--- /dev/null
+/* Early (pre-RA) rematerialization
+ Copyright (C) 2017 Free Software Foundation, Inc.
+
+This file is part of GCC.
+
+GCC is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free
+Software Foundation; either version 3, or (at your option) any later
+version.
+
+GCC is distributed in the hope that it will be useful, but WITHOUT ANY
+WARRANTY; without even the implied warranty of MERCHANTABILITY or
+FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+for more details.
+
+You should have received a copy of the GNU General Public License
+along with GCC; see the file COPYING3. If not see
+<http://www.gnu.org/licenses/>. */
+
+#include "config.h"
+#include "system.h"
+#include "coretypes.h"
+#include "backend.h"
+#include "rtl.h"
+#include "df.h"
+#include "tree-pass.h"
+#include "memmodel.h"
+#include "emit-rtl.h"
+#include "insn-config.h"
+#include "recog.h"
+/* FIXME: The next two are only needed for gen_move_insn. */
+#include "tree.h"
+#include "expr.h"
+#include "target.h"
+#include "inchash.h"
+#include "rtlhash.h"
+#include "print-rtl.h"
+#include "rtl-iter.h"
+
+/* This pass runs before register allocation and implements an aggressive
+ form of rematerialization. It looks for pseudo registers R of mode M
+ for which:
+
+ (a) there are no call-preserved registers of mode M; and
+ (b) spilling R to the stack is expensive.
+
+ The assumption is that it's better to recompute R after each call instead
+ of spilling it, even if this extends the live ranges of other registers.
+
+ The motivating example for which these conditions hold are AArch64 SVE
+ vectors and predicates. Spilling them to the stack makes the frame
+ variable-sized, which we'd like to avoid if possible. It's also very
+ rare for SVE values to be "naturally" live across a call: usually this
+ happens as a result of CSE or other code motion.
+
+ The pass is split into the following phases:
+
+ Collection phase
+ ================
+
+ First we go through all pseudo registers looking for any that meet
+ the conditions above. For each such register R, we go through each
+ instruction that defines R to see whether any of them are suitable
+ rematerialization candidates. If at least one is, we treat all the
+ instructions that define R as candidates, but record which ones are
+ not in fact suitable. These unsuitable candidates exist only for the
+ sake of calculating reaching definitions (see below).
+
+ A "candidate" is a single instruction that we want to rematerialize
+ and a "candidate register" is a register that is set by at least one
+ candidate.
+
+ Candidate sorting
+ =================
+
+ Next we sort the candidates based on the cfg postorder, so that if
+ candidate C1 uses candidate C2, C1 has a lower index than C2.
+ This is useful when iterating through candidate bitmaps.
+
+ Reaching definition calculation
+ ===============================
+
+ We then compute standard reaching-definition sets for each candidate.
+ Each set specifies which candidates might provide the current definition
+ of a live candidate register.
+
+ From here on, a candidate C is "live" at a point P if the candidate
+ register defined by C is live at P and if C's definition reaches P.
+ An instruction I "uses" a candidate C if I takes the register defined by
+ C as input and if C is one of the reaching definitions of that register.
+
+ Candidate validation and value numbering
+ ========================================
+
+ Next we simultaneously decide which candidates are valid and look
+ for candidates that are equivalent to each other, assigning numbers
+ to each unique candidate value. A candidate C is invalid if:
+
+ (a) C uses an invalid candidate;
+
+ (b) there is a cycle of candidate uses involving C; or
+
+ (c) C takes a candidate register R as input and the reaching
+ definitions of R do not have the same value number.
+
+ We assign a "representative" candidate C to each value number and from
+ here on replace references to other candidates with that value number
+ with references to C. It is then only possible to rematerialize a
+ register R at point P if (after this replacement) there is a single
+ reaching definition of R at P.
+
+ Local phase
+ ===========
+
+ During this phase we go through each block and look for cases in which:
+
+ (a) an instruction I comes between two call instructions CI1 and CI2;
+
+ (b) I uses a candidate register R;
+
+ (c) a candidate C provides the only reaching definition of R; and
+
+ (d) C does not come between CI1 and I.
+
+ We then emit a copy of C after CI1, as well as the transitive closure
+ TC of the candidates used by C. The copies of TC might use the original
+ candidate registers or new temporary registers, depending on circumstances.
+
+ For example, if elsewhere we have:
+
+ C3: R3 <- f3 (...)
+ ...
+ C2: R2 <- f2 (...)
+ ...
+ C1: R1 <- f1 (R2, R3, ...) // uses C2 and C3
+
+ then for a block containing:
+
+ CI1: call
+ ...
+ I: use R1 // uses C1
+ ...
+ CI2: call
+
+ we would emit:
+
+ CI1: call
+ C3': R3' <- f3 (...)
+ C2': R2' <- f2 (...)
+ C1': R1 <- f1 (R2', R3', ...)
+ ...
+ I: use R1
+ ...
+ CI2: call
+
+ where R2' and R3' might be fresh registers. If instead we had:
+
+ CI1: call
+ ...
+ I1: use R1 // uses C1
+ ...
+ I2: use R3 // uses C3
+ ...
+ CI2: call
+
+ we would keep the original R3:
+
+ CI1: call
+ C3': R3 <- f3 (...)
+ C2': R2' <- f2 (...)
+ C1': R1 <- f1 (R2', R3, ...)
+ ...
+ I1: use R1 // uses C1
+ ...
+ I2: use R3 // uses C3
+ ...
+ CI2: call
+
+ We also record the last call in each block (if any) and compute:
+
+ rd_after_call:
+ The set of candidates that either (a) are defined outside the block
+ and are live after the last call or (b) are defined within the block
+ and reach the end of the last call. (We don't track whether the
+ latter values are live or not.)
+
+ required_after_call:
+ The set of candidates that need to be rematerialized after the
+ last call in order to satisfy uses in the block itself.
+
+ required_in:
+ The set of candidates that are live on entry to the block and are
+ used without an intervening call.
+
+ In addition, we compute the initial values of the sets required by
+ the global phase below.
+
+ Global phase
+ ============
+
+ We next compute a maximal solution to the following availability
+ problem:
+
+ available_in:
+ The set of candidates that are live on entry to a block and can
+ be used at that point without rematerialization.
+
+ available_out:
+ The set of candidates that are live on exit from a block and can
+ be used at that point without rematerialization.
+
+ available_locally:
+ The subset of available_out that is due to code in the block itself.
+ It contains candidates that are defined or used in the block and
+ not invalidated by a later call.
+
+ We then go through each block B and look for an appropriate place
+ to insert copies of required_in - available_in. Conceptually we
+ start by placing the copies at the head of B, but then move the
+ copy of a candidate C to predecessors if:
+
+ (a) that seems cheaper;
+
+ (b) there is more than one reaching definition of C's register at
+ the head of B; or
+
+ (c) copying C would clobber a hard register that is live on entry to B.
+
+ Moving a copy of C to a predecessor block PB involves:
+
+ (1) adding C to PB's required_after_call, if PB contains a call; or
+
+ (2) adding C PB's required_in otherwise.
+
+ C is then available on output from each PB and on input to B.
+
+ Once all this is done, we emit instructions for the final required_in
+ and required_after_call sets. */
+
+namespace {
+
+/* An invalid candidate index, used to indicate that there is more than
+ one reaching definition. */
+const unsigned int MULTIPLE_CANDIDATES = -1U;
+
+/* Pass-specific information about one basic block. */
+struct remat_block_info {
+ /* The last call instruction in the block. */
+ rtx_insn *last_call;
+
+ /* The set of candidates that are live on entry to the block. NULL is
+ equivalent to an empty set. */
+ bitmap rd_in;
+
+ /* The set of candidates that are live on exit from the block. This might
+ reuse rd_in. NULL is equivalent to an empty set. */
+ bitmap rd_out;
+
+ /* The subset of RD_OUT that comes from local definitions. NULL is
+ equivalent to an empty set. */
+ bitmap rd_gen;
+
+ /* The set of candidates that the block invalidates (because it defines
+ the register to something else, or because the register's value is
+ no longer important). NULL is equivalent to an empty set. */
+ bitmap rd_kill;
+
+ /* The set of candidates that either (a) are defined outside the block
+ and are live after LAST_CALL or (b) are defined within the block
+ and reach the instruction after LAST_CALL. (We don't track whether
+ the latter values are live or not.)
+
+ Only used if LAST_CALL is nonnull. NULL is equivalent to an
+ empty set. */
+ bitmap rd_after_call;
+
+ /* Candidates that are live and available without rematerialization
+ on entry to the block. NULL is equivalent to an empty set. */
+ bitmap available_in;
+
+ /* Candidates that become available without rematerialization within the
+ block, and remain so on exit. NULL is equivalent to an empty set. */
+ bitmap available_locally;
+
+ /* Candidates that are available without rematerialization on exit from
+ the block. This might reuse available_in or available_locally. */
+ bitmap available_out;
+
+ /* Candidates that need to be rematerialized either at the start of the
+ block or before entering the block. */
+ bitmap required_in;
+
+ /* Candidates that need to be rematerialized after LAST_CALL.
+ Only used if LAST_CALL is nonnull. */
+ bitmap required_after_call;
+
+ /* The number of candidates in the block. */
+ unsigned int num_candidates;
+
+ /* The earliest candidate in the block (i.e. the one with the
+ highest index). Only valid if NUM_CANDIDATES is nonzero. */
+ unsigned int first_candidate;
+
+ /* The best (lowest) execution frequency for rematerializing REQUIRED_IN.
+ This is the execution frequency of the block if LOCAL_REMAT_CHEAPER_P,
+ otherwise it is the sum of the execution frequencies of whichever
+ predecessor blocks would do the rematerialization. */
+ int remat_frequency;
+
+ /* True if the block ends with an abnormal call. */
+ unsigned int abnormal_call_p : 1;
+
+ /* Used to record whether a graph traversal has visited this block. */
+ unsigned int visited_p : 1;
+
+ /* True if we have calculated REMAT_FREQUENCY. */
+ unsigned int remat_frequency_valid_p : 1;
+
+ /* True if it is cheaper to rematerialize candidates at the start of
+ the block, rather than moving them to predecessor blocks. */
+ unsigned int local_remat_cheaper_p : 1;
+};
+
+/* Information about a group of candidates with the same value number. */
+struct remat_equiv_class {
+ /* The candidates that have the same value number. */
+ bitmap members;
+
+ /* The candidate that was first added to MEMBERS. */
+ unsigned int earliest;
+
+ /* The candidate that represents the others. This is always the one
+ with the highest index. */
+ unsigned int representative;
+};
+
+/* Information about an instruction that we might want to rematerialize. */
+struct remat_candidate {
+ /* The pseudo register that the instruction sets. */
+ unsigned int regno;
+
+ /* A temporary register used when rematerializing uses of this candidate,
+ if REGNO doesn't have the right value or isn't worth using. */
+ unsigned int copy_regno;
+
+ /* True if we intend to rematerialize this instruction by emitting
+ a move of a constant into REGNO, false if we intend to emit a
+ copy of the original instruction. */
+ unsigned int constant_p : 1;
+
+ /* True if we still think it's possible to rematerialize INSN. */
+ unsigned int can_copy_p : 1;
+
+ /* Used to record whether a graph traversal has visited this candidate. */
+ unsigned int visited_p : 1;
+
+ /* True if we have verified that it's possible to rematerialize INSN.
