[ms-inline asm] Add a new Inline Asm Non-Standard Dialect attribute.

This new attribute is intended to be used by the backend to determine how
the inline asm string should be parsed/printed. This patch adds the 
ia_nsdialect attribute and also adds a test case to ensure the IR is
correctly parsed, but there is no functional change at this time.

The standard dialect is assumed to be AT&T.  Therefore, this attribute
should only be added to MS-style inline assembly statements, which use
the Intel dialect.  If we ever support more dialects we'll need to
add additional state to the attribute.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@161641 91177308-0d34-0410-b5e6-96231b3b80d8

docs/LangRef.html

@@ -1208,6 +1208,13 @@ define void @f() optsize { ... }
       may make calls to the function faster, at the cost of extra program
       startup time if the function is not called during program startup.</dd>
 
+  <dt><tt><b>ia_nsdialect</b></tt></dt>
+  <dd>This attribute indicates the associated inline assembly call is using a
+      non-standard assembly dialect.  The standard dialect is ATT, which is
+      assumed when this attribute is not present.  When present, the dialect
+      is assumed to be Intel.  Currently, ATT and Intel are the only supported
+      dialects.</dd>
+
   <dt><tt><b>inlinehint</b></tt></dt>
   <dd>This attribute indicates that the source code contained a hint that inlining
       this function is desirable (such as the "inline" keyword in C/C++).  It

include/llvm/Attributes.h

@@ -134,6 +134,9 @@ DECLARE_LLVM_ATTRIBUTE(NonLazyBind,1U<<31) ///< Function is called early and/or
                                             /// often, so lazy binding isn't
                                             /// worthwhile.
 DECLARE_LLVM_ATTRIBUTE(AddressSafety,1ULL<<32) ///< Address safety checking is on.
+DECLARE_LLVM_ATTRIBUTE(IANSDialect,1ULL<<33) ///< Inline asm non-standard dialect.
+                                           /// When not set, ATT dialect assumed.
+                                           /// When set implies the Intel dialect.
 
 #undef DECLARE_LLVM_ATTRIBUTE
 
@@ -159,7 +162,8 @@ const AttrConst FunctionOnly = {NoReturn_i | NoUnwind_i | ReadNone_i |
   ReadOnly_i | NoInline_i | AlwaysInline_i | OptimizeForSize_i |
   StackProtect_i | StackProtectReq_i | NoRedZone_i | NoImplicitFloat_i |
   Naked_i | InlineHint_i | StackAlignment_i |
-  UWTable_i | NonLazyBind_i | ReturnsTwice_i | AddressSafety_i};
+  UWTable_i | NonLazyBind_i | ReturnsTwice_i | AddressSafety_i |
+  IANSDialect_i};
 
 /// @brief Parameter attributes that do not apply to vararg call arguments.
 const AttrConst VarArgsIncompatible = {StructRet_i};

lib/AsmParser/LLLexer.cpp

@@ -553,6 +553,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   KEYWORD(naked);
   KEYWORD(nonlazybind);
   KEYWORD(address_safety);
+  KEYWORD(ia_nsdialect);
 
   KEYWORD(type);
   KEYWORD(opaque);

lib/AsmParser/LLParser.cpp

@@ -962,6 +962,7 @@ bool LLParser::ParseOptionalAttrs(Attributes &Attrs, unsigned AttrKind) {
     case lltok::kw_naked:           Attrs |= Attribute::Naked; break;
     case lltok::kw_nonlazybind:     Attrs |= Attribute::NonLazyBind; break;
     case lltok::kw_address_safety:  Attrs |= Attribute::AddressSafety; break;
+    case lltok::kw_ia_nsdialect:    Attrs |= Attribute::IANSDialect; break;
 
     case lltok::kw_alignstack: {
       unsigned Alignment;

lib/AsmParser/LLToken.h

@@ -105,6 +105,7 @@ namespace lltok {
     kw_naked,
     kw_nonlazybind,
     kw_address_safety,
+    kw_ia_nsdialect,
 
     kw_type,
     kw_opaque,

lib/VMCore/Attributes.cpp

@@ -88,6 +88,9 @@ std::string Attribute::getAsString(Attributes Attrs) {
     Result += utostr(Attribute::getAlignmentFromAttrs(Attrs));
     Result += " ";
   }
+  if (Attrs & Attribute::IANSDialect)
+    Result += "ia_nsdialect ";
+
   // Trim the trailing space.
   assert(!Result.empty() && "Unknown attribute!");
   Result.erase(Result.end()-1);

utils/llvm.grm

@@ -175,6 +175,7 @@ FuncAttr      ::= noreturn
  | returns_twice
  | nonlazybind
  | address_safety
+ | ia_nsdialect
  ;
 
 OptFuncAttrs  ::= + _ | OptFuncAttrs FuncAttr ;