[llvm] [HWASAN] Implement selective instrumentation based on profiling information (PR #83503)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-transforms

Author: Kirill Stoimenov (kstoimenov)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/83503.diff


1 Files Affected:

- (modified) llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp (+49-2) 


``````````diff
diff --git a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
index 33add6d4cd767b..bf59f10723c2db 100644
--- a/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/HWAddressSanitizer.cpp
@@ -15,11 +15,14 @@
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Analysis/DomTreeUpdater.h"
 #include "llvm/Analysis/GlobalsModRef.h"
 #include "llvm/Analysis/PostDominators.h"
+#include "llvm/Analysis/BlockFrequencyInfo.h"
+#include "llvm/Analysis/ProfileSummaryInfo.h"
 #include "llvm/Analysis/StackSafetyAnalysis.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/ValueTracking.h"
@@ -177,6 +180,22 @@ static cl::opt<bool> ClWithTls(
              "platforms that support this"),
     cl::Hidden, cl::init(true));
 
+static cl::opt<bool>
+    CSkipHotCode("hwasan-skip-hot-code",
+                 cl::desc("Do not instument hot functions based on FDO."),
+                 cl::Hidden, cl::init(false));
+
+static cl::opt<int> HotPercentileCutoff("hwasan-percentile-cutoff-hot",
+                                        cl::init(0));
+
+STATISTIC(NumTotalFuncs, "Number of funcs seen by HWASAN");
+STATISTIC(NumHwasanCtors, "Number of HWASAN ctors");
+STATISTIC(NumNoSanitizeFuncs, "Number of no-sanitize HWASAN funcs");
+STATISTIC(NumConsideredFuncs, "Number of funcs considered for HWASAN");
+STATISTIC(NumInstrumentedFuncs, "Number of HWASAN instrumented funcs");
+STATISTIC(NumNoProfileSummaryFuncs, "Number of HWASAN funcs without PS");
+STATISTIC(NumSkippedHotFuncs, "Number of skipped hot HWASAN funcs");
+
 // Mode for selecting how to insert frame record info into the stack ring
 // buffer.
 enum RecordStackHistoryMode {
@@ -1501,11 +1520,39 @@ bool HWAddressSanitizer::instrumentStack(memtag::StackInfo &SInfo,
 
 void HWAddressSanitizer::sanitizeFunction(Function &F,
                                           FunctionAnalysisManager &FAM) {
-  if (&F == HwasanCtorFunction)
+  NumTotalFuncs++;
+  if (&F == HwasanCtorFunction) {
+    NumHwasanCtors++;
     return;
+  }
 
-  if (!F.hasFnAttribute(Attribute::SanitizeHWAddress))
+  if (!F.hasFnAttribute(Attribute::SanitizeHWAddress)) {
+    NumNoSanitizeFuncs++;
     return;
+  }
+
+  NumConsideredFuncs++;
+  if (CSkipHotCode) {
+    auto &MAMProxy = FAM.getResult<ModuleAnalysisManagerFunctionProxy>(F);
+    ProfileSummaryInfo *PSI =
+        MAMProxy.getCachedResult<ProfileSummaryAnalysis>(*F.getParent());
+    if (PSI != nullptr && PSI->hasProfileSummary()) {
+      auto &BFI = FAM.getResult<BlockFrequencyAnalysis>(F);
+      const bool is_hot =
+          (HotPercentileCutoff.getNumOccurrences() && HotPercentileCutoff >= 0)
+              ? PSI->isFunctionHotInCallGraphNthPercentile(HotPercentileCutoff,
+                                                           &F, BFI)
+              : PSI->isFunctionEntryHot(&F);
+
+      if (is_hot) {
+        ++NumSkippedHotFuncs;
+        return;
+      }
+    } else {
+      ++NumNoProfileSummaryFuncs;
+    }
+  }
+  NumInstrumentedFuncs++;
 
   LLVM_DEBUG(dbgs() << "Function: " << F.getName() << "\n");
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/83503