[Bug target/97442] New: Wrong represenation of AArch64 saba in RTL

["ktkachov at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97442

            Bug ID: 97442
           Summary: Wrong represenation of AArch64 saba in RTL
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ktkachov at gcc dot gnu.org
  Target Milestone: ---
            Target: aarch64

This is similar to the issue fixed in
https://gcc.gnu.org/git/?p=gcc.git&a=commit;h=8544ed6eea68a80999504c8a4b21b77d29cd86e2

The representation of the SABA (and UABA) in RTL is not correct and the below
testcase will abort at -O3 -fwrapv:

#define N 16
signed char a[] = {-100, -100, -100, -100,-100, -100, -100, -100, -100, -100,
-100, -100, -100, -100, -100, -100 };
signed char b[] = { 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100,
100, 100, 100, 100 };

signed char out[N] = { 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100,
100, 100, 100, 100, 100 };

__attribute__ ((noinline,noipa))
void
foo (void)
{
  for (int i = 0; i < N; i++)
    {
      signed char diff = b[i] - a[i];
      out[i] += diff > 0 ? diff : -diff;
    }
}

signed char out2[N] = { 100, 100, 100, 100, 100, 100, 100, 100, 100, 100, 100,
100, 100, 100, 100, 100 };

__attribute__ ((noinline,noipa))
void
foo_scalar (void)
{
  for (int i = 0; i < N; i++)
    {
      asm volatile ("");
      signed char diff = b[i] - a[i];
      out2[i] += diff > 0 ? diff : -diff;
    }
}

int
main (void)
{
  foo ();
  foo_scalar ();
  for (int i = 0; i < N; i++)
    if (out[i] != out2[i])
      __builtin_abort ();

  return 0;
}

due to function foo generating a saba when it shouldn't