+ Once this is true, both it and CAN_COPY_P remain true. */
+ unsigned int validated_p : 1;
+
+ /* True if we have "stabilized" INSN, i.e. ensured that all non-candidate
+ registers read by INSN will have the same value when rematerializing INSN.
+ Only ever true if CAN_COPY_P. */
+ unsigned int stabilized_p : 1;
+
+ /* Hash value used for value numbering. */
+ hashval_t hash;
+
+ /* The instruction that sets REGNO. */
+ rtx_insn *insn;
+
+ /* If CONSTANT_P, the value that should be moved into REGNO when
+ rematerializing, otherwise the pattern of the instruction that
+ should be used. */
+ rtx remat_rtx;
+
+ /* The set of candidates that INSN takes as input. NULL is equivalent
+ to the empty set. All candidates in this set have a higher index
+ than the current candidate. */
+ bitmap uses;
+
+ /* The set of hard registers that would be clobbered by rematerializing
+ the candidate, including (transitively) all those that would be
+ clobbered by rematerializing USES. */
+ bitmap clobbers;
+
+ /* The equivalence class to which the candidate belongs, or null if none. */
+ remat_equiv_class *equiv_class;
+};
+
+/* Hash functions used for value numbering. */
+struct remat_candidate_hasher : nofree_ptr_hash <remat_candidate>
+{
+ typedef value_type compare_type;
+ static hashval_t hash (const remat_candidate *);
+ static bool equal (const remat_candidate *, const remat_candidate *);
+};
+
+/* Main class for this pass. */
+class early_remat {
+public:
+ early_remat (function *, sbitmap);
+ ~early_remat ();
+
+ void run (void);
+
+private:
+ bitmap alloc_bitmap (void);
+ bitmap get_bitmap (bitmap *);
+ void init_temp_bitmap (bitmap *);
+ void copy_temp_bitmap (bitmap *, bitmap *);
+
+ void dump_insn_id (rtx_insn *);
+ void dump_candidate_bitmap (bitmap);
+ void dump_all_candidates (void);
+ void dump_edge_list (basic_block, bool);
+ void dump_block_info (basic_block);
+ void dump_all_blocks (void);
+
+ bool interesting_regno_p (unsigned int);
+ remat_candidate *add_candidate (rtx_insn *, unsigned int, bool);
+ bool maybe_add_candidate (rtx_insn *, unsigned int);
+ bool collect_candidates (void);
+ void init_block_info (void);
+ void sort_candidates (void);
+ void finalize_candidate_indices (void);
+ void record_equiv_candidates (unsigned int, unsigned int);
+ static bool rd_confluence_n (edge);
+ static bool rd_transfer (int);
+ void compute_rd (void);
+ unsigned int canon_candidate (unsigned int);
+ void canon_bitmap (bitmap *);
+ unsigned int resolve_reaching_def (bitmap);
+ bool check_candidate_uses (unsigned int);
+ void compute_clobbers (unsigned int);
+ void assign_value_number (unsigned int);
+ void decide_candidate_validity (void);
+ bool stable_use_p (unsigned int);
+ void emit_copy_before (unsigned int, rtx, rtx);
+ void stabilize_pattern (unsigned int);
+ void replace_dest_with_copy (unsigned int);
+ void stabilize_candidate_uses (unsigned int, bitmap, bitmap, bitmap,
+ bitmap);
+ void emit_remat_insns (bitmap, bitmap, bitmap, rtx_insn *);
+ bool set_available_out (remat_block_info *);
+ void process_block (basic_block);
+ void local_phase (void);
+ static bool avail_confluence_n (edge);
+ static bool avail_transfer (int);
+ void compute_availability (void);
+ void unshare_available_sets (remat_block_info *);
+ bool can_move_across_edge_p (edge);
+ bool local_remat_cheaper_p (unsigned int);
+ bool need_to_move_candidate_p (unsigned int, unsigned int);
+ void compute_minimum_move_set (unsigned int, bitmap);
+ void move_to_predecessors (unsigned int, bitmap, bitmap);
+ void choose_rematerialization_points (void);
+ void emit_remat_insns_for_block (basic_block);
+ void global_phase (void);
+
+ /* The function that we're optimizing. */
+ function *m_fn;
+
+ /* The modes that we want to rematerialize. */
+ sbitmap m_selected_modes;
+
+ /* All rematerialization candidates, identified by their index into the
+ vector. */
+ auto_vec<remat_candidate> m_candidates;
+
+ /* The set of candidate registers. */
+ bitmap_head m_candidate_regnos;
+
+ /* Temporary sets. */
+ bitmap_head m_tmp_bitmap;
+ bitmap m_available;
+ bitmap m_required;
+
+ /* Information about each basic block. */
+ auto_vec<remat_block_info> m_block_info;
+
+ /* A mapping from register numbers to the set of associated candidates.
+ Only valid for registers in M_CANDIDATE_REGNOS. */
+ auto_vec<bitmap> m_regno_to_candidates;
+
+ /* An obstack used for allocating bitmaps, so that we can free them all
+ in one go. */
+ bitmap_obstack m_obstack;
+
+ /* A hash table of candidates used for value numbering. If a candidate
+ in the table is in an equivalence class, the candidate is marked as
+ the earliest member of the class. */
+ hash_table<remat_candidate_hasher> m_value_table;
+
+ /* Used temporarily by callback functions. */
+ static early_remat *er;
+};
+
+}
+
+early_remat *early_remat::er;
+
+/* rtx_equal_p_cb callback that treats any two SCRATCHes as equal.
+ This allows us to compare two copies of a pattern, even though their
+ SCRATCHes are always distinct. */
+
+static int
+scratch_equal (const_rtx *x, const_rtx *y, rtx *nx, rtx *ny)
+{
+ if (GET_CODE (*x) == SCRATCH && GET_CODE (*y) == SCRATCH)
+ {
+ *nx = const0_rtx;
+ *ny = const0_rtx;
+ return 1;
+ }
+ return 0;
+}
+
+/* Hash callback functions for remat_candidate. */
+
+hashval_t
+remat_candidate_hasher::hash (const remat_candidate *cand)
+{
+ return cand->hash;
+}
+
+bool
+remat_candidate_hasher::equal (const remat_candidate *cand1,
+ const remat_candidate *cand2)
+{
+ return (cand1->regno == cand2->regno
+ && cand1->constant_p == cand2->constant_p
+ && (cand1->constant_p
+ ? rtx_equal_p (cand1->remat_rtx, cand2->remat_rtx)
+ : rtx_equal_p_cb (cand1->remat_rtx, cand2->remat_rtx,
+ scratch_equal))
+ && (!cand1->uses || bitmap_equal_p (cand1->uses, cand2->uses)));
+}
+
+/* Return true if B is null or empty. */
+
+inline bool
+empty_p (bitmap b)
+{
+ return !b || bitmap_empty_p (b);
+}
+
+/* Allocate a new bitmap. It will be automatically freed at the end of
+ the pass. */
+
+inline bitmap
+early_remat::alloc_bitmap (void)
+{
+ return bitmap_alloc (&m_obstack);
+}
+
+/* Initialize *PTR to an empty bitmap if it is currently null. */
+
+inline bitmap
+early_remat::get_bitmap (bitmap *ptr)
+{
+ if (!*ptr)
+ *ptr = alloc_bitmap ();
+ return *ptr;
+}
+
+/* *PTR is either null or empty. If it is null, initialize it to an
+ empty bitmap. */
+
+inline void
+early_remat::init_temp_bitmap (bitmap *ptr)
+{
+ if (!*ptr)
+ *ptr = alloc_bitmap ();
+ else
+ gcc_checking_assert (bitmap_empty_p (*ptr));
+}
+
+/* Move *SRC to *DEST and leave *SRC empty. */
+
+inline void
+early_remat::copy_temp_bitmap (bitmap *dest, bitmap *src)
+{
+ if (!empty_p (*src))
+ {
+ *dest = *src;
+ *src = NULL;
+ }
+ else
+ *dest = NULL;
+}
+
+/* Print INSN's identifier to the dump file. */
+
+void
+early_remat::dump_insn_id (rtx_insn *insn)
+{
+ fprintf (dump_file, "%d[bb:%d]", INSN_UID (insn),
+ BLOCK_FOR_INSN (insn)->index);
+}
+
+/* Print candidate set CANDIDATES to the dump file, with a leading space. */
+
+void
+early_remat::dump_candidate_bitmap (bitmap candidates)
+{
+ if (empty_p (candidates))
+ {
+ fprintf (dump_file, " none");
+ return;
+ }
+
+ unsigned int cand_index;
+ bitmap_iterator bi;
+ EXECUTE_IF_SET_IN_BITMAP (candidates, 0, cand_index, bi)
+ fprintf (dump_file, " %d", cand_index);
+}
+
+/* Print information about all candidates to the dump file. */
+
+void
+early_remat::dump_all_candidates (void)
+{
+ fprintf (dump_file, "\n;; Candidates:\n;;\n");
+ fprintf (dump_file, ";; %5s %5s %8s %s\n", "#", "reg", "mode", "insn");
+ fprintf (dump_file, ";; %5s %5s %8s %s\n", "=", "===", "====", "====");
+ unsigned int cand_index;
+ remat_candidate *cand;
+ FOR_EACH_VEC_ELT (m_candidates, cand_index, cand)
+ {
+ fprintf (dump_file, ";; %5d %5d %8s ", cand_index, cand->regno,
+ GET_MODE_NAME (GET_MODE (regno_reg_rtx[cand->regno])));
+ dump_insn_id (cand->insn);
+ if (!cand->can_copy_p)
+ fprintf (dump_file, " -- can't copy");
+ fprintf (dump_file, "\n");
+ }
+
+ fprintf (dump_file, "\n;; Register-to-candidate mapping:\n;;\n");
+ unsigned int regno;
+ bitmap_iterator bi;
+ EXECUTE_IF_SET_IN_BITMAP (&m_candidate_regnos, 0, regno, bi)
+ {
+ fprintf (dump_file, ";; %5d:", regno);
+ dump_candidate_bitmap (m_regno_to_candidates[regno]);
+ fprintf (dump_file, "\n");
+ }
+}
+
+/* Print the predecessors or successors of BB to the dump file, with a
