Reland "Avoid some unnecessary fast-properties map creations."

This relands commit ea74f0f8.

The revert was due to failures in cctest/test-heap/ReleaseOverReservedPages,
caused by apparent changes to memory layout and fragmentation of the
first page. Eliminating a situation in messages.js where this CL has had
an effect on map transitions seems to solve the issue.

R=verwaest@chromium.org

Review URL: https://codereview.chromium.org/714883003

Cr-Commit-Position: refs/heads/master@{#25266}
git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@25266 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
parent 1d17f826
......@@ -1224,7 +1224,6 @@ function SetUpError() {
// Define all the expected properties directly on the error
// object. This avoids going through getters and setters defined
// on prototype objects.
%AddNamedProperty(this, 'stack', UNDEFINED, DONT_ENUM);
if (!IS_UNDEFINED(m)) {
%AddNamedProperty(this, 'message', ToString(m), DONT_ENUM);
}
......
......@@ -9609,13 +9609,17 @@ void JSObject::OptimizeAsPrototype(Handle<JSObject> object,
JSObject::NormalizeProperties(object, KEEP_INOBJECT_PROPERTIES, 0,
"NormalizeAsPrototype");
}
bool has_just_copied_map = false;
if (!object->HasFastProperties()) {
JSObject::MigrateSlowToFast(object, 0, "OptimizeAsPrototype");
has_just_copied_map = true;
}
if (mode == FAST_PROTOTYPE && object->HasFastProperties() &&
!object->map()->is_prototype_map()) {
Handle<Map> new_map = Map::Copy(handle(object->map()), "CopyAsPrototype");
JSObject::MigrateToMap(object, new_map);
if (!has_just_copied_map) {
Handle<Map> new_map = Map::Copy(handle(object->map()), "CopyAsPrototype");
JSObject::MigrateToMap(object, new_map);
}
object->map()->set_is_prototype_map(true);
}
}
......
......@@ -1454,10 +1454,8 @@ RUNTIME_FUNCTION(Runtime_DefineAccessorPropertyUnchecked) {
RUNTIME_ASSERT((unchecked & ~(READ_ONLY | DONT_ENUM | DONT_DELETE)) == 0);
PropertyAttributes attr = static_cast<PropertyAttributes>(unchecked);
bool fast = obj->HasFastProperties();
RETURN_FAILURE_ON_EXCEPTION(
isolate, JSObject::DefineAccessor(obj, name, getter, setter, attr));
if (fast) JSObject::MigrateSlowToFast(obj, 0, "RuntimeDefineAccessor");
return isolate->heap()->undefined_value();
}
......
......@@ -303,7 +303,7 @@ assertTrue(Object.isFrozen(Object.freeze(function(){"use strict";})));
// Also test a simpler case
obj = {};
Object.defineProperty(obj, 'accessor', {
Object.defineProperty(obj, 'accessor2', {
get: function() { return 42 },
set: function() { accessorDidRun = true },
configurable: true,
......
......@@ -44,5 +44,4 @@ assertTrue(%HaveSameMap(o, o2));
Object.defineProperty(o, "foo", { set: setter, configurable: true });
Object.defineProperty(o2, "foo", { set: setter, configurable: true });
// TODO(ishell): this should eventually become assertTrue().
assertFalse(%HaveSameMap(o, o2));
assertTrue(%HaveSameMap(o, o2));
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