On Jan 20, 2026, Richard Biener <[email protected]> wrote:
> I think you want to XFAIL instead with a comment why.
testsuite: arm: update fast-math-complex-mls-half-float.c
Since the addition of DCE after complex lowering, reassoc1 has no
longer been impeded by COMPLEX_EXPRs, so it changes (a - (b + c)),
where (b + c) is the imaginary part of an intermediate complex value,
to ((a - b) - c), and this prevents the vectorizer from recognizing
the expected COMPLEX_ADD_ROT270 pattern in fms_elemconjsnd.
Stop expecting that pattern to be found on that test.
Retested with arm-eabi on gcc-15. Ok to install?
for gcc/testsuite/ChangeLog
* gcc.dg/vect/complex/fast-math-complex-mls-half-float.c:
Don't expect COMPLEX_ADD_ROT270.
---
.../complex/fast-math-complex-mls-half-float.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git
a/gcc/testsuite/gcc.dg/vect/complex/fast-math-complex-mls-half-float.c
b/gcc/testsuite/gcc.dg/vect/complex/fast-math-complex-mls-half-float.c
index fb7e9a5619e9e..438426d1c6a46 100644
--- a/gcc/testsuite/gcc.dg/vect/complex/fast-math-complex-mls-half-float.c
+++ b/gcc/testsuite/gcc.dg/vect/complex/fast-math-complex-mls-half-float.c
@@ -7,6 +7,10 @@
#define TYPE _Float16
#define N 200
#include "complex-mls-template.c"
-/* { dg-final { scan-tree-dump "Found COMPLEX_ADD_ROT270" "vect" } } */
+/* COMPLEX_ADD_ROT270 is no longer recognized in fms_elemconjsnd.
+ The COMPLEX_EXPR that prevented reassoc from changing X - (Y + Z)
+ into (X + (-Y)) + (-Z) has been removed since the introduction of
+ DCE at the end of cplxlower1. */
+/* { dg-final { scan-tree-dump "Found COMPLEX_ADD_ROT270" "vect" { xfail *-*-*
} } } */
/* { dg-final { scan-tree-dump "Found COMPLEX_FMS_CONJ" "vect" } } */
/* { dg-final { scan-tree-dump "Found COMPLEX_FMS" "vect" } } */
--
Alexandre Oliva, happy hacker https://blog.lx.oliva.nom.br/
Free Software Activist FSFLA co-founder GNU Toolchain Engineer
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