[Bug middle-end/66702] New: #pragma omp declare simd uniform and linear issues

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66702

            Bug ID: 66702
           Summary: #pragma omp declare simd uniform and linear issues
           Product: gcc
           Version: 5.1.1
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: middle-end
          Assignee: unassigned at gcc dot gnu.org
          Reporter: jakub at gcc dot gnu.org
  Target Milestone: ---

void
bar (int &a, int &b, int *&c, int &d)
{
  volatile int x;
  int *volatile y;
  x = a; a = x;
  x = b; b = x;
  y = c; c = y;
  x = d; d = x;
}

void (*volatile barp) (int &, int &, int *&, int &) = bar;

#pragma omp declare simd uniform(b, c) linear(d:2) aligned(c:32) notinbranch
int
foo (int a, int b, int *c, int d)
{
  a++;
  b++;
  c += 8;
  d += 2;
  barp (a, b, c, d);
  return a + b + *c + d;
}

volatile int e = 5;
int c[64] __attribute__((aligned (32)));

int
main ()
{
  int d = 7, r = 0;
  int b = e;
  for (int i = 0; i < 64; i++)
    c[i] = i;
  #pragma omp simd reduction(+:r) linear(d:2)
  for (int i = 0; i < 64; i++)
    {
      r += foo (i, b, c, d);
      d += 2;
    }
  if (r != 7584)
    __builtin_abort ();
}

is miscompiled with -O2 -fopenmp, because uniform and linear clauses were
properly handled only for non-addressable variables of gimple type.
For addressable vars (both linear and uniform) or for non-gimple types or C++
args passed by invisible reference (uniform only), if the arguments are
modified in the function, we need to make a copy of the initial var and restore
it for each VL.