+ leading space. DO_SUCC is true to print successors and false to print
+ predecessors. */
+
+void
+early_remat::dump_edge_list (basic_block bb, bool do_succ)
+{
+ edge e;
+ edge_iterator ei;
+ FOR_EACH_EDGE (e, ei, do_succ ? bb->succs : bb->preds)
+ dump_edge_info (dump_file, e, 0, do_succ);
+}
+
+/* Print information about basic block BB to the dump file. */
+
+void
+early_remat::dump_block_info (basic_block bb)
+{
+ remat_block_info *info = &m_block_info[bb->index];
+ fprintf (dump_file, ";;\n;; Block %d:", bb->index);
+ int width = 25;
+
+ fprintf (dump_file, "\n;;%*s:", width, "predecessors");
+ dump_edge_list (bb, false);
+
+ fprintf (dump_file, "\n;;%*s:", width, "successors");
+ dump_edge_list (bb, true);
+
+ fprintf (dump_file, "\n;;%*s: %d", width, "frequency",
+ bb->count.to_frequency (m_fn));
+
+ if (info->last_call)
+ fprintf (dump_file, "\n;;%*s: %d", width, "last call",
+ INSN_UID (info->last_call));
+
+ if (!empty_p (info->rd_in))
+ {
+ fprintf (dump_file, "\n;;%*s:", width, "RD in");
+ dump_candidate_bitmap (info->rd_in);
+ }
+ if (!empty_p (info->rd_kill))
+ {
+ fprintf (dump_file, "\n;;%*s:", width, "RD kill");
+ dump_candidate_bitmap (info->rd_kill);
+ }
+ if (!empty_p (info->rd_gen))
+ {
+ fprintf (dump_file, "\n;;%*s:", width, "RD gen");
+ dump_candidate_bitmap (info->rd_gen);
+ }
+ if (!empty_p (info->rd_after_call))
+ {
+ fprintf (dump_file, "\n;;%*s:", width, "RD after call");
+ dump_candidate_bitmap (info->rd_after_call);
+ }
+ if (!empty_p (info->rd_out))
+ {
+ fprintf (dump_file, "\n;;%*s:", width, "RD out");
+ if (info->rd_in == info->rd_out)
+ fprintf (dump_file, " RD in");
+ else
+ dump_candidate_bitmap (info->rd_out);
+ }
+ if (!empty_p (info->available_in))
+ {
+ fprintf (dump_file, "\n;;%*s:", width, "available in");
+ dump_candidate_bitmap (info->available_in);
+ }
+ if (!empty_p (info->available_locally))
+ {
+ fprintf (dump_file, "\n;;%*s:", width, "available locally");
+ dump_candidate_bitmap (info->available_locally);
+ }
+ if (!empty_p (info->available_out))
+ {
+ fprintf (dump_file, "\n;;%*s:", width, "available out");
+ if (info->available_in == info->available_out)
+ fprintf (dump_file, " available in");
+ else if (info->available_locally == info->available_out)
+ fprintf (dump_file, " available locally");
+ else
+ dump_candidate_bitmap (info->available_out);
+ }
+ if (!empty_p (info->required_in))
+ {
+ fprintf (dump_file, "\n;;%*s:", width, "required in");
+ dump_candidate_bitmap (info->required_in);
+ }
+ if (!empty_p (info->required_after_call))
+ {
+ fprintf (dump_file, "\n;;%*s:", width, "required after call");
+ dump_candidate_bitmap (info->required_after_call);
+ }
+ fprintf (dump_file, "\n");
+}
+
+/* Print information about all basic blocks to the dump file. */
+
+void
+early_remat::dump_all_blocks (void)
+{
+ basic_block bb;
+ FOR_EACH_BB_FN (bb, m_fn)
+ dump_block_info (bb);
+}
+
+/* Return true if REGNO is worth rematerializing. */
+
+bool
+early_remat::interesting_regno_p (unsigned int regno)
+{
+ /* Ignore unused registers. */
+ rtx reg = regno_reg_rtx[regno];
+ if (!reg || DF_REG_DEF_COUNT (regno) == 0)
+ return false;
+
+ /* Make sure the register has a mode that we want to rematerialize. */
+ if (!bitmap_bit_p (m_selected_modes, GET_MODE (reg)))
+ return false;
+
+ /* Ignore values that might sometimes be used uninitialized. We could
+ instead add dummy candidates for the entry block definition, and so
+ handle uses that are definitely not uninitialized, but the combination
+ of the two should be rare in practice. */
+ if (bitmap_bit_p (DF_LR_OUT (ENTRY_BLOCK_PTR_FOR_FN (m_fn)), regno))
+ return false;
+
+ return true;
+}
+
+/* Record the set of register REGNO in instruction INSN as a
+ rematerialization candidate. CAN_COPY_P is true unless we already
+ know that rematerialization is impossible (in which case the candidate
+ only exists for the reaching definition calculation).
+
+ The candidate's index is not fixed at this stage. */
+
+remat_candidate *
+early_remat::add_candidate (rtx_insn *insn, unsigned int regno,
+ bool can_copy_p)
+{
+ remat_candidate cand;
+ memset (&cand, 0, sizeof (cand));
+ cand.regno = regno;
+ cand.insn = insn;
+ cand.remat_rtx = PATTERN (insn);
+ cand.can_copy_p = can_copy_p;
+ m_candidates.safe_push (cand);
+
+ bitmap_set_bit (&m_candidate_regnos, regno);
+
+ return &m_candidates.last ();
+}
+
+/* Return true if we can rematerialize the set of register REGNO in
+ instruction INSN, and add it as a candidate if so. When returning
+ false, print the reason to the dump file. */
+
+bool
+early_remat::maybe_add_candidate (rtx_insn *insn, unsigned int regno)
+{
+#define FAILURE_FORMAT ";; Can't rematerialize set of reg %d in %d[bb:%d]: "
+#define FAILURE_ARGS regno, INSN_UID (insn), BLOCK_FOR_INSN (insn)->index
+
+ /* The definition must come from an ordinary instruction. */
+ basic_block bb = BLOCK_FOR_INSN (insn);
+ if (!NONJUMP_INSN_P (insn)
+ || (insn == BB_END (bb)
+ && has_abnormal_or_eh_outgoing_edge_p (bb)))
+ {
+ if (dump_file)
+ fprintf (dump_file, FAILURE_FORMAT "insn alters control flow\n",
+ FAILURE_ARGS);
+ return false;
+ }
+
+ /* Prefer to rematerialize constants directly -- it's much easier. */
+ machine_mode mode = GET_MODE (regno_reg_rtx[regno]);
+ if (rtx note = find_reg_equal_equiv_note (insn))
+ {
+ rtx val = XEXP (note, 0);
+ if (CONSTANT_P (val)
+ && targetm.legitimate_constant_p (mode, val))
+ {
+ remat_candidate *cand = add_candidate (insn, regno, true);
+ cand->constant_p = true;
+ cand->remat_rtx = val;
+ return true;
+ }
+ }
+
+ /* See whether the target has reasons to prevent a copy. */
+ if (targetm.cannot_copy_insn_p && targetm.cannot_copy_insn_p (insn))
+ {
+ if (dump_file)
+ fprintf (dump_file, FAILURE_FORMAT "target forbids copying\n",
+ FAILURE_ARGS);
+ return false;
+ }
+
+ /* We can't copy trapping instructions. */
+ rtx pat = PATTERN (insn);
+ if (may_trap_p (pat))
+ {
+ if (dump_file)
+ fprintf (dump_file, FAILURE_FORMAT "insn might trap\n", FAILURE_ARGS);
+ return false;
+ }
+
+ /* We can't copy instructions that read memory, unless we know that
+ the contents never change. */
+ subrtx_iterator::array_type array;
+ FOR_EACH_SUBRTX (iter, array, pat, ALL)
+ if (MEM_P (*iter) && !MEM_READONLY_P (*iter))
+ {
+ if (dump_file)
+ fprintf (dump_file, FAILURE_FORMAT "insn references non-constant"
+ " memory\n", FAILURE_ARGS);
+ return false;
+ }
+
+ /* Check each defined register. */
+ df_ref ref;
+ FOR_EACH_INSN_DEF (ref, insn)
+ {
+ unsigned int def_regno = DF_REF_REGNO (ref);
+ if (def_regno == regno)
+ {
+ /* Make sure the definition is write-only. (Partial definitions,
+ such as setting the low part and clobbering the high part,
+ are otherwise OK.) */
+ if (DF_REF_FLAGS_IS_SET (ref, DF_REF_READ_WRITE))
+ {
+ if (dump_file)
+ fprintf (dump_file, FAILURE_FORMAT "destination is"
+ " read-modify-write\n", FAILURE_ARGS);
+ return false;
+ }
+ }
+ else
+ {
+ /* The instruction can set additional registers, provided that
+ they're call-clobbered hard registers. This is useful for
+ instructions that alter the condition codes. */
+ if (!HARD_REGISTER_NUM_P (def_regno))
+ {
+ if (dump_file)
+ fprintf (dump_file, FAILURE_FORMAT "insn also sets"
+ " pseudo reg %d\n", FAILURE_ARGS, def_regno);
+ return false;
+ }
+ if (global_regs[def_regno])
+ {
+ if (dump_file)
+ fprintf (dump_file, FAILURE_FORMAT "insn also sets"
+ " global reg %d\n", FAILURE_ARGS, def_regno);
+ return false;
+ }
+ if (!TEST_HARD_REG_BIT (regs_invalidated_by_call, def_regno))
+ {
+ if (dump_file)
+ fprintf (dump_file, FAILURE_FORMAT "insn also sets"
+ " call-preserved reg %d\n", FAILURE_ARGS, def_regno);
+ return false;
+ }
+ }
+ }
+
+ /* If the instruction uses fixed hard registers, check that those
+ registers have the same value throughout the function. If the
+ instruction uses non-fixed hard registers, check that we can
+ replace them with pseudos. */
+ FOR_EACH_INSN_USE (ref, insn)
+ {
+ unsigned int use_regno = DF_REF_REGNO (ref);
+ if (HARD_REGISTER_NUM_P (use_regno) && fixed_regs[use_regno])
+ {
+ if (rtx_unstable_p (DF_REF_REAL_REG (ref)))
+ {
+ if (dump_file)
+ fprintf (dump_file, FAILURE_FORMAT "insn uses fixed hard reg"
+ " %d\n", FAILURE_ARGS, use_regno);
+ return false;
+ }
+ }
+ else if (HARD_REGISTER_NUM_P (use_regno))
+ {
+ /* Allocate a dummy pseudo register and temporarily install it.
