https://gcc.gnu.org/g:887c27b6da2fbb04cbe20a85378366819aabbd26
commit 887c27b6da2fbb04cbe20a85378366819aabbd26
Author: Alexandre Oliva <ol...@adacore.com>
Date: Thu Nov 21 22:40:45 2024 -0300
ifcombine: skip fallback conjunction on noncontiguous blocks
When everything else fails, if enabled by the target or by a
parameter, and when other requirements are satisfied, ifcombine
generates an AND of both conditions.
That may be good for contiguous conditions, but it's unlikely to be an
optimization when the blocks are separate.
Add contiguity to the set of requirements for this fallback
transformation.
for gcc/ChangeLog
* tree-ssa-ifcombine.cc (ifcombine_ifandif): Avoid fallback
conjunction of noncontiguous conditions.
Diff:
---
gcc/tree-ssa-ifcombine.cc | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/gcc/tree-ssa-ifcombine.cc b/gcc/tree-ssa-ifcombine.cc
index 9b9dc10cd220..51f37f15a9ef 100644
--- a/gcc/tree-ssa-ifcombine.cc
+++ b/gcc/tree-ssa-ifcombine.cc
@@ -974,6 +974,10 @@ ifcombine_ifandif (basic_block inner_cond_bb, bool
inner_inv,
gimple_cond_rhs (outer_cond),
gimple_bb (outer_cond))))
{
+ /* Only combine conditions in this fallback case if the blocks are
+ neighbors. */
+ if (single_pred (inner_cond_bb) != outer_cond_bb)
+ return false;
tree t1, t2;
bool logical_op_non_short_circuit = LOGICAL_OP_NON_SHORT_CIRCUIT;
if (param_logical_op_non_short_circuit != -1)
