Stage two of getting CFE top correct.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@39734 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/Parse/ParseExpr.cpp b/Parse/ParseExpr.cpp
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+++ b/Parse/ParseExpr.cpp
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+//===--- ParseExpr.cpp - Expression Parsing -------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by Chris Lattner and is distributed under
+// the University of Illinois Open Source License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements the Expression parsing implementation.  Expressions in
+// C99 basically consist of a bunch of binary operators with unary operators and
+// other random stuff at the leaves.
+//
+// In the C99 grammar, these unary operators bind tightest and are represented
+// as the 'cast-expression' production.  Everything else is either a binary
+// operator (e.g. '/') or a ternary operator ("?:").  The unary leaves are
+// handled by ParseCastExpression, the higher level pieces are handled by
+// ParseBinaryExpression.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Parse/Parser.h"
+#include "clang/Basic/Diagnostic.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/SmallString.h"
+using namespace clang;
+
+/// PrecedenceLevels - These are precedences for the binary/ternary operators in
+/// the C99 grammar.  These have been named to relate with the C99 grammar
+/// productions.  Low precedences numbers bind more weakly than high numbers.
+namespace prec {
+  enum Level {
+    Unknown        = 0,    // Not binary operator.
+    Comma          = 1,    // ,
+    Assignment     = 2,    // =, *=, /=, %=, +=, -=, <<=, >>=, &=, ^=, |=
+    Conditional    = 3,    // ?
+    LogicalOr      = 4,    // ||
+    LogicalAnd     = 5,    // &&
+    InclusiveOr    = 6,    // |
+    ExclusiveOr    = 7,    // ^
+    And            = 8,    // &
+    Equality       = 9,    // ==, !=
+    Relational     = 10,   //  >=, <=, >, <
+    Shift          = 11,   // <<, >>
+    Additive       = 12,   // -, +
+    Multiplicative = 13    // *, /, %
+  };
+}
+
+
+/// getBinOpPrecedence - Return the precedence of the specified binary operator
+/// token.  This returns:
+///
+static prec::Level getBinOpPrecedence(tok::TokenKind Kind) {
+  switch (Kind) {
+  default:                        return prec::Unknown;
+  case tok::comma:                return prec::Comma;
+  case tok::equal:
+  case tok::starequal:
+  case tok::slashequal:
+  case tok::percentequal:
+  case tok::plusequal:
+  case tok::minusequal:
+  case tok::lesslessequal:
+  case tok::greatergreaterequal:
+  case tok::ampequal:
+  case tok::caretequal:
+  case tok::pipeequal:            return prec::Assignment;
+  case tok::question:             return prec::Conditional;
+  case tok::pipepipe:             return prec::LogicalOr;
+  case tok::ampamp:               return prec::LogicalAnd;
+  case tok::pipe:                 return prec::InclusiveOr;
+  case tok::caret:                return prec::ExclusiveOr;
+  case tok::amp:                  return prec::And;
+  case tok::exclaimequal:
+  case tok::equalequal:           return prec::Equality;
+  case tok::lessequal:
+  case tok::less:
+  case tok::greaterequal:
+  case tok::greater:              return prec::Relational;
+  case tok::lessless:
+  case tok::greatergreater:       return prec::Shift;
+  case tok::plus:
+  case tok::minus:                return prec::Additive;
+  case tok::percent:
+  case tok::slash:
+  case tok::star:                 return prec::Multiplicative;
+  }
+}
+
+
+/// ParseExpression - Simple precedence-based parser for binary/ternary
+/// operators.
+///
+/// Note: we diverge from the C99 grammar when parsing the assignment-expression
+/// production.  C99 specifies that the LHS of an assignment operator should be
+/// parsed as a unary-expression, but consistency dictates that it be a
+/// conditional-expession.  In practice, the important thing here is that the
+/// LHS of an assignment has to be an l-value, which productions between
+/// unary-expression and conditional-expression don't produce.  Because we want
+/// consistency, we parse the LHS as a conditional-expression, then check for
+/// l-value-ness in semantic analysis stages.
