[PATCH] D70171: [Scalarizer] Treat values from unreachable blocks as undef

[Mikael Holmén via Phabricator via llvm-commits]

uabelho created this revision.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

When scalarizing PHI nodes we might try to examine/rewrite
InsertElement nodes in predecessors. If those predecessors
are unreachable from entry, then the IR in those blocks could
have unexpected properties resulting in infinite loops in
Scatterer::operator[].
By simply treating values originating from instructions in
unreachable blocks as undef we do not need to analyse them
further.

This fixes PR41723.


Repository:
  rL LLVM

https://reviews.llvm.org/D70171

Files:
  llvm/lib/Transforms/Scalar/Scalarizer.cpp
  llvm/test/Transforms/Scalarizer/phi-unreachable-pred.ll

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