Revision: 3815
Author: [email protected]
Date: Mon Feb 8 06:00:50 2010
Log: Optimize concat for one argument (two if you count 'this').
Review URL: http://codereview.chromium.org/584006
http://code.google.com/p/v8/source/detail?r=3815
Modified:
/branches/bleeding_edge/src/string.js
=======================================
--- /branches/bleeding_edge/src/string.js Thu Jan 7 04:18:56 2010
+++ /branches/bleeding_edge/src/string.js Mon Feb 8 06:00:50 2010
@@ -87,14 +87,18 @@
// ECMA-262, section 15.5.4.6
function StringConcat() {
- var len = %_ArgumentsLength() + 1;
- var parts = new $Array(len);
- parts[0] = IS_STRING(this) ? this : ToString(this);
- for (var i = 1; i < len; i++) {
- var part = %_Arguments(i - 1);
- parts[i] = IS_STRING(part) ? part : ToString(part);
- }
- return %StringBuilderConcat(parts, len, "");
+ var len = %_ArgumentsLength();
+ var this_as_string = IS_STRING(this) ? this : ToString(this);
+ if (len === 1) {
+ return this_as_string + %_Arguments(0);
+ }
+ var parts = new $Array(len + 1);
+ parts[0] = this_as_string;
+ for (var i = 0; i < len; i++) {
+ var part = %_Arguments(i);
+ parts[i + 1] = IS_STRING(part) ? part : ToString(part);
+ }
+ return %StringBuilderConcat(parts, len + 1, "");
}
// Match ES3 and Safari
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