+///
+///       multiplicative-expression: [C99 6.5.5]
+///         cast-expression
+///         multiplicative-expression '*' cast-expression
+///         multiplicative-expression '/' cast-expression
+///         multiplicative-expression '%' cast-expression
+///
+///       additive-expression: [C99 6.5.6]
+///         multiplicative-expression
+///         additive-expression '+' multiplicative-expression
+///         additive-expression '-' multiplicative-expression
+///
+///       shift-expression: [C99 6.5.7]
+///         additive-expression
+///         shift-expression '<<' additive-expression
+///         shift-expression '>>' additive-expression
+///
+///       relational-expression: [C99 6.5.8]
+///         shift-expression
+///         relational-expression '<' shift-expression
+///         relational-expression '>' shift-expression
+///         relational-expression '<=' shift-expression
+///         relational-expression '>=' shift-expression
+///
+///       equality-expression: [C99 6.5.9]
+///         relational-expression
+///         equality-expression '==' relational-expression
+///         equality-expression '!=' relational-expression
+///
+///       AND-expression: [C99 6.5.10]
+///         equality-expression
+///         AND-expression '&' equality-expression
+///
+///       exclusive-OR-expression: [C99 6.5.11]
+///         AND-expression
+///         exclusive-OR-expression '^' AND-expression
+///
+///       inclusive-OR-expression: [C99 6.5.12]
+///         exclusive-OR-expression
+///         inclusive-OR-expression '|' exclusive-OR-expression
+///
+///       logical-AND-expression: [C99 6.5.13]
+///         inclusive-OR-expression
+///         logical-AND-expression '&&' inclusive-OR-expression
+///
+///       logical-OR-expression: [C99 6.5.14]
+///         logical-AND-expression
+///         logical-OR-expression '||' logical-AND-expression
+///
+///       conditional-expression: [C99 6.5.15]
+///         logical-OR-expression
+///         logical-OR-expression '?' expression ':' conditional-expression
+/// [GNU]   logical-OR-expression '?' ':' conditional-expression
+///
+///       assignment-expression: [C99 6.5.16]
+///         conditional-expression
+///         unary-expression assignment-operator assignment-expression
+///
+///       assignment-operator: one of
+///         = *= /= %= += -= <<= >>= &= ^= |=
+///
+///       expression: [C99 6.5.17]
+///         assignment-expression
+///         expression ',' assignment-expression
+///
+Parser::ExprResult Parser::ParseExpression() {
+  ExprResult LHS = ParseCastExpression(false);
+  if (LHS.isInvalid) return LHS;
+  
+  return ParseRHSOfBinaryExpression(LHS, prec::Comma);
+}
+
+/// ParseAssignmentExpression - Parse an expr that doesn't include commas.
+///
+Parser::ExprResult Parser::ParseAssignmentExpression() {
+  ExprResult LHS = ParseCastExpression(false);
+  if (LHS.isInvalid) return LHS;
+  
+  return ParseRHSOfBinaryExpression(LHS, prec::Assignment);
+}
+
+Parser::ExprResult Parser::ParseConstantExpression() {
+  ExprResult LHS = ParseCastExpression(false);
+  if (LHS.isInvalid) return LHS;
+  
+  // TODO: Validate that this is a constant expr!
+  return ParseRHSOfBinaryExpression(LHS, prec::Conditional);
+}
+
+/// ParseExpressionWithLeadingIdentifier - This special purpose method is used
+/// in contexts where we have already consumed an identifier (which we saved in
+/// 'IdTok'), then discovered that the identifier was really the leading token
+/// of part of an expression.  For example, in "A[1]+B", we consumed "A" (which
+/// is now in 'IdTok') and the current token is "[".
+Parser::ExprResult Parser::
+ParseExpressionWithLeadingIdentifier(const LexerToken &IdTok) {
+  // We know that 'IdTok' must correspond to this production:
+  //   primary-expression: identifier
+  
+  // Let the actions module handle the identifier.
+  ExprResult Res = Actions.ParseIdentifierExpr(CurScope, IdTok.getLocation(),
+                                               *IdTok.getIdentifierInfo(),
+                                               Tok.getKind() == tok::l_paren);
+  
+  // Because we have to parse an entire cast-expression before starting the
+  // ParseRHSOfBinaryExpression method (which parses any trailing binops), we
+  // need to handle the 'postfix-expression' rules.  We do this by invoking
+  // ParsePostfixExpressionSuffix to consume any postfix-expression suffixes:
+  Res = ParsePostfixExpressionSuffix(Res);
+  if (Res.isInvalid) return Res;
+
+  // At this point, the "A[1]" part of "A[1]+B" has been consumed. Once this is
+  // done, we know we don't have to do anything for cast-expression, because the
+  // only non-postfix-expression production starts with a '(' token, and we know
+  // we have an identifier.  As such, we can invoke ParseRHSOfBinaryExpression
+  // to consume any trailing operators (e.g. "+" in this example) and connected
+  // chunks of the expression.
+  return ParseRHSOfBinaryExpression(Res, prec::Comma);
+}
+
+/// ParseExpressionWithLeadingIdentifier - This special purpose method is used
+/// in contexts where we have already consumed an identifier (which we saved in
+/// 'IdTok'), then discovered that the identifier was really the leading token
+/// of part of an assignment-expression.  For example, in "A[1]+B", we consumed
+/// "A" (which is now in 'IdTok') and the current token is "[".
+Parser::ExprResult Parser::
+ParseAssignmentExprWithLeadingIdentifier(const LexerToken &IdTok) {
+  // We know that 'IdTok' must correspond to this production:
+  //   primary-expression: identifier
+  
+  // Let the actions module handle the identifier.
+  ExprResult Res = Actions.ParseIdentifierExpr(CurScope, IdTok.getLocation(),
+                                               *IdTok.getIdentifierInfo(),
+                                               Tok.getKind() == tok::l_paren);
+  
+  // Because we have to parse an entire cast-expression before starting the
+  // ParseRHSOfBinaryExpression method (which parses any trailing binops), we
+  // need to handle the 'postfix-expression' rules.  We do this by invoking
+  // ParsePostfixExpressionSuffix to consume any postfix-expression suffixes:
+  Res = ParsePostfixExpressionSuffix(Res);
+  if (Res.isInvalid) return Res;
+  
+  // At this point, the "A[1]" part of "A[1]+B" has been consumed. Once this is
+  // done, we know we don't have to do anything for cast-expression, because the
+  // only non-postfix-expression production starts with a '(' token, and we know
+  // we have an identifier.  As such, we can invoke ParseRHSOfBinaryExpression
+  // to consume any trailing operators (e.g. "+" in this example) and connected
+  // chunks of the expression.
