Hi Alex,
> On 15 Jul 2025, at 14:59, Alex Coplan <alex.cop...@arm.com> wrote:
>
> Hi,
>
> The predication of the SVE2 FP8 dot product insns was relying on the
> architectural dependency:
>
> FEAT_FP8DOT2 => FEAT_FP8DOT4
>
> which was relaxed in GCC as of
> r15-7480-g299a8e2dc667e795991bc439d2cad5ea5bd379e2, thus leading to
> unrecognisable insn ICEs when compiling a two-way FDOT with just
> +fp8dot2. This patch fixes the predication of the insns to test for
> the correct feature bit depending on the value of the mode iterator.
>
> Bootstrapped/regtested on aarch64-linux-gnu, OK for trunk and backport
> to GCC 15?
>
> Thanks,
> Alex
>
> gcc/ChangeLog:
>
> PR target/120986
> * config/aarch64/aarch64-sve2.md (@aarch64_sve_dot<mode>):
> Adjust insn predicate to use new mode attribute which checks
> for the correct feature bit depending on the mode.
> (@aarch64_sve_dot_lane<mode>): Likewise.
> * config/aarch64/iterators.md (HAVE_FP8_DOT_INSN): New.
>
> gcc/testsuite/ChangeLog:
>
> PR target/120986
> * gcc.target/aarch64/torture/pr120986-1.c: New test.
> ---
> gcc/config/aarch64/aarch64-sve2.md | 4 ++--
> gcc/config/aarch64/iterators.md | 4 ++++
> gcc/testsuite/gcc.target/aarch64/torture/pr120986-1.c | 10 ++++++++++
> 3 files changed, 16 insertions(+), 2 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/aarch64/torture/pr120986-1.c
>
> <0001-aarch64-Fix-predication-of-FP8-FDOT-insns-PR120986.patch>
+(define_mode_attr HAVE_FP8_DOT_INSN [(VNx4SF "TARGET_SSVE_FP8DOT4")
+ (VNx8HF "TARGET_SSVE_FP8DOT2")])
+
+
I think a more natural way would be to have a new mode iterator with the same
contents as SVE_FULL_HSF, say SVE_FULL_HSF_FP8 but have the TARGET_* conditions
guarding those modes.
For example:
(define_mode_iterator SVE_FULL_HSF_FP8 [(VNx4SF "TARGET_SSVE_FP8DOT4") (VNx8HF
“TARGET_SSVE_FP8DOT2")])
diff --git a/gcc/testsuite/gcc.target/aarch64/torture/pr120986-1.c
b/gcc/testsuite/gcc.target/aarch64/torture/pr120986-1.c
new file mode 100644
index 00000000000..8777f1b7711
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/torture/pr120986-1.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-march=armv8.2-a+sve2+fp8dot2" } */
Very minor but this bug is about arch gating rather than something that’s hit
with optimization, I don’t think there’s value in putting it in the torture
directory. I’d put it under normal gcc.target/aarch64.
Ok with these changes if you agree.
Thanks,
Kyrill
