[PATCH] Fix expand_errno_check with tail calls (PR rtl-optimization/36017)

[Richard Guenther]

On Wed, Apr 23, 2008 at 12:00 AM, Jakub Jelinek <jakub@redhat.com> wrote:
> Hi!
>
>  If a math builtin is called as a tail call with CALL_EXPR_TAILCALL
>  set and errno check is done using a library call, in GCC 4.3+ the original
>  CALL_EXPR is used with a modified argument (SAVE_EXPR) and thus it can
>  be expanded as a tail call.  But expand_errno_check in the non-error case
>  jumps around it, and the tail call doesn't return.  Fixed by making
>  sure the error handling library call isn't a tail call (which is what
>  4.2 and earlier did because it recreated a CALL_EXPR).  The likely code
>  path is to jump around the library call, so if it doesn't end up being
>  a tail call, it shouldn't be a big deal.
>
>  Bootstrapped/regtested on x86_64-linux, ok for trunk?

Ok.

Thanks,
Richard.

>  2008-04-22  Jakub Jelinek  <jakub@redhat.com>
>
>         PR rtl-optimization/36017
>         * builtins.c (expand_errno_check): Clear CALL_EXPR_TAILCALL before
>         expanding the library call.
>
>         * gcc.dg/pr36017.c: New test.
>
>  --- gcc/builtins.c.jj   2008-04-08 11:27:38.000000000 +0200
>  +++ gcc/builtins.c      2008-04-22 22:13:00.000000000 +0200
>  @@ -1804,6 +1804,9 @@ expand_errno_check (tree exp, rtx target
>      }
>   #endif
>
>  +  /* Make sure the library call isn't expanded as a tail call.  */
>  +  CALL_EXPR_TAILCALL (exp) = 0;
>  +
>    /* We can't set errno=EDOM directly; let the library call do it.
>       Pop the arguments right away in case the call gets deleted.  */
>    NO_DEFER_POP;
>  --- gcc/testsuite/gcc.dg/pr36017.c.jj   2008-04-22 22:11:49.000000000 +0200
>  +++ gcc/testsuite/gcc.dg/pr36017.c      2008-04-22 22:11:25.000000000 +0200
>  @@ -0,0 +1,29 @@
>  +/* PR rtl-optimization/36017 */
>  +/* { dg-do run { target i?86-*-linux* x86_64-*-linux* } } */
>  +/* { dg-options "-O2 -lm" } */
>  +
>  +extern double sqrt (double);
>  +extern void abort (void);
>  +
>  +__attribute__((noinline)) double
>  +foo (double a)
>  +{
>  +  double b, c, d = 0.7;
>  +  if (a <= d)
>  +    b = sqrt (d * a);
>  +  else
>  +    {
>  +      c = (1.0 - d) * (1.0 - a);
>  +      b = c > 0 ? 1.0 - sqrt (c) : 1.0;
>  +    }
>  +  return b;
>  +}
>  +
>  +int
>  +main (void)
>  +{
>  +  double c = foo (0.5);
>  +  if (c > 0.5917)
>  +    abort ();
>  +  return 0;
>  +}
>
>         Jakub
>