[Bug tree-optimization/46398] New: early FRE miscompiles simple testcase

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46398

           Summary: early FRE miscompiles simple testcase
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Keywords: wrong-code
          Severity: normal
          Priority: P3
         Component: tree-optimization
        AssignedTo: unassig...@gcc.gnu.org
        ReportedBy: rgue...@gcc.gnu.org


Inserting an early FRE pass after pass_sra_early causes us to miscompile the
following testcase (reduced from cp/parser.c).

int __attribute__((noinline))
test (int token)
{
  int done = 0;
  int virtual_p = 0;
  while (!done)
    {
      if (token == 42)
        virtual_p = 1;
      else
        done = 1;
    }
  return virtual_p;
}
extern void abort (void);
int
main()
{
  if (test (0) != 0)
    abort ();
  return 0;
}