| /* Early (pre-RA) rematerialization |
| Copyright (C) 2017-2022 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" |
| #include "regs.h" |
| #include "function-abi.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); |
| void restrict_remat_for_unavail_regs (bitmap, const_bitmap); |
| void restrict_remat_for_call (bitmap, rtx_insn *); |
| 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, TDF_NONE, 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 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 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, true); |
| } |
| |
| /* 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 (), true); |
| 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; |
| } |
| 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); |
| } |
| } |
| |
| /* Remove any candidates in CANDIDATES that would clobber a register in |
| UNAVAIL_REGS. */ |
| |
| void |
| early_remat::restrict_remat_for_unavail_regs (bitmap candidates, |
| const_bitmap unavail_regs) |
| { |
| bitmap_clear (&m_tmp_bitmap); |
| unsigned int cand_index; |
| bitmap_iterator bi; |
| EXECUTE_IF_SET_IN_BITMAP (candidates, 0, cand_index, bi) |
| { |
| remat_candidate *cand = &m_candidates[cand_index]; |
| if (cand->clobbers |
| && bitmap_intersect_p (cand->clobbers, unavail_regs)) |
| bitmap_set_bit (&m_tmp_bitmap, cand_index); |
| } |
| bitmap_and_compl_into (candidates, &m_tmp_bitmap); |
| } |
| |
| /* Remove any candidates in CANDIDATES that would clobber a register |
| that is potentially live across CALL. */ |
| |
| void |
| early_remat::restrict_remat_for_call (bitmap candidates, rtx_insn *call) |
| { |
| /* We don't know whether partially-clobbered registers are live |
| across the call or not, so assume that they are. */ |
| bitmap_view<HARD_REG_SET> call_preserved_regs |
| (~insn_callee_abi (call).full_reg_clobbers ()); |
| restrict_remat_for_unavail_regs (candidates, call_preserved_regs); |
| } |
| |
| /* 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. */ |
| restrict_remat_for_call (m_required, last_call); |
| 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. */ |
| while (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)) |
| { |
| restrict_remat_for_call (info->required_after_call, info->last_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); |
| restrict_remat_for_unavail_regs (info->required_in, DF_LR_IN (bb)); |
| 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); |
| } |