+  return ParseRHSOfBinaryExpression(Res, prec::Assignment);
+}
+
+
+/// ParseAssignmentExpressionWithLeadingStar - This special purpose method is
+/// used in contexts where we have already consumed a '*' (which we saved in
+/// 'StarTok'), then discovered that the '*' was really the leading token of an
+/// expression.  For example, in "*(int*)P+B", we consumed "*" (which is
+/// now in 'StarTok') and the current token is "(".
+Parser::ExprResult Parser::
+ParseAssignmentExpressionWithLeadingStar(const LexerToken &StarTok) {
+  // We know that 'StarTok' must correspond to this production:
+  //  unary-expression: unary-operator cast-expression
+  // where 'unary-operator' is '*'.
+  
+  // Parse the cast-expression that follows the '*'.  This will parse the
+  // "*(int*)P" part of "*(int*)P+B".
+  ExprResult Res = ParseCastExpression(false);
+  if (Res.isInvalid) return Res;
+
+  // Combine StarTok + Res to get the new AST for the combined expression..
+  Res = Actions.ParseUnaryOp(StarTok.getLocation(), tok::star, Res.Val);
+  if (Res.isInvalid) return Res;
+  
+  
+  // We have to parse an entire cast-expression before starting the
+  // ParseRHSOfBinaryExpression method (which parses any trailing binops). Since
+  // we know that the only production above us is the cast-expression
+  // production, and because the only alternative productions start with a '('
+  // token (we know we had a '*'), there is no work to do to get a whole
+  // cast-expression.
+  
+  // At this point, the "*(int*)P" part of "*(int*)P+B" has been consumed. Once
+  // this is done, we can invoke ParseRHSOfBinaryExpression to consume any
+  // trailing operators (e.g. "+" in this example) and connected chunks of the
+  // assignment-expression.
+  return ParseRHSOfBinaryExpression(Res, prec::Assignment);
+}
+
+
+/// ParseRHSOfBinaryExpression - Parse a binary expression that starts with
+/// LHS and has a precedence of at least MinPrec.
+Parser::ExprResult
+Parser::ParseRHSOfBinaryExpression(ExprResult LHS, unsigned MinPrec) {
+  unsigned NextTokPrec = getBinOpPrecedence(Tok.getKind());
+  SourceLocation ColonLoc;
+
+  while (1) {
+    // If this token has a lower precedence than we are allowed to parse (e.g.
+    // because we are called recursively, or because the token is not a binop),
+    // then we are done!
+    if (NextTokPrec < MinPrec)
+      return LHS;
+
+    // Consume the operator, saving the operator token for error reporting.
+    LexerToken OpToken = Tok;
+    ConsumeToken();
+    
+    // Special case handling for the ternary operator.
+    ExprResult TernaryMiddle(true);
+    if (NextTokPrec == prec::Conditional) {
+      if (Tok.getKind() != tok::colon) {
+        // Handle this production specially:
+        //   logical-OR-expression '?' expression ':' conditional-expression
+        // In particular, the RHS of the '?' is 'expression', not
+        // 'logical-OR-expression' as we might expect.
+        TernaryMiddle = ParseExpression();
+        if (TernaryMiddle.isInvalid) return TernaryMiddle;
+      } else {
+        // Special case handling of "X ? Y : Z" where Y is empty:
+        //   logical-OR-expression '?' ':' conditional-expression   [GNU]
+        TernaryMiddle = ExprResult(false);
+        Diag(Tok, diag::ext_gnu_conditional_expr);
+      }
+      
+      if (Tok.getKind() != tok::colon) {
+        Diag(Tok, diag::err_expected_colon);
+        Diag(OpToken, diag::err_matching, "?");
+        return ExprResult(true);
+      }
+      
+      // Eat the colon.
+      ColonLoc = ConsumeToken();
+    }
+    
+    // Parse another leaf here for the RHS of the operator.
+    ExprResult RHS = ParseCastExpression(false);
+    if (RHS.isInvalid) return RHS;
+
+    // Remember the precedence of this operator and get the precedence of the
+    // operator immediately to the right of the RHS.
+    unsigned ThisPrec = NextTokPrec;
+    NextTokPrec = getBinOpPrecedence(Tok.getKind());
+
+    // Assignment and conditional expressions are right-associative.
+    bool isRightAssoc = NextTokPrec == prec::Conditional ||
+                        NextTokPrec == prec::Assignment;
+
+    // Get the precedence of the operator to the right of the RHS.  If it binds
+    // more tightly with RHS than we do, evaluate it completely first.
+    if (ThisPrec < NextTokPrec ||
+        (ThisPrec == NextTokPrec && isRightAssoc)) {
+      // If this is left-associative, only parse things on the RHS that bind
+      // more tightly than the current operator.  If it is left-associative, it
+      // is okay, to bind exactly as tightly.  For example, compile A=B=C=D as
+      // A=(B=(C=D)), where each paren is a level of recursion here.
