[PATCH] D83976: [Mem2Reg] Teach promote to register about droppable instructions

[Johannes Doerfert via Phabricator via llvm-commits]

jdoerfert created this revision.
jdoerfert added reviewers: Tyker, fhahn, lebedev.ri, nicholas.
Herald added subscribers: bollu, hiraditya.
Herald added a project: LLVM.

This is the first of two patches to address PR46753. We basically allow
mem2reg to promote allocas that are used in doppable instructions, for
now that means `llvm.assume`. The uses of the alloca (or a bitcast or
zero offset GEP from there) are replaced by `undef` in the droppable
instructions.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D83976

Files:
  llvm/include/llvm/Analysis/ValueTracking.h
  llvm/lib/Analysis/ValueTracking.cpp
  llvm/lib/Transforms/Utils/PromoteMemoryToRegister.cpp
  llvm/test/Transforms/Mem2Reg/ignore-droppable.ll

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