[PATCH] D105374: [SimplifyCFG] simplifyUnreachable(): erase instructions iff they are guaranteed to transfer execution to unreachable

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri created this revision.
lebedev.ri added reviewers: spatel, nikic, efriedma, nlopes, jdoerfert.
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Herald added subscribers: jfb, hiraditya, nemanjai.
lebedev.ri requested review of this revision.

This synces the code with InstCombine's implementation in `InstCombinerImpl::visitUnreachableInst()`,
with one exception that here in SimplifyCFG we are allowed to remove EH instructions.

Effectively, this now allows SimplifyCFG to remove calls (iff they won't throw and will return),
arithmetic/logic operations, etc.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D105374

Files:
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
  llvm/lib/Transforms/Utils/SimplifyCFG.cpp
  llvm/test/CodeGen/PowerPC/2007-11-16-landingpad-split.ll
  llvm/test/Transforms/SimplifyCFG/simplifyUnreachable-degenerate-conditional-branch-with-matching-destinations.ll
  llvm/test/Transforms/SimplifyCFG/switch-range-to-icmp.ll

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