[PATCH] D24173: Explicitly require DominatorTreeAnalysis pass for instsimplify pass.

[Dehao Chen via llvm-commits]

danielcdh added a comment.

In https://reviews.llvm.org/D24173#535251, @davidxl wrote:

> What breaks without the change?


When I enable LoopSink pass, I need to add InstSimplifierPass pass after it to do some cleanup. However, if I directly invoke InstSimplifierPass pass, it will fail due to lack of DT.

>From the InstSimplifierPass implementation, it uses DT without checking if it is nullptr. So I think we should explicitly require DT for this pass.

A typical use of DT from InstSimplifierPass is:

llvm::SimplifyInstruction->
llvm::SimplifyICmpInst->
SimplifyICmpInst ->
computePointerICmp->
llvm::isKnownNonNullAt (ValueTracking.cpp) ->
isKnownNonNullFromDominatingCondition (ValueTracking.cpp) ->
llvm::DominatorTree::dominates (Dominators.cpp)


https://reviews.llvm.org/D24173