clin1 added inline comments.

================
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.
----------------
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?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D98757/new/

https://reviews.llvm.org/D98757

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