+ Make the register number depend on the mode, which should
+ provide enough sharing for match_dup while also weeding
+ out cases in which operands with different modes are
+ explicitly tied. */
+ rtx *loc = DF_REF_REAL_LOC (ref);
+ unsigned int size = RTX_CODE_SIZE (REG);
+ rtx new_reg = (rtx) alloca (size);
+ memset (new_reg, 0, size);
+ PUT_CODE (new_reg, REG);
+ set_mode_and_regno (new_reg, GET_MODE (*loc),
+ LAST_VIRTUAL_REGISTER + 1 + GET_MODE (*loc));
+ validate_change (insn, loc, new_reg, 1);
+ }
+ }
+ bool ok_p = verify_changes (0);
+ cancel_changes (0);
+ if (!ok_p)
+ {
+ if (dump_file)
+ fprintf (dump_file, FAILURE_FORMAT "insn does not allow hard"
+ " register inputs to be replaced\n", FAILURE_ARGS);
+ return false;
+ }
+
+#undef FAILURE_ARGS
+#undef FAILURE_FORMAT
+
+ add_candidate (insn, regno, true);
+ return true;
+}
+
+/* Calculate the set of rematerialization candidates. Return true if
+ we find at least one. */
+
+bool
+early_remat::collect_candidates (void)
+{
+ unsigned int nregs = DF_REG_SIZE (df);
+ for (unsigned int regno = FIRST_PSEUDO_REGISTER; regno < nregs; ++regno)
+ if (interesting_regno_p (regno))
+ {
+ /* Create candidates for all suitable definitions. */
+ bitmap_clear (&m_tmp_bitmap);
+ unsigned int bad = 0;
+ unsigned int id = 0;
+ for (df_ref ref = DF_REG_DEF_CHAIN (regno); ref;
+ ref = DF_REF_NEXT_REG (ref))
+ {
+ rtx_insn *insn = DF_REF_INSN (ref);
+ if (maybe_add_candidate (insn, regno))
+ bitmap_set_bit (&m_tmp_bitmap, id);
+ else
+ bad += 1;
+ id += 1;
+ }
+
+ /* If we found at least one suitable definition, add dummy
+ candidates for the rest, so that we can see which definitions
+ are live where. */
+ if (!bitmap_empty_p (&m_tmp_bitmap) && bad)
+ {
+ id = 0;
+ for (df_ref ref = DF_REG_DEF_CHAIN (regno); ref;
+ ref = DF_REF_NEXT_REG (ref))
+ {
+ if (!bitmap_bit_p (&m_tmp_bitmap, id))
+ add_candidate (DF_REF_INSN (ref), regno, false);
+ id += 1;
+ }
+ }
+ }
+
+
+ return !m_candidates.is_empty ();
+}
+
+/* Initialize the m_block_info array. */
+
+void
+early_remat::init_block_info (void)
+{
+ unsigned int n_blocks = last_basic_block_for_fn (m_fn);
+ m_block_info.safe_grow_cleared (n_blocks);
+}
+
+/* Maps basic block indices to their position in the post order. */
+static unsigned int *postorder_index;
+
+/* Order remat_candidates X_IN and Y_IN according to the cfg postorder. */
+
+static int
+compare_candidates (const void *x_in, const void *y_in)
+{
+ const remat_candidate *x = (const remat_candidate *) x_in;
+ const remat_candidate *y = (const remat_candidate *) y_in;
+ basic_block x_bb = BLOCK_FOR_INSN (x->insn);
+ basic_block y_bb = BLOCK_FOR_INSN (y->insn);
+ if (x_bb != y_bb)
+ /* Make X and Y follow block postorder. */
+ return postorder_index[x_bb->index] - postorder_index[y_bb->index];
+
+ /* Make X and Y follow a backward traversal of the containing block. */
+ return DF_INSN_LUID (y->insn) - DF_INSN_LUID (x->insn);
+}
+
+/* Sort the collected rematerialization candidates so that they follow
+ cfg postorder. */
+
+void
+early_remat::sort_candidates (void)
+{
+ /* Make sure the DF LUIDs are up-to-date for all the blocks we
+ care about. */
+ bitmap_clear (&m_tmp_bitmap);
+ unsigned int cand_index;
+ remat_candidate *cand;
+ FOR_EACH_VEC_ELT (m_candidates, cand_index, cand)
+ {
+ basic_block bb = BLOCK_FOR_INSN (cand->insn);
+ if (bitmap_set_bit (&m_tmp_bitmap, bb->index))
+ df_recompute_luids (bb);
+ }
+
+ /* Create a mapping from block numbers to their position in the
+ postorder. */
+ unsigned int n_blocks = last_basic_block_for_fn (m_fn);
+ int *postorder = df_get_postorder (DF_BACKWARD);
+ unsigned int postorder_len = df_get_n_blocks (DF_BACKWARD);
+ postorder_index = new unsigned int[n_blocks];
+ for (unsigned int i = 0; i < postorder_len; ++i)
+ postorder_index[postorder[i]] = i;
+
+ m_candidates.qsort (compare_candidates);
+
+ delete postorder_index;
+}
+
+/* Commit to the current candidate indices and initialize cross-references. */
+
+void
+early_remat::finalize_candidate_indices (void)
+{
+ /* Create a bitmap for each candidate register. */
+ m_regno_to_candidates.safe_grow (max_reg_num ());
+ unsigned int regno;
+ bitmap_iterator bi;
+ EXECUTE_IF_SET_IN_BITMAP (&m_candidate_regnos, 0, regno, bi)
+ m_regno_to_candidates[regno] = alloc_bitmap ();
+
+ /* Go through each candidate and record its index. */
+ unsigned int cand_index;
+ remat_candidate *cand;
+ FOR_EACH_VEC_ELT (m_candidates, cand_index, cand)
+ {
+ basic_block bb = BLOCK_FOR_INSN (cand->insn);
+ remat_block_info *info = &m_block_info[bb->index];
+ info->num_candidates += 1;
+ info->first_candidate = cand_index;
+ bitmap_set_bit (m_regno_to_candidates[cand->regno], cand_index);
+ }
+}
+
+/* Record that candidates CAND1_INDEX and CAND2_INDEX are equivalent.
+ CAND1_INDEX might already have an equivalence class, but CAND2_INDEX
+ doesn't. */
+
+void
+early_remat::record_equiv_candidates (unsigned int cand1_index,
+ unsigned int cand2_index)
+{
+ if (dump_file)
+ fprintf (dump_file, ";; Candidate %d is equivalent to candidate %d\n",
+ cand2_index, cand1_index);
+
+ remat_candidate *cand1 = &m_candidates[cand1_index];
+ remat_candidate *cand2 = &m_candidates[cand2_index];
+ gcc_checking_assert (!cand2->equiv_class);
+
+ remat_equiv_class *ec = cand1->equiv_class;
+ if (!ec)
+ {
+ ec = XOBNEW (&m_obstack.obstack, remat_equiv_class);
+ ec->members = alloc_bitmap ();
+ bitmap_set_bit (ec->members, cand1_index);
+ ec->earliest = cand1_index;
+ ec->representative = cand1_index;
+ cand1->equiv_class = ec;
+ }
+ cand1 = &m_candidates[ec->representative];
+ cand2->equiv_class = ec;
+ bitmap_set_bit (ec->members, cand2_index);
+ if (cand2_index > ec->representative)
+ ec->representative = cand2_index;
+}
+
+/* Propagate information from the rd_out set of E->src to the rd_in set
+ of E->dest, when computing global reaching definitions. Return true
+ if something changed. */
+
+bool
+early_remat::rd_confluence_n (edge e)
+{
+ remat_block_info *src = &er->m_block_info[e->src->index];
+ remat_block_info *dest = &er->m_block_info[e->dest->index];
+
+ /* available_in temporarily contains the set of candidates whose
+ registers are live on entry. */
+ if (empty_p (src->rd_out) || empty_p (dest->available_in))
+ return false;
+
+ return bitmap_ior_and_into (er->get_bitmap (&dest->rd_in),
+ src->rd_out, dest->available_in);
+}
+
+/* Propagate information from the rd_in set of block BB_INDEX to rd_out.
+ Return true if something changed. */
+
+bool
+early_remat::rd_transfer (int bb_index)
+{
+ remat_block_info *info = &er->m_block_info[bb_index];
+
+ if (empty_p (info->rd_in))
+ return false;
+
+ if (empty_p (info->rd_kill))
+ {
+ gcc_checking_assert (empty_p (info->rd_gen));
+ if (!info->rd_out)
+ info->rd_out = info->rd_in;
+ else
+ gcc_checking_assert (info->rd_out == info->rd_in);
+ /* Assume that we only get called if something changed. */
+ return true;
+ }
+
+ if (empty_p (info->rd_gen))
+ return bitmap_and_compl (er->get_bitmap (&info->rd_out),
+ info->rd_in, info->rd_kill);
+
+ return bitmap_ior_and_compl (er->get_bitmap (&info->rd_out), info->rd_gen,
+ info->rd_in, info->rd_kill);
+}
+
+/* Calculate the rd_* sets for each block. */
+
+void
+early_remat::compute_rd (void)
+{
+ /* First calculate the rd_kill and rd_gen sets, using the fact
+ that m_candidates is sorted in order of decreasing LUID. */
+ unsigned int cand_index;
+ remat_candidate *cand;
+ FOR_EACH_VEC_ELT_REVERSE (m_candidates, cand_index, cand)
+ {
+ rtx_insn *insn = cand->insn;
+ basic_block bb = BLOCK_FOR_INSN (insn);
+ remat_block_info *info = &m_block_info[bb->index];
+ bitmap kill = m_regno_to_candidates[cand->regno];
+ bitmap_ior_into (get_bitmap (&info->rd_kill), kill);
+ if (bitmap_bit_p (DF_LR_OUT (bb), cand->regno))
+ {
+ bitmap_and_compl_into (get_bitmap (&info->rd_gen), kill);
+ bitmap_set_bit (info->rd_gen, cand_index);
+ }
+ }
+
+ /* Set up the initial values of the other sets. */
+ basic_block bb;
+ FOR_EACH_BB_FN (bb, m_fn)
+ {
+ remat_block_info *info = &m_block_info[bb->index];
+ unsigned int regno;
+ bitmap_iterator bi;
+ EXECUTE_IF_AND_IN_BITMAP (DF_LR_IN (bb), &m_candidate_regnos,
+ 0, regno, bi)
+ {
+ /* Use available_in to record the set of candidates whose
+ registers are live on entry (i.e. a maximum bound on rd_in). */
+ bitmap_ior_into (get_bitmap (&info->available_in),
+ m_regno_to_candidates[regno]);
+
+ /* Add registers that die in a block to the block's kill set,
+ so that we don't needlessly propagate them through the rest
+ of the function. */
+ if (!bitmap_bit_p (DF_LR_OUT (bb), regno))
+ bitmap_ior_into (get_bitmap (&info->rd_kill),
+ m_regno_to_candidates[regno]);
+ }
+
+ /* Initialize each block's rd_out to the minimal set (the set of
+ local definitions). */
+ if (!empty_p (info->rd_gen))
+ bitmap_copy (get_bitmap (&info->rd_out), info->rd_gen);
+ }
+
+ /* Iterate until we reach a fixed point. */
+ er = this;
+ bitmap_clear (&m_tmp_bitmap);
+ bitmap_set_range (&m_tmp_bitmap, 0, last_basic_block_for_fn (m_fn));
+ df_simple_dataflow (DF_FORWARD, NULL, NULL, rd_confluence_n, rd_transfer,
+ &m_tmp_bitmap, df_get_postorder (DF_FORWARD),
+ df_get_n_blocks (DF_FORWARD));
+ er = 0;
+
+ /* Work out which definitions reach which candidates, again taking
+ advantage of the candidate order. */
+ bitmap_head reaching;
+ bitmap_initialize (&reaching, &m_obstack);
+ basic_block old_bb = NULL;
+ FOR_EACH_VEC_ELT_REVERSE (m_candidates, cand_index, cand)
+ {
+ bb = BLOCK_FOR_INSN (cand->insn);
+ if (bb != old_bb)
+ {
+ /* Get the definitions that reach the start of the new block. */
+ remat_block_info *info = &m_block_info[bb->index];
+ if (info->rd_in)
+ bitmap_copy (&reaching, info->rd_in);
+ else
+ bitmap_clear (&reaching);
+ old_bb = bb;
+ }
+ else
+ {
+ /* Process the definitions of the previous instruction. */
+ bitmap kill = m_regno_to_candidates[cand[1].regno];
+ bitmap_and_compl_into (&reaching, kill);
+ bitmap_set_bit (&reaching, cand_index + 1);
+ }
+
+ if (cand->can_copy_p && !cand->constant_p)
+ {
+ df_ref ref;
+ FOR_EACH_INSN_USE (ref, cand->insn)
+ {
+ unsigned int regno = DF_REF_REGNO (ref);
+ if (bitmap_bit_p (&m_candidate_regnos, regno))
+ {
+ bitmap defs = m_regno_to_candidates[regno];
+ bitmap_and (&m_tmp_bitmap, defs, &reaching);
+ bitmap_ior_into (get_bitmap (&cand->uses), &m_tmp_bitmap);
+ }
+ }
+ }
+ }
+ bitmap_clear (&reaching);
+}
+
+/* If CAND_INDEX is in an equivalence class, return the representative
+ of the class, otherwise return CAND_INDEX. */
+
+inline unsigned int
+early_remat::canon_candidate (unsigned int cand_index)
+{
+ if (remat_equiv_class *ec = m_candidates[cand_index].equiv_class)
+ return ec->representative;
+ return cand_index;
+}
+
+/* Make candidate set *PTR refer to candidates using the representative
+ of each equivalence class. */
+
+void
+early_remat::canon_bitmap (bitmap *ptr)
+{
+ bitmap old_set = *ptr;
