[Bug tree-optimization/85063] New: Switch conversion in openacc routine introduces unsupported construct

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85063

            Bug ID: 85063
           Summary: Switch conversion in openacc routine introduces
                    unsupported construct
           Product: gcc
           Version: 8.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vries at gcc dot gnu.org
  Target Milestone: ---

Consider this test-case (filed earlier at lto PR84592):
...
/* { dg-additional-options "-ftree-switch-conversion" } */

#include <stdio.h>

#pragma acc routine seq
static int __attribute__((noinline)) foo (int n)
{
  switch (n & 3)
    {
    case 0: return 4;
    case 1: return 3;
    case 2: return 2;
    default:
      return 1;
    }
}

int
main (void)
{
  int n[1];
  n[0] = 4;
#pragma acc parallel copy(n)
  {
    n[0] = foo (n[0]); 
  }
  printf ("n: %d\n", n[0]);

  return 0;
}
...

When compiling this at -O2, we run into an ICE in lto1.

Switch conversion triggers for this example, which introduces a function static
var, and the ICE happens when processing the function static var (which is what
PR84592 is about).

However, OpenACC forbids function static vars in routines. So, switch
conversion shouldn't run on OpenACC routines.