Struct-path aware TBAA: uniformize scalar tag and path tag.

For struct-path aware TBAA, we used to use scalar type node as the scalar tag,
which has an incompatible format with the struct path tag. We now use the same
format: base type, access type and offset.

We also uniformize the scalar type node and the struct type node: name, a list
of pairs (offset + pointer to MDNode). For scalar type, we have a single pair.
These are to make implementaiton of aliasing rules easier.

llvm-svn: 179335

1 files changed, 11 insertions, 2 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index e8e3d1ae76e..4126bea295b 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -242,9 +242,18 @@ 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.
+/// When ConvertTypeToTag is true, we create a tag based on the scalar type.
 void CodeGenModule::DecorateInstruction(llvm::Instruction *Inst,
-                                        llvm::MDNode *TBAAInfo) {
-  Inst->setMetadata(llvm::LLVMContext::MD_tbaa, TBAAInfo);
+                                        llvm::MDNode *TBAAInfo,
+                                        bool ConvertTypeToTag) {
+  if (ConvertTypeToTag && TBAA && CodeGenOpts.StructPathTBAA)
+    Inst->setMetadata(llvm::LLVMContext::MD_tbaa,
+                      TBAA->getTBAAScalarTagInfo(TBAAInfo));
+  else
+    Inst->setMetadata(llvm::LLVMContext::MD_tbaa, TBAAInfo);
 }
 
 bool CodeGenModule::isTargetDarwin() const {