+ if (empty_p (old_set))
+ return;
+
+ bitmap new_set = NULL;
+ unsigned int old_index;
+ bitmap_iterator bi;
+ EXECUTE_IF_SET_IN_BITMAP (old_set, 0, old_index, bi)
+ {
+ unsigned int new_index = canon_candidate (old_index);
+ if (old_index != new_index)
+ {
+ if (!new_set)
+ {
+ new_set = alloc_bitmap ();
+ bitmap_copy (new_set, old_set);
+ }
+ bitmap_clear_bit (new_set, old_index);
+ bitmap_set_bit (new_set, new_index);
+ }
+ }
+ if (new_set)
+ {
+ BITMAP_FREE (*ptr);
+ *ptr = new_set;
+ }
+}
+
+/* If the candidates in REACHING all have the same value, return the
+ earliest instance of that value (i.e. the first one to be added
+ to m_value_table), otherwise return MULTIPLE_CANDIDATES. */
+
+unsigned int
+early_remat::resolve_reaching_def (bitmap reaching)
+{
+ unsigned int cand_index = bitmap_first_set_bit (reaching);
+ if (remat_equiv_class *ec = m_candidates[cand_index].equiv_class)
+ {
+ if (!bitmap_intersect_compl_p (reaching, ec->members))
+ return ec->earliest;
+ }
+ else if (bitmap_single_bit_set_p (reaching))
+ return cand_index;
+
+ return MULTIPLE_CANDIDATES;
+}
+
+/* Check whether all candidate registers used by candidate CAND_INDEX have
+ unique definitions. Return true if so, replacing the candidate's uses
+ set with the appropriate form for value numbering. */
+
+bool
+early_remat::check_candidate_uses (unsigned int cand_index)
+{
+ remat_candidate *cand = &m_candidates[cand_index];
+
+ /* Process the uses for each register in turn. */
+ bitmap_head uses;
+ bitmap_initialize (&uses, &m_obstack);
+ bitmap_copy (&uses, cand->uses);
+ bitmap uses_ec = alloc_bitmap ();
+ while (!bitmap_empty_p (&uses))
+ {
+ /* Get the register for the lowest-indexed candidate remaining,
+ and the reaching definitions of that register. */
+ unsigned int first = bitmap_first_set_bit (&uses);
+ unsigned int regno = m_candidates[first].regno;
+ bitmap_and (&m_tmp_bitmap, &uses, m_regno_to_candidates[regno]);
+
+ /* See whether all reaching definitions have the same value and if
+ so get the index of the first candidate we saw with that value. */
+ unsigned int def = resolve_reaching_def (&m_tmp_bitmap);
+ if (def == MULTIPLE_CANDIDATES)
+ {
+ if (dump_file)
+ fprintf (dump_file, ";; Removing candidate %d because there is"
+ " more than one reaching definition of reg %d\n",
+ cand_index, regno);
+ cand->can_copy_p = false;
+ break;
+ }
+ bitmap_set_bit (uses_ec, def);
+ bitmap_and_compl_into (&uses, &m_tmp_bitmap);
+ }
+ BITMAP_FREE (cand->uses);
+ cand->uses = uses_ec;
+ return cand->can_copy_p;
+}
+
+/* Calculate the set of hard registers that would be clobbered by
+ rematerializing candidate CAND_INDEX. At this point the candidate's
+ set of uses is final. */
+
+void
+early_remat::compute_clobbers (unsigned int cand_index)
+{
+ remat_candidate *cand = &m_candidates[cand_index];
+ if (cand->uses)
+ {
+ unsigned int use_index;
+ bitmap_iterator bi;
+ EXECUTE_IF_SET_IN_BITMAP (cand->uses, 0, use_index, bi)
+ if (bitmap clobbers = m_candidates[use_index].clobbers)
+ bitmap_ior_into (get_bitmap (&cand->clobbers), clobbers);
+ }
+
+ df_ref ref;
+ FOR_EACH_INSN_DEF (ref, cand->insn)
+ {
+ unsigned int def_regno = DF_REF_REGNO (ref);
+ if (def_regno != cand->regno)
+ bitmap_set_bit (get_bitmap (&cand->clobbers), def_regno);
+ }
+}
+
+/* Mark candidate CAND_INDEX as validated and add it to the value table. */
+
+void
+early_remat::assign_value_number (unsigned int cand_index)
+{
+ remat_candidate *cand = &m_candidates[cand_index];
+ gcc_checking_assert (cand->can_copy_p && !cand->validated_p);
+
+ compute_clobbers (cand_index);
+ cand->validated_p = true;
+
+ inchash::hash h;
+ h.add_int (cand->regno);
+ inchash::add_rtx (cand->remat_rtx, h);
+ cand->hash = h.end ();
+
+ remat_candidate **slot
+ = m_value_table.find_slot_with_hash (cand, cand->hash, INSERT);
+ if (!*slot)
+ {
+ *slot = cand;
+ if (dump_file)
+ fprintf (dump_file, ";; Candidate %d is not equivalent to"
+ " others seen so far\n", cand_index);
+ }
+ else
+ record_equiv_candidates (*slot - m_candidates.address (), cand_index);
+}
+
+/* Make a final decision about which candidates are valid and assign
+ value numbers to those that are. */
+
+void
+early_remat::decide_candidate_validity (void)
+{
+ auto_vec<unsigned int, 16> stack;
+ unsigned int cand1_index;
+ remat_candidate *cand1;
+ FOR_EACH_VEC_ELT_REVERSE (m_candidates, cand1_index, cand1)
+ {
+ if (!cand1->can_copy_p || cand1->validated_p)
+ continue;
+
+ if (empty_p (cand1->uses))
+ {
+ assign_value_number (cand1_index);
+ continue;
+ }
+
+ stack.safe_push (cand1_index);
+ while (!stack.is_empty ())
+ {
+ unsigned int cand2_index = stack.last ();
+ unsigned int watermark = stack.length ();
+ remat_candidate *cand2 = &m_candidates[cand2_index];
+ if (!cand2->can_copy_p || cand2->validated_p)
+ {
+ stack.pop ();
+ continue;
+ }
+ cand2->visited_p = true;
+ unsigned int cand3_index;
+ bitmap_iterator bi;
+ EXECUTE_IF_SET_IN_BITMAP (cand2->uses, 0, cand3_index, bi)
+ {
+ remat_candidate *cand3 = &m_candidates[cand3_index];
+ if (!cand3->can_copy_p)
+ {
+ if (dump_file)
+ fprintf (dump_file, ";; Removing candidate %d because"
+ " it uses removed candidate %d\n", cand2_index,
+ cand3_index);
+ cand2->can_copy_p = false;
+ break;
+ }
+ if (!cand3->validated_p)
+ {
+ if (empty_p (cand3->uses))
+ assign_value_number (cand3_index);
+ else if (cand3->visited_p)
+ {
+ if (dump_file)
+ fprintf (dump_file, ";; Removing candidate %d"
+ " because its definition is cyclic\n",
+ cand2_index);
+ cand2->can_copy_p = false;
+ break;
+ }
+ else
+ stack.safe_push (cand3_index);
+ }
+ }
+ if (!cand2->can_copy_p)
+ {
+ cand2->visited_p = false;
+ stack.truncate (watermark - 1);
+ }
+ else if (watermark == stack.length ())
+ {
+ cand2->visited_p = false;
+ if (check_candidate_uses (cand2_index))
+ assign_value_number (cand2_index);
+ stack.pop ();
+ }
+ }
+ }
+
+ /* Ensure that the candidates always use the same candidate index
+ to refer to an equivalence class. */
+ FOR_EACH_VEC_ELT_REVERSE (m_candidates, cand1_index, cand1)
+ if (cand1->can_copy_p && !empty_p (cand1->uses))
+ {
+ canon_bitmap (&cand1->uses);
+ gcc_checking_assert (bitmap_first_set_bit (cand1->uses) > cand1_index);
+ }
+}
+
+/* Assuming that every path reaching a point P contains a copy of a
+ use U of REGNO, return true if another copy of U at P would have
+ access to the same value of REGNO. */
+
+bool
+early_remat::stable_use_p (unsigned int regno)
+{
+ /* Conservatively assume not for hard registers. */
+ if (HARD_REGISTER_NUM_P (regno))
+ return false;
+
+ /* See if REGNO has a single definition and is never used uninitialized.
+ In this case the definition of REGNO dominates the common dominator
+ of the uses U, which in turn dominates P. */
+ if (DF_REG_DEF_COUNT (regno) == 1
+ && !bitmap_bit_p (DF_LR_OUT (ENTRY_BLOCK_PTR_FOR_FN (m_fn)), regno))
+ return true;
+
+ return false;
+}
+
+/* Emit a copy from register DEST to register SRC before candidate
+ CAND_INDEX's instruction. */
+
+void
+early_remat::emit_copy_before (unsigned int cand_index, rtx dest, rtx src)
+{
+ remat_candidate *cand = &m_candidates[cand_index];
+ if (dump_file)
+ {
+ fprintf (dump_file, ";; Stabilizing insn ");
+ dump_insn_id (cand->insn);
+ fprintf (dump_file, " by copying source reg %d:%s to temporary reg %d\n",
+ REGNO (src), GET_MODE_NAME (GET_MODE (src)), REGNO (dest));
+ }
+ emit_insn_before (gen_move_insn (dest, src), cand->insn);
+}
+
+/* Check whether any inputs to candidate CAND_INDEX's instruction could
+ change at rematerialization points and replace them with new pseudo
+ registers if so. */
+
+void
+early_remat::stabilize_pattern (unsigned int cand_index)
+{
+ remat_candidate *cand = &m_candidates[cand_index];
+ if (cand->stabilized_p)
+ return;
+
+ remat_equiv_class *ec = cand->equiv_class;
+ gcc_checking_assert (!ec || cand_index == ec->representative);
+
+ /* Record the replacements we've made so far, so that we don't
+ create two separate registers for match_dups. Lookup is O(n),
+ but the n is very small. */
+ typedef std::pair<rtx, rtx> reg_pair;
+ auto_vec<reg_pair, 16> reg_map;
+
+ rtx_insn *insn = cand->insn;
+ df_ref ref;
+ FOR_EACH_INSN_USE (ref, insn)
+ {
+ unsigned int old_regno = DF_REF_REGNO (ref);
+ rtx *loc = DF_REF_REAL_LOC (ref);
+
+ if (HARD_REGISTER_NUM_P (old_regno) && fixed_regs[old_regno])
+ {
+ /* We checked when adding the candidate that the value is stable. */
+ gcc_checking_assert (!rtx_unstable_p (*loc));
+ continue;
+ }
+
+ if (bitmap_bit_p (&m_candidate_regnos, old_regno))
+ /* We already know which candidate provides the definition
+ and will handle it during copying. */
+ continue;
+
+ if (stable_use_p (old_regno))
+ /* We can continue to use the existing register. */
+ continue;
+
+ /* We need to replace the register. See whether we've already
+ created a suitable copy. */
+ rtx old_reg = *loc;
+ rtx new_reg = NULL_RTX;
+ machine_mode mode = GET_MODE (old_reg);
+ reg_pair *p;
+ unsigned int pi;
+ FOR_EACH_VEC_ELT (reg_map, pi, p)
+ if (REGNO (p->first) == old_regno
+ && GET_MODE (p->first) == mode)
+ {
+ new_reg = p->second;
+ break;
+ }
+
+ if (!new_reg)
+ {
+ /* Create a new register and initialize it just before
+ the instruction. */
+ new_reg = gen_reg_rtx (mode);
+ reg_map.safe_push (reg_pair (old_reg, new_reg));
+ if (ec)
+ {
+ unsigned int member_index;
+ bitmap_iterator bi;
+ EXECUTE_IF_SET_IN_BITMAP (ec->members, 0, member_index, bi)
+ emit_copy_before (member_index, new_reg, old_reg);
+ }
+ else
+ emit_copy_before (cand_index, new_reg, old_reg);
+ }
+ validate_change (insn, loc, new_reg, true);
+ }
+ if (num_changes_pending ())
+ {
+ if (!apply_change_group ())
+ /* We checked when adding the candidates that the pattern allows
+ hard registers to be replaced. Nothing else should make the
+ changes invalid. */
+ gcc_unreachable ();
+
+ if (ec)
+ {
+ /* Copy the new pattern to other members of the equivalence
+ class. */
+ unsigned int member_index;
+ bitmap_iterator bi;
+ EXECUTE_IF_SET_IN_BITMAP (ec->members, 0, member_index, bi)
+ if (cand_index != member_index)
+ {
+ rtx_insn *other_insn = m_candidates[member_index].insn;
+ if (!validate_change (other_insn, &PATTERN (other_insn),
+ copy_insn (PATTERN (insn)), 0))
+ /* If the original instruction was valid then the copy
+ should be too. */
+ gcc_unreachable ();
+ }
+ }
+ }
+
+ cand->stabilized_p = true;
+}
+
+/* Change CAND's instruction so that it sets CAND->copy_regno instead
+ of CAND->regno. */
+
+void
+early_remat::replace_dest_with_copy (unsigned int cand_index)
+{
+ remat_candidate *cand = &m_candidates[cand_index];
+ df_ref def;
+ FOR_EACH_INSN_DEF (def, cand->insn)
+ if (DF_REF_REGNO (def) == cand->regno)
+ validate_change (cand->insn, DF_REF_REAL_LOC (def),
+ regno_reg_rtx[cand->copy_regno], 1);
+}
+
+/* Make sure that the candidates used by candidate CAND_INDEX are available.
