[builtins] Port TFS StringRepeat to Torque.

Bug: v8:8996
Change-Id: I035c380768c324d8912aa8bc414d533dbf7f3e5a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1524640
Commit-Queue: Peter Wong <peter.wm.wong@gmail.com>
Reviewed-by: Simon Zünd <szuend@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#60292}

BUILD.gn

@@ -934,6 +934,7 @@ torque_files = [
   "src/builtins/iterator.tq",
   "src/builtins/string-endswith.tq",
   "src/builtins/string-html.tq",
+  "src/builtins/string-repeat.tq",
   "src/builtins/string-startswith.tq",
   "src/builtins/typed-array.tq",
   "src/builtins/typed-array-createtypedarray.tq",
@@ -977,6 +978,7 @@ torque_namespaces = [
   "object",
   "string",
   "string-html",
+  "string-repeat",
   "test",
   "typed-array",
   "typed-array-createtypedarray",

src/builtins/builtins-definitions.h

@@ -113,7 +113,6 @@ namespace internal {
   TFS(StringIndexOf, kReceiver, kSearchString, kPosition)                      \
   TFC(StringLessThan, Compare)                                                 \
   TFC(StringLessThanOrEqual, Compare)                                          \
-  TFS(StringRepeat, kString, kCount)                                           \
   TFC(StringSubstring, StringSubstring)                                        \
                                                                                \
   /* OrderedHashTable helpers */                                               \

src/builtins/builtins-string-gen.cc

@@ -1227,54 +1227,6 @@ TF_BUILTIN(StringPrototypeRepeat, StringBuiltinsAssembler) {
   }
 }
 
-// Helper with less checks
-TF_BUILTIN(StringRepeat, StringBuiltinsAssembler) {
-  Node* const context = Parameter(Descriptor::kContext);
-  Node* const string = Parameter(Descriptor::kString);
-  TNode<Smi> const count = CAST(Parameter(Descriptor::kCount));
-
-  CSA_ASSERT(this, IsString(string));
-  CSA_ASSERT(this, Word32BinaryNot(IsEmptyString(string)));
-  CSA_ASSERT(this, TaggedIsPositiveSmi(count));
-
-  // The string is repeated with the following algorithm:
-  //   let n = count;
-  //   let power_of_two_repeats = string;
-  //   let result = "";
-  //   while (true) {
-  //     if (n & 1) result += s;
-  //     n >>= 1;
-  //     if (n === 0) return result;
-  //     power_of_two_repeats += power_of_two_repeats;
-  //   }
-  VARIABLE(var_result, MachineRepresentation::kTagged, EmptyStringConstant());
-  VARIABLE(var_temp, MachineRepresentation::kTagged, string);
-  TVARIABLE(Smi, var_count, count);
-
-  Label loop(this, {&var_count, &var_result, &var_temp}), return_result(this);
-  Goto(&loop);
-  BIND(&loop);
-  {
-    {
-      Label next(this);
-      GotoIfNot(SmiToInt32(SmiAnd(var_count.value(), SmiConstant(1))), &next);
-      var_result.Bind(CallBuiltin(Builtins::kStringAdd_CheckNone, context,
-                                  var_result.value(), var_temp.value()));
-      Goto(&next);
-      BIND(&next);
-    }
-
-    var_count = SmiShr(var_count.value(), 1);
-    GotoIf(SmiEqual(var_count.value(), SmiConstant(0)), &return_result);
-    var_temp.Bind(CallBuiltin(Builtins::kStringAdd_CheckNone, context,
-                              var_temp.value(), var_temp.value()));
-    Goto(&loop);
-  }
-
-  BIND(&return_result);
-  Return(var_result.value());
-}
-
 // ES6 #sec-string.prototype.replace
 TF_BUILTIN(StringPrototypeReplace, StringBuiltinsAssembler) {
   Label out(this);

src/builtins/string-repeat.tq

@@ -0,0 +1,26 @@
+// Copyright 2019 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.
+
+namespace string_repeat {
+  builtin StringRepeat(implicit context: Context)(string: String, count: Smi):
+      String {
+    assert(count >= 0);
+    assert(string != kEmptyString);
+
+    let result: String = kEmptyString;
+    let powerOfTwoRepeats: String = string;
+    let n: intptr = Convert<intptr>(count);
+
+    while (true) {
+      if ((n & 1) == 1) result = result + powerOfTwoRepeats;
+
+      n = n >> 1;
+      if (n == 0) break;
+
+      powerOfTwoRepeats = powerOfTwoRepeats + powerOfTwoRepeats;
+    }
+
+    return result;
+  }
+}