[PATCH] Fix PR middle-end/17813

[Eric Botcazou]

> with this patch (configured for i486-linux) I get until:
>
> Bootstrap comparison failure!
> ada/a-except.o differs
> ada/ali-util.o differs
> ada/s-crc32.o differs
> make[3]: *** [gnucompare] Error 1

The stage3 s-crc32.o is miscompiled by the stage2 compiler because the stage2 
uintp.o is miscompiled by the stage1 compiler because of PR middle-end/18045.

I'm testing a fix for the latter on a full bootstrap (a C+Ada bootstrap 
already completed, even without stumbling upon PR tree-opt/17986).

-- 
Eric Botcazou