If statements without an else clause generated jumps to the next
instruction, this commit fixes the if statement generation so that it
dosen't produce them anymore.
This is an example of JS code that generates the useless jumps
(a => if(a){}) ();
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;
The order of precedence with the `*` operator sometimes makes it a bit
harder to detect whether or not the result is actually used. Let's fail
compilation if anyone tries to discard the result.
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.
Printing the whole array causes wpt
console/console-log-large-array.any.html to crash.
This limits logged arrays to 100 elements and
truncates the rest with ...
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.
https://github.com/whatwg/console/pull/240 is an editorial change to use
the term "implementation-defined" more consistently. This seems to be
the only instance in the spec text which we quote verbatim.
Fixes a bug when "'Await' expression is not allowed in formal parameters
of an async function" is thrown for "await" encountered in a function
definition assigned to a default function parameter.
Fixes loading of https://excalidraw.com/
This didn't make any sense, and was already handled by pushing a new
execution context anyway.
By simply removing these bogus lines of code, we fix a bug where
throwing inside a function whose bytecode was shorter than the calling
function would crash trying to generate an Error stack trace (because
the bytecode offset we were trying to symbolicate was actually from
the longer caller function, and not valid in the callee function.)
This makes --log-all-js-exceptions less crash prone and more helpful.
In some cases, we have a timestamp as a double in milliseconds. We then
would convert it to nanoseconds as a BigInt, just to bring it back to a
double for TZDB lookups. Add an overload to avoid this needless round
trip.
Even though the underlying time zone is already cached by LibUnicode, JS
performs additional expensive lookups with that time zone. There's no
need to do those lookups again until the system time zone has changed.
