Speed up parsing of smis

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 895 matching lines @@
     AddLiteralCharAdvance();
 }
 
 
 Token::Value Scanner::ScanNumber(bool seen_period) {
   DCHECK(IsDecimalDigit(c0_));  // the first digit of the number or the fraction
 
   enum { DECIMAL, HEX, OCTAL, IMPLICIT_OCTAL, BINARY } kind = DECIMAL;
 
   LiteralScope literal(this);
+  bool at_start = !seen_period;
   if (seen_period) {
     // we have already seen a decimal point of the float
     AddLiteralChar('.');
     ScanDecimalDigits();  // we know we have at least one digit
 
   } else {
     // if the first character is '0' we must check for octals and hex
     if (c0_ == '0') {
       int start_pos = source_pos();  // For reporting octal positions.
       AddLiteralCharAdvance();
@@ skipping 29 matching lines @@
           return Token::ILLEGAL;
         }
         while (IsBinaryDigit(c0_)) {
           AddLiteralCharAdvance();
         }
       } else if ('0' <= c0_ && c0_ <= '7') {
         // (possible) octal number
         kind = IMPLICIT_OCTAL;
         while (true) {
           if (c0_ == '8' || c0_ == '9') {
+            at_start = false;
             kind = DECIMAL;
             break;
           }
           if (c0_  < '0' || '7'  < c0_) {
             // Octal literal finished.
             octal_pos_ = Location(start_pos, source_pos());
             break;
           }
           AddLiteralCharAdvance();
         }
       }
     }
 
     // Parse decimal digits and allow trailing fractional part.
     if (kind == DECIMAL) {
+      if (at_start) {
+        int value = 0;
+        while (IsDecimalDigit(c0_)) {
+          value = 10 * value + (c0_ - '0');
+          AddLiteralCharAdvance();
+        }
+
+        if (next_.literal_chars->one_byte_literal().length() < 10 &&
+            c0_ != '.' && c0_ != 'e' && c0_ != 'E') {
+          smi_value_ = value;
+          literal.Complete();
+          return Token::SMI;
+        }
+      }
+
       ScanDecimalDigits();  // optional
       if (c0_ == '.') {
         AddLiteralCharAdvance();
         ScanDecimalDigits();  // optional
       }
     }
   }
 
   // scan exponent, if any
   if (c0_ == 'e' || c0_ == 'E') {
@@ skipping 497 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