This greatly reduces the number of compilations necessary when functions
declaring local functions are re-executed.
For example Octane/typescript.js goes from 58080 bytecode executables
to 960.
This patch adds two macros to declare per-type allocators:
- JS_DECLARE_ALLOCATOR(TypeName)
- JS_DEFINE_ALLOCATOR(TypeName)
When used, they add a type-specific CellAllocator that the Heap will
delegate allocation requests to.
The result of this is that GC objects of the same type always end up
within the same HeapBlock, drastically reducing the ability to perform
type confusion attacks.
It also improves HeapBlock utilization, since each block now has cells
sized exactly to the type used within that block. (Previously we only
had a handful of block sizes available, and most GC allocations ended
up with a large amount of slack in their tails.)
There is a small performance hit from this, but I'm sure we can make
up for it elsewhere.
Note that the old size-based allocators still exist, and we fall back
to them for any type that doesn't have its own CellAllocator.
This patch makes it possible for JS::Object::internal_set() to populate
a CacheablePropertyMetadata, and uses this to implement a basic
monomorphic cache for the most common form of property write access.
We can use `ensure_capacity` for binding vectors if we know their sizes
in advance. This ensures that binding vectors aren't reallocated during
the `function_declaration_instantiation` execution.
With this change, `try_grow_capacity()` and `shrink_to_fit()` are no
longer visible in the `function_declaration_instantiation()` profiles
when running React-Redux-TodoMVC from Speedometer.
We don't need to check if a function parameter is already declared
while creating bindings for them because we deduplicate their names by
storing them in a hash table in one of the previous steps.
This change makes React-Redux-TodoMVC test in Speedometer run 2%
faster.
This change moves steps that can be executed only once and then reused
in subsequent function instantiations from
`function_declaration_instantiation` to the ECMAScriptFunctionObject:
- Determine if there are any parameters with duplicate names.
- Determine if there are any parameters with expressions.
- Determine if an arguments object needs to be created.
- Create a list of distinct function names for which bindings need to
be created.
- Create a list of distinct variable names for which bindings need to
be created.
This change makes React-Redux-TodoMVC test in Speedometer
run 10% faster :)
This works by adding source start/end offset to every bytecode
instruction. In the future we can make this more efficient by keeping
a map of bytecode ranges to source ranges in the Executable instead,
but let's just get traces working first.
Co-Authored-By: Andrew Kaster <akaster@serenityos.org>
Stop worrying about tiny OOMs. Work towards #20449.
While going through these, I also changed the function signature in many
places where returning ThrowCompletionOr<T> is no longer necessary.
This loosens the connection to the AST interpreter and will allow us to
generate SourceRanges for the Bytecode interpreter in the future as well
Moves UnrealizedSourceRanges from TracebackFrame to the JS namespace for
this
These passes have not been shown to actually optimize any JS, and tests
have become very flaky with optimizations enabled. Until some measurable
benefit is shown, remove the optimization passes to reduce overhead of
maintaining bytecode operations and to reduce CI churn. The framework
for optimizations will live on in git history, and can be restored once
proven useful.
Previously, the usage of local variables was limited for all function
declarations. This change relaxes the restriction and only prohibits
locals for hoistable annexB declarations.
Since AST interpreter switches to bytecode to execute generator
functions, arguments stored in local variables always need to be
initialized for such functions.
Using local variables to store function parameters makes Kraken tests
run 7-10% faster.
For now this optimization is limited to only be applied if:
- Parameter does not use destructuring assignment
- None of the function params has default value
- There is no access to "arguments" variable inside function body
- 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
Now ExecutionContext has vector of values that will represent values
of local variables.
This vector is initialized in ECMAScriptFunctionObject::internal_call()
or ECMAScriptFunctionObject::internal_const() using number of local
variables provided to ECMAScriptFunctionObject by the parser.
Saving vector of local variables names in ECMAScriptFunctionObject
will allow to get a name by index in case message of ReferenceError
needs to contain a variable name.
If an exception is thrown by FunctionDeclarationInstantiation for an
async or async-generator function, we still need to return a promise.
We can't just throw the exception.
81 new passes on test262. :^)
The JS::VM now owns the one Bytecode::Interpreter. We no longer have
multiple bytecode interpreters, and there is no concept of a "current"
bytecode interpreter.
If you ask for VM::bytecode_interpreter_if_exists(), it will return null
if we're not running the program in "bytecode enabled" mode.
If you ask for VM::bytecode_interpreter(), it will return a bytecode
interpreter in all modes. This is used for situations where even the AST
interpreter switches to bytecode mode (generators, etc.)
Instead of trying to implement this AO in bytecode, we can just let it
be a C++ thing. Once we implement fast uncaptured locals, we won't even
be calling it super often.
Some of these are allocated upon initialization of the intrinsics, and
some lazily, but in neither case the getters actually return a nullptr.
This saves us a whole bunch of pointer dereferences (as NonnullGCPtr has
an `operator T&()`), and also has the interesting side effect of forcing
us to explicitly use the FunctionObject& overload of call(), as passing
a NonnullGCPtr is ambigous - it could implicitly be turned into a Value
_or_ a FunctionObject& (so we have to dereference manually).
Comes with the usual benefit of saving some space on the stack, as well
as making a situation where both or neither Optionals hold a value
impossible.
The various unwrapping additions are required as we can no longer
construct a ThrowCompletionOr<T> from an Optional<T> - rightfully so.
This includes an Error::create overload to create an Error from a UTF-8
StringView. If creating a String from that view fails, the factory will
return an OOM InternalError instead. VM::throw_completion can also make
use of this overload via its perfect forwarding.
