Replace C++ bitfields with our own BitFields

src/scanner.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Features shared by parsing and pre-parsing scanners.
 
 #include <stdint.h>
 
 #include <cmath>
 
@@ skipping 227 matching lines @@
   // Spidermonkey.
   return c == 0xFFFE;
 }
 
 
 bool Scanner::SkipWhiteSpace() {
   int start_position = source_pos();
 
   while (true) {
     while (true) {
+      // The unicode cache accepts unsigned inputs.
+      if (c0_ < 0) break;

[Sven Panne, 2014/11/05 09:11:49]

How is this related to the bitfield fiddling?

[Jakob Kummerow, 2014/11/05 12:13:46]

As the comment says, the unicode_cache_ only accepts unsigned inputs. Since it's
now using BitField, it trips over a DCHECK that the implicitly-converted -1
(which signals EOS) can actually be stored.

       // Advance as long as character is a WhiteSpace or LineTerminator.
       // Remember if the latter is the case.
       if (unicode_cache_->IsLineTerminator(c0_)) {
         has_line_terminator_before_next_ = true;
       } else if (!unicode_cache_->IsWhiteSpace(c0_) &&
                  !IsLittleEndianByteOrderMark(c0_)) {
         break;
       }
       Advance();
     }
@@ skipping 360 matching lines @@
 
       case '?':
         token = Select(Token::CONDITIONAL);
         break;
 
       case '~':
         token = Select(Token::BIT_NOT);
         break;
 
       default:
-        if (unicode_cache_->IsIdentifierStart(c0_)) {
+        if (c0_ < 0) {
+          token = Token::EOS;

[Sven Panne, 2014/11/05 09:11:49]

Same here...

+        } else if (unicode_cache_->IsIdentifierStart(c0_)) {
           token = ScanIdentifierOrKeyword();
         } else if (IsDecimalDigit(c0_)) {
           token = ScanNumber(false);
         } else if (SkipWhiteSpace()) {
           token = Token::WHITESPACE;
-        } else if (c0_ < 0) {
-          token = Token::EOS;
         } else {
           token = Select(Token::ILLEGAL);
         }
         break;
     }
 
     // Continue scanning for tokens as long as we're just skipping
     // whitespace.
   } while (token == Token::WHITESPACE);
 
@@ skipping 698 matching lines @@
     }
     backing_store_.Add(static_cast<uint8_t>((one_byte_length >> 7) | 0x80u));
   }
   backing_store_.Add(static_cast<uint8_t>(one_byte_length & 0x7f));
 
   backing_store_.AddBlock(bytes);
   return backing_store_.EndSequence().start();
 }
 
 } }  // namespace v8::internal