On 10/20/24 3:18 PM, Andrew Pinski wrote:
The gimple (and generic) levels have this optmization since
r12-2041-g7d6979197274a662da7bdc5.
It seems like a good idea to add a similar one to rtl just in case it is not
caught at the
gimple level.
Note the loop case in csel-neg-1.c is not handled at the gimple level (even
with phiopt turned back on),
this is because of casts to avoid signed integer overflow; a patch to fix this
at the gimple level will be
submitted seperately.
Build and tested for aarch64-linux-gnu.
PR rtl-optimization/58195
gcc/ChangeLog:
* simplify-rtx.cc (simplify_context::simplify_ternary_operation): Handle
`a != 0 ? -a : 0` and `a == 0 ? 0 : -a`.
gcc/testsuite/ChangeLog:
* gcc.target/aarch64/csel-neg-1.c: New test.
Signed-off-by: Andrew Pinski <quic_apin...@quicinc.com>
---
gcc/simplify-rtx.cc | 22 +++++++++++++
gcc/testsuite/gcc.target/aarch64/csel-neg-1.c | 31 +++++++++++++++++++
2 files changed, 53 insertions(+)
create mode 100644 gcc/testsuite/gcc.target/aarch64/csel-neg-1.c
diff --git a/gcc/simplify-rtx.cc b/gcc/simplify-rtx.cc
index 4d024ec523b..93a1b707425 100644
--- a/gcc/simplify-rtx.cc
+++ b/gcc/simplify-rtx.cc
@@ -6909,6 +6909,28 @@ simplify_context::simplify_ternary_operation (rtx_code
code, machine_mode mode,
&& rtx_equal_p (XEXP (op0, 1), op1))))
return op2;
+ /* Convert a != 0 ? -a : 0 into "-a". */
+ if (GET_CODE (op0) == NE
+ && ! side_effects_p (op0)
+ && ! HONOR_NANS (mode)
+ && ! HONOR_SIGNED_ZEROS (mode)
+ && XEXP (op0, 1) == const0_rtx
+ && op2 == const0_rtx
Shouldn't we be using CONST0_RTX (mode) rather than referencing
const0_rtx directly?
OK with that change in both clauses.
Jeff
