Revision: 4304
Author: [email protected]
Date: Mon Mar 29 04:17:34 2010
Log: Optimization for parsing integers of limited length (in digits).
Review URL: http://codereview.chromium.org/1367004
http://code.google.com/p/v8/source/detail?r=4304
Modified:
/branches/bleeding_edge/src/conversions.cc
/branches/bleeding_edge/test/mjsunit/parse-int-float.js
=======================================
--- /branches/bleeding_edge/src/conversions.cc Thu Mar 25 07:39:39 2010
+++ /branches/bleeding_edge/src/conversions.cc Mon Mar 29 04:17:34 2010
@@ -377,6 +377,7 @@
int significant_digits = 0;
int insignificant_digits = 0;
bool nonzero_digit_dropped = false;
+ bool fractional_part = false;
double signed_zero = 0.0;
@@ -454,8 +455,6 @@
}
if (*current == '.') {
- ASSERT(buffer_pos < kBufferSize);
- buffer[buffer_pos++] = '.';
++current;
if (current == end) {
if (significant_digits == 0 && !leading_zero) {
@@ -475,6 +474,10 @@
exponent--; // Move this 0 into the exponent.
}
}
+
+ ASSERT(buffer_pos < kBufferSize);
+ buffer[buffer_pos++] = '.';
+ fractional_part = true;
// There is the fractional part.
while (*current >= '0' && *current <= '9') {
@@ -579,6 +582,11 @@
if (insignificant_digits) buffer[buffer_pos++] = '.';
buffer[buffer_pos++] = '1';
}
+
+ // If the number has no more than kMaxDigitsInInt digits and doesn't have
+ // fractional part it could be parsed faster (without checks for
+ // spaces, overflow, etc.).
+ const int kMaxDigitsInInt = 9 * sizeof(int) / 4; // NOLINT
if (exponent != 0) {
ASSERT(buffer_pos < kBufferSize);
@@ -597,6 +605,16 @@
}
ASSERT(exponent == 0);
buffer_pos += exp_digits;
+ } else if (!fractional_part && significant_digits <= kMaxDigitsInInt) {
+ if (significant_digits == 0) return signed_zero;
+ ASSERT(buffer_pos > 0);
+ int num = 0;
+ int start_pos = (buffer[0] == '-' ? 1 : 0);
+ for (int i = start_pos; i < buffer_pos; i++) {
+ ASSERT(buffer[i] >= '0' && buffer[i] <= '9');
+ num = 10 * num + (buffer[i] - '0');
+ }
+ return static_cast<double>(start_pos == 0 ? num : -num);
}
ASSERT(buffer_pos < kBufferSize);
=======================================
--- /branches/bleeding_edge/test/mjsunit/parse-int-float.js Tue Nov 17
05:54:05 2009
+++ /branches/bleeding_edge/test/mjsunit/parse-int-float.js Mon Mar 29
04:17:34 2010
@@ -47,6 +47,7 @@
assertEquals(0.1, parseFloat('0.1'));
assertEquals(0.1, parseFloat('0.1aaa'));
+assertEquals(0, parseFloat('0aaa'));
assertEquals(0, parseFloat('0x12'));
assertEquals(77, parseFloat('077'));
--
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