[Bug tree-optimization/104394] New: Failure to optimize vector pattern for x < 0

[gabravier at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104394

            Bug ID: 104394
           Summary: Failure to optimize vector pattern for x < 0
           Product: gcc
           Version: 12.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: gabravier at gmail dot com
  Target Milestone: ---

#include <stdint.h>

typedef int32_t v4i32 __attribute__((vector_size(16)));

v4i32 get_cmpmask(v4i32 mask)
{
    v4i32 signmask{(int32_t)0x80000000, (int32_t)0x80000000,
(int32_t)0x80000000, (int32_t)0x80000000};
    return ((signmask & mask) == signmask);
}

This can be optimized to `return mask < 0;`. This transformation is done by
LLVM, but not by GCC.