+ There are two ways of doing this for an input candidate I:
+
+ (1) Using the existing register number and ensuring that I is available.
+
+ (2) Using a new register number (recorded in copy_regno) and adding I
+ to VIA_COPY. This guarantees that making I available does not
+ conflict with other uses of the original register.
+
+ REQUIRED is the set of candidates that are required but not available
+ before the copy of CAND_INDEX. AVAILABLE is the set of candidates
+ that are already available before the copy of CAND_INDEX. REACHING
+ is the set of candidates that reach the copy of CAND_INDEX. VIA_COPY
+ is the set of candidates that will use new register numbers recorded
+ in copy_regno instead of the original ones. */
+
+void
+early_remat::stabilize_candidate_uses (unsigned int cand_index,
+ bitmap required, bitmap available,
+ bitmap reaching, bitmap via_copy)
+{
+ remat_candidate *cand = &m_candidates[cand_index];
+ df_ref use;
+ FOR_EACH_INSN_USE (use, cand->insn)
+ {
+ unsigned int regno = DF_REF_REGNO (use);
+ if (!bitmap_bit_p (&m_candidate_regnos, regno))
+ continue;
+
+ /* Work out which candidate provides the definition. */
+ bitmap defs = m_regno_to_candidates[regno];
+ bitmap_and (&m_tmp_bitmap, cand->uses, defs);
+ gcc_checking_assert (bitmap_single_bit_set_p (&m_tmp_bitmap));
+ unsigned int def_index = bitmap_first_set_bit (&m_tmp_bitmap);
+
+ /* First see if DEF_INDEX is the only reaching definition of REGNO
+ at this point too and if it is or will become available. We can
+ continue to use REGNO if so. */
+ bitmap_and (&m_tmp_bitmap, reaching, defs);
+ if (bitmap_single_bit_set_p (&m_tmp_bitmap)
+ && bitmap_first_set_bit (&m_tmp_bitmap) == def_index
+ && ((available && bitmap_bit_p (available, def_index))
+ || bitmap_bit_p (required, def_index)))
+ {
+ if (dump_file)
+ fprintf (dump_file, ";; Keeping reg %d for use of candidate %d"
+ " in candidate %d\n", regno, def_index, cand_index);
+ continue;
+ }
+
+ /* Otherwise fall back to using a copy. There are other cases
+ in which we *could* continue to use REGNO, but there's not
+ really much point. Using a separate register ought to make
+ things easier for the register allocator. */
+ remat_candidate *def_cand = &m_candidates[def_index];
+ rtx *loc = DF_REF_REAL_LOC (use);
+ rtx new_reg;
+ if (bitmap_set_bit (via_copy, def_index))
+ {
+ new_reg = gen_reg_rtx (GET_MODE (*loc));
+ def_cand->copy_regno = REGNO (new_reg);
+ if (dump_file)
+ fprintf (dump_file, ";; Creating reg %d for use of candidate %d"
+ " in candidate %d\n", REGNO (new_reg), def_index,
+ cand_index);
+ }
+ else
+ new_reg = regno_reg_rtx[def_cand->copy_regno];
+ validate_change (cand->insn, loc, new_reg, 1);
+ }
+}
+
+/* Rematerialize the candidates in REQUIRED after instruction INSN,
+ given that the candidates in AVAILABLE are already available
+ and that REACHING is the set of candidates live after INSN.
+ REQUIRED and AVAILABLE are disjoint on entry.
+
+ Clear REQUIRED on exit. */
+
+void
+early_remat::emit_remat_insns (bitmap required, bitmap available,
+ bitmap reaching, rtx_insn *insn)
+{
+ /* Quick exit if there's nothing to do. */
+ if (empty_p (required))
+ return;
+
+ /* Only reaching definitions should be available or required. */
+ gcc_checking_assert (!bitmap_intersect_compl_p (required, reaching));
+ if (available)
+ gcc_checking_assert (!bitmap_intersect_compl_p (available, reaching));
+
+ bitmap_head via_copy;
+ bitmap_initialize (&via_copy, &m_obstack);
+ while (!bitmap_empty_p (required) || !bitmap_empty_p (&via_copy))
+ {
+ /* Pick the lowest-indexed candidate left. */
+ unsigned int required_index = (bitmap_empty_p (required)
+ ? ~0U : bitmap_first_set_bit (required));
+ unsigned int via_copy_index = (bitmap_empty_p (&via_copy)
+ ? ~0U : bitmap_first_set_bit (&via_copy));
+ unsigned int cand_index = MIN (required_index, via_copy_index);
+ remat_candidate *cand = &m_candidates[cand_index];
+
+ bool via_copy_p = (cand_index == via_copy_index);
+ if (via_copy_p)
+ bitmap_clear_bit (&via_copy, cand_index);
+ else
+ {
+ /* Remove all candidates for the same register from REQUIRED. */
+ bitmap_and (&m_tmp_bitmap, reaching,
+ m_regno_to_candidates[cand->regno]);
+ bitmap_and_compl_into (required, &m_tmp_bitmap);
+ gcc_checking_assert (!bitmap_bit_p (required, cand_index));
+
+ /* Only rematerialize if we have a single reaching definition
+ of the register. */
+ if (!bitmap_single_bit_set_p (&m_tmp_bitmap))
+ {
+ if (dump_file)
+ {
+ fprintf (dump_file, ";; Can't rematerialize reg %d after ",
+ cand->regno);
+ dump_insn_id (insn);
+ fprintf (dump_file, ": more than one reaching definition\n");
+ }
+ continue;
+ }
+
+ /* Skip candidates that can't be rematerialized. */
+ if (!cand->can_copy_p)
+ continue;
+
+ /* Check the function precondition. */
+ gcc_checking_assert (!available
+ || !bitmap_bit_p (available, cand_index));
+ }
+
+ /* Invalid candidates should have been weeded out by now. */
+ gcc_assert (cand->can_copy_p);
+
+ rtx new_pattern;
+ if (cand->constant_p)
+ {
+ /* Emit a simple move. */
+ unsigned int regno = via_copy_p ? cand->copy_regno : cand->regno;
+ new_pattern = gen_move_insn (regno_reg_rtx[regno], cand->remat_rtx);
+ }
+ else
+ {
+ /* If this is the first time we've copied the instruction, make
+ sure that any inputs will have the same value after INSN. */
+ stabilize_pattern (cand_index);
+
+ /* Temporarily adjust the original instruction so that it has
+ the right form for the copy. */
+ if (via_copy_p)
+ replace_dest_with_copy (cand_index);
+ if (cand->uses)
+ stabilize_candidate_uses (cand_index, required, available,
+ reaching, &via_copy);
+
+ /* Get the new instruction pattern. */
+ new_pattern = copy_insn (cand->remat_rtx);
+
+ /* Undo the temporary changes. */
+ cancel_changes (0);
+ }
+
+ /* Emit the new instruction. */
+ rtx_insn *new_insn = emit_insn_after (new_pattern, insn);
+
+ if (dump_file)
+ {
+ fprintf (dump_file, ";; Rematerializing candidate %d after ",
+ cand_index);
+ dump_insn_id (insn);
+ if (via_copy_p)
+ fprintf (dump_file, " with new destination reg %d",
+ cand->copy_regno);
+ fprintf (dump_file, ":\n\n");
+ print_rtl_single (dump_file, new_insn);
+ fprintf (dump_file, "\n");
+ }
+ }
+}
+
+/* Recompute INFO's available_out set, given that it's distinct from
+ available_in and available_locally. */
+
+bool
+early_remat::set_available_out (remat_block_info *info)
+{
+ if (empty_p (info->available_locally))
+ return bitmap_and_compl (get_bitmap (&info->available_out),
+ info->available_in, info->rd_kill);
+
+ if (empty_p (info->rd_kill))
+ return bitmap_ior (get_bitmap (&info->available_out),
+ info->available_locally, info->available_in);
+
+ return bitmap_ior_and_compl (get_bitmap (&info->available_out),
+ info->available_locally, info->available_in,
+ info->rd_kill);
+}
+
+/* If BB has more than one call, decide which candidates should be
+ rematerialized after the non-final calls and emit the associated
+ instructions. Record other information about the block in preparation
+ for the global phase. */
+
+void
+early_remat::process_block (basic_block bb)
+{
+ remat_block_info *info = &m_block_info[bb->index];
+ rtx_insn *last_call = NULL;
+ rtx_insn *insn;
+
+ /* Ensure that we always use the same candidate index to refer to an
+ equivalence class. */
+ if (info->rd_out == info->rd_in)
+ {
+ canon_bitmap (&info->rd_in);
+ info->rd_out = info->rd_in;
+ }
+ else
+ {
+ canon_bitmap (&info->rd_in);
+ canon_bitmap (&info->rd_out);
+ }
+ canon_bitmap (&info->rd_kill);
+ canon_bitmap (&info->rd_gen);
+
+ /* The set of candidates that should be rematerialized on entry to the
+ block or after the previous call (whichever is more recent). */
+ init_temp_bitmap (&m_required);
+
+ /* The set of candidates that reach the current instruction (i.e. are
+ live just before the instruction). */
+ bitmap_head reaching;
+ bitmap_initialize (&reaching, &m_obstack);
+ if (info->rd_in)
+ bitmap_copy (&reaching, info->rd_in);
+