+      RHS = ParseRHSOfBinaryExpression(RHS, ThisPrec + !isRightAssoc);
+      if (RHS.isInvalid) return RHS;
+
+      NextTokPrec = getBinOpPrecedence(Tok.getKind());
+    }
+    assert(NextTokPrec <= ThisPrec && "Recursion didn't work!");
+  
+    // Combine the LHS and RHS into the LHS (e.g. build AST).
+    if (TernaryMiddle.isInvalid)
+      LHS = Actions.ParseBinOp(OpToken.getLocation(), OpToken.getKind(),
+                               LHS.Val, RHS.Val);
+    else
+      LHS = Actions.ParseConditionalOp(OpToken.getLocation(), ColonLoc,
+                                       LHS.Val, TernaryMiddle.Val, RHS.Val);
+  }
+}
+
+/// ParseCastExpression - Parse a cast-expression, or, if isUnaryExpression is
+/// true, parse a unary-expression.
+///
+///       cast-expression: [C99 6.5.4]
+///         unary-expression
+///         '(' type-name ')' cast-expression
+///
+///       unary-expression:  [C99 6.5.3]
+///         postfix-expression
+///         '++' unary-expression
+///         '--' unary-expression
+///         unary-operator cast-expression
+///         'sizeof' unary-expression
+///         'sizeof' '(' type-name ')'
+/// [GNU]   '__alignof' unary-expression
+/// [GNU]   '__alignof' '(' type-name ')'
+/// [GNU]   '&&' identifier
+///
+///       unary-operator: one of
+///         '&'  '*'  '+'  '-'  '~'  '!'
+/// [GNU]   '__extension__'  '__real'  '__imag'
+///
+///       primary-expression: [C99 6.5.1]
+///         identifier
+///         constant
+///         string-literal
+/// [C++]   boolean-literal  [C++ 2.13.5]
+///         '(' expression ')'
+///         '__func__'        [C99 6.4.2.2]
+/// [GNU]   '__FUNCTION__'
+/// [GNU]   '__PRETTY_FUNCTION__'
+/// [GNU]   '(' compound-statement ')'
+/// [GNU]   '__builtin_va_arg' '(' assignment-expression ',' type-name ')'
+/// [GNU]   '__builtin_offsetof' '(' type-name ',' offsetof-member-designator')'
+/// [GNU]   '__builtin_choose_expr' '(' assign-expr ',' assign-expr ','
+///                                     assign-expr ')'
+/// [GNU]   '__builtin_types_compatible_p' '(' type-name ',' type-name ')'
+/// [OBC]   '[' objc-receiver objc-message-args ']'    [TODO]
+/// [OBC]   '@selector' '(' objc-selector-arg ')'      [TODO]
+/// [OBC]   '@protocol' '(' identifier ')'             [TODO]
+/// [OBC]   '@encode' '(' type-name ')'                [TODO]
+/// [OBC]   objc-string-literal                        [TODO]
+/// [C++]   'const_cast' '<' type-name '>' '(' expression ')'       [C++ 5.2p1]
+/// [C++]   'dynamic_cast' '<' type-name '>' '(' expression ')'     [C++ 5.2p1]
+/// [C++]   'reinterpret_cast' '<' type-name '>' '(' expression ')' [C++ 5.2p1]
+/// [C++]   'static_cast' '<' type-name '>' '(' expression ')'      [C++ 5.2p1]
+///
+///       constant: [C99 6.4.4]
+///         integer-constant
+///         floating-constant
+///         enumeration-constant -> identifier
+///         character-constant
+///
+Parser::ExprResult Parser::ParseCastExpression(bool isUnaryExpression) {
+  ExprResult Res;
+  tok::TokenKind SavedKind = Tok.getKind();
+  
+  // This handles all of cast-expression, unary-expression, postfix-expression,
+  // and primary-expression.  We handle them together like this for efficiency
+  // and to simplify handling of an expression starting with a '(' token: which
+  // may be one of a parenthesized expression, cast-expression, compound literal
+  // expression, or statement expression.
+  //
+  // If the parsed tokens consist of a primary-expression, the cases below
+  // call ParsePostfixExpressionSuffix to handle the postfix expression
+  // suffixes.  Cases that cannot be followed by postfix exprs should
+  // return without invoking ParsePostfixExpressionSuffix.
+  switch (SavedKind) {
+  case tok::l_paren: {
+    // If this expression is limited to being a unary-expression, the parent can
+    // not start a cast expression.
+    ParenParseOption ParenExprType =
+      isUnaryExpression ? CompoundLiteral : CastExpr;
+    TypeTy *CastTy;
+    SourceLocation LParenLoc = Tok.getLocation();
+    SourceLocation RParenLoc;
+    Res = ParseParenExpression(ParenExprType, CastTy, RParenLoc);
+    if (Res.isInvalid) return Res;
+    
+    switch (ParenExprType) {
+    case SimpleExpr:   break;    // Nothing else to do.
+    case CompoundStmt: break;  // Nothing else to do.
