TBAA: use the same format for scalar TBAA and struct-path aware TBAA.

An updated version of r191586 with bug fix.

Struct-path aware TBAA generates tags to specify the access path,
while scalar TBAA only generates tags to scalar types.

We should not generate a TBAA tag with null being the first field. When
a TBAA type node is null, the tag should be null too. Make sure we
don't decorate an instruction with a null TBAA tag.

Added a testing case for the bug reported by Richard with -relaxed-aliasing
and -fsanitizer=thread.

llvm-svn: 192145

1 files changed, 4 insertions, 4 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 6c126718431..17bca0a6f38 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -243,14 +243,14 @@ llvm::MDNode *CodeGenModule::getTBAAStructTagInfo(QualType BaseTy,
   return TBAA->getTBAAStructTagInfo(BaseTy, AccessN, O);
 }
 
-/// Decorate the instruction with a TBAA tag. For scalar TBAA, the tag
-/// is the same as the type. For struct-path aware TBAA, the tag
-/// is different from the type: base type, access type and offset.
+/// Decorate the instruction with a TBAA tag. For both scalar TBAA
+/// and struct-path aware TBAA, the tag has the same format:
+/// base type, access type and offset.
 /// When ConvertTypeToTag is true, we create a tag based on the scalar type.
 void CodeGenModule::DecorateInstruction(llvm::Instruction *Inst,
                                         llvm::MDNode *TBAAInfo,
                                         bool ConvertTypeToTag) {
-  if (ConvertTypeToTag && TBAA && CodeGenOpts.StructPathTBAA)
+  if (ConvertTypeToTag && TBAA)
     Inst->setMetadata(llvm::LLVMContext::MD_tbaa,
                       TBAA->getTBAAScalarTagInfo(TBAAInfo));
   else