Here is a description of the background and design of split window in Chrome and V8:
https://docs.google.com/a/google.com/Doc?id=chhjkpg_47fwddxbfr
This change list splits the window object into two parts: 1) an inner window object used as the global object of contexts; 2) an outer window object exposed to JavaScript and accessible by the name 'window'. Firefox did it awhile ago, here are some discussions: https://wiki.mozilla.org/Gecko:SplitWindow. One additional benefit of splitting window in Chrome is that accessing global variables don't need security checks anymore, it can improve applications that use many global variables.
V8 support of split window:
There are a small number of changes on V8 api to support split window:
Security context is removed from V8, so does related API functions;
A global object can be detached from its context and reused by a new context;
Access checks on an object template can be turned on/off by default;
An object can turn on its access checks later;
V8 has a new object type, ApiGlobalObject, which is the outer window object type. The existing JSGlobalObject becomes the inner window object type. Security checks are moved from JSGlobalObject to ApiGlobalObject. ApiGlobalObject is the one exposed to JavaScript, it is accessible through Context::Global(). ApiGlobalObject's prototype is set to JSGlobalObject so that property lookups are forwarded to JSGlobalObject. ApiGlobalObject forwards all other property access requests to JSGlobalObject, such as SetProperty, DeleteProperty, etc.
Security token is moved to a global context, and ApiGlobalObject has a reference to its global context. JSGlobalObject has a reference to its global context as well. When accessing properties on a global object in JavaScript, the domain security check is performed by comparing the security token of the lexical context (Top::global_context()) to the token of global object's context. The check is only needed when the receiver is a window object, such as 'window.document'. Accessing global variables, such as 'var foo = 3; foo' does not need checks because the receiver is the inner window object.
When an outer window is detached from its global context (when a frame navigates away from a page), it is completely detached from the inner window. A new context is created for the new page, and the outer global object is reused. At this point, the access check on the DOMWindow wrapper of the old context is turned on. The code in old context is still able to access DOMWindow properties, but it has to go through domain security checks.
It is debatable on how to implement the outer window object. Currently each property access function has to check if the receiver is ApiGlobalObject type. This approach might be error-prone that one may forget to check the receiver when adding new functions. It is unlikely a performance issue because accessing global variables are more common than 'window.foo' style coding.
I am still working on the ARM port, and I'd like to hear comments and suggestions on the best way to support it in V8.
Review URL: http://codereview.chromium.org/7366
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@540 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
- Reduce it to half size if the pattern is ASCII, saving on initialization
- If pattern is ASCII and subject is not, any non-ASCII char can cause a
full pattern-length shift, even if we haven't indexed the entire pattern.
- Use memset to initialize buffer in the common case where the pattern is
shorter than the max significant suffix limit.
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@519 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
* Patch from Erik Corry to separate BM-algoritm into special case
functions. Also changes condition for bailing out of simple search.
* Added simple search with no bailout for very short patterns.
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@513 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
to be insufficient.x
Changed order of tests in loop in simple text search.
Changed limit on pattern length for when we pick simple search.
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@496 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
underlying string representation of the two strings involved.
- Renamed ascii and two byte string classes to sequential ascii and
sequential two byte, and renamed IsAscii and friends to
IsAsciiRepresentation. This is to make a clear distinction between
strings with an ascii/two-byte representation, of which there is
four, and flat sequential ascii/two-byte string.
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@474 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
- Added the FLOOR macro that only works on Number objects.
- Added LocalTimeNoCheck in the date code to eliminate some isNaN checks.
- Change computation of four_year_cycle_table to load time.
- Added fast case check to EQUALS and STRICT_EQUALS.
Review URL: http://codereview.chromium.org/6531
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@458 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
instances->set(i, *GetScriptWrapper(script));
GetScriptWrapper can call GC. The failure have only been seen on ARM, where
the g++ compiler pulls out the object from the instances handle to a register
before calling GetScriptWrapper causing set to be called on an object which
may have moved.
Marked a test on ARM as no longer flaky, whereas two other fails consistently
but that is no longer related to the problem fixed above.
BUG=1308895
Review URL: http://codereview.chromium.org/6271
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@444 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
All uses of %AddProperty are replaced by %SetProperty. A few uses of
IgnoreAttributesAndSetLocalProperty are added, and the runtime version
of it adds a PropertyAttributes argument. Only the JSObject class
in objects.cc now uses AddProperty, and it can become private.
Review URL: http://codereview.chromium.org/6445
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@426 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
canonicalize maps for object literals. JSON objects
with the same set of properties names will then
share the same map.
This reduces the amount of generated code associated
with object literals.
- Added a flag canonicalize_object_literal_maps.
(default true)
- Changed the format of a function's literal array.
Only the global context is now stored in the literal prefix.
Review URL: http://codereview.chromium.org/4078
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@371 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
upper case. Moved it into the RelocInfo class together with the associated
is_xxx functions. Renamed is_xxx to IsXxx in the process.
Removed the exit_js_frame mode as it was no longer used.
Patch Set 2 renames RELOC_MODE_COUNT to NUMBER_OF_MODES and fixes a couple of lint errors.
Review URL: http://codereview.chromium.org/3186
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@354 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
- Simplified frame entry and frame exit code.
- Added ArgumentsAdaptorTrampoline and check for matching argument counts in the InvokePrologue.
- Removed definition and uses of USE_OLD_CALLING_CONVENTIONS.
- Changed MacroAssembler::InvokeBuiltin to match ia32 version.
- Start introducing convenience instructions in the ARM assembler as needed. These instructions take all Register parameters to avoid extra typing of "Operand(reg)".
To keep the architectures in sync these changes have been made to the ia32 files:
- Changed MacroAssembler::EnterFrame(StackFrame::Type type) to MacroAssembler::EnterInternalFrame().
These parts are still missing:
- unimplemented: Builtins::Generate_FunctionApply - large limit
- unimplemented: Builtins::Generate_ArgumentsAdaptorTrampoline - non-function call
- The files have not been lint'd yet.
Review URL: http://codereview.chromium.org/1930
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@289 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
it for scripts too. In the context of Chromium, this should
have a very positive impact on memory consumption for web apps
that run multiple tabs from the same domain with a lot of the
same JavaScript code.
For now, the cache retirement policy is really simple:
Whenever a mark-sweep collection is started we clear the
cache. This guarantees that this change will not have a
huge negative impact on memory consumption, but it may
not be ideal. We should consider a more sophisticated LRU
scheme.
Review URL: http://codereview.chromium.org/1933
git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@270 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
