[builtins] Array.prototype.filter implemented as a TurboFan code stub.

src/bootstrapper.cc

Index: src/bootstrapper.cc
diff --git a/src/bootstrapper.cc b/src/bootstrapper.cc
index d67985a5e0ad3ea27caafdd5790ef86079638996..f31ce74f4d35a387202948a3843a387c55f5129f 100644
--- a/src/bootstrapper.cc
+++ b/src/bootstrapper.cc
@@ -3674,6 +3674,7 @@ void Genesis::InitializeGlobal_enable_fast_array_builtins() {
                      factory->NewStringFromAsciiChecked("prototype"),
                      LookupIterator::OWN_SKIP_INTERCEPTOR);
   Handle<Object> array_prototype = Object::GetProperty(&it2).ToHandleChecked();
+
   LookupIterator it3(array_prototype,
                      factory->NewStringFromAsciiChecked("forEach"),
                      LookupIterator::OWN_SKIP_INTERCEPTOR);
@@ -3704,6 +3705,19 @@ void Genesis::InitializeGlobal_enable_fast_array_builtins() {
   Handle<JSFunction>::cast(some_function)
       ->shared()
       ->set_code(isolate->builtins()->builtin(Builtins::kArraySome));
+
+  if (FLAG_csa_builtin_filter) {

[danno, 2017/03/20 08:06:25]

Instead of introducing a new flag, how about you just remove the implication
from --turbo on FLAG_enable_fast_array_builtins, and then use that flag to
check/bail out here if it's not set, and all new "experimental" builtins would
be installed after that check.

[mvstanton, 2017/03/20 16:10:52]

I like the idea, but right now the filter implementation still needs work (for
example the CreateDataProperty call we want to eliminate). Being able to turn it
on and off (and it'll be off by default in this first CL) lets me run the
microbenchmarks at the command prompt and see the difference. I don't want to
permute the environment by turning off our other CSAs...

The flag is temporary and should disappear within a couple weeks...would that be
okay?

+    LookupIterator it6(array_prototype,
+                       factory->NewStringFromAsciiChecked("filter"),
+                       LookupIterator::OWN_SKIP_INTERCEPTOR);
+    Handle<Object> filter_function =
+        Object::GetProperty(&it6).ToHandleChecked();
+    Handle<JSFunction>::cast(filter_function)
+        ->set_code(isolate->builtins()->builtin(Builtins::kArrayFilter));
+    Handle<JSFunction>::cast(filter_function)
+        ->shared()
+        ->set_code(isolate->builtins()->builtin(Builtins::kArrayFilter));
+  }
 }
 
 void Genesis::InitializeGlobal_harmony_sharedarraybuffer() {