Implement lock summaries for interprocedural analysis in LockOwnership

[michael-schwarz]

Replaces full exit state propagation at call sites with precise lock summaries tracking which locks a function may release and which it must acquire.

Changes

• Data structures: Extended FuncStateTy with MayUnlock and MustLock sets

  • MayUnlock: Locks held at entry but not at exit (released on some path)
  • MustLock: Locks held at exit but not at entry (newly acquired on all paths)

• Summary computation: In buildSummary(), compute summaries by comparing entry and exit states

  • Handles both absent locks and explicitly unlocked locks in state maps

• Call edge handling: In applyTransferFunc(), apply summaries instead of full exit state

  • Remove locks in callee's MayUnlock from current lockset
  • Add locks in callee's MustLock to current lockset

Example

// Before: Replaced entire lockset with callee's exit state
for (const auto &[Lock, State] : FuncStateIt->second.ExitState) {
  if (State.IsLocked) handleLock(InState, I, Lock);
  else handleUnlock(InState, I, Lock);
}

// After: Selectively apply lock changes
for (const Value *Lock : FuncStateIt->second.MayUnlock) {
  if (InState.find(Lock) != InState.end())
    handleUnlock(InState, I, Lock);
}
for (const Value *Lock : FuncStateIt->second.MustLock) {
  handleLock(InState, I, Lock);
}

This enables more precise tracking of lock state changes across function boundaries, particularly for functions that partially modify the lockset.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Use lock summaries in LockOwnership.cpp</issue_title>
<issue_description>Make a PR against the branch tsan-with-ea-IPA. In this PR, on top of computing the currently held lockset, for each procedure also compute a summary consisting of two sets:

• A set of mutexes that may be unlocked anywhere in the function and not relocked
• A set of mutexes that were not known to locked at the start of the function but are known to be locked now.

Then, we computing the effect of a call edge to f, take the current lockset, remove any mutexes that f may unlock and add those that f must lock.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Use lock summaries in LockOwnership.cpp michael-schwarz/llvm-project#1

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