Speed up adding literal chars when the buffer is known to be one-byte

src/parsing/scanner.h

 // 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.
 
 #ifndef V8_PARSING_SCANNER_H_
 #define V8_PARSING_SCANNER_H_
 
 #include "src/allocation.h"
@@ skipping 140 matching lines @@
 
 // ----------------------------------------------------------------------------
 // LiteralBuffer -  Collector of chars of literals.
 
 class LiteralBuffer {
  public:
   LiteralBuffer() : is_one_byte_(true), position_(0), backing_store_() { }
 
   ~LiteralBuffer() { backing_store_.Dispose(); }
 
-  INLINE(void AddChar(uint32_t code_unit)) {
+  INLINE(void AddChar(char code_unit)) {
+    if (position_ >= backing_store_.length()) ExpandBuffer();
+    DCHECK(is_one_byte_);

[vogelheim, 2016/06/09 12:05:15]

Maybe also dcheck whether code_unit is actually ascii. (e.g: DCHECK(0 <=
code_unit && code_unit <= kMaxAscii);

+    backing_store_[position_] = static_cast<byte>(code_unit);
+    position_ += kOneByteSize;
+    return;
+  }
+
+  INLINE(void AddChar(uc32 code_unit)) {
     if (position_ >= backing_store_.length()) ExpandBuffer();
     if (is_one_byte_) {
       if (code_unit <= unibrow::Latin1::kMaxChar) {
         backing_store_[position_] = static_cast<byte>(code_unit);
         position_ += kOneByteSize;
         return;
       }
       ConvertToTwoByte();
     }
     if (code_unit <= unibrow::Utf16::kMaxNonSurrogateCharCode) {
@@ skipping 378 matching lines @@
                   : &raw_literal_buffer0_;
     free_buffer->Reset();
     next_.raw_literal_chars = free_buffer;
   }
 
   INLINE(void AddLiteralChar(uc32 c)) {
     DCHECK_NOT_NULL(next_.literal_chars);
     next_.literal_chars->AddChar(c);
   }
 
+  INLINE(void AddLiteralChar(char c)) {
+    DCHECK_NOT_NULL(next_.literal_chars);
+    next_.literal_chars->AddChar(c);
+  }
+
   INLINE(void AddRawLiteralChar(uc32 c)) {
     DCHECK_NOT_NULL(next_.raw_literal_chars);
     next_.raw_literal_chars->AddChar(c);
   }
 
   INLINE(void ReduceRawLiteralLength(int delta)) {
     DCHECK_NOT_NULL(next_.raw_literal_chars);
     next_.raw_literal_chars->ReduceLength(delta);
   }
 
@@ skipping 237 matching lines @@
   bool allow_harmony_exponentiation_operator_;
 
   MessageTemplate::Template scanner_error_;
   Location scanner_error_location_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_SCANNER_H_