[llvm] ded1f3e - [TSan] Add option to ignore capturing behavior when instrumenting (#148156)
via llvm-commits
llvm-commits at lists.llvm.org
Wed Aug 6 06:47:36 PDT 2025
Author: Yussur Mustafa Oraji
Date: 2025-08-06T15:47:33+02:00
New Revision: ded1f3ec96bc3de2951094dff5a8d2e12f7402c8
URL: https://github.com/llvm/llvm-project/commit/ded1f3ec96bc3de2951094dff5a8d2e12f7402c8
DIFF: https://github.com/llvm/llvm-project/commit/ded1f3ec96bc3de2951094dff5a8d2e12f7402c8.diff
LOG: [TSan] Add option to ignore capturing behavior when instrumenting (#148156)
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.
Added:
llvm/test/Instrumentation/ThreadSanitizer/capture-no-omit.ll
Modified:
llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
llvm/test/Instrumentation/ThreadSanitizer/capture.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
index 5485998164f1e..0d48a350254ee 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 +454,8 @@ 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
diff erent thread and participate in a data race
// (see llvm/Analysis/CaptureTracking.h for details).
diff --git a/llvm/test/Instrumentation/ThreadSanitizer/capture-no-omit.ll b/llvm/test/Instrumentation/ThreadSanitizer/capture-no-omit.ll
new file mode 100644
index 0000000000000..cae04936002cd
--- /dev/null
+++ b/llvm/test/Instrumentation/ThreadSanitizer/capture-no-omit.ll
@@ -0,0 +1,92 @@
+; RUN: opt < %s -passes=tsan -tsan-omit-by-pointer-capturing=0 -S | FileCheck %s
+
+target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64-S128"
+
+declare void @escape(ptr)
+
+ at sink = global ptr null, align 4
+
+
+define void @captured2() nounwind uwtable sanitize_thread {
+entry:
+ %ptr = alloca i32, align 4
+ %tmp = alloca ptr, align 8
+ ; transitive escape
+ store ptr %ptr, ptr %tmp, align 8
+ %0 = load ptr, ptr %tmp, align 8
+ store ptr %0, ptr @sink, align 8
+ store i32 42, ptr %ptr, align 4
+ ret void
+}
+; CHECK-LABEL: define void @captured2
+; CHECK: __tsan_write
+; CHECK: __tsan_read
+; CHECK: __tsan_write
+; CHECK: __tsan_write
+; CHECK: ret void
+
+define void @captured3() nounwind uwtable sanitize_thread {
+entry:
+ %stkobj = alloca [2 x i32], align 8
+ ; escapes due to store into global
+ store ptr %stkobj, ptr @sink, align 8
+ ; derived is captured as its base object is captured
+ %derived = getelementptr inbounds i32, ptr %stkobj, i64 1
+ store i32 42, ptr %derived, align 4
+ ret void
+}
+; CHECK-LABEL: define void @captured3
+; CHECK: __tsan_write
+; CHECK: __tsan_write
+; CHECK: ret void
+
+define void @notcaptured2() nounwind uwtable sanitize_thread {
+entry:
+ %ptr = alloca i32, align 4
+ %tmp = alloca ptr, align 8
+ store i32 42, ptr %ptr, align 4
+ ; transitive escape
+ store ptr %ptr, ptr %tmp, align 8
+ %0 = load ptr, ptr %tmp, align 8
+ store ptr %0, ptr @sink, align 8
+ ret void
+}
+; CHECK-LABEL: define void @notcaptured2
+; CHECK: __tsan_write
+; CHECK: __tsan_write
+; CHECK: __tsan_read
+; CHECK: __tsan_write
+; CHECK: ret void
+
+define void @notcaptured3(i1 %cond) nounwind uwtable sanitize_thread {
+entry:
+ %stkobj = alloca [2 x i32], align 8
+ %derived = getelementptr inbounds i32, ptr %stkobj, i64 1
+ %ptr = select i1 %cond, ptr %derived, ptr %stkobj
+ store i32 42, ptr %ptr, align 4
+ ret void
+}
+; CHECK-LABEL: define void @notcaptured3
+; CHECK: __tsan_write
+; CHECK: ret void
+
+define void @notcaptured4() nounwind uwtable sanitize_thread {
+entry:
+ %stkobj = alloca [10 x i8], align 1
+ br label %loop
+
+exit:
+ ret void
+
+loop:
+ %count = phi i32 [ 0, %entry ], [ %addone, %loop ]
+ %derived = phi ptr [ %stkobj, %entry ], [ %ptraddone, %loop ]
+ store i32 %count, ptr %derived, align 4
+ %ptraddone = getelementptr inbounds i32, ptr %derived, i64 1
+ %addone = add nuw nsw i32 %count, 1
+ %eq10 = icmp eq i32 %addone, 10
+ br i1 %eq10, label %exit, label %loop
+}
+; CHECK-LABEL: define void @notcaptured4
+; CHECK: ret void
+; CHECK: __tsan_write
diff --git a/llvm/test/Instrumentation/ThreadSanitizer/capture.ll b/llvm/test/Instrumentation/ThreadSanitizer/capture.ll
index e1b9e03b88446..5083c790011c6 100644
--- a/llvm/test/Instrumentation/ThreadSanitizer/capture.ll
+++ b/llvm/test/Instrumentation/ThreadSanitizer/capture.ll
@@ -45,6 +45,7 @@ entry:
; CHECK-LABEL: define void @captured2
; CHECK: __tsan_write
; CHECK: __tsan_write
+; CHECK-NOT: __tsan_write
; CHECK: ret void
define void @captured3() nounwind uwtable sanitize_thread {
@@ -101,6 +102,7 @@ entry:
; CHECK-LABEL: define void @notcaptured2
; CHECK: __tsan_write
; CHECK: __tsan_write
+; CHECK-NOT: __tsan_write
; CHECK: ret void
define void @notcaptured3(i1 %cond) nounwind uwtable sanitize_thread {
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