[PATCH] D98757: [AMX] Not fold constant bitcast into amx intrisic

[Chang Lin via Phabricator via cfe-commits]

clin1 added inline comments.


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Comment at: llvm/lib/Analysis/ConstantFolding.cpp:101
 /// Constant fold bitcast, symbolically evaluating it with DataLayout.
 /// This always returns a non-null constant, but it may be a
 /// ConstantExpr if unfoldable.
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xiangzhangllvm wrote:
> clin1 wrote:
> > API for this function always returns non-null: can we return ConstantExpr::getBitCast(C,DestTy) instead? Then the change in SCCP is not needed either.
> I tried, the SCCP will also fold the bitcast into the following instruction.
I see, that makes sense. But are we sure that all callers of FoldBitCast are doing a null check: for example, FoldReinterpretLoadFromConstPtr calls FoldBitCast several times, and null is not checked before dereference. Maybe the AMX type cannot happen in this case?
Alternative: can AMX be checked in SCCP?


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  https://reviews.llvm.org/D98757/new/

https://reviews.llvm.org/D98757