SIL: In textual SIL allow global SIL names starting with '$'.

For example: @$S1m3fooyyF
It's needed to change the mangling prefix to $S.
The parser change only affects SIL (and not swift).

I didn't add test case because it will be fully tested when changing the mangling prefix.

Author: eeckstein

lib/Parse/Lexer.cpp

@@ -852,8 +852,9 @@ void Lexer::lexDollarIdent() {
   const char *tokStart = CurPtr-1;
   assert(*tokStart == '$');
 
-  // In a SIL function body, '$' is a token by itself.
-  if (InSILBody)
+  // In a SIL function body, '$' is a token by itself, except it's a SIL global
+  // name. SIL global identifiers may start with a '$', e.g. @$S1m3fooyyF.
+  if (InSILBody && NextToken.getKind() != tok::at_sign)
     return formToken(tok::sil_dollar, tokStart);
 
   bool isAllDigits = true;
@@ -881,7 +882,7 @@ void Lexer::lexDollarIdent() {
 
   // We reserve $nonNumeric for persistent bindings in the debugger.
   if (!isAllDigits) {
-    if (!LangOpts.EnableDollarIdentifiers)
+    if (!LangOpts.EnableDollarIdentifiers && !InSILBody)
       diagnose(tokStart, diag::expected_dollar_numeric);
 
     // Even if we diagnose, we go ahead and form an identifier token,

lib/ParseSIL/ParseSIL.cpp

@@ -433,6 +433,7 @@ bool SILParser::parseSILIdentifier(Identifier &Result, SourceLoc &Loc,
                                    const Diagnostic &D) {
   switch (P.Tok.getKind()) {
   case tok::identifier:
+  case tok::dollarident:
     Result = P.Context.getIdentifier(P.Tok.getText());
     break;
   case tok::string_literal: {