgraph (dump_file
);
1364 ipa_print_order (dump_file
, "reduced for nothrow", order
, order_pos
);
1367 /* Propagate the local information thru the call graph to produce
1368 the global information. All the nodes within a cycle will have
1369 the same info so we collapse cycles first. Then we can do the
1370 propagation in one pass from the leaves to the roots. */
1371 for (i
= 0; i
< order_pos
; i
++ )
1373 bool can_throw
= false;
1376 /* Find the worst state for any node in the cycle. */
1380 struct cgraph_edge
*e
, *ie
;
1381 funct_state w_l
= get_function_state (w
);
1384 || cgraph_function_body_availability (w
) == AVAIL_OVERWRITABLE
)
1390 for (e
= w
->callees
; e
; e
= e
->next_callee
)
1392 struct cgraph_node
*y
= e
->callee
;
1394 if (cgraph_function_body_availability (y
) > AVAIL_OVERWRITABLE
)
1396 funct_state y_l
= get_function_state (y
);
1400 if (y_l
->can_throw
&& !TREE_NOTHROW (w
->decl
)
1401 && e
->can_throw_external
)
1404 else if (e
->can_throw_external
&& !TREE_NOTHROW (y
->decl
))
1407 for (ie
= node
->indirect_calls
; ie
; ie
= ie
->next_callee
)
1408 if (ie
->can_throw_external
)
1410 w_info
= (struct ipa_dfs_info
*) w
->aux
;
1411 w
= w_info
->next_cycle
;
1414 /* Copy back the region's pure_const_state which is shared by
1415 all nodes in the region. */
1419 funct_state w_l
= get_function_state (w
);
1420 if (!can_throw
&& !TREE_NOTHROW (w
->decl
))
1422 struct cgraph_edge
*e
;
1423 cgraph_set_nothrow_flag (w
, true);
1424 for (e
= w
->callers
; e
; e
= e
->next_caller
)
1425 e
->can_throw_external
= false;
1427 fprintf (dump_file
, "Function found to be nothrow: %s\n",
1428 cgraph_node_name (w
));
1430 else if (can_throw
&& !TREE_NOTHROW (w
->decl
))
1431 w_l
->can_throw
= true;
1432 w_info
= (struct ipa_dfs_info
*) w
->aux
;
1433 w
= w_info
->next_cycle
;
1437 ipa_free_postorder_info ();
1442 /* Produce the global information by preforming a transitive closure
1443 on the local information that was produced by generate_summary. */
1448 struct cgraph_node
*node
;
1450 cgraph_remove_function_insertion_hook (function_insertion_hook_holder
);
1451 cgraph_remove_node_duplication_hook (node_duplication_hook_holder
);
1452 cgraph_remove_node_removal_hook (node_removal_hook_holder
);
1454 /* Nothrow makes more function to not lead to return and improve
1456 propagate_nothrow ();
1457 propagate_pure_const ();
1460 for (node
= cgraph_nodes
; node
; node
= node
->next
)
1461 if (has_function_state (node
))
1462 free (get_function_state (node
));
1463 VEC_free (funct_state
, heap
, funct_state_vec
);
1469 gate_pure_const (void)
1471 return (flag_ipa_pure_const
1472 /* Don't bother doing anything if the program has errors. */
1476 struct ipa_opt_pass_d pass_ipa_pure_const
=
1480 "pure-const", /* name */
1481 gate_pure_const
, /* gate */
1482 propagate
, /* execute */
1485 0, /* static_pass_number */
1486 TV_IPA_PURE_CONST
, /* tv_id */
1487 0, /* properties_required */
1488 0, /* properties_provided */
1489 0, /* properties_destroyed */
1490 0, /* todo_flags_start */
1491 0 /* todo_flags_finish */
1493 generate_summary
, /* generate_summary */
1494 pure_const_write_summary
, /* write_summary */
1495 pure_const_read_summary
, /* read_summary */
1496 NULL
, /* write_optimization_summary */
1497 NULL
, /* read_optimization_summary */
1498 NULL
, /* stmt_fixup */
1500 NULL
, /* function_transform */
1501 NULL
/* variable_transform */
1504 /* Return true if function should be skipped for local pure const analysis. */
1507 skip_function_for_local_pure_const (struct cgraph_node
