If we find a property in the prototype-chain that we can overwrite, and
we have a transition, keep the holder in the lookup-result as the actual
holder. We will need it for the consistency-check in GenerateStoreField.
By directly checking the entire chain we avoid having to lazily bail out
to a copy of the miss stub while generating the Field Store IC.
Currently this CL disallows a normal non-receiver holder, given that
that would require a positive lookup + details verification to ensure
the property did not become read-only. This fixes the regressions in the
attached tests.
Review URL: https://chromiumcodereview.appspot.com/12810006
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@14061 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Since symbols and strings share a common representation, most of this change is about consistently replacing 'String' with 'Name' in all places where property names are expected. In particular, no new logic at all is necessary for maps, property dictionaries, or transitions. :) The only places where an actual case distinction is needed have to do with generated type checks, and with conversions of names to strings (especially in logger and profiler).
Left in some TODOs wrt to the API: interceptors and native getters don't accept symbols as property names yet, because that would require extending the external v8.h.
(Baseline CL: https://codereview.chromium.org/12296026/)
R=verwaest@chromium.org,mstarzinger@chromium.org
BUG=v8:2158
Review URL: https://codereview.chromium.org/12330012
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13811 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
in preparation of the introduction of ES6 'symbols' (aka private/unique names).
The SymbolTable became the StringTable. I also made sure to adapt all comments. The only remaining use of the term "symbol" (other than unrelated uses in the parser and such) is now 'NewSymbol' in the API and the 'V8.KeyedLoadGenericSymbol' counter, changing which might break embedders.
The one functional change in this CL is that I removed the former 'empty_string' constant, since it is redundant given the 'empty_symbol' constant that we also had (and both were used inconsistently).
R=yangguo@chromium.org
BUG=
Review URL: https://codereview.chromium.org/12210083
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13781 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This moves the __proto__ property to Object.prototype and turns it into
a callback property actually present in the descriptor array as opposed
to a hack in the properties lookup. For now it still is a "magic" data
property using foreign callbacks and not an accessor property visible to
JavaScript.
The second effect of this change is that JSON.parse() no longer treats
the __proto__ property specially, it will be defined as any other data
property. Note that object literals still have their special handling.
R=rossberg@chromium.org
BUG=v8:621,v8:1949,v8:2441
TEST=mjsunit,cctest,test262
Review URL: https://codereview.chromium.org/12212011
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@13728 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
This CL adds multiple things:
Transition arrays do not directly point at their descriptor array anymore, but rather do so via an indirect pointer (a JSGlobalPropertyCell).
An ownership bit is added to maps indicating whether it owns its own descriptor array or not.
Maps owning a descriptor array can pass on ownership if a transition from that map is generated; but only if the descriptor array stays exactly the same; or if a descriptor is added.
Maps that don't have ownership get ownership back if their direct child to which ownership was passed is cleared in ClearNonLiveTransitions.
To detect which descriptors in an array are valid, each map knows its own NumberOfOwnDescriptors. Since the descriptors are sorted in order of addition, if we search and find a descriptor with index bigger than this number, it is not valid for the given map.
We currently still build up an enumeration cache (although this may disappear). The enumeration cache is always built for the entire descriptor array, even if not all descriptors are owned by the map. Once a descriptor array has an enumeration cache for a given map; this invariant will always be true, even if the descriptor array was extended. The extended array will inherit the enumeration cache from the smaller descriptor array. If a map with more descriptors needs an enumeration cache, it's EnumLength will still be set to invalid, so it will have to recompute the enumeration cache. This new cache will also be valid for smaller maps since they have their own enumlength; and use this to loop over the cache. If the EnumLength is still invalid, but there is already a cache present that is big enough; we just initialize the EnumLength field for the map.
When we apply ClearNonLiveTransitions and descriptor ownership is passed back to a parent map, the descriptor array is trimmed in-place and resorted. At the same time, the enumeration cache is trimmed in-place.
Only transition arrays contain descriptor arrays. If we transition to a map and pass ownership of the descriptor array along, the child map will not store the descriptor array it owns. Rather its parent will keep the pointer. So for every leaf-map, we find the descriptor array by following the back pointer, reading out the transition array, and fetching the descriptor array from the JSGlobalPropertyCell. If a map has a transition array, we fetch it from there. If a map has undefined as its back-pointer and has no transition array; it is considered to have an empty descriptor array.
When we modify properties, we cannot share the descriptor array. To accommodate this, the child map will get its own transition array; even if there are not necessarily any transitions leaving from the child map. This is necessary since it's the only way to store its own descriptor array.
Review URL: https://chromiumcodereview.appspot.com/10909007
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12492 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
The order by name is maintained as secondary order by using unused bits in the property details.
This is preliminary work towards sharing descriptors arrays.
The change allows us
- to get rid of the LastAdded bits in the map, binding it to the number of valid descriptors for the given map
- to avoid resorting by enumeration index to create the cache
- (maybe in the future, depending on performance) to get rid of the enumeration cache altogether.
Although generally the number_of_descriptors equals the NumberOfOwnDescriptors in the current version, this is preliminary work towards sharing descriptors, where maps may have more descriptors than are valid for the map.
Review URL: https://chromiumcodereview.appspot.com/10879013
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12385 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
AccessorPair related transitions are now also stored as single map links, simplifying the code that handles transitions. AccessorPairs can now be shared between descriptor arrays, since they can only be mutated after another transition anyway; during which the pair is copied before writing.
Review URL: https://chromiumcodereview.appspot.com/10784014
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12097 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
The LastAdded points to the descriptor that was last added to the array. From the descriptor we can deduce the NextEnumerationIndex. This allows us to quickly find the property that we are transitioning to, which is necessary for transition-intensive code, eg JSON parsing.
