For performance, it is desirable to defer evaluation of intrinsics that
are stored on the GlobalObject for every created Realm. To support this,
Object now maintains a global storage map to store lambdas that will
return the associated intrinsic when evaluated. Once accessed, the
instrinsic is moved from this global map to normal Object storage.
To prevent this flow from becoming observable, when a deferred intrinsic
is stored, we still place an empty object in the normal Object storage.
This is so we still create the metadata for the object, and in doing so,
can preserve insertion order of the Object storage. Otherwise, this will
be observable by way of Object.getOwnPropertyDescriptors.
This changes Intrinsics to not initialize most of its constructors and
prototype right away. We still initialize a few that are needed before
some others are created, though we may eventually be able to "link"
dependencies at compile time to avoid this.
This patch does two things:
- We now use u32 instead of size_t for the hops and index fields
in EnvironmentCoordinate. This means we're limited to an environment
nesting level and variable count of 4Gs respectively.
- Instead of wrapping it in an Optional, EnvironmentCoordinate now has
a custom valid/invalid state using a magic marker value.
These two changes reduce the size of Identifier by 16 bytes. :^)
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!) :^)
We can't be nuking the ESO while its owned execution context is still on
the VM's execution context stack, as that may lead to a use-after-free.
This patch solves this by adding a `context_owner` field to each context
and treating it as a GC root.
We were mistakenly trying to append UTF-16 code units to a StringBuilder
via the append(char) API. This patch fixes that by accumulating the
result in a Vector<u16> instead.
This'll be a bit worse for performance, since we're now doing additional
UTF-16 string conversions, but we're going for correctness at this stage
and can worry about performance later.
These lambdas were marked mutable as they captured a Ptr wrapper
class by value, which then only returned const-qualified references
to the value they point from the previous const pointer operators.
Nothing is actually mutating in the lambdas state here, and now
that the Ptr operators don't add extra const qualifiers these
can be removed.
This is only visible with something like `Object.getOwnPropertyNames` on
the global object. All other declaration instantiations put the
functions on an environment making the order invisible.
Note that spec order is not quite tree order as in non-strict mode
functions which get hoisted out of blocks appear before top level
functions.
Co-authored-by: Hendiadyoin1 <leon.a@serenityos.org>
This patch adds a special EnvironmentCoordinate::global_marker value
that signifies that a binding lookup ended up searching the global
environment. It doesn't matter if we find it there or not, the global
marker is always returned. This allows us to bypass other environments
on subsequent access, going directly to the global environment.
