Turns out this was hurting performance instead of helping it.
By removing the inline capacity, we shrink the size of ExecutionContext
by 512 bytes, which substantially reduces the stack pressure created by
JS recursion (each call creates a new ExecutionContext on the stack).
4.4% speed-up on the entire Kraken benchmark :^)
Previously every file that included Executable.h (which is pretty much
most LibJS and LibHTML files, given that VM.h needs it) had the whole
definition of LibRegex, which was slowing down source parsing.
- Update ECMAScriptFunctionObject::function_declaration_instantiation
to initialize local variables
- Introduce GetLocal, SetLocal, TypeofLocal that will be used to
operate on local variables.
- Update bytecode generator to emit instructions for local variables
This uses a new Iterator type called IteratorHelper. This does not
implement IteratorHelper.prototype.return as that relies on generator
objects (i.e. the internal slots of JS::GeneratorObject), which are not
hooked up here.
Iterator.from creates an Iterator from either an existing iterator or
an iterator-like object. In the latter case, it sets the prototype of
the returned iterator to WrapForValidIteratorPrototype to wrap around
the iterator-like object's iteration methods.
Before this change, each AST node had a 64-byte SourceRange member.
This SourceRange had the following layout:
filename: StringView (16 bytes)
start: Position (24 bytes)
end: Position (24 bytes)
The Position structs have { line, column, offset }, all members size_t.
To reduce memory consumption, AST nodes now only store the following:
source_code: NonnullRefPtr<SourceCode> (8 bytes)
start_offset: u32 (4 bytes)
end_offset: u32 (4 bytes)
SourceCode is a new ref-counted data structure that keeps the filename
and original parsed source code in a single location, and all AST nodes
have a pointer to it.
The start_offset and end_offset can be turned into (line, column) when
necessary by calling SourceCode::range_from_offsets(). This will walk
the source code string and compute line/column numbers on the fly, so
it's not necessarily fast, but it should be rare since this information
is primarily used for diagnostics and exception stack traces.
With this, ASTNode shrinks from 80 bytes to 32 bytes. This gives us a
~23% reduction in memory usage when loading twitter.com/awesomekling
(330 MiB before, 253 MiB after!) :^)
A struct with three raw pointers to other GC'd types is a pretty big
liability, let's just turn this into a Cell itself.
This comes with the additional benefit of being able to capture it in
a lambda effortlessly, without having to create handles for individual
members.
This will allow us to move the underlying console from GlobalObject to
ConsoleObject without still having to do a 'console' property lookup on
the GlobalObject.
Intrinsics, i.e. mostly constructor and prototype objects, but also
things like empty and new object shape now live on a new heap-allocated
JS::Intrinsics object, thus completing the long journey of taking all
the magic away from the global object.
This represents the Realm's [[Intrinsics]] slot in the spec and matches
its existing [[GlobalObject]] / [[GlobalEnv]] slots in terms of
architecture.
In the majority of cases it should now be possibly to fully allocate a
regular object without the global object existing, and in fact that's
what we do now - the realm is allocated before the global object, and
the intrinsics between both :^)
The Intl mathematical value is much like ECMA-262's mathematical value
in that it is meant to represent an arbitrarily precise number. The Intl
MV further allows positive/negative infinity, negative zero, and NaN.
This implementation is *not* arbitrarily precise. Rather, it is a
replacement for the use of Value within Intl.NumberFormat. The exact
syntax of the Intl MV is still being worked on, but abstracting this
away into its own class will allow hooking in the finalized Intl MV
more easily, and makes implementing Intl.NumberFormat.formatRange
easier.
Note the methods added here are essentially the same as the static
helpers in Intl/NumberFormat.cpp.
This was defined twice, despite being the very same thing:
- ClassElement::ClassFieldDefinition
- ECMAScriptFunctionObject::InstanceField
Move the former to a new header and use it everywhere. Also update the
define_field() AO to take a single field instead of separate name and
initializer arguments.
