Avoid setting tbaa on the store of return type of call to inline asse…

…mbler.

In 32bit mode, attaching TBAA metadata to the store following the call
to inline assembler results in describing the wrong type by making a
fake lvalue(i.e., whatever the inline assembler happens to leave in
EAX:EDX.) Even if inline assembler somehow describes the correct type,
setting TBAA information on return type of call to inline assembler is
likely not correct, since TBAA rules need not apply to inline assembler.

Differential Revision: https://reviews.llvm.org/D115320

clang/lib/CodeGen/CGStmt.cpp

@@ -2454,7 +2454,7 @@ void CodeGenFunction::EmitAsmStmt(const AsmStmt &S) {
     const ABIArgInfo &RetAI = CurFnInfo->getReturnInfo();
     if (RetAI.isDirect() || RetAI.isExtend()) {
       // Make a fake lvalue for the return value slot.
-      LValue ReturnSlot = MakeAddrLValue(ReturnValue, FnRetTy);
+      LValue ReturnSlot = MakeAddrLValueWithoutTBAA(ReturnValue, FnRetTy);
       CGM.getTargetCodeGenInfo().addReturnRegisterOutputs(
           *this, ReturnSlot, Constraints, ResultRegTypes, ResultTruncRegTypes,
           ResultRegDests, AsmString, S.getNumOutputs());

clang/lib/CodeGen/CodeGenFunction.h

@@ -2504,6 +2504,13 @@ class CodeGenFunction : public CodeGenTypeCache {
                             BaseInfo, TBAAInfo);
   }
 
+  LValue
+  MakeAddrLValueWithoutTBAA(Address Addr, QualType T,
+                            AlignmentSource Source = AlignmentSource::Type) {
+    return LValue::MakeAddr(Addr, T, getContext(), LValueBaseInfo(Source),
+                            TBAAAccessInfo());
+  }
+
   LValue MakeNaturalAlignPointeeAddrLValue(llvm::Value *V, QualType T);
   LValue MakeNaturalAlignAddrLValue(llvm::Value *V, QualType T);
 

clang/test/CodeGen/avoidTBAAonASMstore.cpp

@@ -0,0 +1,11 @@
+// RUN: %clang_cc1 -triple i386-unknown-linux-gnu -O2 -disable-llvm-passes -fasm-blocks %s -emit-llvm -o - | FileCheck --check-prefix=STORE-LINE %s
+double foo(double z) {
+  // STORE-LINE-LABEL: define{{.*}} double @_Z3food
+  unsigned short ControlWord;
+  __asm { fnstcw word ptr[ControlWord]}
+  ;
+  // STORE-LINE: store i64 %{{.*}}, i64* %{{.*}},
+  // STORE-LINE-NOT: align 4, !tbaa
+  // STORE-LINE-SAME: align 4
+  return z;
+}