TBAA: add isTBAAVtableAccess to MDNode so clients can call the function

instead of having its own implementation.

The implementation of isTBAAVtableAccess is in TypeBasedAliasAnalysis.cpp
since it is related to the format of TBAA metadata.

The path for struct-path tbaa will be exercised by
test/Instrumentation/ThreadSanitizer/read_from_global.ll, vptr_read.ll, and
vptr_update.ll when struct-path tbaa is on by default.

llvm-svn: 190216

3 files changed, 24 insertions, 6 deletions

diff --git a/llvm/include/llvm/IR/Metadata.h b/llvm/include/llvm/IR/Metadata.h
index acd84d7cc18..49eb8950314 100644
--- a/llvm/include/llvm/IR/Metadata.h
+++ b/llvm/include/llvm/IR/Metadata.h
@@ -161,6 +161,9 @@ public:
     return V->getValueID() == MDNodeVal;
   }
 
+  /// Check whether MDNode is a vtable access.
+  bool isTBAAVtableAccess() const;
+
   /// Methods for metadata merging.
   static MDNode *getMostGenericTBAA(MDNode *A, MDNode *B);
   static MDNode *getMostGenericFPMath(MDNode *A, MDNode *B);
diff --git a/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp b/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
index bbf3c3a2a5c..ac3965feb88 100644
--- a/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
+++ b/llvm/lib/Analysis/TypeBasedAliasAnalysis.cpp
@@ -458,6 +458,25 @@ TypeBasedAliasAnalysis::getModRefInfo(ImmutableCallSite CS1,
   return AliasAnalysis::getModRefInfo(CS1, CS2);
 }
 
+bool MDNode::isTBAAVtableAccess() const {
+  if (!EnableStructPathTBAA) {
+    if (getNumOperands() < 1) return false;
+    if (MDString *Tag1 = dyn_cast<MDString>(getOperand(0))) {
+      if (Tag1->getString() == "vtable pointer") return true;
+    }
+    return false;
+  }
+
+  // For struct-path aware TBAA, we use the access type of the tag.
+  if (getNumOperands() < 2) return false;
+  MDNode *Tag = cast_or_null<MDNode>(getOperand(1));
+  if (!Tag) return false;
+  if (MDString *Tag1 = dyn_cast<MDString>(Tag->getOperand(0))) {
+    if (Tag1->getString() == "vtable pointer") return true;
+  }
+  return false;  
+}
+
 MDNode *MDNode::getMostGenericTBAA(MDNode *A, MDNode *B) {
   if (!A || !B)
     return NULL;
diff --git a/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
index e19ceba4d16..2c8a7c4118e 100644
--- a/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/ThreadSanitizer.cpp
@@ -240,12 +240,8 @@ bool ThreadSanitizer::doInitialization(Module &M) {
 }
 
 static bool isVtableAccess(Instruction *I) {
-  if (MDNode *Tag = I->getMetadata(LLVMContext::MD_tbaa)) {
-    if (Tag->getNumOperands() < 1) return false;
-    if (MDString *Tag1 = dyn_cast<MDString>(Tag->getOperand(0))) {
-      if (Tag1->getString() == "vtable pointer") return true;
-    }
-  }
+  if (MDNode *Tag = I->getMetadata(LLVMContext::MD_tbaa))
+    return Tag->isTBAAVtableAccess();
   return false;
 }