gcc/testsuite/gcc.dg/fold-reassoc-1.c

   1 /* { dg-do compile } */
   2 /* { dg-options "-O -ffast-math -fdump-tree-original" } */
   3
   4 double foo (double x)
   5 {
   6   return (x + 0.5 - x - 0.5);
   7 }
   8
   9 /* { dg-final { scan-tree-dump "return 0.0;" "original" } } */
  10 /* { dg-final { cleanup-tree-dump "original" } } */