[Bug tree-optimization/41577] Broken code with -O -ftree-vrp

[magnus dot christensson at acm dot org]

------- Comment #8 from magnus dot christensson at acm dot org  2009-10-05 12:36 -------
(In reply to comment #7)
> A fix is to write
> 
> uint32 res = ((uint32)(uint16)(cpu->gprs[12]  >> 16)
>               * (uint32)(uint16)(cpu->gprs[16] >> 16));
> 
> instead to force the multiplication in an unsigned type.
> 

Thanks. It wasn't obvious to me that a multiply on two unsigned variables would
be promoted to signed. The uint32 trick will work here, but won't work if your
target machine has 64-bit integers.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=41577