This prevents the variables declared inside a class static initializer
to escape to the nearest containing function causing all sorts of memory
corruptions.
These were *extremely* hot in profiles (noticed when looking at
disassembly).
Now that we've made the special empty JS::Value much harder to create
accidentally, we can feel better about turning these into ASSERT and
catching them in debug builds.
The special empty value (that we use for array holes, Optional<Value>
when empty and a few other other placeholder/sentinel tasks) still
exists, but you now create one via JS::js_special_empty_value() and
check for it with Value::is_special_empty_value().
The main idea here is to make it very unlikely to accidentally create an
unexpected special empty value.
Before, If the cache was empty we would try and evict non-existant
entries and crash. So the fix is to make sure that we don't saturate
the cache with a single parse result.
This commit removes the -Wno-unusued-private-field flag, thus
reenabling the warning. Unused field were either removed or marked
[[maybe_unused]] when unsure.
This patch adds a workaround for a Swift issue where boolean bitfields
with getters and setters in SWIFT_UNSAFE_REFERENCE types are improperly
imported, causing an ICE.
Basically convert o["foo"]=x into o.foo=x when emitting bytecode.
These are effectively the same thing, and the latter format opts
into using an inline cache for the property lookups.
Basically convert o["foo"] into o.foo when emitting bytecode. These are
effectively the same thing, and the latter format opts into using an
inline cache for the property lookups.
If a class field initializer is just a simple literal, we can skip
creating (and calling) a wrapper function for it entirely.
1.44x speedup on JetStream3/raytrace-private-class-fields.js
1.53x speedup on JetStream3/raytrace-public-class-fields.js
This is the same PRNG used by major browser engines, and although it's
a step down in randomness, it massively improves performance of
Math.random().
1.20x speedup on JetStream3/sync-file-system.js :^)
Instead of returning internal generator results as ordinary JS::Objects
with properties, we now use GeneratorResult and CompletionCell which
both inherit from Cell directly and allow efficient access to state.
1.59x speedup on JetStream3/lazy-collections.js :^)
By moving the LHS and RHS pointers used by rope strings into a
RopeString subclass, we shrink PrimitiveString by 16 bytes. Most strings
are not rope strings, so this ends up saving quite a bit of memory.
Previously, all `GC::Cell` derived classes were Weakable. Marking only
those classes that require this functionality as Weakable allows us to
reduce the memory footprint of some frequently used classes.
PrimitiveString is now internally either UTF-8, UTF-16, or both.
We no longer convert them to/from ByteString anywhere, nor does VM have
a ByteString cache.
If we don't have parameter expressions, we don't need to collect
metadata about whether instantiated var names collide with parameter
names or function names, as these flags are only used in the parameter
code path.
This avoids going through all the shape transitions when setting up the
most common form of ESFO.
This is extremely hot on Uber Eats, and this provides some relief.
We can use the index's invalid state to signal an empty optional.
This makes Optional<IdentifierTableIndex> 4 bytes instead of 8,
shrinking every bytecode instruction that uses these.
Instead of making a copy of the Vector<FunctionParameter> from the AST
every time we instantiate an ECMAScriptFunctionObject, we now keep the
parameters in a ref-counted FunctionParameters object.
This reduces memory usage, and also allows us to cache the bytecode
executables for default parameter expressions without recompiling them
for every instantiation. :^)
This works because at the end of the finally chunk, a
ContinuePendingUnwind is generated which copies the saved return value
register into the return value register. In cases where
ContinuePendingUnwind is not generated such as when there is a break
statement in the finally block, the fonction will return undefined which
is consistent with V8 and SpiderMonkey.
The JS runtime is full of checks for is<NumberObject> and friends.
They were showing up in a Speedometer profile as ~1% spent in
dynamic_cast, and this basically chops that down to nothing.
