[turbofan] Add new StringFromCharCode simplified operator.

test/unittests/compiler/js-builtin-reducer-unittest.cc

 // Copyright 2014 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.
 
 #include "src/compiler/js-builtin-reducer.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/node-properties.h"
 #include "src/compiler/simplified-operator.h"
 #include "src/compiler/typer.h"
 #include "src/isolate-inl.h"
@@ skipping 31 matching lines @@
         JSObject::GetProperty(isolate()->global_object(),
                               isolate()->factory()->NewStringFromAsciiChecked(
                                   "Math")).ToHandleChecked();
     Handle<JSFunction> f = Handle<JSFunction>::cast(
         Object::GetProperty(
             m, isolate()->factory()->NewStringFromAsciiChecked(name))
             .ToHandleChecked());
     return HeapConstant(f);
   }
 
+  Node* StringFunction(const char* name) {
+    Handle<Object> m =
+        JSObject::GetProperty(
+            isolate()->global_object(),
+            isolate()->factory()->NewStringFromAsciiChecked("String"))
+            .ToHandleChecked();
+    Handle<JSFunction> f = Handle<JSFunction>::cast(
+        Object::GetProperty(
+            m, isolate()->factory()->NewStringFromAsciiChecked(name))
+            .ToHandleChecked());
+    return HeapConstant(f);
+  }
+
   JSOperatorBuilder* javascript() { return &javascript_; }
 
  private:
   JSOperatorBuilder javascript_;
 };
 
 
 namespace {
 
 Type* const kIntegral32Types[] = {Type::UnsignedSmall(), Type::Negative32(),
@@ skipping 120 matching lines @@
     Node* call = graph()->NewNode(javascript()->CallFunction(3), function,
                                   UndefinedConstant(), p0, context, frame_state,
                                   frame_state, effect, control);
     Reduction r = Reduce(call);
 
     ASSERT_TRUE(r.Changed());
     EXPECT_THAT(r.replacement(), IsTruncateFloat64ToFloat32(p0));
   }
 }
 
+// -----------------------------------------------------------------------------
+// String.fromCharCode
+
+TEST_F(JSBuiltinReducerTest, StringFromCharCode) {
+  Node* function = StringFunction("fromCharCode");
+
+  Node* effect = graph()->start();
+  Node* control = graph()->start();
+  Node* context = UndefinedConstant();
+  Node* frame_state = graph()->start();
+  TRACED_FOREACH(Type*, t0, kNumberTypes) {
+    Node* p0 = Parameter(t0, 0);
+    Node* call = graph()->NewNode(javascript()->CallFunction(3), function,
+                                  UndefinedConstant(), p0, context, frame_state,
+                                  frame_state, effect, control);
+    Reduction r = Reduce(call);
+
+    ASSERT_TRUE(r.Changed());
+    EXPECT_THAT(r.replacement(), IsStringFromCharCode(p0));
+  }
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8