From d913faaf6d68e3e5f0a160876b51639c05f7df64 Mon Sep 17 00:00:00 2001
From: "yangguo@chromium.org" <yangguo@chromium.org>
Date: Fri, 17 Oct 2014 10:01:38 +0000
Subject: [PATCH] Improve String.repeat.

Adapted from patch contributed by Isiah Meadows <impinball@gmail.com>.

R=jkummerow@chromium.org

Review URL: https://codereview.chromium.org/657863002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24687 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
---
 AUTHORS                               |  1 +
 src/harmony-string.js                 | 15 +++++++++------
 test/mjsunit/harmony/string-repeat.js |  3 +++
 3 files changed, 13 insertions(+), 6 deletions(-)

diff --git a/AUTHORS b/AUTHORS
index d406a6c..89caae6 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -39,6 +39,7 @@ Fedor Indutny <fedor@indutny.com>
 Filipe David Manana <fdmanana@gmail.com>
 Haitao Feng <haitao.feng@intel.com>
 Ioseb Dzmanashvili <ioseb.dzmanashvili@gmail.com>
+Isiah Meadows <impinball@gmail.com>
 Jacob Bramley <jacob.bramley@arm.com>
 Jan de Mooij <jandemooij@gmail.com>
 Jay Freeman <saurik@saurik.com>
diff --git a/src/harmony-string.js b/src/harmony-string.js
index ae13745..1c477e2 100644
--- a/src/harmony-string.js
+++ b/src/harmony-string.js
@@ -17,16 +17,19 @@ function StringRepeat(count) {
 
   var s = TO_STRING_INLINE(this);
   var n = ToInteger(count);
-  if (n < 0 || !NUMBER_IS_FINITE(n)) {
+  // The maximum string length is stored in a smi, so a longer repeat
+  // must result in a range error.
+  if (n < 0 || n > %_MaxSmi()) {
     throw MakeRangeError("invalid_count_value", []);
   }
 
-  var elements = new InternalArray(n);
-  for (var i = 0; i < n; i++) {
-    elements[i] = s;
+  var r = "";
+  while (true) {
+    if (n & 1) r += s;
+    n >>= 1;
+    if (n === 0) return r;
+    s += s;
   }
-
-  return %StringBuilderConcat(elements, n, "");
 }
 
 
diff --git a/test/mjsunit/harmony/string-repeat.js b/test/mjsunit/harmony/string-repeat.js
index 761089b..0af7448 100644
--- a/test/mjsunit/harmony/string-repeat.js
+++ b/test/mjsunit/harmony/string-repeat.js
@@ -61,8 +61,11 @@ assertEquals("", "".repeat(5));
 assertEquals("", "abc".repeat(0));
 assertEquals("abcabc", "abc".repeat(2.0));
 
+assertEquals("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa", "a".repeat(37));
 assertThrows('"a".repeat(-1)', RangeError);
 assertThrows('"a".repeat(Number.POSITIVE_INFINITY)', RangeError);
+assertThrows('"a".repeat(Math.pow(2, 30))', RangeError);
+assertThrows('"a".repeat(Math.pow(2, 40))', RangeError);
 
 var myobj = {
   toString: function() {
-- 
2.7.4