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Subject: [Bug middle-end/47383] ivopts miscompiles Pmode != ptr_mode
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47383

--- Comment #7 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-01-21 12:38:22 UTC ---
(In reply to comment #6)
> Sent from my Palm Pre on AT&amp;T
> On Jan 20, 2011 21:34, hjl.tools at gmail dot com
> &lt;gcc-bugzilla@gcc.gnu.org&gt; wrote: 
> 
> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47383
> 
> 
> 
> --- Comment #4 from H.J. Lu &lt;hjl.tools at gmail dot com&gt; 2011-01-21
> 05:33:53 UTC ---
> 
> (In reply to comment #3)
> 
> &gt; The ivopts pass transforms
> 
> &gt; 
> 
> &gt; 
> 
> &gt;   unsigned int D.2715;
> 
> &gt;   unsigned int D.2716;
> 
> &gt; ...
> 
> &gt;   D.2715_43 = (unsigned int) elems_3(D);
> 
> &gt;   D.2716_42 = D.2715_43 + 4294967295;
> 
> &gt;   n_49 = (int) D.2716_42;
> 
> &gt; 
> 
> &gt; leads o the wrong result when Pmode != unsigned int. Adding
> 
> &gt; -fno-ivopts fixes the bug.
> 
> &gt; 
> 
> 
> 
> This is OK due to cast to int. But
> 
> 
> 
>   long unsigned int D.2757;
> 
>   long unsigned int D.2749;
> 
>   long unsigned int D.2750;
> 
>   unsigned int ivtmp.20;
> 
>   int D.2748;
> 
>   unsigned int ivtmp.17;
> 
> ...
> 
>   D.2749_6 = (long unsigned int) prephitmp.8_18;
> 
>   D.2750_34 = ivtmp.17_28 - D.2749_6;
> 
>   MEM[symbol: heap, index: D.2750_34, step: 8, offset: 2296B] = n_11;
> 
> 
> 
> Mem here should have been rejected.
> 
> 
> looks wrong since it assumes D.2750_34 can be negative. But

sizetype values are sign-extended.

> D.2750_34 is unsigned. It won't work when ptr_mode == unsigned
> 
> and Pmode is unsigned long long.