[Bug middle-end/37103] [4.3/4.4 Regression] possible integer codegen bug

["rguenther at suse dot de" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #5 from rguenther at suse dot de  2008-08-13 21:05 -------
Subject: Re:  [4.3/4.4 Regression] possible integer
 codegen bug

On Wed, 13 Aug 2008, jakub at gcc dot gnu dot org wrote:

> ------- Comment #4 from jakub at gcc dot gnu dot org  2008-08-13 18:30 -------
> Verified the regression was introduced by PR35163 fix.
> http://gcc.gnu.org/ml/gcc-patches/2008-04/msg00720.html
> should have been IMNSHO applied for shorter_type bigger or equal than
> arg1_unw's type, not just when they are equal.  If shorter_type is bigger and
> the signs are different, then the bits above shorter_type bits might be all 1's
> in one case and all 0's in the second case.

Yeah, you are right.  Patch is pre-approved.

Richard.

> Patch I'll be regtesting:
> 
> 2008-08-13  Jakub Jelinek  <jakub@redhat.com>
> 
> PR middle-end/37103
> * fold-const.c (fold_widened_comparison): Do not allow
> sign changes that change the result even if shorter type
> is wider than arg1_unw's type.
> 
> * gcc.c-torture/execute/20080813-1.c: New test.
> 
> --- gcc/fold-const.c.jj2008-08-13 19:46:11.000000000 +0200
> +++ gcc/fold-const.c2008-08-13 20:18:21.000000000 +0200
> @@ -6733,10 +6733,8 @@ fold_widened_comparison (enum tree_code 
>    if ((code == EQ_EXPR || code == NE_EXPR
>         || TYPE_UNSIGNED (TREE_TYPE (arg0)) == TYPE_UNSIGNED (shorter_type))
>        && (TREE_TYPE (arg1_unw) == shorter_type
> -  || (TYPE_PRECISION (shorter_type)
> -      > TYPE_PRECISION (TREE_TYPE (arg1_unw)))
>    || ((TYPE_PRECISION (shorter_type)
> -       == TYPE_PRECISION (TREE_TYPE (arg1_unw)))
> +       >= TYPE_PRECISION (TREE_TYPE (arg1_unw)))
>        && (TYPE_UNSIGNED (shorter_type)
>    == TYPE_UNSIGNED (TREE_TYPE (arg1_unw))))
>    || (TREE_CODE (arg1_unw) == INTEGER_CST
> --- gcc/testsuite/gcc.c-torture/execute/20080813-1.c.jj2008-08-13
> 20:22:56.000000000 +0200
> +++ gcc/testsuite/gcc.c-torture/execute/20080813-1.c2008-08-13
> 20:22:10.000000000 +0200
> @@ -0,0 +1,30 @@
> +/* PR middle-end/37103 */
> +
> +extern void abort (void);
> +
> +void
> +foo (unsigned short x)
> +{
> +  signed char y = -1;
> +  if (x == y)
> +    abort ();
> +}
> +
> +void
> +bar (unsigned short x)
> +{
> +  unsigned char y = -1;
> +  if (x == y)
> +    abort ();
> +}
> +
> +int
> +main (void)
> +{
> +  if (sizeof (int) == sizeof (short))
> +    return 0;
> +  foo (-1);
> +  if (sizeof (short) > 1)
> +    bar (-1);
> +  return 0;
> +}
> 
> 
> 


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37103