[builtins] Port String.prototype.{padStart, padEnd} to CSA

- Extract core StringPrototypeRepeat code into a TFS builtin (StringRepeat)
  - Assumes arguments are a string and smi (no range checks)
- Add StringPrototypePadStart and StringPrototypePadEnd TFJ builtins
  - Added StringPadAssembler to ensure common behavior
- Removed functionality from string.js

A quick benchmark shows significant performance gains for unoptimized
code (2.1x to 2.46x) and optimized code (1.03x - 1.56x).

https: //github.com/peterwmwong/v8-perf/blob/master/string-pad/README.md
Bug: v8:5049
Change-Id: I6e4fe99fb62a3edb3d6906fd4f78b3576b5b0d13
Reviewed-on: https://chromium-review.googlesource.com/720067
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48595}

src/bootstrapper.cc

@@ -1992,6 +1992,10 @@ void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
     SimpleInstallFunction(prototype, "normalize",
                           Builtins::kStringPrototypeNormalize, 0, false);
 #endif  // V8_INTL_SUPPORT
+    SimpleInstallFunction(prototype, "padEnd", Builtins::kStringPrototypePadEnd,
+                          1, false);
+    SimpleInstallFunction(prototype, "padStart",
+                          Builtins::kStringPrototypePadStart, 1, false);
     SimpleInstallFunction(prototype, "repeat", Builtins::kStringPrototypeRepeat,
                           1, true);
     SimpleInstallFunction(prototype, "replace",

src/builtins/builtins-definitions.h

@@ -99,6 +99,7 @@ namespace internal {
   TFS(StringIndexOf, kReceiver, kSearchString, kPosition)                      \
   TFC(StringLessThan, Compare, 1)                                              \
   TFC(StringLessThanOrEqual, Compare, 1)                                       \
+  TFS(StringRepeat, kString, kCount)                                           \
                                                                                \
   /* OrderedHashTable helpers */                                               \
   TFS(OrderedHashTableHealIndex, kTable, kIndex)                               \
@@ -939,6 +940,11 @@ namespace internal {
   TFJ(StringPrototypeMatch, 1, kRegexp)                                        \
   /* ES6 #sec-string.prototype.localecompare */                                \
   CPP(StringPrototypeLocaleCompare)                                            \
+  /* ES6 #sec-string.prototype.padEnd */                                       \
+  TFJ(StringPrototypePadEnd, SharedFunctionInfo::kDontAdaptArgumentsSentinel)  \
+  /* ES6 #sec-string.prototype.padStart */                                     \
+  TFJ(StringPrototypePadStart,                                                 \
+      SharedFunctionInfo::kDontAdaptArgumentsSentinel)                         \
   /* ES6 #sec-string.prototype.repeat */                                       \
   TFJ(StringPrototypeRepeat, 1, kCount)                                        \
   /* ES6 #sec-string.prototype.replace */                                      \

src/debug/debug-evaluate.cc

@@ -609,6 +609,8 @@ bool BuiltinHasNoSideEffect(Builtins::Name id) {
     case Builtins::kStringPrototypeItalics:
     case Builtins::kStringPrototypeLastIndexOf:
     case Builtins::kStringPrototypeLink:
+    case Builtins::kStringPrototypePadEnd:
+    case Builtins::kStringPrototypePadStart:
     case Builtins::kStringPrototypeRepeat:
     case Builtins::kStringPrototypeSlice:
     case Builtins::kStringPrototypeSmall:

src/js/string.js

@@ -13,67 +13,6 @@
 
 var GlobalString = global.String;
 
-//-------------------------------------------------------------------
-
-function StringPad(thisString, maxLength, fillString) {
-  maxLength = TO_LENGTH(maxLength);
-  var stringLength = thisString.length;
-
-  if (maxLength <= stringLength) return "";
-
-  if (IS_UNDEFINED(fillString)) {
-    fillString = " ";
-  } else {
-    fillString = TO_STRING(fillString);
-    if (fillString === "") {
-      // If filler is the empty String, return S.
-      return "";
-    }
-  }
-
-  var fillLength = maxLength - stringLength;
-  var repetitions = (fillLength / fillString.length) | 0;
-  var remainingChars = (fillLength - fillString.length * repetitions) | 0;
-
-  var filler = "";
-  while (true) {
-    if (repetitions & 1) filler += fillString;
-    repetitions >>= 1;
-    if (repetitions === 0) break;
-    fillString += fillString;
-  }
-
-  if (remainingChars) {
-    filler += %_SubString(fillString, 0, remainingChars);
-  }
-
-  return filler;
-}
-
-DEFINE_METHODS_LEN(
-  GlobalString.prototype,
-  {
-    /* ES#sec-string.prototype.padstart */
-    /* String.prototype.padStart(maxLength [, fillString]) */
-    padStart(maxLength, fillString) {
-      CHECK_OBJECT_COERCIBLE(this, "String.prototype.padStart");
-      var thisString = TO_STRING(this);
-
-      return StringPad(thisString, maxLength, fillString) + thisString;
-    }
-
-    /* ES#sec-string.prototype.padend */
-    /* String.prototype.padEnd(maxLength [, fillString]) */
-    padEnd(maxLength, fillString) {
-      CHECK_OBJECT_COERCIBLE(this, "String.prototype.padEnd");
-      var thisString = TO_STRING(this);
-
-      return thisString + StringPad(thisString, maxLength, fillString);
-    }
-  },
-  1  /* Set functions length */
-);
-
 // -------------------------------------------------------------------
 // String methods related to templates
 

test/mjsunit/harmony/harmony-string-pad-end.js

@@ -94,3 +94,14 @@
 (function TestTruncation() {
   assertEquals("ab", "a".padEnd(2, "bc"));
 })();
+
+
+(function TestMaxLength() {
+  assertThrows(() => "123".padEnd(Math.pow(2, 40)), RangeError);
+  assertThrows(() => "123".padEnd(1 << 30), RangeError);
+})();
+
+
+(function TestNoArguments() {
+  assertEquals("abc", "abc".padEnd());
+})();

test/mjsunit/harmony/harmony-string-pad-start.js

@@ -94,3 +94,14 @@
 (function TestTruncation() {
   assertEquals("ba", "a".padStart(2, "bc"));
 })();
+
+
+(function TestMaxLength() {
+  assertThrows(() => "123".padStart(Math.pow(2, 40)), RangeError);
+  assertThrows(() => "123".padStart(1 << 30), RangeError);
+})();
+
+
+(function TestNoArguments() {
+  assertEquals("abc", "abc".padStart());
+})();

test/mjsunit/messages.js

@@ -449,6 +449,14 @@ test(function() {
 }, "Invalid typed array length: -1", RangeError);
 
 // kThrowInvalidStringLength
+test(function() {
+  "a".padEnd(1 << 30);
+}, "Invalid string length", RangeError);
+
+test(function() {
+  "a".padStart(1 << 30);
+}, "Invalid string length", RangeError);
+
 test(function() {
   "a".repeat(1 << 30);
 }, "Invalid string length", RangeError);