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ifcvt: Run second pass if it is possible to omit a temporary.
If one of the to-be-converted SETs requires the original comparison (i.e. in order to generate a min/max insn) but no other insn after it does, we can omit creating temporaries, thus facilitating costing. gcc/ChangeLog: * ifcvt.cc (noce_convert_multiple_sets_1): New function. (noce_convert_multiple_sets): Call function a second time if we can improve the first try.
This commit is contained in:
Robin Dapp
parent
d249933e6b
commit
92efc019ed
227
gcc/ifcvt.cc
227
gcc/ifcvt.cc
@ -100,6 +100,12 @@ static void noce_emit_move_insn (rtx, rtx);
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static rtx_insn *block_has_only_trap (basic_block);
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static void need_cmov_or_rewire (basic_block, hash_set<rtx_insn *> *,
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hash_map<rtx_insn *, int> *);
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static bool noce_convert_multiple_sets_1 (struct noce_if_info *,
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hash_set<rtx_insn *> *,
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hash_map<rtx_insn *, int> *,
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auto_vec<rtx> *,
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auto_vec<rtx> *,
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auto_vec<rtx_insn *> *, int *);
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/* Count the number of non-jump active insns in BB. */
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@ -3256,9 +3262,6 @@ noce_convert_multiple_sets (struct noce_if_info *if_info)
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rtx x = XEXP (cond, 0);
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rtx y = XEXP (cond, 1);
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rtx cc_cmp = cond_exec_get_condition (jump);
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rtx rev_cc_cmp = cond_exec_get_condition (jump, /* get_reversed */ true);
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/* The true targets for a conditional move. */
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auto_vec<rtx> targets;
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/* The temporaries introduced to allow us to not consider register
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@ -3266,13 +3269,139 @@ noce_convert_multiple_sets (struct noce_if_info *if_info)
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auto_vec<rtx> temporaries;
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/* The insns we've emitted. */
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auto_vec<rtx_insn *> unmodified_insns;
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int count = 0;
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hash_set<rtx_insn *> need_no_cmov;
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hash_map<rtx_insn *, int> rewired_src;
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need_cmov_or_rewire (then_bb, &need_no_cmov, &rewired_src);
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int last_needs_comparison = -1;
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bool ok = noce_convert_multiple_sets_1
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(if_info, &need_no_cmov, &rewired_src, &targets, &temporaries,
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&unmodified_insns, &last_needs_comparison);
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if (!ok)
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return false;
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/* If there are insns that overwrite part of the initial
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comparison, we can still omit creating temporaries for
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the last of them.
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As the second try will always create a less expensive,
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valid sequence, we do not need to compare and can discard
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the first one. */
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if (last_needs_comparison != -1)
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{
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end_sequence ();
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start_sequence ();
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ok = noce_convert_multiple_sets_1
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(if_info, &need_no_cmov, &rewired_src, &targets, &temporaries,
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&unmodified_insns, &last_needs_comparison);
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/* Actually we should not fail anymore if we reached here,
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but better still check. */
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if (!ok)
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return false;
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}
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/* We must have seen some sort of insn to insert, otherwise we were
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given an empty BB to convert, and we can't handle that. */
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gcc_assert (!unmodified_insns.is_empty ());
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/* Now fixup the assignments. */
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for (unsigned i = 0; i < targets.length (); i++)
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if (targets[i] != temporaries[i])
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noce_emit_move_insn (targets[i], temporaries[i]);
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/* Actually emit the sequence if it isn't too expensive. */
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rtx_insn *seq = get_insns ();
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if (!targetm.noce_conversion_profitable_p (seq, if_info))
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{
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end_sequence ();
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return FALSE;
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}
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for (insn = seq; insn; insn = NEXT_INSN (insn))
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set_used_flags (insn);
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/* Mark all our temporaries and targets as used. */
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for (unsigned i = 0; i < targets.length (); i++)
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{
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set_used_flags (temporaries[i]);
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set_used_flags (targets[i]);
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}
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set_used_flags (cond);
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set_used_flags (x);
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set_used_flags (y);
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unshare_all_rtl_in_chain (seq);
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end_sequence ();
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if (!seq)
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return FALSE;
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for (insn = seq; insn; insn = NEXT_INSN (insn))
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if (JUMP_P (insn)
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|| recog_memoized (insn) == -1)
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return FALSE;
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emit_insn_before_setloc (seq, if_info->jump,
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INSN_LOCATION (unmodified_insns.last ()));
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/* Clean up THEN_BB and the edges in and out of it. */
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remove_edge (find_edge (test_bb, join_bb));
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remove_edge (find_edge (then_bb, join_bb));
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redirect_edge_and_branch_force (single_succ_edge (test_bb), join_bb);
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delete_basic_block (then_bb);
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num_true_changes++;
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/* Maybe merge blocks now the jump is simple enough. */
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if (can_merge_blocks_p (test_bb, join_bb))
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{
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merge_blocks (test_bb, join_bb);
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num_true_changes++;
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}
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num_updated_if_blocks++;
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if_info->transform_name = "noce_convert_multiple_sets";
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return TRUE;
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}
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/* This goes through all relevant insns of IF_INFO->then_bb and tries to
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create conditional moves. In case a simple move sufficis the insn
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should be listed in NEED_NO_CMOV. The rewired-src cases should be
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specified via REWIRED_SRC. TARGETS, TEMPORARIES and UNMODIFIED_INSNS
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are specified and used in noce_convert_multiple_sets and should be passed
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to this function.. */
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static bool
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noce_convert_multiple_sets_1 (struct noce_if_info *if_info,
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hash_set<rtx_insn *> *need_no_cmov,
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hash_map<rtx_insn *, int> *rewired_src,
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auto_vec<rtx> *targets,
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auto_vec<rtx> *temporaries,
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auto_vec<rtx_insn *> *unmodified_insns,
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int *last_needs_comparison)
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{
