The current shadow realm constructor implementation was based off a
merge request to the shadow realm proposal for integration into the
web platform. However, this merge request had a bug which we had
applied a workaround for by popping off the execution stack.
Since then, the spec has had an update of:
https://github.com/tc39/proposal-shadowrealm/commit/28b0cc
Which closer aligned the mainline spec to the proposed merge request.
Now, the original shadow realm proposal merge request has been closed
and a new one has been reopened with a much more minimal set of changes
that merely adds extra arguments to HostInitializeShadowRealm, which
this commit aligns with.
Noone needs to use this any more :^)
This is somewhat AD-HOC in the constructor as it is based on an open
shadow realm merge request, but applies the intent of the change without
any change in behaviour.
The use of extract_parameter_arguments_and_body() here is to make things
a little less awkward. If we were to exactly follow spec there would be
an awkward handling of the case that no arguments were provided and we
needed to provide an empty string.
To do this, we would need to either:
- Provide an Optional<Value> for bodyString to CreateDynamicFunction
- Create a new empty PrimitiveString wrapped in a JS Value.
Either case is somewhat awkward. Instead, just refactor this logic
outside of CreateDynamicFunction and make the caller do it.
Otherwise, this commit prepares for the new definition of
HostEnsureCanCompileStrings.
This fixes structured serialization of DataView. It was expected
to be uniform with TypedArray, which returns u32 for byte_offset().
This was covered by a number of WPT infrastructure tests, which this
commit also imports.
The `[[GetOwnProperty]]` internal method invocation in
`OrdinarySetWithOwnDescriptor` was being invocated again with the same
parameters in the `[[DefineOwnProperty]]` internal method that is also
later called in `OrdinarySetWithOwnDescriptor`.
The `PlatformObject.[[DefineOwnProperty]]` has similair logic.
This change adds an optional parameter to the `[[DefineOwnProperty]]`
internal method so the results of the previous `[[GetOwnProperty]]`
internal method invocation can be re-used.
This is just a wrapper to easily construct an Array from a span. This
avoids creating a Vector of values that are possiby Objects. One such
case is in ArrayIteratorPrototype::next.
This avoids having to do O(n) contains() in the various flag accessors.
Yields a ~20% speed-up on the following microbenchmark:
const re = /foo/dgimsvy;
for (let i = 0; i < 1_000_000; ++i)
re.flags;
We were already caching UTF-8 and byte strings, so let's add a cache
for UTF-16 strings as well. This is particularly profitable whenever we
run regular expressions, since the output of regex execution is a set of
UTF-16 strings.
Note that this is a weak cache like the other JS string caches, meaning
that strings are removed from the cache as they are garbage collected.
This avoids billions of PrimitiveString allocations across a run of WPT,
significantly reducing GC activity.
`find_binding_and_index` was doing a linear search, and while most
environments are small, websites using JavaScript bundlers can have
functions with very large environments, like youtube.com, which has
environments with over 13K bindings, causing environment lookups to
take a noticeable amount of time, showing up high while profiling.
Adding a HashMap significantly increases performance on such websites.
This allows us to align our implementation in the same order as the
specification.
No functional change with the current implementation of this AO.
However, this change is required in order to correctly implement a
proposed update of the shadow realm proposal for integration with
the HTML spec host bindings in order to give the ShadowRealm
object the correct 'intrinsic' realm.
This is due to that proposed change adding a step which manipulates the
currently executing Javascript execution context, making the ordering
important.
1.25x speed-up on this microbenchmark:
let o = { get x() { return 1; } };
for (let i = 0; i < 10_000_000; ++i)
o.x;
I looked into this because I noticed getter invocation when profiling
long-running WPT tests. We already had the mechanism for non-getter
properties, and the change to support getters turned out to be trivial.
Instead of re-symbolicating entire stacks from scratch every time
we want a JS VM backtrace, we now use the ExecutionContext object as
cache storage via a new CachedSourceRange object.
This means that once a stack frame has been symbolicated, we don't
have to resymbolicate it again (unless the program counter moves
within that stack frame).
This drastically reduces time spent in symbolication in some WPT tests.
Loading Ladybird on Github results in 37 debug logs about being unable
to parse an empty Date string. This log is intended to catch Date
formats we do not support to detect web compatability problems, which
makes this case not particuarly useful to log.
Instead of trying to parse all of the different date formats and
logging that the string is not valid, let's just return NAN immediately.
Instead of creating a unique new prototype shape every time a function
object is instantiated, we now keep one cached with the intrinsics.
This avoids a whole lot of shape allocations, reducing GC pressure.
