gcc/testsuite/gcc.dg/nrv5.c

   1 /* Verify that NRV optimizations are prohibited when the LHS is
   2    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 typedef struct { int a; S b; } T;
   8 S nrv_candidate (void);
   9 void use_result (S);
  10 void make_escape (S *);
  11 void foo (void)
  12 {
  13   S result;
  14   T result_arr[10][5];
  15
  16   make_escape (&result);
  17   make_escape (&(result_arr[3][4].b));
  18
  19   /* Neither call should be allowed to use NRV optimization.  */
  20   result = nrv_candidate ();
  21   result_arr[3][4].b = nrv_candidate ();
  22
  23   use_result (result);
  24   use_result (result_arr[3][4].b);
  25 }
  26
  27 /* { dg-final { scan-tree-dump-times "return slot optimization" 0 "optimized" } } */