+    case CompoundLiteral:
+      // We parsed '(' type-name ')' '{' ... '}'.  If any suffixes of
+      // postfix-expression exist, parse them now.
+      break;
+    case CastExpr:
+      // We parsed '(' type-name ')' and the thing after it wasn't a '{'.  Parse
+      // the cast-expression that follows it next.
+      // TODO: For cast expression with CastTy.
+      Res = ParseCastExpression(false);
+      if (!Res.isInvalid)
+        Res = Actions.ParseCastExpr(LParenLoc, CastTy, RParenLoc, Res.Val);
+      return Res;
+    }
+      
+    // These can be followed by postfix-expr pieces.
+    return ParsePostfixExpressionSuffix(Res);
+  }
+    
+    // primary-expression
+  case tok::numeric_constant:
+    // constant: integer-constant
+    // constant: floating-constant
+    
+    Res = Actions.ParseNumericConstant(Tok);
+    ConsumeToken();
+    
+    // These can be followed by postfix-expr pieces.
+    return ParsePostfixExpressionSuffix(Res);
+
+  case tok::kw_true:
+  case tok::kw_false:
+    return ParseCXXBoolLiteral();
+
+  case tok::identifier: {      // primary-expression: identifier
+                               // constant: enumeration-constant
+    // Consume the identifier so that we can see if it is followed by a '('.
+    // Function designators are allowed to be undeclared (C99 6.5.1p2), so we
+    // need to know whether or not this identifier is a function designator or
+    // not.
+    IdentifierInfo &II = *Tok.getIdentifierInfo();
+    SourceLocation L = ConsumeToken();
+    Res = Actions.ParseIdentifierExpr(CurScope, L, II,
+                                      Tok.getKind() == tok::l_paren);
+    // These can be followed by postfix-expr pieces.
+    return ParsePostfixExpressionSuffix(Res);
+  }
+  case tok::char_constant:     // constant: character-constant
+    Res = Actions.ParseCharacterConstant(Tok);
+    ConsumeToken();
+    // These can be followed by postfix-expr pieces.
+    return ParsePostfixExpressionSuffix(Res);    
+  case tok::kw___func__:       // primary-expression: __func__ [C99 6.4.2.2]
+  case tok::kw___FUNCTION__:   // primary-expression: __FUNCTION__ [GNU]
+  case tok::kw___PRETTY_FUNCTION__:  // primary-expression: __P..Y_F..N__ [GNU]
+    Res = Actions.ParseSimplePrimaryExpr(Tok.getLocation(), SavedKind);
+    ConsumeToken();
+    // These can be followed by postfix-expr pieces.
+    return ParsePostfixExpressionSuffix(Res);
+  case tok::string_literal:    // primary-expression: string-literal
+  case tok::wide_string_literal:
+    Res = ParseStringLiteralExpression();
+    if (Res.isInvalid) return Res;
+    // This can be followed by postfix-expr pieces (e.g. "foo"[1]).
+    return ParsePostfixExpressionSuffix(Res);
+  case tok::kw___builtin_va_arg:
+  case tok::kw___builtin_offsetof:
+  case tok::kw___builtin_choose_expr:
+  case tok::kw___builtin_types_compatible_p:
+    return ParseBuiltinPrimaryExpression();
+  case tok::plusplus:      // unary-expression: '++' unary-expression
+  case tok::minusminus: {  // unary-expression: '--' unary-expression
+    SourceLocation SavedLoc = ConsumeToken();
+    Res = ParseCastExpression(true);
+    if (!Res.isInvalid)
+      Res = Actions.ParseUnaryOp(SavedLoc, SavedKind, Res.Val);
+    return Res;
+  }
+  case tok::amp:           // unary-expression: '&' cast-expression
+  case tok::star:          // unary-expression: '*' cast-expression
+  case tok::plus:          // unary-expression: '+' cast-expression
+  case tok::minus:         // unary-expression: '-' cast-expression
+  case tok::tilde:         // unary-expression: '~' cast-expression
+  case tok::exclaim:       // unary-expression: '!' cast-expression
+  case tok::kw___real:     // unary-expression: '__real' cast-expression [GNU]
+  case tok::kw___imag:     // unary-expression: '__imag' cast-expression [GNU]
+  case tok::kw___extension__:{//unary-expression:'__extension__' cast-expr [GNU]
+    // FIXME: Extension not handled correctly here!
+    SourceLocation SavedLoc = ConsumeToken();
+    Res = ParseCastExpression(false);
+    if (!Res.isInvalid)
+      Res = Actions.ParseUnaryOp(SavedLoc, SavedKind, Res.Val);
+    return Res;
+  }
+  case tok::kw_sizeof:     // unary-expression: 'sizeof' unary-expression
+                           // unary-expression: 'sizeof' '(' type-name ')'
+  case tok::kw___alignof:  // unary-expression: '__alignof' unary-expression
+                           // unary-expression: '__alignof' '(' type-name ')'
+    return ParseSizeofAlignofExpression();
+  case tok::ampamp: {      // unary-expression: '&&' identifier
+    SourceLocation AmpAmpLoc = ConsumeToken();
+    if (Tok.getKind() != tok::identifier) {
+      Diag(Tok, diag::err_expected_ident);
+      return ExprResult(true);
+    }
+    
+    Diag(AmpAmpLoc, diag::ext_gnu_address_of_label);
+    Res = Actions.ParseAddrLabel(AmpAmpLoc, Tok.getLocation(),
+                                 Tok.getIdentifierInfo());
+    ConsumeToken();
+    return Res;
+  }
+  case tok::kw_const_cast:
+  case tok::kw_dynamic_cast:
+  case tok::kw_reinterpret_cast:
+  case tok::kw_static_cast:
+    return ParseCXXCasts();
+  default:
+    Diag(Tok, diag::err_expected_expression);
+    return ExprResult(true);
+  }
+  
+  // unreachable.
