From: Chris Lattner <sabre@nondot.org>
Date: Sun, 6 Apr 2008 05:26:30 +0000 (+0000)
Subject: Use token lookahead to simplify some code that is rarely executed.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=5dcc6ce4a68b3bd4b89c5697c9728e1533e71e03;p=clang

Use token lookahead to simplify some code that is rarely executed.
Since it is rare, the cost is not significant and we enjoy the
simplification.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@49263 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/include/clang/Parse/Parser.h b/include/clang/Parse/Parser.h
index 962b3370b7..01879479a8 100644
--- a/include/clang/Parse/Parser.h
+++ b/include/clang/Parse/Parser.h
@@ -336,7 +336,6 @@ private:
   ExprResult ParseExpressionWithLeadingIdentifier(const Token &Tok);
   ExprResult ParseExpressionWithLeadingAt(SourceLocation AtLoc);
   ExprResult ParseAssignmentExprWithLeadingIdentifier(const Token &Tok);
-  ExprResult ParseAssignmentExpressionWithLeadingStar(const Token &Tok);
 
   ExprResult ParseRHSOfBinaryExpression(ExprResult LHS, unsigned MinPrec);
   ExprResult ParseCastExpression(bool isUnaryExpression);
diff --git a/lib/Parse/ParseDecl.cpp b/lib/Parse/ParseDecl.cpp
index 9b8ecf8bd3..1659af30e6 100644
--- a/lib/Parse/ParseDecl.cpp
+++ b/lib/Parse/ParseDecl.cpp
@@ -1440,24 +1440,20 @@ void Parser::ParseBracketDeclarator(Declarator &D) {
   // Handle "direct-declarator [ type-qual-list[opt] * ]".
   bool isStar = false;
   ExprResult NumElements(false);
-  if (Tok.is(tok::star)) {
+  
+  // Handle the case where we have '[*]' as the array size.  However, a leading
+  // star could be the start of an expression, for example 'X[*p + 4]'.  Verify
+  // the the token after the star is a ']'.  Since stars in arrays are
+  // infrequent, use of lookahead is not costly here.
+  if (Tok.is(tok::star) && GetLookAheadToken(1).is(tok::r_square)) {
     // Remember the '*' token, in case we have to un-get it.
     Token StarTok = Tok;
     ConsumeToken();
 
-    // Check that the ']' token is present to avoid incorrectly parsing
-    // expressions starting with '*' as [*].
-    if (Tok.is(tok::r_square)) {
-      if (StaticLoc.isValid())
-        Diag(StaticLoc, diag::err_unspecified_vla_size_with_static);
-      StaticLoc = SourceLocation();  // Drop the static.
-      isStar = true;
-    } else {
-      // Otherwise, the * must have been some expression (such as '*ptr') that
-      // started an assignment-expr.  We already consumed the token, but now we
-      // need to reparse it.  This handles cases like 'X[*p + 4]'
-      NumElements = ParseAssignmentExpressionWithLeadingStar(StarTok);
-    }
+    if (StaticLoc.isValid())
+      Diag(StaticLoc, diag::err_unspecified_vla_size_with_static);
+    StaticLoc = SourceLocation();  // Drop the static.
+    isStar = true;
   } else if (Tok.isNot(tok::r_square)) {
     // Parse the assignment-expression now.
     NumElements = ParseAssignmentExpression();
diff --git a/lib/Parse/ParseExpr.cpp b/lib/Parse/ParseExpr.cpp
index 46714b73ea..dff7c14524 100644
--- a/lib/Parse/ParseExpr.cpp
+++ b/lib/Parse/ParseExpr.cpp
@@ -270,42 +270,6 @@ ParseAssignmentExprWithLeadingIdentifier(const Token &IdTok) {
 }
 
 
-/// 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 Token &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.ActOnUnaryOp(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