[PATCH] D63928: [ARM][SCEV][LSR] Prevent using undefined value in binops

[Eugene Leviant via Phabricator via llvm-commits]

evgeny777 added a comment.

> so maybe we could try to introduce a map of updated values so that we don't reuse 'dead' instructions?

I tried this initially but the problem is that previous result of `expand` could be invalidated by subsequent call:

  Value *A = expand(Op1);
  Value *B = expand(Op2); 
  // A may become invalid at this point

There are lot of such potential "points of failure" in SCEVExpander and I don't easy way to address them all.
On the other hand it's much easier to strip extra IR cast instructions in SCEVExpander::clear (doing RAUW and eraseFromParent), but they will be eliminated by machine passes anyway,
so I wonder if it's worth doing


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  https://reviews.llvm.org/D63928/new/

https://reviews.llvm.org/D63928