https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125988
Bug ID: 125988
Summary: `store_bit_field_1` drops insertion into
multi-register vector destination with -O3
-favoid-store-forwarding
Product: gcc
Version: 17.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: rtl-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: konstantinos.eleftheriou at vrull dot eu
Target Milestone: ---
Created attachment 64854
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=64854&action=edit
reduced testcase
The attached testcase aborts at runtime when compiled with `-O3
-favoid-store-forwarding` on aarch64. The `vld4_lane_bf16` insertion
into a `bfloat16x4x4_t` tuple is silently dropped: each verified lane
carries the value originally loaded by `vld1_bf16`, not the
overwriting value.
Output:
$ gcc -O3 -favoid-store-forwarding -march=armv8.2-a+bf16 testcase.c
Aborted (core dumped) ./a.out
$ gcc -v
Using built-in specs.
COLLECT_GCC=/home/keleftheriou/gcc-master/install/usr/local/bin/gcc
COLLECT_LTO_WRAPPER=/home/keleftheriou/gcc-master/install/usr/local/bin/../libexec/gcc/aarch64-unknown-linux-gnu/17.0.0/lto-wrapper
Target: aarch64-unknown-linux-gnu
Configured with: ../gcc/configure --enable-shared --enable-checking=yes,extra
--with-system-zlib --enable-__cxa_atexit --enable-linker-build-id
--enable-plugin --with-isl --enable-lto --disable-nls --enable-languages=all
--disable-bootstrap --disable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 17.0.0 20260622 (experimental) (GCC)
