gcc/testsuite/gcc.dg/nrv4.c

   1 /* Verify that NRV optimizations are prohibited when the LHS is an
   2    indirect reference to something that may be call-clobbered. */
   3 /* { dg-do compile } */
   4 /* { dg-options "-O -fdump-tree-optimized" } */
   5
   6 typedef struct { int x[20]; void *y; } S;
   7 S nrv_candidate (void);
   8 void use_result (S);
   9 void make_escape (S *);
  10 S global_S;
  11 void foo (void)
  12 {
  13   S *result;
  14   S local_S;
  15
  16   /* We can't perform return slot optimization because global_S is
  17      global and may be clobbered by nrv_candidate.  */
  18   result = &global_S;
  19   *result = nrv_candidate ();
  20   use_result (*result);
  21
  22   /* We can't perform return slot optimization because local_S is
  23      call_clobbered (its address escapes prior to invoking
  24      nrv_candidate).  */
  25   make_escape (&local_S);
  26   result = &local_S;
  27   *result = nrv_candidate ();
  28   use_result (*result);
  29 }
  30
  31 /* { dg-final { scan-tree-dump-times "return slot optimization" 0 "optimized" } } */
  32