[Microsoft][C++] Clang doesn't support a use of "this" pointer inside inline asm

Clang doesn’t support a use of “this” pointer inside inline asm.
When I tried to compile a class or a struct (see example) with an inline asm that contains "this" pointer.
Clang returns with an error.
This patch fixes that.

error: expected unqualified-id
For example:
'''
struct A {
    void f() {
          __asm mov eax, this
              // error: expected unqualified-id
                  }
};
'''
Differential Revision: http://reviews.llvm.org/D15115

llvm-svn: 255645

clang/lib/CodeGen/CGStmt.cpp

@@ -1696,7 +1696,8 @@ llvm::Value* CodeGenFunction::EmitAsmInput(
   if (Info.allowsRegister() || !Info.allowsMemory())
     if (CodeGenFunction::hasScalarEvaluationKind(InputExpr->getType()))
       return EmitScalarExpr(InputExpr);
-
+  if (InputExpr->getStmtClass() == Expr::CXXThisExprClass)
+    return EmitScalarExpr(InputExpr);
   InputExpr = InputExpr->IgnoreParenNoopCasts(getContext());
   LValue Dest = EmitLValue(InputExpr);
   return EmitAsmInputLValue(Info, Dest, InputExpr->getType(), ConstraintStr,

clang/lib/Parse/ParseStmtAsm.cpp

@@ -215,17 +215,22 @@ ExprResult Parser::ParseMSAsmIdentifier(llvm::SmallVectorImpl<Token> &LineToks,
   // Require an identifier here.
   SourceLocation TemplateKWLoc;
   UnqualifiedId Id;
-  bool Invalid =
+  bool Invalid = true;
+  ExprResult Result;
+  if (Tok.is(tok::kw_this)) {
+    Result = ParseCXXThis();
+    Invalid = false;
+  } else {
+    Invalid =
         ParseUnqualifiedId(SS,
                            /*EnteringContext=*/false,
                            /*AllowDestructorName=*/false,
                            /*AllowConstructorName=*/false,
                            /*ObjectType=*/ParsedType(), TemplateKWLoc, Id);
-
     // Perform the lookup.
-  ExprResult Result = Actions.LookupInlineAsmIdentifier(
-      SS, TemplateKWLoc, Id, Info, IsUnevaluatedContext);
-
+    Result = Actions.LookupInlineAsmIdentifier(SS, TemplateKWLoc, Id, Info,
+                                               IsUnevaluatedContext);
+  }
   // While the next two tokens are 'period' 'identifier', repeatedly parse it as
   // a field access. We have to avoid consuming assembler directives that look
   // like '.' 'else'.

clang/test/CodeGen/ms_this.cpp

@@ -0,0 +1,49 @@
+// RUN: %clang_cc1 -fasm-blocks -emit-llvm %s -o - | FileCheck %s
+class t1 {
+public:
+  double a;
+  void runc();
+};
+
+class t2 {
+public:
+  double a;
+  void runc();
+};
+
+void t2::runc() {
+  double num = 0;
+  __asm {
+      mov rax,[this]
+      //CHECK: %this.addr = alloca %class.t2*
+      //CHECK: call void asm sideeffect inteldialect "mov rax,qword ptr $1{{.*}}%class.t2* %this1
+      mov rbx,[rax]
+      mov num, rbx
+	   };
+}
+
+void t1::runc() {
+  double num = 0;
+  __asm {
+       mov rax,[this]
+      //CHECK: %this.addr = alloca %class.t1*
+      //CHECK: call void asm sideeffect inteldialect "mov rax,qword ptr $1{{.*}}%class.t1* %this1
+        mov rbx,[rax]
+        mov num, rbx
+	   };
+}
+
+struct s {
+  int a;
+  void func() {
+    __asm mov rax, [this]
+    //CHECK: %this.addr = alloca %struct.s*
+    //CHECK: call void asm sideeffect inteldialect "mov rax, qword ptr $0{{.*}}%struct.s* %this1
+  }
+} f3;
+
+int main() {
+  f3.func();
+  f3.a=1;
+  return 0;
+}