------- Comment #7 from rguenther at suse dot de 2008-08-27 09:40 -------
Subject: Re: missed FRE opportunity because of
signedness of addition
On Wed, 27 Aug 2008, bonzini at gnu dot org wrote:
>
>
> ------- Comment #4 from bonzini at gnu dot org 2008-08-27 06:41 -------
> Minimized testcase:
>
> int m(int *y, int x)
> {
> int a = y[x + 1];
> int b = y[++x];
> return a - b;
> }
>
> should be optimized to "return 0"
Because fold folds (unsigned)(x + 1) to (unsigned)x + 1 but doesn't
touch (unsigned) ++x which gets gimplified to a signed addition.
Richard.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37242
