[PATCH] [AArch64] Improve and enable the SeparateConstOffsetFromGEP for AArch64 backend.

[hfinkel at anl.gov]

> And most important is that it will also transform complex GEPs into a "ptrtoint + arithmetic + inttoptr" form, so that it is able to find CSE opportunities across basic blocks. 

You'll need to disable this transformation when AA is enabled in CodeGen. You can do this just like CGP does (essentially by calling TM->getSubtarget<TargetSubtargetInfo>().useAA()). CGP splits the GEPs into simpler GEPs when AA is in use, and uses inttoptr otherwise. This all relates to the way that we use BasicAA to override TBAA and catch cases of basic type punning -- but BasicAA does not analyze inttoptr, and so can no longer fulfill this need after new inttoptrs are introduced. You could try using simpler GEPs like CGP does when AA is in use, or just disable this part of the transformation for now. Either is fine with me.

http://reviews.llvm.org/D5864