+ /* The set of candidates that are live and available without
+ rematerialization just before the current instruction. This only
+ accounts for earlier candidates in the block, or those that become
+ available by being added to M_REQUIRED. */
+ init_temp_bitmap (&m_available);
+
+ /* Get the range of candidates in the block. */
+ unsigned int next_candidate = info->first_candidate;
+ unsigned int num_candidates = info->num_candidates;
+ remat_candidate *next_def = (num_candidates > 0
+ ? &m_candidates[next_candidate]
+ : NULL);
+
+ FOR_BB_INSNS (bb, insn)
+ {
+ if (!NONDEBUG_INSN_P (insn))
+ continue;
+
+ /* First process uses, since this is a forward walk. */
+ df_ref ref;
+ FOR_EACH_INSN_USE (ref, insn)
+ {
+ unsigned int regno = DF_REF_REGNO (ref);
+ if (bitmap_bit_p (&m_candidate_regnos, regno))
+ {
+ bitmap defs = m_regno_to_candidates[regno];
+ bitmap_and (&m_tmp_bitmap, defs, &reaching);
+ gcc_checking_assert (!bitmap_empty_p (&m_tmp_bitmap));
+ if (!bitmap_intersect_p (defs, m_available))
+ {
+ /* There has been no definition of the register since
+ the last call or the start of the block (whichever
+ is most recent). Mark the reaching definitions
+ as required at that point and thus available here. */
+ bitmap_ior_into (m_required, &m_tmp_bitmap);
+ bitmap_ior_into (m_available, &m_tmp_bitmap);
+ }
+ }
+ }
+
+ if (CALL_P (insn))
+ {
+ if (!last_call)
+ {
+ /* The first call in the block. Record which candidates are
+ required at the start of the block. */
+ copy_temp_bitmap (&info->required_in, &m_required);
+ init_temp_bitmap (&m_required);
+ }
+ else
+ /* The fully-local case: candidates that need to be
+ rematerialized after a previous call in the block. */
+ emit_remat_insns (m_required, NULL, info->rd_after_call,
+ last_call);
+ last_call = insn;
+ bitmap_clear (m_available);
+ gcc_checking_assert (empty_p (m_required));
+ }
+
+ /* Now process definitions. */
+ if (next_def && insn == next_def->insn)
+ {
+ unsigned int gen = canon_candidate (next_candidate);
+
+ /* Other candidates with the same regno are not available
+ any more. */
+ bitmap kill = m_regno_to_candidates[next_def->regno];
+ bitmap_and_compl_into (m_available, kill);
+ bitmap_and_compl_into (&reaching, kill);
+
+ /* Record that this candidate is available without
+ rematerialization. */
+ bitmap_set_bit (m_available, gen);
+ bitmap_set_bit (&reaching, gen);
+
+ /* Find the next candidate in the block. */
+ num_candidates -= 1;
+ next_candidate -= 1;
+ if (num_candidates > 0)
+ next_def -= 1;
+ else
+ next_def = NULL;
+ }
+
+ if (insn == last_call)
+ bitmap_copy (get_bitmap (&info->rd_after_call), &reaching);
+ }
+ bitmap_clear (&reaching);
+ gcc_checking_assert (num_candidates == 0);
+
+ /* Remove values from the available set if they aren't live (and so
+ aren't interesting to successor blocks). */
+ if (info->rd_out)
+ bitmap_and_into (m_available, info->rd_out);
+
+ /* Record the accumulated information. */
+ info->last_call = last_call;
+ info->abnormal_call_p = (last_call
+ && last_call == BB_END (bb)
+ && has_abnormal_or_eh_outgoing_edge_p (bb));
+ copy_temp_bitmap (&info->available_locally, &m_available);
+ if (last_call)
+ copy_temp_bitmap (&info->required_after_call, &m_required);
+ else
+ copy_temp_bitmap (&info->required_in, &m_required);
+
+ /* Assume at first that all live-in values are available without
+ rematerialization (i.e. start with the most optimistic assumption). */
+ if (info->available_in)
+ {
+ if (info->rd_in)
+ bitmap_copy (info->available_in, info->rd_in);
+ else
+ BITMAP_FREE (info->available_in);
+ }
+
+ if (last_call || empty_p (info->available_in))
+ /* The values available on exit from the block are exactly those that
+ are available locally. This set doesn't change. */
+ info->available_out = info->available_locally;
+ else if (empty_p (info->available_locally) && empty_p (info->rd_kill))
+ /* The values available on exit are the same as those available on entry.
+ Updating one updates the other. */
+ info->available_out = info->available_in;
+ else
+ set_available_out (info);
+}
+
+/* Process each block as for process_block, visiting dominators before
+ the blocks they dominate. */
+
+void
+early_remat::local_phase (void)
+{
+ if (dump_file)
+ fprintf (dump_file, "\n;; Local phase:\n");
+
+ int *postorder = df_get_postorder (DF_BACKWARD);
+ unsigned int postorder_len = df_get_n_blocks (DF_BACKWARD);
+ for (unsigned int i = postorder_len; i-- > 0; )
+ if (postorder[i] >= NUM_FIXED_BLOCKS)
+ process_block (BASIC_BLOCK_FOR_FN (m_fn, postorder[i]));
+}
+
+/* Return true if available values survive across edge E. */
+
+static inline bool
+available_across_edge_p (edge e)
+{
+ return (e->flags & EDGE_EH) == 0;
+}
+
+/* Propagate information from the available_out set of E->src to the
+ available_in set of E->dest, when computing global availability.
+ Return true if something changed. */
+
+bool
+early_remat::avail_confluence_n (edge e)
+{
+ remat_block_info *src = &er->m_block_info[e->src->index];
+ remat_block_info *dest = &er->m_block_info[e->dest->index];
+
+ if (!available_across_edge_p (e))
+ return false;
+
+ if (empty_p (dest->available_in))
+ return false;
+
+ if (!src->available_out)
+ {
+ bitmap_clear (dest->available_in);
+ return true;
+ }
+
+ return bitmap_and_into (dest->available_in, src->available_out);
+}
+
+/* Propagate information from the available_in set of block BB_INDEX
+ to available_out. Return true if something changed. */
+
+bool
+early_remat::avail_transfer (int bb_index)
+{
+ remat_block_info *info = &er->m_block_info[bb_index];
+
+ if (info->available_out == info->available_locally)
+ return false;
+
+ if (info->available_out == info->available_in)
+ /* Assume that we are only called if the input changed. */
+ return true;
+
+ return er->set_available_out (info);
+}
+
+/* Compute global availability for the function, starting with the local
+ information computed by local_phase. */
+
+void
+early_remat::compute_availability (void)
+{
+ /* We use df_simple_dataflow instead of the lcm routines for three reasons:
+
+ (1) it avoids recomputing the traversal order;
+ (2) many of the sets are likely to be sparse, so we don't necessarily
+ want to use sbitmaps; and
+ (3) it means we can avoid creating an explicit kill set for the call. */
+ er = this;
+ bitmap_clear (&m_tmp_bitmap);
+ bitmap_set_range (&m_tmp_bitmap, 0, last_basic_block_for_fn (m_fn));
+ df_simple_dataflow (DF_FORWARD, NULL, NULL,
+ avail_confluence_n, avail_transfer,
+ &m_tmp_bitmap, df_get_postorder (DF_FORWARD),
+ df_get_n_blocks (DF_FORWARD));
+ er = 0;
+
+ /* Restrict the required_in sets to values that aren't available. */
+ basic_block bb;
+ FOR_EACH_BB_FN (bb, m_fn)
+ {
+ remat_block_info *info = &m_block_info[bb->index];
+ if (info->required_in && info->available_in)
+ bitmap_and_compl_into (info->required_in, info->available_in);
+ }
+}
+
+/* Make sure that INFO's available_out and available_in sets are unique. */
+
+inline void
+early_remat::unshare_available_sets (remat_block_info *info)
+{
+ if (info->available_in && info->available_in == info->available_out)
+ {
+ info->available_in = alloc_bitmap ();
+ bitmap_copy (info->available_in, info->available_out);
+ }
+}
+
+/* Return true if it is possible to move rematerializations from the
+ destination of E to the source of E. */
+
+inline bool
+early_remat::can_move_across_edge_p (edge e)
+{
+ return (available_across_edge_p (e)
+ && !m_block_info[e->src->index].abnormal_call_p);
+}
+
+/* Return true if it is cheaper to rematerialize values at the head of
+ block QUERY_BB_INDEX instead of rematerializing in its predecessors. */
+
+bool
+early_remat::local_remat_cheaper_p (unsigned int query_bb_index)
+{
+ if (m_block_info[query_bb_index].remat_frequency_valid_p)
+ return m_block_info[query_bb_index].local_remat_cheaper_p;
+
+ /* Iteratively compute the cost of rematerializing values in the
+ predecessor blocks, then compare that with the cost of
+ rematerializing at the head of the block.
