Robin Dapp <rd...@linux.ibm.com> writes: > This patch duplicates the previous noce_emit_cmove logic. First it > passes the canonical comparison emits the sequence and costs it. > Then, a second, separate sequence is created by passing the cc compare > we extracted before. The costs of both sequences are compared and the > cheaper one is emitted. > --- > gcc/ifcvt.c | 106 +++++++++++++++++++++++++++++++++++++++++++++++----- > 1 file changed, 97 insertions(+), 9 deletions(-) > > diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c > index 3db707e1fd1..955f9541f60 100644 > --- a/gcc/ifcvt.c > +++ b/gcc/ifcvt.c > @@ -3208,8 +3208,11 @@ noce_convert_multiple_sets (struct noce_if_info > *if_info) > > hash_map<rtx, bool> need_temps; > > - if (!cc_cmp) > - check_need_temps (then_bb, &need_temps, cond); > + /* If we newly set a CC before a cmov, we might need a temporary > + even though the compare will be removed by a later pass. Costing > + of a sequence with these will be inaccurate. */ > + > + check_need_temps (then_bb, &need_temps, cond); > > hash_map<rtx, bool> temps_created; > > @@ -3298,18 +3301,103 @@ noce_convert_multiple_sets (struct noce_if_info > *if_info) > old_val = lowpart_subreg (dst_mode, old_val, src_mode); > } > > - /* Actually emit the conditional move. */ > - rtx temp_dest = noce_emit_cmove (if_info, temp, cond_code, > - x, y, new_val, old_val, cc_cmp); > + /* Try emitting a conditional move passing the backend the > + canonicalized comparison. This can e.g. be used to recognize > + expressions like > + > + if (a < b) > + { > + ... > + b = a; > + } > + > + A backend can recognize this and emit a min/max insn. > + We will still emit a superfluous CC comparison before the > + min/max, though, which complicates costing. > + */ > + > + rtx_insn *seq, *seq1 = 0, *seq2 = 0; > + rtx temp_dest, temp_dest1, temp_dest2; > + unsigned int cost1 = 0, cost2 = 0; > + bool speed_p = if_info->speed_p; > + push_topmost_sequence ();
Why do we need the push_topmost_sequence/pop_topmost_sequence? start_sequence/end_sequence ought to be enough. > + > + { > + start_sequence (); > + temp_dest1 = noce_emit_cmove (if_info, temp, cond_code, > + x, y, new_val, old_val, NULL_RTX); Nit: arguments should be indented below "if_info, ". > + > + /* If we failed to expand the conditional move, drop out and don't > + try to continue. */ > + if (temp_dest1 == NULL_RTX) > + { > + seq1 = NULL; > + cost1 = COSTS_N_INSNS (100); > + } > + else > + { > + seq1 = get_insns (); > + cost1 = seq_cost (seq1, speed_p); > + rtx_insn *ii; > + for (ii = seq1; ii; ii = NEXT_INSN (ii)) > + if (recog_memozied (ii) == -1) > + cost1 += 10000; > + } > + end_sequence (); Don't think we should use fake costs for failure. Just setting seq1 to null should be enough, and should be OK for the recog_memoized case too. Can break the loop as soon as we find a failure. > + } > + > + /* Now try emitting one passing a non-canonicalized cc comparison. > + This allows the backend to emit a cmov directly without additional > + compare. */ > + { > + start_sequence (); > + temp_dest2 = noce_emit_cmove (if_info, target, cond_code, > + x, y, new_val, old_val, cc_cmp); > + > + /* If we failed to expand the conditional move, drop out and don't > + try to continue. */ > + if (temp_dest2 == NULL_RTX) > + { > + seq2 = NULL; > + cost2 = COSTS_N_INSNS (100); > + } > + else > + { > + seq2 = get_insns (); > + cost2 = seq_cost (seq2, speed_p); > + rtx_insn *ii; > + for (ii = seq2; ii; ii = NEXT_INSN (ii)) > + if (recog_memozied (ii) == -1) > + cost2 += 10000; > + } > + end_sequence (); > + } Same comments here. Would be nice to split this out into a subroutine rather than duplicate it. Thanks, Richard > > - /* If we failed to expand the conditional move, drop out and don't > - try to continue. */ > - if (temp_dest == NULL_RTX) > + /* Check which version is less expensive. */ > + if (cost1 <= cost2 && seq1 != NULL_RTX) > + { > + temp_dest = temp_dest1; > + seq = seq1; > + } > + else if (seq2 != NULL_RTX) > + { > + /* We do not require a temp register, so remove it from the list. */ > + seq = seq2; > + temp_dest = temp_dest2; > + temps_created.remove (temp); > + } > + else > { > + /* Nothing worked, bail out. */ > + pop_topmost_sequence (); > end_sequence (); > - return FALSE; > + return false; > } > > + /* End the sub sequence and emit to the main sequence. */ > + pop_topmost_sequence (); > + emit_insn (seq); > + > /* Bookkeeping. */ > count++; > targets.safe_push (target);