[LLVMdev] Alias Analysis Problem in LICM

Anshuman Dasgupta adasgupt at codeaurora.org
Fri Nov 4 08:37:58 PDT 2011


On 11/4/2011 3:29 AM, Nick Lewycky wrote:
> I suspect that GCC is doing option 2, or something else I haven't 
> thought of (TBAA? if so, why doesn't our TBAA do as well?). 

Nick,

The problem is that LLVM's implementation of TBAA does not distinguish 
between these two types: i32*** @AAA and i32** %arrayidx. We believe 
that type based alias analysis should, in general, be able to figure out 
that those two variables cannot meaningfully alias.

-Anshu

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