Review URL: https://chromiumcodereview.appspot.com/10695120
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@12042 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
In this design maps contain descriptor arrays, which in turn can contain transition arrays. If transitions are needed when no descriptor array is present, a descriptor array without real descriptors is inserted just so it can point at the transition array.
The transition array does not contain details about the field it transitions to. In order to weed out transitions to FIELDs from CONSTANT_FUNCTION (what used to be MAP_TRANSITION vs CONSTANT_TRANSITION), the transition needs to be followed and the details need to be looked up in the target map. CALLBACKS transitions are still easy to recognize since the transition targets are stored as an AccessorPair containing the maps, rather than the maps directly.
Currently AccessorPairs containing a transition and an accessor are shared between the descriptor array and the transition array. This simplifies lookup since we only have to look in one of both arrays. This will change in subsequent revisions, when descriptor arrays will become shared between multiple maps, since transitions cannot be shared.
Review URL: https://chromiumcodereview.appspot.com/10697015
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11994 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Instead of overwriting non-live transitions with NULL_DESCRIPTORs, we remove them from the array by compacting the array (shifting live values to the left) and in-place trimming the array. If the final descriptor array contains no live values (only contained transitions which are now all cleared), we move bit_field3 back from the descriptor array to the map. The descriptor array itself will be collected in the next GC.
BUG=
TEST=
Review URL: https://chromiumcodereview.appspot.com/10575032
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11922 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
- Ensure that IsFound() is only used when not in combination with other
checks. To do so, the default type is NONEXISTENT rather than NORMAL;
and NotFound() also resets the type to NONEXISTENT.
- Use test methods rather than .type() == A_PROPERTY_TYPE.
Review URL: https://chromiumcodereview.appspot.com/10626004
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@11899 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Main change from the original CL: Call::ComputeTarget does not use IsProperty
anymore, because this would potentially need a holder, which we don't have
here. Using Map::LookupInDescriptors with a NULL holder is a bit fishy in
general, because one has to be *extremely* careful when using its LookupResult.
The original CL made Chrome's NetInternalsTest.netInternalsTourTabs browser test
fail, but it's a mystery how this could happen: We should never reach
Call::ComputeTarget via Call::RecordTypeFeedback with a CALLBACKS property,
because we never consider calls to them monomorphic, which is in turn because of
the stub cache leaving them in the pre-monomorphic state. Therefore, I don't
have a clue how to write a regression test for this...
As an additional tiny bonus, the --trace-opt output for deoptimizations has been
improved.
Review URL: https://chromiumcodereview.appspot.com/9584003
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10906 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
With transitions in AccessorPairs, it is not enough to look at the PropertyType
alone to decide whether we look at a property or not: For objects with
JavaScript accessors, we have to look into the AccessorPair itself and see if
one of its 2 parts is actually a JavaScript accessor. Therefore, a predicate
with a PropertyType argument alone doesn't make sense anymore, we might need the
associated value, too.
Things are complicated by the fact that the holder in a LookupResult can be
NULL, so we must be careful to retrieve its value only when it is really
needed. To achieve the needed call-by-name semantics, a new Entry is introduced,
which is basically a closure over a DescriptorArray and an index into this array
(C++0x to the rescue!). GCC is clever enough to inline this class, so we pay no
runtime penalty for this abstraction.
It's all a bit ugly, but this is caused by the current structure of Descriptor,
DescriptorArray and LookupResult: Things would be much easier if DescriptorArray
were, well, an array of Descriptors, and LookupResult were a 'Maybe Descriptor'
(in Haskell-terms).
Review URL: https://chromiumcodereview.appspot.com/9466047
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10847 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
With the upcoming changes to CALLBACKS properties, a predicate on the transition
type alone doesn't make sense anymore: For CALLBACKS one has to look into the
property's value to decide, and there is even the possibility of having a an
accessor function *and* a transition in the same property.
I am not completely happy with some parts of this CL, because they contain
redundant code, but given the various representations we currently have for
property type/value pairs, I can see no easy way around that. Perhaps one can
improve this a bit in a different CL, the current diversity really, really hurts
productivity...
As a bonus, this CL includes a few minor things:
* CaseClause::RecordTypeFeedback has been cleaned up and it handles the
NULL_DESCRIPTOR case correctly now. Under some (very unlikely) circumstances,
we previously missed some opportunities for monomorphic calls. In general, it
is rather unfortunate that NULL_DESCRIPTOR "shines through", it is just a
hack for the inability to remove a descriptor entry during GC, something
callers shouldn't have to be aware of.
* DescriptorArray::CopyInsert has been cleaned up a bit, preparing it for later
CALLBACKS-related changes.
* LookupResult::Print is now more informative for CONSTANT_TRANSITION.
Review URL: https://chromiumcodereview.appspot.com/9320066
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10600 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Replaced FIRST_PHANTOM_PROPERTY_TYPE by a predicate. Removed the (hopefully)
last default cases for switches on PropertyType. Benchmarks show that both
changes are performace-neutral.
Now every value of PropertyType should either be handled by an explicit case in
a switch or by an equality operator. Therefore, the C++ compiler should finally
be able to tell us which places to touch when changing PropertyType.
Review URL: http://codereview.chromium.org/8506004
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9930 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Do not rely on 'default' clauses or 'if's when analysing a PropertyType, because
this makes it hard to find the relevant places when a new type is added. Note
that the detection of "phantom property types" is left untouched, because this
might have a performance impact, especially for the GC (to be investigated).
This is a preliminary step for introducing a new kind of map transition.
Review URL: http://codereview.chromium.org/8491016
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@9900 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
