Revision: 10652
Author: [email protected]
Date: Thu Feb 9 01:11:04 2012
Log: Promote double arrays to FAST_ELEMENT that use generic KeyedLoadIC
Review URL: https://chromiumcodereview.appspot.com/9111036
http://code.google.com/p/v8/source/detail?r=10652
Modified:
/branches/bleeding_edge/src/ic.cc
/branches/bleeding_edge/src/runtime.cc
=======================================
--- /branches/bleeding_edge/src/ic.cc Mon Jan 23 04:01:47 2012
+++ /branches/bleeding_edge/src/ic.cc Thu Feb 9 01:11:04 2012
@@ -1120,6 +1120,17 @@
} else if (key->IsSmi() && (target() !=
*non_strict_arguments_stub())) {
stub = ComputeStub(receiver, LOAD, kNonStrictMode, stub);
}
+ // If the IC is being replaced by the generic stub, loads from
+ // FAST_DOUBLE_ELEMENTS arrays will cause unboxing in Crankshafted
+ // code. To prevent these expensive allocations, proactively
promote
+ // arrays to FAST_ELEMENTS ElementKinds.
+ if (*stub == *generic_stub()) {
+ if (receiver->HasFastDoubleElements()) {
+ MaybeObject* maybe_object =
+ receiver->TransitionElementsKind(FAST_ELEMENTS);
+ if (maybe_object->IsFailure()) return maybe_object;
+ }
+ }
}
} else {
TRACE_GENERIC_IC("KeyedLoadIC", "force generic");
=======================================
--- /branches/bleeding_edge/src/runtime.cc Wed Feb 8 07:39:41 2012
+++ /branches/bleeding_edge/src/runtime.cc Thu Feb 9 01:11:04 2012
@@ -4270,14 +4270,24 @@
// If value is the hole do the general lookup.
}
}
- } else if (FLAG_smi_only_arrays && args.at<Object>(1)->IsSmi()) {
+ } else if (args.at<Object>(1)->IsSmi()) {
+ // Getting properties from FAST_DOUBLE_ELEMENTS arrays causes
boxing. To
+ // proactively avoid excessive boxing, transition
FAST_DOUBLE_ELEMENTS
+ // arrays to FAST_ELEMENTS if they are accessed via this function,
which
+ // is called by the KeyedLoadIC::GenericStub.
+ Handle<JSObject> js_object(args.at<JSObject>(0));
+ if (js_object->HasFastDoubleElements()) {
+ MaybeObject* maybe_object =
+ js_object->TransitionElementsKind(FAST_ELEMENTS);
+ if (maybe_object->IsFailure()) return maybe_object;
+ }
+
// JSObject without a string key. If the key is a Smi, check for a
// definite out-of-bounds access to elements, which is a strong
indicator
// that subsequent accesses will also call the runtime. Proactively
// transition elements to FAST_ELEMENTS to avoid excessive boxing of
// doubles for those future calls in the case that the elements would
// become FAST_DOUBLE_ELEMENTS.
- Handle<JSObject> js_object(args.at<JSObject>(0));
ElementsKind elements_kind = js_object->GetElementsKind();
if (elements_kind == FAST_SMI_ONLY_ELEMENTS ||
elements_kind == FAST_DOUBLE_ELEMENTS) {
--
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