[PATCH] D126269: [ASan] Skip pointer comparison and subtraction inserted by another instrumentation.

[Mingjie Xu via Phabricator via llvm-commits]

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When using ASan/pointer-compare together with UBSan/pointer-overflow under optimization level O1 <https://reviews.llvm.org/owners/package/1/>, then there will be a false positive in ASan. see https://github.com/google/sanitizers/issues/1508

This patch and D126270 <https://reviews.llvm.org/D126270> together will fix the false positive.

This patch: [ASan] Skip pointer comparison and subtraction instructions with !nosanitize metadata.
D126270 <https://reviews.llvm.org/D126270>: [InstCombine] Preserve !nosanitize for newly created instructions if old instructions have !nosanitize metadata.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D126269

Files:
  llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp


Index: llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
===================================================================
--- llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -1397,6 +1397,8 @@
 // false negatives. The proper implementation requires cooperation with
 // the frontend.
 static bool isInterestingPointerComparison(Instruction *I) {
+  if (I->hasMetadata("nosanitize"))
+    return false;
   if (ICmpInst *Cmp = dyn_cast<ICmpInst>(I)) {
     if (!Cmp->isRelational())
       return false;
@@ -1411,6 +1413,8 @@
 // false negatives. The proper implementation requires cooperation with
 // the frontend.
 static bool isInterestingPointerSubtraction(Instruction *I) {
+  if (I->hasMetadata("nosanitize"))
+    return false;
   if (BinaryOperator *BO = dyn_cast<BinaryOperator>(I)) {
     if (BO->getOpcode() != Instruction::Sub)
       return false;


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