[PATCH] D60617: MSan: handle llvm.lifetime.start intrinsic

[Alexander Potapenko via Phabricator via llvm-commits]

glider created this revision.
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When a variable goes into scope several times within a single function
or when two variables from different scopes share a stack slot it may
be incorrect to poison such scoped locals at the beginning of the
function.
In the former case it may lead to false negatives (see
https://github.com/google/sanitizers/issues/590), in the latter - to
incorrect reports (because only one origin remains on the stack).

If Clang emits lifetime intrinsics with known size for such scoped
variables we insert code poisoning them after each call to
llvm.lifetime.start(). This is done on a best-effort basis.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D60617

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

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