This is an editorial change in the Temporal spec.
See: https://github.com/tc39/proposal-temporal/commit/983902e
We already had these defined as structs, but now they're properly
defined in the spec (opposed to the previous anonymous records), and we
don't have to make up our own names anymore :^)
Note that while we're usually not including 'record' in the name, in
this case the 'Duration Record' has a name clash with the Duration
object. Additionally, later editorial changes introduce CreateFooRecord
AOs, so let's just go with FooRecord structs here.
Note: MarkedVector is still relatively new and has zero users right now,
so these changes don't affect any code other than the class itself.
Reasons for this are the rather limited API:
- Despite the name and unlike MarkedValueList, MarkedVector isn't
actually a Vector, it *wraps* a Vector. This means that plenty of
convenient APIs are unavailable and have to be exported on the class
separately and forwarded to the internal Vector, or need to go through
the exposed Span - both not great options.
- Exposing append(Cell*) and prepend(Cell*) on the base class means that
it was possible to append any Cell type, not just T! All the strong
typing guarantees are basically gone, and MarkedVector doesn't do much
more than casting Cells to the appropriate type through the exposed
Span.
All of this combined means that MarkedVector - in its current form -
doesn't provide much value over MarkedValueList, and that we have to
maintain two separate, yet almost identical classes.
Let's fix this!
The updated MarkedVector steals various concepts from the existing
MarkedValueList, especially the ability to copy. On the other hand, it
remains generic enough to handle both Cell* and Value for T, making
MarkedValueList effectively redundant :^)
Additionally, by inheriting from Vector we get all the current and
future APIs without having to select and expose them separately.
MarkedVectorBase remains and takes care of communicating creation and
destruction of the class to the heap. Visiting the contained values is
handled via a pure virtual method gather_roots(), which is being called
by the Heap's function of the same name; much like the VM has one.
From there, values are added to the roots HashTable if they are cells
for T = Value, and unconditionally for any other T.
As a small additional improvement the template now also takes an
inline_capacity parameter, defaulting to 32, and forwards it to the
Vector template; allowing for possible future optimizations of current
uses of MarkedValueList, which hard-codes it to 32.
The environment settings object is effectively the context a piece of
script is running under, for example, it contains the origin,
responsible document, realm, global object and event loop for the
current context. This effectively replaces ScriptExecutionContext, but
it cannot be removed in this commit as EventTarget still depends on it.
https://html.spec.whatwg.org/multipage/webappapis.html#environment-settings-object
This commit removes all exception related code:
Remove VM::exception(), VM::throw_exception() etc. Any leftover
throw_exception calls are moved to throw_completion.
The one method left is clear_exception() which is now a no-op. Most of
these calls are just to clear whatever exception might have been thrown
when handling a Completion. So to have a cleaner commit this will be
removed in a next commit.
It also removes the actual Exception and TemporaryClearException classes
since these are no longer used.
In any spot where the exception was actually used an attempt was made to
preserve that behavior. However since it is no longer tracked by the VM
we cannot access exceptions which were thrown in previous calls.
There are two such cases which might have different behavior:
- In Web::DOM::Document::interpreter() the on_call_stack_emptied hook
used to print any uncaught exception but this is now no longer
possible as the VM does not store uncaught exceptions.
- In js the code used to be interruptable by throwing an exception on
the VM. This is no longer possible but was already somewhat fragile
before as you could happen to throw an exception just before a VERIFY.
Given we usually call objects Foo{Object,Constructor,Prototype} or
Foo{,Constructor,Prototype}, this name was an odd choice.
The new one matches the spec better, which calls it the "Generator
Prototype Object", so we simply omit the Object suffix as usual as it's
implied.
This abstracts a vector of Cell* with a strongly typed span() accessor
that gives you Span<T*> instead of Span<Cell*>.
It is intended to replace MarkedValueList in situations where you only
need to store pointers to Cell (or an even more specific type of Cell).
The API can definitely be improved, it's just the bare basics for now.
