Improve fasta scanner performance

pkg/front_end/lib/src/fasta/scanner/abstract_scanner.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library fasta.scanner.abstract_scanner;
 
 import '../scanner.dart' show
     ErrorToken,
     Scanner,
     buildUnexpectedCharacterToken;
@@ skipping 213 matching lines @@
       next = advance();
       // Sequences of spaces are common, so advance through them fast.
       while (identical(next, $SPACE)) {
         // We don't invoke [:appendWhiteSpace(next):] here for efficiency,
         // assuming that it does not do anything for space characters.
         next = advance();
       }
       return next;
     }
 
-    if ($a <= next && next <= $z) {
+    int nextLower = next | 0x20;
+
+    if ($a <= nextLower && nextLower <= $z) {
       if (identical($r, next)) {
         return tokenizeRawStringKeywordOrIdentifier(next);
       }
       return tokenizeKeywordOrIdentifier(next, true);
     }
 
-    if (($A <= next && next <= $Z) ||
-        identical(next, $_) ||
-        identical(next, $$)) {
+    if (identical(next, $CLOSE_PAREN)) {
+      return appendEndGroup(CLOSE_PAREN_INFO, OPEN_PAREN_TOKEN);
+    }
+
+    if (identical(next, $OPEN_PAREN)) {
+      appendBeginGroup(OPEN_PAREN_INFO);
+      return advance();
+    }
+
+    if (identical(next, $SEMICOLON)) {
+      appendPrecedenceToken(SEMICOLON_INFO);
+      // Type parameters and arguments cannot contain semicolon.
+      discardOpenLt();
+      return advance();
+    }
+
+    if (identical(next, $PERIOD)) {
+      return tokenizeDotsOrNumber(next);
+    }
+
+    if (identical(next, $COMMA)) {
+      appendPrecedenceToken(COMMA_INFO);
+      return advance();
+    }
+
+    if (identical(next, $EQ)) {
+      return tokenizeEquals(next);
+    }
+
+    if (identical(next, $CLOSE_CURLY_BRACKET)) {
+      return appendEndGroup(CLOSE_CURLY_BRACKET_INFO, OPEN_CURLY_BRACKET_TOKEN);
+    }
+
+    if (identical(next, $SLASH)) {
+      return tokenizeSlashOrComment(next);
+    }
+
+
+    if (identical(next, $OPEN_CURLY_BRACKET)) {
+      appendBeginGroup(OPEN_CURLY_BRACKET_INFO);
+      return advance();
+    }
+
+    if (identical(next, $DQ) || identical(next, $SQ)) {
+      return tokenizeString(next, scanOffset, false);
+    }
+
+    if(identical(next, $_)){
       return tokenizeKeywordOrIdentifier(next, true);
     }
 
+    if (identical(next, $COLON)) {
+      appendPrecedenceToken(COLON_INFO);
+      return advance();
+    }
+
     if (identical(next, $LT)) {
       return tokenizeLessThan(next);
     }
 
     if (identical(next, $GT)) {
       return tokenizeGreaterThan(next);
     }
 
-    if (identical(next, $EQ)) {
-      return tokenizeEquals(next);
-    }
-
     if (identical(next, $BANG)) {
       return tokenizeExclamation(next);
     }
 
+    if (identical(next, $OPEN_SQUARE_BRACKET)) {
+      return tokenizeOpenSquareBracket(next);
+    }
+
+    if (identical(next, $CLOSE_SQUARE_BRACKET)) {
+      return appendEndGroup(
+          CLOSE_SQUARE_BRACKET_INFO, OPEN_SQUARE_BRACKET_TOKEN);
+    }
+
+    if (identical(next, $AT)) {
+      return tokenizeAt(next);
+    }
+
+    if (next >= $1 && next <= $9) {
+      return tokenizeNumber(next);
+    }
+
+    if (identical(next, $AMPERSAND)) {
+      return tokenizeAmpersand(next);
+    }
+
+    if (identical(next, $0)) {
+      return tokenizeHexOrNumber(next);
+    }
+
+    if (identical(next, $QUESTION)) {
+      return tokenizeQuestion(next);
+    }
+
+    if (identical(next, $BAR)) {
+      return tokenizeBar(next);
+    }
+
     if (identical(next, $PLUS)) {
       return tokenizePlus(next);
     }
 