+  abort();
+}
+
+/// ParsePostfixExpressionSuffix - Once the leading part of a postfix-expression
+/// is parsed, this method parses any suffixes that apply.
+///
+///       postfix-expression: [C99 6.5.2]
+///         primary-expression
+///         postfix-expression '[' expression ']'
+///         postfix-expression '(' argument-expression-list[opt] ')'
+///         postfix-expression '.' identifier
+///         postfix-expression '->' identifier
+///         postfix-expression '++'
+///         postfix-expression '--'
+///         '(' type-name ')' '{' initializer-list '}'
+///         '(' type-name ')' '{' initializer-list ',' '}'
+///
+///       argument-expression-list: [C99 6.5.2]
+///         argument-expression
+///         argument-expression-list ',' assignment-expression
+///
+Parser::ExprResult Parser::ParsePostfixExpressionSuffix(ExprResult LHS) {
+  
+  // Now that the primary-expression piece of the postfix-expression has been
+  // parsed, see if there are any postfix-expression pieces here.
+  SourceLocation Loc;
+  while (1) {
+    switch (Tok.getKind()) {
+    default:  // Not a postfix-expression suffix.
+      return LHS;
+    case tok::l_square: {  // postfix-expression: p-e '[' expression ']'
+      Loc = ConsumeBracket();
+      ExprResult Idx = ParseExpression();
+      
+      SourceLocation RLoc = Tok.getLocation();
+      
+      if (!LHS.isInvalid && !Idx.isInvalid && Tok.getKind() == tok::r_square)
+        LHS = Actions.ParseArraySubscriptExpr(LHS.Val, Loc, Idx.Val, RLoc);
+      else 
+        LHS = ExprResult(true);
+
+      // Match the ']'.
+      MatchRHSPunctuation(tok::r_square, Loc);
+      break;
+    }
+      
+    case tok::l_paren: {   // p-e: p-e '(' argument-expression-list[opt] ')'
+      llvm::SmallVector<ExprTy*, 8> ArgExprs;
+      llvm::SmallVector<SourceLocation, 8> CommaLocs;
+      bool ArgExprsOk = true;
+      
+      Loc = ConsumeParen();
+      
+      if (Tok.getKind() != tok::r_paren) {
+        while (1) {
+          ExprResult ArgExpr = ParseAssignmentExpression();
+          if (ArgExpr.isInvalid) {
+            ArgExprsOk = false;
+            SkipUntil(tok::r_paren);
+            break;
+          } else
+            ArgExprs.push_back(ArgExpr.Val);
+          
+          if (Tok.getKind() != tok::comma)
+            break;
+          // Move to the next argument, remember where the comma was.
+          CommaLocs.push_back(ConsumeToken());
+        }
+      }
+        
+      // Match the ')'.
+      if (!LHS.isInvalid && ArgExprsOk && Tok.getKind() == tok::r_paren) {
+        assert((ArgExprs.size() == 0 || ArgExprs.size()-1 == CommaLocs.size())&&
+               "Unexpected number of commas!");
+        LHS = Actions.ParseCallExpr(LHS.Val, Loc, &ArgExprs[0], ArgExprs.size(),
+                                    &CommaLocs[0], Tok.getLocation());
+      }
+      
+      if (ArgExprsOk)
+        MatchRHSPunctuation(tok::r_paren, Loc);
+      break;
+    }
+    case tok::arrow:       // postfix-expression: p-e '->' identifier
+    case tok::period: {    // postfix-expression: p-e '.' identifier
+      tok::TokenKind OpKind = Tok.getKind();
+      SourceLocation OpLoc = ConsumeToken();  // Eat the "." or "->" token.
+      
+      if (Tok.getKind() != tok::identifier) {
+        Diag(Tok, diag::err_expected_ident);
+        return ExprResult(true);
+      }
+      
+      if (!LHS.isInvalid)
+        LHS = Actions.ParseMemberReferenceExpr(LHS.Val, OpLoc, OpKind,
+                                               Tok.getLocation(),
+                                               *Tok.getIdentifierInfo());
+      ConsumeToken();
+      break;
+    }
+    case tok::plusplus:    // postfix-expression: postfix-expression '++'
+    case tok::minusminus:  // postfix-expression: postfix-expression '--'
+      if (!LHS.isInvalid)
+        LHS = Actions.ParsePostfixUnaryOp(Tok.getLocation(), Tok.getKind(),
+                                          LHS.Val);
+      ConsumeToken();
+      break;
+    }
+  }
+}
+
+
+/// ParseSizeofAlignofExpression - Parse a sizeof or alignof expression.
