gcc/testsuite/gcc.target/i386/pr9771-1.c

   1 /* PR rtl-optimization/9771 */
   2 /* { dg-do run } */
   3 /* { dg-require-effective-target ia32 } */
   4 /* { dg-options "-O2 -fomit-frame-pointer -ffixed-ebp" } */
   5
   6 extern void abort(void);
   7 extern void exit(int);
   8
   9 register long *B asm ("ebp");
  10
  11 long x = 10;
  12 long y = 20;
  13
  14 void bar(void)
  15 {
  16   B = &y;
  17 }
  18
  19 void foo()
  20 {
  21   long *adr = B;
  22   long save = *adr;
  23
  24   *adr = 123;
  25
  26   bar();
  27
  28   *adr = save;
  29 }
  30
  31 /* This must not be inlined because main() requires the frame pointer
  32    for stack alignment.  */
  33 void test(void) __attribute__((noinline));
  34 void test(void)
  35 {
  36   B = &x;
  37
  38   foo();
  39
  40   if (x != 10 || y != 20)
  41     abort();
  42
  43   /* We can't return, as our caller may assume %ebp is preserved!  */
  44   /* We could save/restore it (like foo), but its easier to exit.  */
  45   exit(0);
  46 }
  47
  48 /* main usually performs dynamic realignment of the stack in case
  49    _start would fail to properly align the stack, but for dynamic
  50    stack realignment we need frame pointer which is incompatible
  51    with -ffixed-ebp and the global register var.  So, cheat here
  52    and hide from the compiler that main is really main.  */
  53 #define ASMNAME(cname)  ASMNAME2 (__USER_LABEL_PREFIX__, cname)
  54 #define ASMNAME2(prefix, cname) STRING (prefix) cname
  55 #define STRING(x)    #x
  56 int real_main() __asm (ASMNAME ("main"));
  57
  58 int real_main()
  59 {
  60   test();
  61   return 0;
  62
  63 }