[csa] Migrate String.prototype.concat to TurboFan builtin.

R=yangguo@chromium.org
BUG=v8:5049

Review-Url: https://codereview.chromium.org/2766593002
Cr-Commit-Position: refs/heads/master@{#43961}

src/bootstrapper.cc

@@ -1688,6 +1688,8 @@ void Genesis::InitializeGlobal(Handle<JSGlobalObject> global_object,
                           1, true);
     SimpleInstallFunction(prototype, "charCodeAt",
                           Builtins::kStringPrototypeCharCodeAt, 1, true);
+    SimpleInstallFunction(prototype, "concat", Builtins::kStringPrototypeConcat,
+                          1, false);
     SimpleInstallFunction(prototype, "endsWith",
                           Builtins::kStringPrototypeEndsWith, 1, false);
     SimpleInstallFunction(prototype, "includes",

src/builtins/builtins-string-gen.cc

@@ -662,6 +662,30 @@ TF_BUILTIN(StringPrototypeCharCodeAt, CodeStubAssembler) {
   Return(result);
 }
 
+// ES6 String.prototype.concat(...args)
+// #sec-string.prototype.concat
+TF_BUILTIN(StringPrototypeConcat, CodeStubAssembler) {
+  CodeStubArguments arguments(
+      this, ChangeInt32ToIntPtr(Parameter(BuiltinDescriptor::kArgumentsCount)));
+  Node* receiver = arguments.GetReceiver();
+  Node* context = Parameter(BuiltinDescriptor::kContext);
+
+  // Check that {receiver} is coercible to Object and convert it to a String.
+  receiver = ToThisString(context, receiver, "String.prototype.concat");
+
+  // Concatenate all the arguments passed to this builtin.
+  Variable var_result(this, MachineRepresentation::kTagged);
+  var_result.Bind(receiver);
+  arguments.ForEach(
+      CodeStubAssembler::VariableList({&var_result}, zone()),
+      [this, context, &var_result](Node* arg) {
+        arg = CallStub(CodeFactory::ToString(isolate()), context, arg);
+        var_result.Bind(CallStub(CodeFactory::StringAdd(isolate()), context,
+                                 var_result.value(), arg));
+      });
+  arguments.PopAndReturn(var_result.value());
+}
+
 void StringBuiltinsAssembler::StringIndexOf(
     Node* receiver, Node* instance_type, Node* search_string,
     Node* search_string_instance_type, Node* position,

src/builtins/builtins.h

@@ -774,6 +774,8 @@ class Isolate;
   TFJ(StringPrototypeCharAt, 1)                                                \
   /* ES6 section 21.1.3.2 String.prototype.charCodeAt ( pos ) */               \
   TFJ(StringPrototypeCharCodeAt, 1)                                            \
+  /* ES6 #sec-string.prototype.concat */                                       \
+  TFJ(StringPrototypeConcat, SharedFunctionInfo::kDontAdaptArgumentsSentinel)  \
   /* ES6 section 21.1.3.6 */                                                   \
   /* String.prototype.endsWith ( searchString [ , endPosition ] ) */           \
   CPP(StringPrototypeEndsWith)                                                 \

src/code-factory.h

@@ -108,8 +108,9 @@ class V8_EXPORT_PRIVATE CodeFactory final {
   static Callable Equal(Isolate* isolate);
   static Callable StrictEqual(Isolate* isolate);
 
-  static Callable StringAdd(Isolate* isolate, StringAddFlags flags,
-                            PretenureFlag pretenure_flag);
+  static Callable StringAdd(Isolate* isolate,
+                            StringAddFlags flags = STRING_ADD_CHECK_NONE,
+                            PretenureFlag pretenure_flag = NOT_TENURED);
   static Callable StringCharAt(Isolate* isolate);
   static Callable StringCharCodeAt(Isolate* isolate);
   static Callable StringCompare(Isolate* isolate, Token::Value token);

src/debug/debug-evaluate.cc

@@ -524,6 +524,7 @@ bool BuiltinHasNoSideEffect(Builtins::Name id) {
     case Builtins::kStringConstructor:
     case Builtins::kStringPrototypeCharAt:
     case Builtins::kStringPrototypeCharCodeAt:
+    case Builtins::kStringPrototypeConcat:
     case Builtins::kStringPrototypeEndsWith:
     case Builtins::kStringPrototypeIncludes:
     case Builtins::kStringPrototypeIndexOf:

src/js/string.js

@@ -15,19 +15,6 @@ var searchSymbol = utils.ImportNow("search_symbol");
 
 //-------------------------------------------------------------------
 
-// ECMA-262, section 15.5.4.6
-function StringConcat(other /* and more */) {  // length == 1
-  "use strict";
-  CHECK_OBJECT_COERCIBLE(this, "String.prototype.concat");
-  var s = TO_STRING(this);
-  var len = arguments.length;
-  for (var i = 0; i < len; ++i) {
-    s = s + TO_STRING(arguments[i]);
-  }
-  return s;
-}
-
-
 // ES6 21.1.3.11.
 function StringMatchJS(pattern) {
   CHECK_OBJECT_COERCIBLE(this, "String.prototype.match");
@@ -288,7 +275,6 @@ utils.InstallFunctions(GlobalString, DONT_ENUM, [
 // Set up the non-enumerable functions on the String prototype object.
 utils.InstallFunctions(GlobalString.prototype, DONT_ENUM, [
   "codePointAt", StringCodePointAt,
-  "concat", StringConcat,
   "match", StringMatchJS,
   "repeat", StringRepeat,
   "search", StringSearch,