[Bug target/108177] New: MVE predicated stores to same address get optimized away

[avieira at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108177

            Bug ID: 108177
           Summary: MVE predicated stores to same address get optimized
                    away
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: avieira at gcc dot gnu.org
  Target Milestone: ---

GCC currently generates wrong code for predicated MVE stores to the same
address. Like:

#include <arm_mve.h>

uint8x16_t foo (uint8x16_t a, uint8_t *pa, mve_pred16_t p1, mve_pred16_t p2)
{
    vstrbq_p_u8 (pa, a, p1);
    vstrbq_p_u8 (pa, a, p2);
}

with 'gcc -mcpu=cortex-m55 -mfloat-abi=hard -O3' it will only generate the
second MVE store. Though if (p2 | p1) != p2 then the second store will not
fully overwrite the first.