[llvm] [TSan] Add option to ignore capturing behavior when instrumenting (PR #148156)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Yussur Mustafa Oraji (N00byKing)

<details>
<summary>Changes</summary>

While not needed for most applications, some tools such as [MUST](https://www.i12.rwth-aachen.de/cms/i12/forschung/forschungsschwerpunkte/lehrstuhl-fuer-hochleistungsrechnen/~nrbe/must/) depend on the instrumentation being present.
MUST uses the ThreadSanitizer annotation interface to detect data races in MPI programs, where the capture tracking is detrimental as it has no bearing on MPI data races, leading to missed races.



---
Full diff: https://github.com/llvm/llvm-project/pull/148156.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp (+5-1) 


``````````diff
diff --git a/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
index 5485998164f1e..d24ee09abebe5 100644
--- a/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
@@ -80,6 +80,10 @@ static cl::opt<bool> ClCompoundReadBeforeWrite(
     "tsan-compound-read-before-write", cl::init(false),
     cl::desc("Emit special compound instrumentation for reads-before-writes"),
     cl::Hidden);
+static cl::opt<bool> ClOmitNonCaptured(
+    "tsan-omit-by-pointer-capturing", cl::init(true),
+    cl::desc("Omit accesses due to pointer capturing"),
+    cl::Hidden);
 
 STATISTIC(NumInstrumentedReads, "Number of instrumented reads");
 STATISTIC(NumInstrumentedWrites, "Number of instrumented writes");
@@ -450,7 +454,7 @@ void ThreadSanitizer::chooseInstructionsToInstrument(
 
     const AllocaInst *AI = findAllocaForValue(Addr);
     // Instead of Addr, we should check whether its base pointer is captured.
-    if (AI && !PointerMayBeCaptured(AI, /*ReturnCaptures=*/true)) {
+    if (AI && !PointerMayBeCaptured(AI, /*ReturnCaptures=*/true) && ClOmitNonCaptured) {
       // The variable is addressable but not captured, so it cannot be
       // referenced from a different thread and participate in a data race
       // (see llvm/Analysis/CaptureTracking.h for details).

``````````

</details>


https://github.com/llvm/llvm-project/pull/148156