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basic_block then_bb = if_info->then_bb;
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rtx_insn *jump = if_info->jump;
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rtx_insn *cond_earliest;
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/* Decompose the condition attached to the jump. */
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rtx cond = noce_get_condition (jump, &cond_earliest, false);
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rtx cc_cmp = cond_exec_get_condition (jump);
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rtx rev_cc_cmp = cond_exec_get_condition (jump, /* get_reversed */ true);
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rtx_insn *insn;
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int count = 0;
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targets->truncate (0);
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temporaries->truncate (0);
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unmodified_insns->truncate (0);
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bool second_try = *last_needs_comparison != -1;
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FOR_BB_INSNS (then_bb, insn)
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{
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/* Skip over non-insns. */
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@ -3286,9 +3415,9 @@ noce_convert_multiple_sets (struct noce_if_info *if_info)
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rtx temp;
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rtx new_val = SET_SRC (set);
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if (int *ii = rewired_src.get (insn))
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new_val = simplify_replace_rtx (new_val, targets[*ii],
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temporaries[*ii]);
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if (int *ii = rewired_src->get (insn))
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new_val = simplify_replace_rtx (new_val, (*targets)[*ii],
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(*temporaries)[*ii]);
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rtx old_val = target;
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/* As we are transforming
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@ -3316,8 +3445,12 @@ noce_convert_multiple_sets (struct noce_if_info *if_info)
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Therefore we introduce a temporary every time we are about to
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overwrite a variable used in the check. Costing of a sequence with
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these is going to be inaccurate so only use temporaries when
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needed. */
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if (reg_overlap_mentioned_p (target, cond))
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needed.
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If performing a second try, we know how many insns require a
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temporary. For the last of these, we can omit creating one. */
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if (reg_overlap_mentioned_p (target, cond)
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&& (!second_try || count < *last_needs_comparison))
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temp = gen_reg_rtx (GET_MODE (target));
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else
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temp = target;
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@ -3325,7 +3458,7 @@ noce_convert_multiple_sets (struct noce_if_info *if_info)
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/* We have identified swap-style idioms before. A normal
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set will need to be a cmov while the first instruction of a swap-style
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idiom can be a regular move. This helps with costing. */
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bool need_cmov = !need_no_cmov.contains (insn);
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bool need_cmov = !need_no_cmov->contains (insn);
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/* If we had a non-canonical conditional jump (i.e. one where
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the fallthrough is to the "else" case) we need to reverse
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@ -3400,6 +3533,8 @@ noce_convert_multiple_sets (struct noce_if_info *if_info)
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{
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seq = seq1;
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temp_dest = temp_dest1;
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if (!second_try)
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*last_needs_comparison = count;
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}
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else if (seq2 != NULL_RTX)
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{
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@ -3418,76 +3553,16 @@ noce_convert_multiple_sets (struct noce_if_info *if_info)
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/* Bookkeeping. */
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count++;
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targets.safe_push (target);
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temporaries.safe_push (temp_dest);
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unmodified_insns.safe_push (insn);
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targets->safe_push (target);
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temporaries->safe_push (temp_dest);
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unmodified_insns->safe_push (insn);
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}
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/* We must have seen some sort of insn to insert, otherwise we were
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given an empty BB to convert, and we can't handle that. */
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gcc_assert (!unmodified_insns.is_empty ());
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/* Now fixup the assignments. */
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for (int i = 0; i < count; i++)
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if (targets[i] != temporaries[i])
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noce_emit_move_insn (targets[i], temporaries[i]);
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/* Actually emit the sequence if it isn't too expensive. */
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rtx_insn *seq = get_insns ();
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if (!targetm.noce_conversion_profitable_p (seq, if_info))
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{
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end_sequence ();
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return FALSE;
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}
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for (insn = seq; insn; insn = NEXT_INSN (insn))
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set_used_flags (insn);
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/* Mark all our temporaries and targets as used. */
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for (int i = 0; i < count; i++)
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{
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set_used_flags (temporaries[i]);
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set_used_flags (targets[i]);
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}
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set_used_flags (cond);
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set_used_flags (x);
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set_used_flags (y);
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unshare_all_rtl_in_chain (seq);
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end_sequence ();
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if (!seq)
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return FALSE;
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for (insn = seq; insn; insn = NEXT_INSN (insn))
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if (JUMP_P (insn)
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|| recog_memoized (insn) == -1)
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return FALSE;
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emit_insn_before_setloc (seq, if_info->jump,
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INSN_LOCATION (unmodified_insns.last ()));
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/* Clean up THEN_BB and the edges in and out of it. */
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remove_edge (find_edge (test_bb, join_bb));
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remove_edge (find_edge (then_bb, join_bb));
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redirect_edge_and_branch_force (single_succ_edge (test_bb), join_bb);
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delete_basic_block (then_bb);
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num_true_changes++;
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/* Maybe merge blocks now the jump is simple enough. */
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if (can_merge_blocks_p (test_bb, join_bb))
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{
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merge_blocks (test_bb, join_bb);
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num_true_changes++;
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}
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num_updated_if_blocks++;
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if_info->transform_name = "noce_convert_multiple_sets";
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return TRUE;
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return true;
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}
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/* Return true iff basic block TEST_BB is comprised of only
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(SET (REG) (REG)) insns suitable for conversion to a series
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of conditional moves. Also check that we have more than one set
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