[LLVMdev] [cfe-dev] Extend llvm to fix global addresses

David A. Greene greened at obbligato.org
Mon Dec 12 09:20:13 PST 2011

Dan Gohman <gohman at apple.com> writes:

>> But anything which avoids the horrible int* cast has to be a good
>> thing.  For one thing it would cause alias analysis a lot of pain.
> Actually, it wouldn't cause very much pain, if any, in alias analysis.
> LLVM IR already assumes that programmers can't "guess" what the
> address of the stack, global variables, or heap will be. An integer
> constant casted to a pointer is assumed to be non-aliasing with
> "regular" objects in memory.

> I don't mean to shoot you down, but there don't seem to be any
> compelling motivations for this feature.

I agree.  We make use of this property to turn some pretty ugly frontend
pointer arithmetic using integers into somewhat less ugly GEP operations
which LLVM can understand.

So ptrtoint/inttoptr isn't really a problem as long as you know it's


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