[PATCH] D137707: Move "auto-init" instruction to the dominator of their use

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As a result of `-ftrivial-auto-var-init`,  clang generates instructions to set alloca'd memory to a given pattern, right after the allocation site. In some cases, this (somehow costly) operation could be delayed, leading to conditional execution in some cases.

This is not an uncommon situation: it happens ~600 times on the cPython code base, and much more on the LLVM codebase. The benefit greatly varies on the execution path, but it should not regress on performance.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D137707

Files:
  llvm/include/llvm/InitializePasses.h
  llvm/include/llvm/LinkAllPasses.h
  llvm/include/llvm/Transforms/Utils.h
  llvm/include/llvm/Transforms/Utils/MoveAutoInit.h
  llvm/lib/Passes/PassBuilder.cpp
  llvm/lib/Passes/PassBuilderPipelines.cpp
  llvm/lib/Passes/PassRegistry.def
  llvm/lib/Transforms/Utils/CMakeLists.txt
  llvm/lib/Transforms/Utils/MoveAutoInit.cpp
  llvm/test/Other/new-pm-defaults.ll
  llvm/test/Other/new-pm-thinlto-defaults.ll
  llvm/test/Other/new-pm-thinlto-postlink-pgo-defaults.ll
  llvm/test/Other/new-pm-thinlto-postlink-samplepgo-defaults.ll
  llvm/test/Other/new-pm-thinlto-prelink-pgo-defaults.ll
  llvm/test/Other/new-pm-thinlto-prelink-samplepgo-defaults.ll

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