Problem with Fix for PR 35163 ?

[Richard Guenther]

On Tue, Apr 8, 2008 at 5:36 PM, Richard Guenther
<richard.guenther@gmail.com> wrote:
>
> On Tue, Apr 8, 2008 at 4:46 PM, Pranav Bhandarkar
>  <pranav.bhandarkar@gmail.com> wrote:
>  > Hi,
>  >
>  >  Consider the attached testcase.
>  >
>  >  Working on a private port (Infact I see this problem on
>  >  arm-none-eabi-gcc too). I see the following in test.c.003t.original
>  >
>  >  fail = (short int) usi <= ssi;
>  >
>  >  And then in test.c.025t.ssa
>  >   usi.2_5 = (short int) usi_4;
>  >   fail.3_6 = usi.2_5 <= ssi_2;
>  >
>  >  Now ccp1 does constant propagation and we are left with
>  >  usi.2_5 = -256;
>  >
>  >  This causes the test to fail.
>  >
>  >  Clearly the problem seems to be that since usi is unsigned short int a
>  >  short int cant represent all the possible values of usi
>  >
>  >  I reverted the following patch and the test passed.
>  >   PR middle-end/35163
>  >         * fold-const.c (fold_widened_comparison): Use get_unwidened in
>  >         value-preserving mode.  Disallow final truncation.
>  >
>  >  Now with the patch reverted, test.c.003t.original has
>  >
>  >   fail = (int) ssi >= (int) usi;
>  >
>  >  And this problem vanished.
>  >
>  >
>  >  Am I missing something here ?
>
>  Please file a bugreport about this.

Btw, I have a fix.

Richard.