On Jan 22, 2025, Alexandre Oliva <ol...@adacore.com> wrote:
> I have another patch coming up that doesn't raise concerns for me, so
> I'll hold off from installing the above, in case you also prefer the
> other one.
And here's an unrelated bit that came to mind while working on this, but
that I split out before posting.
Don't reject an ifcombine field-merging opportunity just because the
left-hand operands aren't both reversed, if the second compare needs
to be swapped for operands to match.
Also mention that reversep does NOT affect the turning of range tests
into bit tests.
Regstrapped on x86_64-linux-gnu. Ok to install?
for gcc/ChangeLog
* gimple-fold.cc (fold_truth_andor_for_ifcombine): Document
reversep's absence of effects on range tests. Don't reject
reversep mismatches before trying compare swapping.
---
gcc/gimple-fold.cc | 10 ++++++----
1 file changed, 6 insertions(+), 4 deletions(-)
diff --git a/gcc/gimple-fold.cc b/gcc/gimple-fold.cc
index 3c971a29ef045..da3f505c3fcac 100644
--- a/gcc/gimple-fold.cc
+++ b/gcc/gimple-fold.cc
@@ -8090,8 +8090,9 @@ fold_truth_andor_for_ifcombine (enum tree_code code, tree
truth_type,
return 0;
}
- /* Prepare to turn compares of signed quantities with zero into
- sign-bit tests. */
+ /* Prepare to turn compares of signed quantities with zero into sign-bit
+ tests. We need not worry about *_reversep here for these compare
+ rewrites: loads will have already been reversed before compares. */
bool lsignbit = false, rsignbit = false;
if ((lcode == LT_EXPR || lcode == GE_EXPR)
&& integer_zerop (lr_arg)
@@ -8198,10 +8199,11 @@ fold_truth_andor_for_ifcombine (enum tree_code code,
tree truth_type,
the rhs's. If one is a load and the other isn't, we have to be
conservative and avoid the optimization, otherwise we could get
SRAed fields wrong. */
- if (volatilep || ll_reversep != rl_reversep)
+ if (volatilep)
return 0;
- if (! operand_equal_p (ll_inner, rl_inner, 0))
+ if (ll_reversep != rl_reversep
+ || ! operand_equal_p (ll_inner, rl_inner, 0))
{
/* Try swapping the operands. */
if (ll_reversep != rr_reversep
--
Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
Free Software Activist GNU Toolchain Engineer
More tolerance and less prejudice are key for inclusion and diversity
Excluding neuro-others for not behaving ""normal"" is *not* inclusive
