Hi, This patch replaces rtx_cost with insn_cost in forward propagation. In the PR, one constant vector should be propagated and replace a pseudo in a store insn if we know it's a duplicated constant vector. It reduces the insn cost but not rtx cost. In this case, the cost is determined by destination operand (memory or pseudo). Unfortunately, rtx cost can't help.
The test case is added in the second rs6000 specific patch. Compared to previous version, the main changes are: 1. Invalidate recog_data when the cached INSN is swapped out. 2. Pass strict_p according to prop.likely_profitable_p () to change_is_worthwhile. Previous version https://gcc.gnu.org/pipermail/gcc-patches/2024-June/654276.html The patch causes a regression cases on i386 as the pattern cost regulation has a bug. Please refer the patch and discussion here. https://gcc.gnu.org/pipermail/gcc-patches/2024-May/651363.html Bootstrapped and tested on powerpc64-linux BE and LE with no regressions. Is it OK for the trunk? ChangeLog fwprop: invoke change_is_worthwhile to judge if a replacement is worthwhile gcc/ * fwprop.cc (try_fwprop_subst_pattern): Invoke change_is_worthwhile to judge if a replacement is worthwhile. * recog.cc (swap_change): Invalidate recog_data when the cached INSN is swapped out. * rtl-ssa/changes.cc (rtl_ssa::changes_are_worthwhile): Check if the insn cost of new rtl is unknown and fail the replacement. patch.diff diff --git a/gcc/fwprop.cc b/gcc/fwprop.cc index de543923b92..4a9f68b66b1 100644 --- a/gcc/fwprop.cc +++ b/gcc/fwprop.cc @@ -471,29 +471,18 @@ try_fwprop_subst_pattern (obstack_watermark &attempt, insn_change &use_change, redo_changes (0); } - /* ??? In theory, it should be better to use insn costs rather than - set_src_costs here. That would involve replacing this code with - change_is_worthwhile. */ bool ok = recog (attempt, use_change); - if (ok && !prop.changed_mem_p () && !use_insn->is_asm ()) - if (rtx use_set = single_set (use_rtl)) - { - bool speed = optimize_bb_for_speed_p (BLOCK_FOR_INSN (use_rtl)); - temporarily_undo_changes (0); - auto old_cost = set_src_cost (SET_SRC (use_set), - GET_MODE (SET_DEST (use_set)), speed); - redo_changes (0); - auto new_cost = set_src_cost (SET_SRC (use_set), - GET_MODE (SET_DEST (use_set)), speed); - if (new_cost > old_cost - || (new_cost == old_cost && !prop.likely_profitable_p ())) - { - if (dump_file) - fprintf (dump_file, "change not profitable" - " (cost %d -> cost %d)\n", old_cost, new_cost); - ok = false; - } - } + if (ok && !prop.changed_mem_p () && !use_insn->is_asm () + && single_set (use_rtl)) + { + bool strict_p = !prop.likely_profitable_p (); + if (!change_is_worthwhile (use_change, strict_p)) + { + if (dump_file) + fprintf (dump_file, "change not profitable"); + ok = false; + } + } if (!ok) { diff --git a/gcc/recog.cc b/gcc/recog.cc index a6799e3f5e6..56370e40e01 100644 --- a/gcc/recog.cc +++ b/gcc/recog.cc @@ -614,7 +614,11 @@ swap_change (int num) else std::swap (*changes[num].loc, changes[num].old); if (changes[num].object && !MEM_P (changes[num].object)) - std::swap (INSN_CODE (changes[num].object), changes[num].old_code); + { + std::swap (INSN_CODE (changes[num].object), changes[num].old_code); + if (recog_data.insn == changes[num].object) + recog_data.insn = nullptr; + } } /* Temporarily undo all the changes numbered NUM and up, with a view diff --git a/gcc/rtl-ssa/changes.cc b/gcc/rtl-ssa/changes.cc index 11639e81bb7..c5ac4956a19 100644 --- a/gcc/rtl-ssa/changes.cc +++ b/gcc/rtl-ssa/changes.cc @@ -186,6 +186,14 @@ rtl_ssa::changes_are_worthwhile (array_slice<insn_change *const> changes, if (!change->is_deletion ()) { change->new_cost = insn_cost (change->rtl (), for_speed); + /* If the cost is unknown, replacement is not worthwhile. */ + if (!change->new_cost) + { + if (dump_file && (dump_flags & TDF_DETAILS)) + fprintf (dump_file, + "Reject replacement due to unknown insn cost.\n"); + return false; + } new_cost += change->new_cost; if (for_speed) weighted_new_cost += (cfg_bb->count.to_sreal_scale (entry_count)
