Wrong value for sext i1 true in BasicAliasAnalysis

[Yin Ma]

Hi Hal,

 

How are you doing. For your patch db1e51359, you changed offset  computation


from zext to sext. However, I came across a case that expression contains
i1 true to i32.  

true is value 1 for offset. if it is sext to 32bit, the result of sext will
not be 1. Instead, it will 

be -1. Sext true is a special case. This will make AA check failed when one
GEP contains 

i1 true to i32 expression but the other GEP doesn't.

 

I attached my change. How do you think? If it is valid patch, please merge
it to the tip.

 

Thanks,

 

Yin 

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