gcc/testsuite/gcc.dg/pr19633.c

   1 /* { dg-do link } */
   2 /* { dg-options "-O2" } */
   3
   4 struct S
   5 {
   6   int w, x, y, z;
   7 };
   8
   9 struct T
  10 {
  11   int r;
  12   struct S s;
  13 };
  14
  15 void link_error (void);
  16 int bar (struct S, int);
  17
  18 void
  19 foo (int a, struct T b)
  20 {
  21   struct S *c = 0;
  22
  23   if (a)
  24     c = &b.s;
  25
  26   b.s.w = 3;
  27
  28   /* Since 'c' may be pointing to NULL here, we used to flag it as
  29      pointing anywhere, which was forcing the aliaser to mark as
  30      call-clobbered every other variable pointed-to by 'c' ('b' in
  31      this case).  This, in turn, caused the insertion of V_MAY_DEFs
  32      for 'b' at this call-site, which prevented constant propagation
  33      from 'b.s.w = 3' to 'if (b.s.w != 3)'.  */
  34   bar (*c, a);
  35
  36   if (b.s.w != 3)
  37     link_error ();
  38 }
  39
  40 int main ()
  41 {
  42   struct T b;
  43   foo (3, b);
  44   return 0;
  45 }
  46
  47 int X;
  48
  49 int bar (struct S x, int i)
  50 {
  51   X = 3;
  52 }