[PATCH] D129991: [sanitizer] Don't always instrument on every lifetime.start

[luxufan via Phabricator via llvm-commits]

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In D129448 <https://reviews.llvm.org/D129448>, the solution to deal with bypassed variables makes multiple
lifetime start intrinsics for the same alloca object appears in multiple
different basic block. But MemorySanitizer assumes that the variable is
always uninitialized at the place of lifetime.start intrinsic and
instruments poisoning code for it. After D129448 <https://reviews.llvm.org/D129448>, this assumption is broken.

This patch fix the broken assumption by analysis the dominance relation
of lifetime start/end intrinsics.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D129991

Files:
  llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
  llvm/test/Instrumentation/MemorySanitizer/alloca.ll

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