We should initialize jump targets when constructing the jump instruction
instead of doing it later. This was already the case in all construction
sites but one. This first patch converts all those sites to pass final
targets to the constructor directly.
This change makes LibJS correctly report a syntax error when a unary
expression is followed by exponentiation, as the spec requires.
Apparently this is due to that expression being ambiguous ordering.
Strangely this check does not seem to apply in the same way for '++' and
'--' for reasons that I don't fully understand. For example
```
let x = 5;
++x ** 2
```
Since `--5` and `++5` on it's own results in a syntax error anyway, it
seems we do not need to perform this exponentiation check in those
places.
Diff Tests:
+6 ✅ -6 ❌
This reduces the minimum size of a basic block from 4 KiB to 0 bytes.
With this change, memory usage at the end of Speedometer is 1.2 GiB,
down from 1.8 GiB.
Instead of calling out to helper functions for flow control (and then
checking control flags on every iteration), we now simply inline those
ops in the interpreter loop directly.
If we don't have a local unwind context to handle the exception, we can
just return right away. This allows us to remove one check from the
inner loop.
Nuke all the per-instruction bounds checking when iterating instructions
by using raw pointers instead of indexing into a ReadonlyBytes.
The interpreter loop already checks that we're in-bounds anyway.
There is not need to use SafeFunction because
define_native_function or define_native_accessor will pass callback
forward to NativeFunction that uses HeapFunction to visit it.
When there is no `catch` parameter to bind the error, we don't need
to allocate an environment, since there's nothing to add to it.
This avoids one environment allocation every time we catch like this:
try {
...
} catch {
...
}
This was a remnant from the AST/BC hybrid interpreter times. We've had
a VERIFY in here for weeks now that would catch anything depending on
this behavior, and nothing has hit it, so let's remove the unnecessary
code (but leave the VERIFY) :^)
Our implementation of environment.CreateImmutableBinding(name, true)
in this AO was not correctly initializing const variables in strict
mode. This would mean that constant declarations in for loop bodies
would not throw if they were modified.
To fix this, add a new parameter to CreateVariable to set strict mode.
Also remove the vm.is_strict mode check here, as it doesn't look like
anywhere in the spec will change strict mode depending on whether the
script itself is running in script mode or not.
This fixes two of our test-js tests, no change to test262.
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 :)
ArrayBuffer no longer stores a plain ByteBuffer internally, but a
DataBlock instead, which encapsulated the ByteBuffer together with
information if it is shared or not.
This allows us to get rid of property_table_ordered() which was a
heavy-handed way of iterating properties in insertion order by first
copying them to a sorted Vector.
Clients can now simply iterate property_table() directly.
3% speed-up on Kraken/ai-astar.js :^)
We were translating the pattern [\⪾-\⫀] to [\\u2abe-\\u2ac0], which
is a very different pattern; as a code unit converted to the \uhhh
format has no meaning when escaped, this commit makes us simply skip
escaping it when translating the pattern.
for_each_cell_among_possible_pointers() was taking HashTable by value
instead of by const reference for no reason.
The copying was soaking up ~4% of CPU time while loading https://x.com/
Instead of running a big switch statement on the opcode when checking
how long an instruction is, we now simply store that in a member
variable at construction time for instant access.
This yields a 10.2% speed-up on Kraken/ai-astar :^)
Instead of caching start-of-line offsets, we now cache byte offsets
at regular intervals. This fixes an issue where we had terrible
performance on large minified JS, since that often means one very,
VERY long line (with no line endings to cache).
My machine was spending ~35ms per stack frame when throwing errors
on some heavy minified websites, and after this patch, we now spend
<1ms per stack frame.
