[all-commits] [llvm/llvm-project] 9b889f: Thread safety analysis: Warn when demoting locks o...

[Aaron Puchert via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 9b889f826ff587e9758c80823419512d502e457d
      https://github.com/llvm/llvm-project/commit/9b889f826ff587e9758c80823419512d502e457d
  Author: Aaron Puchert <aaron.puchert at sap.com>
  Date:   2021-09-18 (Sat, 18 Sep 2021)

  Changed paths:
    M clang/lib/Analysis/ThreadSafety.cpp
    M clang/test/SemaCXX/warn-thread-safety-analysis.cpp

  Log Message:
  -----------
  Thread safety analysis: Warn when demoting locks on back edges

Previously in D104261 we warned about dropping locks from back edges,
this is the corresponding change for exclusive/shared joins. If we're
entering the loop with an exclusive change, which is then relaxed to a
shared lock before we loop back, we have already analyzed the loop body
with the stronger exclusive lock and thus might have false positives.

There is a minor non-observable change: we modify the exit lock set of a
function, but since that isn't used further it doesn't change anything.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D106713