*node
)
1509 /* Because we do not schedule pass_fixup_cfg over whole program after early optimizations
1510 we must not promote functions that are called by already processed functions. */
1512 if (function_called_by_processed_nodes_p ())
1515 fprintf (dump_file
, "Function called in recursive cycle; ignoring\n");
1518 if (cgraph_function_body_availability (node
) <= AVAIL_OVERWRITABLE
)
1521 fprintf (dump_file
, "Function is not available or overwritable; not analyzing.\n");
1527 /* Simple local pass for pure const discovery reusing the analysis from
1528 ipa_pure_const. This pass is effective when executed together with
1529 other optimization passes in early optimization pass queue. */
1532 local_pure_const (void)
1534 bool changed
= false;
1537 struct cgraph_node
*node
;
1539 node
= cgraph_get_node (current_function_decl
);
1540 skip
= skip_function_for_local_pure_const (node
);
1541 if (!warn_suggest_attribute_const
1542 && !warn_suggest_attribute_pure
1546 l
= analyze_function (node
, false);
1548 /* Do NORETURN discovery. */
1549 if (!skip
&& !TREE_THIS_VOLATILE (current_function_decl
)
1550 && EDGE_COUNT (EXIT_BLOCK_PTR
->preds
) == 0)
1552 warn_function_noreturn (cfun
->decl
);
1554 fprintf (dump_file
, "Function found to be noreturn: %s\n",
1555 lang_hooks
.decl_printable_name (current_function_decl
, 2));
1557 /* Update declaration and reduce profile to executed once. */
1558 TREE_THIS_VOLATILE (current_function_decl
) = 1;
1559 if (node
->frequency
> NODE_FREQUENCY_EXECUTED_ONCE
)
1560 node
->frequency
= NODE_FREQUENCY_EXECUTED_ONCE
;
1565 switch (l
->pure_const_state
)
1568 if (!TREE_READONLY (current_function_decl
))
1570 warn_function_const (current_function_decl
, !l
->looping
);
1573 cgraph_set_const_flag (node
, true, l
->looping
);
1577 fprintf (dump_file
, "Function found to be %sconst: %s\n",
1578 l
->looping
? "looping " : "",
1579 lang_hooks
.decl_printable_name (current_function_decl
,
1582 else if (DECL_LOOPING_CONST_OR_PURE_P (current_function_decl
)
1587 cgraph_set_const_flag (node
, true, false);
1591 fprintf (dump_file
, "Function found to be non-looping: %s\n",
1592 lang_hooks
.decl_printable_name (current_function_decl
,
1598 if (!DECL_PURE_P (current_function_decl
))
1602 cgraph_set_pure_flag (node
, true, l
->looping
);
1605 warn_function_pure (current_function_decl
, !l
->looping
);
1607 fprintf (dump_file
, "Function found to be %spure: %s\n",
1608 l
->looping
? "looping " : "",
1609 lang_hooks
.decl_printable_name (current_function_decl
,
1612 else if (DECL_LOOPING_CONST_OR_PURE_P (current_function_decl
)
1617 cgraph_set_pure_flag (node
, true, false);
1621 fprintf (dump_file
, "Function found to be non-looping: %s\n",
1622 lang_hooks
.decl_printable_name (current_function_decl
,
1630 if (!l
->can_throw
&& !TREE_NOTHROW (current_function_decl
))
1632 struct cgraph_edge
*e
;
1634 cgraph_set_nothrow_flag (node
, true);
1635 for (e
= node
->callers
; e
; e
= e
->next_caller
)
1636 e
->can_throw_external
= false;
1639 fprintf (dump_file
, "Function found to be nothrow: %s\n",
1640 lang_hooks
.decl_printable_name (current_function_decl
,
1645 return execute_fixup_cfg ();
1650 struct gimple_opt_pass pass_local_pure_const
=
1654 "local-pure-const", /* name */
1655 gate_pure_const
, /* gate */
1656 local_pure_const
, /* execute */
1659 0, /* static_pass_number */
1660 TV_IPA_PURE_CONST
, /* tv_id */
1661 0, /* properties_required */
1662 0, /* properties_provided */
1663 0, /* properties_destroyed */
1664 0, /* todo_flags_start */
1665 0 /* todo_flags_finish */