TableGen: Remove unused ParseForeachMode

[nhaehnle]

Summary

Use the default ParseValueMode instead of ParseForeachMode when
parsing the rule

ForeachDeclaration ::= ID '=' '[' ValueList ']'

because the only difference between the two is how an open brace '{'
is handled at the end. In the context of foreach, the 'in' keyword
will appear after the ForeachDeclaration, so this special handling
of '{' is not required.

Change-Id: I4d86bb73bab9ec26752e1273e5213df77cf28d1d

[nhaehnle]

r327119

lib/TableGen/TGParser.h

class TGParser {
   // identifiers map to some existing object but in special cases
   // (e.g. parsing def names) no such object exists yet because we are
   // in the middle of creating in.  For those situations, allow the
   // parser to ignore missing object errors.
   enum IDParseMode {
     ParseValueMode,   // We are parsing a value we expect to look up.
     ParseNameMode,    // We are parsing a name of an object that does not yet
                       // exist.
-    ParseForeachMode  // We are parsing a foreach init.
   };
 
 public:
   TGParser(SourceMgr &SrcMgr, RecordKeeper &records)
       : Lex(SrcMgr), CurMultiClass(nullptr), Records(records) {}
 
   /// ParseFile - Main entrypoint for parsing a tblgen file.  These parser
   /// routines return true on error, or false on success.

lib/TableGen/TGParser.cpp

Init *TGParser::ParseValue(Record *CurRec, RecTy *ItemType, IDParseMode Mode) {
   Init *Result = ParseSimpleValue(CurRec, ItemType, Mode);
   if (!Result) return nullptr;
 
   // Parse the suffixes now if present.
   while (true) {
     switch (Lex.getCode()) {
     default: return Result;
     case tgtok::l_brace: {
-      if (Mode == ParseNameMode || Mode == ParseForeachMode)
+      if (Mode == ParseNameMode)
         // This is the beginning of the object body.
         return Result;
 
       SMLoc CurlyLoc = Lex.getLoc();
       Lex.Lex(); // eat the '{'
       SmallVector<unsigned, 16> Ranges;
       ParseRangeList(Ranges);
       if (Ranges.empty()) return nullptr;
VarInit *TGParser::ParseForeachDeclaration(ListInit *&ForeachListValue) {
   Lex.Lex();  // Eat the '='
 
   RecTy *IterType = nullptr;
   SmallVector<unsigned, 16> Ranges;
 
   switch (Lex.getCode()) {
   default: TokError("Unknown token when expecting a range list"); return nullptr;
   case tgtok::l_square: { // '[' ValueList ']'
-    Init *List = ParseSimpleValue(nullptr, nullptr, ParseForeachMode);
+    Init *List = ParseSimpleValue(nullptr);
     ForeachListValue = dyn_cast<ListInit>(List);
     if (!ForeachListValue) {
       TokError("Expected a Value list");
       return nullptr;
     }
     RecTy *ValueType = ForeachListValue->getType();
     ListRecTy *ListType = dyn_cast<ListRecTy>(ValueType);
     if (!ListType) {