+///       unary-expression:  [C99 6.5.3]
+///         'sizeof' unary-expression
+///         'sizeof' '(' type-name ')'
+/// [GNU]   '__alignof' unary-expression
+/// [GNU]   '__alignof' '(' type-name ')'
+Parser::ExprResult Parser::ParseSizeofAlignofExpression() {
+  assert((Tok.getKind() == tok::kw_sizeof ||
+          Tok.getKind() == tok::kw___alignof) &&
+         "Not a sizeof/alignof expression!");
+  LexerToken OpTok = Tok;
+  ConsumeToken();
+  
+  // If the operand doesn't start with an '(', it must be an expression.
+  ExprResult Operand;
+  if (Tok.getKind() != tok::l_paren) {
+    Operand = ParseCastExpression(true);
+  } else {
+    // If it starts with a '(', we know that it is either a parenthesized
+    // type-name, or it is a unary-expression that starts with a compound
+    // literal, or starts with a primary-expression that is a parenthesized
+    // expression.
+    ParenParseOption ExprType = CastExpr;
+    TypeTy *CastTy;
+    SourceLocation LParenLoc = Tok.getLocation(), RParenLoc;
+    Operand = ParseParenExpression(ExprType, CastTy, RParenLoc);
+    
+    // If ParseParenExpression parsed a '(typename)' sequence only, the this is
+    // sizeof/alignof a type.  Otherwise, it is sizeof/alignof an expression.
+    if (ExprType == CastExpr) {
+      return Actions.ParseSizeOfAlignOfTypeExpr(OpTok.getLocation(),
+                                              OpTok.getKind() == tok::kw_sizeof,
+                                                LParenLoc, CastTy, RParenLoc);
+    }
+  }
+  
+  // If we get here, the operand to the sizeof/alignof was an expresion.
+  if (!Operand.isInvalid)
+    Operand = Actions.ParseUnaryOp(OpTok.getLocation(), OpTok.getKind(),
+                                   Operand.Val);
+  return Operand;
+}
+
+/// ParseBuiltinPrimaryExpression
+///
+///       primary-expression: [C99 6.5.1]
+/// [GNU]   '__builtin_va_arg' '(' assignment-expression ',' type-name ')'
+/// [GNU]   '__builtin_offsetof' '(' type-name ',' offsetof-member-designator')'
+/// [GNU]   '__builtin_choose_expr' '(' assign-expr ',' assign-expr ','
+///                                     assign-expr ')'
+/// [GNU]   '__builtin_types_compatible_p' '(' type-name ',' type-name ')'
+/// 
+/// [GNU] offsetof-member-designator:
+/// [GNU]   identifier
+/// [GNU]   offsetof-member-designator '.' identifier
+/// [GNU]   offsetof-member-designator '[' expression ']'
+///
+Parser::ExprResult Parser::ParseBuiltinPrimaryExpression() {
+  ExprResult Res(false);
+  const IdentifierInfo *BuiltinII = Tok.getIdentifierInfo();
+
+  tok::TokenKind T = Tok.getKind();
+  SourceLocation StartLoc = ConsumeToken();   // Eat the builtin identifier.
+
+  // All of these start with an open paren.
+  if (Tok.getKind() != tok::l_paren) {
+    Diag(Tok, diag::err_expected_lparen_after, BuiltinII->getName());
+    return ExprResult(true);
+  }
+  
+  SourceLocation LParenLoc = ConsumeParen();
+  // TODO: Build AST.
+
+  switch (T) {
+  default: assert(0 && "Not a builtin primary expression!");
+  case tok::kw___builtin_va_arg:
+    Res = ParseAssignmentExpression();
+    if (Res.isInvalid) {
+      SkipUntil(tok::r_paren);
+      return Res;
+    }
+
+    if (ExpectAndConsume(tok::comma, diag::err_expected_comma, "",tok::r_paren))
+      return ExprResult(true);
+
+    ParseTypeName();
+    break;
+    
+  case tok::kw___builtin_offsetof:
+    ParseTypeName();
+
+    if (ExpectAndConsume(tok::comma, diag::err_expected_comma, "",tok::r_paren))
+      return ExprResult(true);
+    
+    // We must have at least one identifier here.
