[Bug target/83920] [nvptx] bad predicate reset

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83920

--- Comment #7 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Tom de Vries from comment #6)
> (In reply to Tom de Vries from comment #3)
> > Likewise, reversing the if-then-else order in gemm.f90 makes the testcase
> > fail on trunk without this patch.
> 
> Minimal version:

An even more minimal c version:
...
/* { dg-do run } */

extern void abort (void);

#define n 10

static void __attribute__((noinline)) __attribute__((noclone))
gemm (int beta, int *c)
{
  #pragma acc parallel copy(c[0:(n * n) - 1]) num_gangs(2)
  #pragma acc loop gang
  for (int j = 0; j < n; ++j)
    if (beta != 1)
      {
        #pragma acc loop vector
        for (int i = 0; i < n; ++i)
          c[i + (j * n)] = 0;
      }
}

int
main (void)
{
  int c[n * n];
  c[0] = 1;
  gemm (0.0, c);
  if (c[0] != 0)
    abort ();
}
...

Passes at O0, fails at O2.