[PATCH] D17663: [JumpThreading] See through Cast Instructions

[Haicheng Wu via llvm-commits]

haicheng added a comment.

In http://reviews.llvm.org/D17663#364437, @gberry wrote:

> Would it not be better to fix SimplifyICmpInst to have some way of returning that it has done some simplification?


I am not sure.  Currently, SimplifyICmpInst either return a ConstantInt or an existing value.  Is it safe to let it return a new value?  Will it break anything?
.
ComputeValueKnownInPredecessors() is very similar to SimplifyInstruction().  Many cases handled in  ComputeValueKnownInPredecessors() (e.g., xor 1 x => not x ) are also the targets of SimplifyInstruction().  However, there are still some subtle differences between them (e.g. they treat undef differently) so that we cannot replace one by the other.  So, I think it might be better just enhancing ComputeValueKnownInPredecessors().


Repository:
  rL LLVM

http://reviews.llvm.org/D17663