Handle llvm.launder.invariant.group in msan.

Summary:
[MSan] handle llvm.launder.invariant.group

    Msan used to give false-positives in

    class Foo {
     public:
      virtual ~Foo() {};
    };

    // Return true iff *x is set.
    bool f1(void **x, bool flag);

    Foo* f() {
      void *p;
      bool found;
      found = f1(&p,flag);
      if (found) {
        // p is always set here.
        return static_cast<Foo*>(p); // False positive here.
      }
      return nullptr;
    }

Patch by Ilya Tokar.

Reviewers: #sanitizers, eugenis

Reviewed By: #sanitizers, eugenis

Subscribers: eugenis, Prazek, hiraditya, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68236

llvm-svn: 373515

1 files changed, 9 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
index 81bd2f3c18a..f9354069da3 100644
--- a/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/MemorySanitizer.cpp
@@ -2562,6 +2562,11 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     return false;
   }
 
+  void handleInvariantGroup(IntrinsicInst &I) {
+    setShadow(&I, getShadow(&I, 0));
+    setOrigin(&I, getOrigin(&I, 0));
+  }
+
   void handleLifetimeStart(IntrinsicInst &I) {
     if (!PoisonStack)
       return;
@@ -2993,6 +2998,10 @@ struct MemorySanitizerVisitor : public InstVisitor<MemorySanitizerVisitor> {
     case Intrinsic::lifetime_start:
       handleLifetimeStart(I);
       break;
+    case Intrinsic::launder_invariant_group:
+    case Intrinsic::strip_invariant_group:
+      handleInvariantGroup(I);
+      break;
     case Intrinsic::bswap:
       handleBswap(I);
       break;