+    if (ExpectAndConsume(tok::identifier, diag::err_expected_ident, "",
+                         tok::r_paren))
+      return ExprResult(true);
+
+    while (1) {
+      if (Tok.getKind() == tok::period) {
+        // offsetof-member-designator: offsetof-member-designator '.' identifier
+        ConsumeToken();
+        
+        if (ExpectAndConsume(tok::identifier, diag::err_expected_ident, "",
+                             tok::r_paren))
+          return ExprResult(true);
+      } else if (Tok.getKind() == tok::l_square) {
+        // offsetof-member-designator: offsetof-member-design '[' expression ']'
+        SourceLocation LSquareLoc = ConsumeBracket();
+        Res = ParseExpression();
+        if (Res.isInvalid) {
+          SkipUntil(tok::r_paren);
+          return Res;
+        }
+
+        MatchRHSPunctuation(tok::r_square, LSquareLoc);
+      } else {
+        break;
+      }
+    }
+    break;
+  case tok::kw___builtin_choose_expr:
+    Res = ParseAssignmentExpression();
+    
+    if (ExpectAndConsume(tok::comma, diag::err_expected_comma, "",tok::r_paren))
+      return ExprResult(true);
+    
+    Res = ParseAssignmentExpression();
+    
+    if (ExpectAndConsume(tok::comma, diag::err_expected_comma, "",tok::r_paren))
+      return ExprResult(true);
+    
+    Res = ParseAssignmentExpression();
+    break;
+  case tok::kw___builtin_types_compatible_p:
+    ParseTypeName();
+    
+    if (ExpectAndConsume(tok::comma, diag::err_expected_comma, "",tok::r_paren))
+      return ExprResult(true);
+    
+    ParseTypeName();
+    break;
+  }      
+  
+  MatchRHSPunctuation(tok::r_paren, LParenLoc);
+  
+  // These can be followed by postfix-expr pieces because they are
+  // primary-expressions.
+  return ParsePostfixExpressionSuffix(Res);
+}
+
+/// ParseParenExpression - This parses the unit that starts with a '(' token,
+/// based on what is allowed by ExprType.  The actual thing parsed is returned
+/// in ExprType.
+///
+///       primary-expression: [C99 6.5.1]
+///         '(' expression ')'
+/// [GNU]   '(' compound-statement ')'      (if !ParenExprOnly)
+///       postfix-expression: [C99 6.5.2]
+///         '(' type-name ')' '{' initializer-list '}'
+///         '(' type-name ')' '{' initializer-list ',' '}'
+///       cast-expression: [C99 6.5.4]
+///         '(' type-name ')' cast-expression
+///
+Parser::ExprResult Parser::ParseParenExpression(ParenParseOption &ExprType,
+                                                TypeTy *&CastTy,
+                                                SourceLocation &RParenLoc) {
+  assert(Tok.getKind() == tok::l_paren && "Not a paren expr!");
+  SourceLocation OpenLoc = ConsumeParen();
+  ExprResult Result(false);
+  CastTy = 0;
+  
+  if (ExprType >= CompoundStmt && Tok.getKind() == tok::l_brace &&
+      !getLang().NoExtensions) {
+    Diag(Tok, diag::ext_gnu_statement_expr);
+    ParseCompoundStatement();
+    ExprType = CompoundStmt;
+    // TODO: Build AST for GNU compound stmt.
+  } else if (ExprType >= CompoundLiteral && isTypeSpecifierQualifier()) {
+    // Otherwise, this is a compound literal expression or cast expression.
+    TypeTy *Ty = ParseTypeName();
+
+    // Match the ')'.
+    if (Tok.getKind() == tok::r_paren)
+      RParenLoc = ConsumeParen();
+    else
+      MatchRHSPunctuation(tok::r_paren, OpenLoc);
+    
+    if (Tok.getKind() == tok::l_brace) {
+      if (!getLang().C99)   // Compound literals don't exist in C90.
+        Diag(OpenLoc, diag::ext_c99_compound_literal);
+      Result = ParseInitializer();
+      ExprType = CompoundLiteral;
+      // TODO: Build AST for compound literal.
+    } else if (ExprType == CastExpr) {
+      // Note that this doesn't parse the subsequence cast-expression, it just
+      // returns the parsed type to the callee.
+      ExprType = CastExpr;
+      CastTy = Ty;
+      return ExprResult(false);
+    } else {
+      Diag(Tok, diag::err_expected_lbrace_in_compound_literal);
+      return ExprResult(true);
+    }
+    return Result;
+  } else {
+    Result = ParseExpression();
+    ExprType = SimpleExpr;
+    if (!Result.isInvalid && Tok.getKind() == tok::r_paren)
+      Result = Actions.ParseParenExpr(OpenLoc, Tok.getLocation(), Result.Val);
+  }
+  
+  // Match the ')'.
+  if (Result.isInvalid)
+    SkipUntil(tok::r_paren);
+  else {
+    if (Tok.getKind() == tok::r_paren)
+      RParenLoc = ConsumeParen();
+    else
+      MatchRHSPunctuation(tok::r_paren, OpenLoc);
+  }
+  
+  return Result;
+}
+
+/// ParseStringLiteralExpression - This handles the various token types that
+/// form string literals, and also handles string concatenation [C99 5.1.1.2,
+/// translation phase #6].
+///
+///       primary-expression: [C99 6.5.1]
+///         string-literal
+Parser::ExprResult Parser::ParseStringLiteralExpression() {
+  assert(isTokenStringLiteral() && "Not a string literal!");
+  
+  // String concat.  Note that keywords like __func__ and __FUNCTION__ are not
+  // considered to be strings for concatenation purposes.
+  llvm::SmallVector<LexerToken, 4> StringToks;
+  
+  do {
+    StringToks.push_back(Tok);
+    ConsumeStringToken();
+  } while (isTokenStringLiteral());
+
+  // Pass the set of string tokens, ready for concatenation, to the actions.
+  return Actions.ParseStringLiteral(&StringToks[0], StringToks.size());
+}