+    if(identical(next, $$)){
+      return tokenizeKeywordOrIdentifier(next, true);
+    }
+
     if (identical(next, $MINUS)) {
       return tokenizeMinus(next);
     }
 
     if (identical(next, $STAR)) {
       return tokenizeMultiply(next);
     }
 
+    if (identical(next, $CARET)) {
+      return tokenizeCaret(next);
+    }
+
+    if (identical(next, $TILDE)) {
+      return tokenizeTilde(next);
+    }
+
     if (identical(next, $PERCENT)) {
       return tokenizePercent(next);
     }
 
-    if (identical(next, $AMPERSAND)) {
-      return tokenizeAmpersand(next);
-    }
-
-    if (identical(next, $BAR)) {
-      return tokenizeBar(next);
-    }
-
-    if (identical(next, $CARET)) {
-      return tokenizeCaret(next);
-    }
-
-    if (identical(next, $OPEN_SQUARE_BRACKET)) {
-      return tokenizeOpenSquareBracket(next);
-    }
-
-    if (identical(next, $TILDE)) {
-      return tokenizeTilde(next);
+    if (identical(next, $BACKPING)) {
+      appendPrecedenceToken(BACKPING_INFO);
+      return advance();
     }
 
     if (identical(next, $BACKSLASH)) {
       appendPrecedenceToken(BACKSLASH_INFO);
       return advance();
     }
 
     if (identical(next, $HASH)) {
       return tokenizeTag(next);
     }
 
-    if (identical(next, $OPEN_PAREN)) {
-      appendBeginGroup(OPEN_PAREN_INFO);
-      return advance();
-    }
-
-    if (identical(next, $CLOSE_PAREN)) {
-      return appendEndGroup(CLOSE_PAREN_INFO, OPEN_PAREN_TOKEN);
-    }
-
-    if (identical(next, $COMMA)) {
-      appendPrecedenceToken(COMMA_INFO);
-      return advance();
-    }
-
-    if (identical(next, $COLON)) {
-      appendPrecedenceToken(COLON_INFO);
-      return advance();
-    }
-
-    if (identical(next, $SEMICOLON)) {
-      appendPrecedenceToken(SEMICOLON_INFO);
-      // Type parameters and arguments cannot contain semicolon.
-      discardOpenLt();
-      return advance();
-    }
-
-    if (identical(next, $QUESTION)) {
-      return tokenizeQuestion(next);
-    }
-
-    if (identical(next, $CLOSE_SQUARE_BRACKET)) {
-      return appendEndGroup(
-          CLOSE_SQUARE_BRACKET_INFO, OPEN_SQUARE_BRACKET_TOKEN);
-    }
-
-    if (identical(next, $BACKPING)) {
-      appendPrecedenceToken(BACKPING_INFO);
-      return advance();
-    }
-
-    if (identical(next, $OPEN_CURLY_BRACKET)) {
-      appendBeginGroup(OPEN_CURLY_BRACKET_INFO);
-      return advance();
-    }
-
-    if (identical(next, $CLOSE_CURLY_BRACKET)) {
-      return appendEndGroup(CLOSE_CURLY_BRACKET_INFO, OPEN_CURLY_BRACKET_TOKEN);
-    }
-
-    if (identical(next, $SLASH)) {
-      return tokenizeSlashOrComment(next);
-    }
-
-    if (identical(next, $AT)) {
-      return tokenizeAt(next);
-    }
-
-    if (identical(next, $DQ) || identical(next, $SQ)) {
-      return tokenizeString(next, scanOffset, false);
-    }
-
-    if (identical(next, $PERIOD)) {
-      return tokenizeDotsOrNumber(next);
-    }
-
-    if (identical(next, $0)) {
-      return tokenizeHexOrNumber(next);
-    }
-
-    // TODO(ahe): Would a range check be faster?
-    if (identical(next, $1) ||
-        identical(next, $2) ||
-        identical(next, $3) ||
-        identical(next, $4) ||
-        identical(next, $5) ||
-        identical(next, $6) ||
-        identical(next, $7) ||
-        identical(next, $8) ||
-        identical(next, $9)) {
-      return tokenizeNumber(next);
-    }
-
-    if (identical(next, $EOF)) {
-      return $EOF;
-    }
     if (next < 0x1f) {
       return unexpected(next);
     }
 
     next = currentAsUnicode(next);
 
     return unexpected(next);
   }
 
   int tokenizeTag(int next) {
@@ skipping 764 matching lines @@
 
 PrecedenceInfo closeBraceInfoFor(BeginGroupToken begin) {
   return const {
     '(': CLOSE_PAREN_INFO,
     '[': CLOSE_SQUARE_BRACKET_INFO,
     '{': CLOSE_CURLY_BRACKET_INFO,
     '<': GT_INFO,
     r'${': CLOSE_CURLY_BRACKET_INFO,
   }[begin.value];
 }