[PATCH] D118426: [InstCombine] Remove side effect of replaced constrained intrinsics

[Serge Pavlov via Phabricator via llvm-commits]

sepavloff created this revision.
sepavloff added reviewers: kpn, nikic, spatel, craig.topper, andrew.w.kaylor.
Herald added a subscriber: hiraditya.
sepavloff requested review of this revision.
Herald added a project: LLVM.

If a constrained intrinsic call was replaced by some value, it was not
removed in some cases. The dangling instruction resulted in useless
instructions executed in runtime. It happened because constrained
intrinsics usually have side effect, it is used to model the interaction
with floating point-environment. In some cases it is correct behavior
but often the side effect is actually absent or can be ignored.

This change adds specific treatment of constrained intrinsics so that
their side effect can be removed if it actually absents.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D118426

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp
  llvm/lib/Transforms/InstCombine/InstCombineInternal.h
  llvm/test/Transforms/InstCombine/constrained.ll

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