Following up on the previous patch, this patch makes
noce_convert_multiple emit two cmov sequences: The same one as before
and a second one that tries to re-use the existing CC. Then their costs
are compared and the cheaper one is selected.
---
gcc/ifcvt.c | 94 ++++++++++++++++++++++++++++++++++++++++++++++++-----
1 file changed, 86 insertions(+), 8 deletions(-)
diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c
index c5b8641e2aa..55405ce9ef7 100644
--- a/gcc/ifcvt.c
+++ b/gcc/ifcvt.c
@@ -3142,6 +3142,47 @@ bb_valid_for_noce_process_p (basic_block test_bb, rtx
cond,
return false;
}
+/* Helper function to emit a cmov sequence. */
+
+static rtx_insn*
+try_emit_cmove_seq (struct noce_if_info *if_info, rtx temp,
+ rtx cond, rtx target,
+ rtx new_val, rtx old_val, bool need_cmov,
+ unsigned *cost, rtx *temp_dest,
+ rtx cc_cmp = NULL, rtx rev_cc_cmp = NULL)
+{
+ rtx_insn *seq = NULL;
+ *cost = 0;
+
+ rtx x = XEXP (cond, 0);
+ rtx y = XEXP (cond, 1);
+ rtx_code cond_code = GET_CODE (cond);
+
+ start_sequence ();
+
+ if (need_cmov)
+ *temp_dest = noce_emit_cmove (if_info, temp, cond_code,
+ x, y, new_val, old_val, cc_cmp, rev_cc_cmp);
+ else
+ {
+ *temp_dest = target;
+ if (if_info->then_else_reversed)
+ noce_emit_move_insn (target, old_val);
+ else
+ noce_emit_move_insn (target, new_val);
+ }
+
+ if (*temp_dest != NULL_RTX)
+ {
+ seq = get_insns ();
+ *cost = seq_cost (seq, if_info->speed_p);
+ }
+
+ end_sequence ();
+
+ return seq;
+}
+
/* We have something like:
if (x > y)
@@ -3199,7 +3240,9 @@ noce_convert_multiple_sets (struct noce_if_info *if_info)
rtx cond = noce_get_condition (jump, &cond_earliest, false);
rtx x = XEXP (cond, 0);
rtx y = XEXP (cond, 1);
- rtx_code cond_code = GET_CODE (cond);
+
+ rtx cc_cmp = cond_exec_get_condition (jump);
+ rtx rev_cc_cmp = noce_get_condition (jump, &cond_earliest, true);
/* The true targets for a conditional move. */
auto_vec<rtx> targets;
@@ -3301,18 +3344,52 @@ 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);
+ /* Try emitting a conditional move passing the backend the
+ canonicalized comparison. The backend is then able to
+ recognize expressions like
- /* If we failed to expand the conditional move, drop out and don't
- try to continue. */
- if (temp_dest == NULL_RTX)
+ if (x > y)
+ y = x;
+
+ as min/max emit an insn, accordingly.
+ We will still emit a superfluous CC comparison before the
+ min/max, though, which complicates costing. */
+ unsigned cost1 = 0, cost2 = 0;
+ rtx_insn *seq, *seq1, *seq2;
+ rtx temp_dest = NULL_RTX, temp_dest1 = NULL_RTX, temp_dest2 = NULL_RTX;
+
+ seq1 = try_emit_cmove_seq (if_info, temp, cond, target,
+ new_val, old_val, need_cmov, &cost1, &temp_dest1);
+
+ /* Here, we try to pass the backend a non-canonicalized cc comparison
+ as well. This allows the backend to emit a cmov directly without
+ creating an additional compare for each. If successful, costing
+ is easier and this sequence is usually preferred. */
+ seq2 = try_emit_cmove_seq (if_info, target, cond, target,
+ new_val, old_val, need_cmov, &cost2, &temp_dest2,
+ cc_cmp, rev_cc_cmp);
+
+ /* Check which version is less expensive. */
+ if (seq1 != NULL_RTX && cost1 <= cost2)
+ {
+ seq = seq1;
+ temp_dest = temp_dest1;
+ }
+ else if (seq2 != NULL_RTX)
+ {
+ seq = seq2;
+ temp_dest = temp_dest2;
+ }
+ else
{
+ /* Nothing worked, bail out. */
end_sequence ();
return FALSE;
}
+ /* End the sub sequence and emit to the main sequence. */
+ emit_insn (seq);
+
/* Bookkeeping. */
count++;
targets.safe_push (target);
@@ -3326,7 +3403,8 @@ noce_convert_multiple_sets (struct noce_if_info *if_info)
/* Now fixup the assignments. */
for (int i = 0; i < count; i++)
- noce_emit_move_insn (targets[i], temporaries[i]);
+ if (targets[i] != temporaries[i])
+ noce_emit_move_insn (targets[i], temporaries[i]);
/* Actually emit the sequence if it isn't too expensive. */
rtx_insn *seq = get_insns ();
--
2.31.1
