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