+
+ A cycle indicates that there is no call on that execution path,
+ so it isn't necessary to rematerialize on that path. */
+ auto_vec<basic_block, 16> stack;
+ stack.quick_push (BASIC_BLOCK_FOR_FN (m_fn, query_bb_index));
+ while (!stack.is_empty ())
+ {
+ basic_block bb = stack.last ();
+ remat_block_info *info = &m_block_info[bb->index];
+ if (info->remat_frequency_valid_p)
+ {
+ stack.pop ();
+ continue;
+ }
+
+ info->visited_p = true;
+ int frequency = 0;
+ bool can_move_p = true;
+ edge e;
+ edge_iterator ei;
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ if (!can_move_across_edge_p (e))
+ {
+ can_move_p = false;
+ break;
+ }
+ else if (m_block_info[e->src->index].last_call)
+ /* We'll rematerialize after the call. */
+ frequency += e->src->count.to_frequency (m_fn);
+ else if (m_block_info[e->src->index].remat_frequency_valid_p)
+ /* Add the cost of rematerializing at the head of E->src
+ or in its predecessors (whichever is cheaper). */
+ frequency += m_block_info[e->src->index].remat_frequency;
+ else if (!m_block_info[e->src->index].visited_p)
+ /* Queue E->src and then revisit this block again. */
+ stack.safe_push (e->src);
+
+ /* Come back to this block later if we need to process some of
+ its predecessors. */
+ if (stack.last () != bb)
+ continue;
+
+ /* If rematerializing in and before the block have equal cost, prefer
+ rematerializing in the block. This should shorten the live range. */
+ int bb_frequency = bb->count.to_frequency (m_fn);
+ if (!can_move_p || frequency >= bb_frequency)
+ {
+ info->local_remat_cheaper_p = true;
+ info->remat_frequency = bb_frequency;
+ }
+ else
+ info->remat_frequency = frequency;
+ info->remat_frequency_valid_p = true;
+ info->visited_p = false;
+ if (dump_file)
+ {
+ if (!can_move_p)
+ fprintf (dump_file, ";; Need to rematerialize at the head of"
+ " block %d; cannot move to predecessors.\n", bb->index);
+ else
+ {
+ fprintf (dump_file, ";; Block %d has frequency %d,"
+ " rematerializing in predecessors has frequency %d",
+ bb->index, bb_frequency, frequency);
+ if (info->local_remat_cheaper_p)
+ fprintf (dump_file, "; prefer to rematerialize"
+ " in the block\n");
+ else
+ fprintf (dump_file, "; prefer to rematerialize"
+ " in predecessors\n");
+ }
+ }
+ stack.pop ();
+ }
+ return m_block_info[query_bb_index].local_remat_cheaper_p;
+}
+
+/* Return true if we cannot rematerialize candidate CAND_INDEX at the head of
+ block BB_INDEX. */
+
+bool
+early_remat::need_to_move_candidate_p (unsigned int bb_index,
+ unsigned int cand_index)
+{
+ remat_block_info *info = &m_block_info[bb_index];
+ remat_candidate *cand = &m_candidates[cand_index];
+ basic_block bb = BASIC_BLOCK_FOR_FN (m_fn, bb_index);
+
+ /* If there is more than one reaching definition of REGNO,
+ we'll need to rematerialize in predecessors instead. */
+ bitmap_and (&m_tmp_bitmap, info->rd_in, m_regno_to_candidates[cand->regno]);
+ if (!bitmap_single_bit_set_p (&m_tmp_bitmap))
+ {
+ if (dump_file)
+ fprintf (dump_file, ";; Cannot rematerialize %d at the"
+ " head of block %d because there is more than one"
+ " reaching definition of reg %d\n", cand_index,
+ bb_index, cand->regno);
+ return true;
+ }
+
+ /* Likewise if rematerializing CAND here would clobber a live register. */
+ if (cand->clobbers
+ && bitmap_intersect_p (cand->clobbers, DF_LR_IN (bb)))
+ {
+ if (dump_file)
+ fprintf (dump_file, ";; Cannot rematerialize %d at the"
+ " head of block %d because it would clobber live"
+ " registers\n", cand_index, bb_index);
+ return true;
+ }
+
+ return false;
+}
+
+/* Set REQUIRED to the minimum set of candidates that must be rematerialized
+ in predecessors of block BB_INDEX instead of at the start of the block. */
+
+void
+early_remat::compute_minimum_move_set (unsigned int bb_index,
+ bitmap required)
+{
+ remat_block_info *info = &m_block_info[bb_index];
+ bitmap_head remaining;
+
+ bitmap_clear (required);
+ bitmap_initialize (&remaining, &m_obstack);
+ bitmap_copy (&remaining, info->required_in);
+ while (!bitmap_empty_p (&remaining))
+ {
+ unsigned int cand_index = bitmap_first_set_bit (&remaining);
+ remat_candidate *cand = &m_candidates[cand_index];
+ bitmap_clear_bit (&remaining, cand_index);
+
+ /* Leave invalid candidates where they are. */
+ if (!cand->can_copy_p)
+ continue;
+
+ /* Decide whether to move this candidate. */
+ if (!bitmap_bit_p (required, cand_index))
+ {
+ if (!need_to_move_candidate_p (bb_index, cand_index))
+ continue;
+ bitmap_set_bit (required, cand_index);
+ }
+
+ /* Also move values used by the candidate, so that we don't
+ rematerialize them twice. */
+ if (cand->uses)
+ {
+ bitmap_ior_and_into (required, cand->uses, info->required_in);
+ bitmap_ior_and_into (&remaining, cand->uses, info->required_in);
+ }
+ }
+}
+
+/* Make the predecessors of BB_INDEX rematerialize the candidates in
+ REQUIRED. Add any blocks whose required_in set changes to
+ PENDING_BLOCKS. */
+
+void
+early_remat::move_to_predecessors (unsigned int bb_index, bitmap required,
+ bitmap pending_blocks)
+{
+ if (empty_p (required))
+ return;
+ remat_block_info *dest_info = &m_block_info[bb_index];
+ basic_block bb = BASIC_BLOCK_FOR_FN (m_fn, bb_index);
+ edge e;
+ edge_iterator ei;
+ FOR_EACH_EDGE (e, ei, bb->preds)
+ {
+ remat_block_info *src_info = &m_block_info[e->src->index];
+
+ /* Restrict the set we add to the reaching definitions. */
+ bitmap_and (&m_tmp_bitmap, required, src_info->rd_out);
+ if (bitmap_empty_p (&m_tmp_bitmap))
+ continue;
+
+ if (!can_move_across_edge_p (e))
+ {
+ /* We can't move the rematerialization and we can't do it at
+ the start of the block either. In this case we just give up
+ and rely on spilling to make the values available across E. */
+ if (dump_file)
+ {
+ fprintf (dump_file, ";; Cannot rematerialize the following"
+ " candidates in block %d:", e->src->index);
+ dump_candidate_bitmap (required);
+ fprintf (dump_file, "\n");
+ }
+ continue;
+ }
+
+ /* Remove candidates that are already available. */
+ if (src_info->available_out)
+ {
+ bitmap_and_compl_into (&m_tmp_bitmap, src_info->available_out);
+ if (bitmap_empty_p (&m_tmp_bitmap))
+ continue;
+ }
+
+ /* Add the remaining candidates to the appropriate required set. */
+ if (dump_file)
+ {
+ fprintf (dump_file, ";; Moving this set from block %d"
+ " to block %d:", bb_index, e->src->index);
+ dump_candidate_bitmap (&m_tmp_bitmap);
+ fprintf (dump_file, "\n");
+ }
+ /* If the source block contains a call, we want to rematerialize
+ after the call, otherwise we want to rematerialize at the start
+ of the block. */
+ bitmap src_required = get_bitmap (src_info->last_call
+ ? &src_info->required_after_call
+ : &src_info->required_in);
+ if (bitmap_ior_into (src_required, &m_tmp_bitmap))
+ {
+ if (!src_info->last_call)
+ bitmap_set_bit (pending_blocks, e->src->index);
+ unshare_available_sets (src_info);
+ bitmap_ior_into (get_bitmap (&src_info->available_out),
+ &m_tmp_bitmap);
+ }
+ }
+
+ /* The candidates are now available on entry to the block. */
+ bitmap_and_compl_into (dest_info->required_in, required);
+ unshare_available_sets (dest_info);
+ bitmap_ior_into (get_bitmap (&dest_info->available_in), required);
+}
+
+/* Go through the candidates that are currently marked as being
+ rematerialized at the beginning of a block. Decide in each case
+ whether that's valid and profitable; if it isn't, move the
+ rematerialization to predecessor blocks instead. */
+
+void
+early_remat::choose_rematerialization_points (void)
+{
+ bitmap_head required;
+ bitmap_head pending_blocks;
+
+ int *postorder = df_get_postorder (DF_BACKWARD);
+ unsigned int postorder_len = df_get_n_blocks (DF_BACKWARD);
+ bitmap_initialize (&required, &m_obstack);
+ bitmap_initialize (&pending_blocks, &m_obstack);
+ do
+ /* Process the blocks in postorder, to reduce the number of iterations
+ of the outer loop. */
+ for (unsigned int i = 0; i < postorder_len; ++i)
+ {
+ unsigned int bb_index = postorder[i];
+ remat_block_info *info = &m_block_info[bb_index];
+ bitmap_clear_bit (&pending_blocks, bb_index);
+
+ if (empty_p (info->required_in))
+ continue;
+
+ if (info->available_in)
+ gcc_checking_assert (!bitmap_intersect_p (info->required_in,
+ info->available_in));
+
+ if (local_remat_cheaper_p (bb_index))
+ {
+ /* We'd prefer to rematerialize at the head of the block.
+ Only move candidates if we need to. */
+ compute_minimum_move_set (bb_index, &required);
+ move_to_predecessors (bb_index, &required, &pending_blocks);
+ }
+ else
+ move_to_predecessors (bb_index, info->required_in,
+ &pending_blocks);
+ }
+ while (!bitmap_empty_p (&pending_blocks));
+ bitmap_clear (&required);
+}
+
+/* Emit all rematerialization instructions queued for BB. */
+
+void
+early_remat::emit_remat_insns_for_block (basic_block bb)
+{
+ remat_block_info *info = &m_block_info[bb->index];
+
+ if (info->last_call && !empty_p (info->required_after_call))
+ emit_remat_insns (info->required_after_call, NULL,
+ info->rd_after_call, info->last_call);
+
+ if (!empty_p (info->required_in))
+ {
+ rtx_insn *insn = BB_HEAD (bb);
+ while (insn != BB_END (bb)
+ && !INSN_P (NEXT_INSN (insn)))
+ insn = NEXT_INSN (insn);
+ emit_remat_insns (info->required_in, info->available_in,
+ info->rd_in, insn);
+ }
+}
+
+/* Decide which candidates in each block's REQUIRED_IN set need to be
+ rematerialized and decide where the rematerialization instructions
+ should go. Emit queued rematerialization instructions at the start
+ of blocks and after the last calls in blocks. */
+
+void
+early_remat::global_phase (void)
+{
+ compute_availability ();
+ if (dump_file)
+ {
+ fprintf (dump_file, "\n;; Blocks after computing global"
+ " availability:\n");
+ dump_all_blocks ();
+ }
+
+ choose_rematerialization_points ();
+ if (dump_file)
+ {
+ fprintf (dump_file, "\n;; Blocks after choosing rematerialization"
+ " points:\n");
+ dump_all_blocks ();
+ }
+
+ basic_block bb;
+ FOR_EACH_BB_FN (bb, m_fn)
+ emit_remat_insns_for_block (bb);
+}
+
+/* Main function for the pass. */
+
+void
+early_remat::run (void)
+{
+ df_analyze ();
+
+ if (!collect_candidates ())
+ return;
+
+ init_block_info ();
+ sort_candidates ();
+ finalize_candidate_indices ();
+ if (dump_file)
+ dump_all_candidates ();
+
+ compute_rd ();
+ decide_candidate_validity ();
+ local_phase ();
+ global_phase ();
+}
+
+early_remat::early_remat (function *fn, sbitmap selected_modes)
+ : m_fn (fn),
+ m_selected_modes (selected_modes),
+ m_available (0),
+ m_required (0),
+ m_value_table (63)
+{
+ bitmap_obstack_initialize (&m_obstack);
+ bitmap_initialize (&m_candidate_regnos, &m_obstack);
+ bitmap_initialize (&m_tmp_bitmap, &m_obstack);
+}
+
+early_remat::~early_remat ()
+{
+ bitmap_obstack_release (&m_obstack);
+}
+
+namespace {
+
+const pass_data pass_data_early_remat =
+{
+ RTL_PASS, /* type */
+ "early_remat", /* name */
+ OPTGROUP_NONE, /* optinfo_flags */
+ TV_EARLY_REMAT, /* tv_id */
+ 0, /* properties_required */
+ 0, /* properties_provided */
+ 0, /* properties_destroyed */
+ 0, /* todo_flags_start */
+ TODO_df_finish, /* todo_flags_finish */
+};
+
+class pass_early_remat : public rtl_opt_pass
+{
+public:
+ pass_early_remat (gcc::context *ctxt)
+ : rtl_opt_pass (pass_data_early_remat, ctxt)
+ {}
+
+ /* opt_pass methods: */
+ virtual bool gate (function *)
+ {
+ return optimize > 1 && NUM_POLY_INT_COEFFS > 1;
+ }
+
+ virtual unsigned int execute (function *f)
+ {
+ auto_sbitmap selected_modes (NUM_MACHINE_MODES);
+ bitmap_clear (selected_modes);
+ targetm.select_early_remat_modes (selected_modes);
+ if (!bitmap_empty_p (selected_modes))
+ early_remat (f, selected_modes).run ();
+ return 0;
+ }
+}; // class pass_early_remat
+
+} // anon namespace
+
+rtl_opt_pass *
+make_pass_early_remat (gcc::context *ctxt)
+{
+ return new pass_early_remat (ctxt);
+}
projects / gcc.git / commitdiff