[ms-inline-asm] Fix bug in single asm statement support

[myatsina]

Summary

Fixing a crash caused by trying to merge a single-line asm statement with an asm block that follows it, e.g:
asm int 4
asm {
int 5
}

Now, only adjacent single-line asm statements that are not surrounded by braces will be merged into one asm call.

[• ehsan]

Thanks, LGTM!

lib/Parse/ParseStmtAsm.cpp

if (!InAsmComment && Tok.is(tok::l_brace)) {
         // if needed and then keep processing the next line as a single
         // line __asm.
         bool isAsm = Tok.is(tok::kw_asm);
         if (SingleLineMode && !isAsm)
           break;
         // We're no longer in a comment.
         InAsmComment = false;
         if (isAsm) {
+          // If this is a new __asm {} block we want to process it seperately
+          // from the single-line __asm statements
+          if (PP.LookAhead(0).is(tok::l_brace))
+            break;
           LineNo = SrcMgr.getLineNumber(ExpLoc.first, ExpLoc.second);
           SkippedStartOfLine = Tok.isAtStartOfLine();
         }
       } else if (!InAsmComment && Tok.is(tok::r_brace)) {
         // In MSVC mode, braces only participate in brace matching and
         // separating the asm statements.  This is an intentional
         // departure from the Apple gcc behavior.
         if (!BraceNesting)

test/CodeGen/ms-inline-asm.c

 // CHECK: t7
 // CHECK: call void asm sideeffect inteldialect "int $$0x2c", "~{dirflag},~{fpsr},~{flags}"()
 // CHECK: call void asm sideeffect inteldialect "", "~{dirflag},~{fpsr},~{flags}"()
 }
 
 int t8() {
   __asm int 4 ; } comments for single-line asm
   __asm {}
-  __asm int 4
+  __asm { int 5}
+  __asm int 6
+  __asm int 7
+  __asm { 
+    int 8
+  }
   return 10;
 // CHECK: t8
-// CHECK: call i32 asm sideeffect inteldialect "int $$4\0A\09int $$4", "={eax},~{dirflag},~{fpsr},~{flags}"()
+// CHECK: call i32 asm sideeffect inteldialect "int $$4", "={eax},~{dirflag},~{fpsr},~{flags}"()
+// CHECK: call i32 asm sideeffect inteldialect "", "={eax},~{dirflag},~{fpsr},~{flags}"()
+// CHECK: call i32 asm sideeffect inteldialect "int $$5", "={eax},~{dirflag},~{fpsr},~{flags}"()
+// CHECK: call i32 asm sideeffect inteldialect "int $$6\0A\09int $$7", "={eax},~{dirflag},~{fpsr},~{flags}"()
+// CHECK: call i32 asm sideeffect inteldialect "int $$8", "={eax},~{dirflag},~{fpsr},~{flags}"()
 // CHECK: ret i32 10
 }
 
 void t9() {
   __asm {
     push ebx
     { mov ebx, 0x07 }
     __asm { pop ebx }

test/Parser/ms-inline-asm.c

 void t11() {
   do { __asm mov eax, 0 __asm { __asm mov edx, 1 } } while(0);
 }
 void t12() {
   __asm jmp label // expected-error {{use of undeclared label 'label'}}
 }
 int t_fail() { // expected-note {{to match this}}
   __asm 
-  __asm { // expected-error 2 {{expected}} expected-note {{to match this}}
+  __asm { // expected-error 3 {{expected}} expected-note {{to match this}}