Instead of scanning through the list of seen constants, we now have a
more structured storage of the constants true, false, null, undefined,
and every possible Int32 value.
This fixes an O(n^2) issue found by Kraken/json-stringify-tinderbox.js
This turns expressions like `(2 + 3) * 8 / 2` into a constant (20)
at bytecode compilation time instead of generating instructions
to calculate the value.
This is a new Bytecode::Generator helper that takes an operand and
returns the same operand, or a copy of it, in case a copy is required
to preserve correct evaluation order.
This can be used in a bunch of places where we're worried about
clobbering some value after obtaining it.
Practically, locals are always copied, and temporary registers as well
as constants are returned as-is.
Functions that don't have a FunctionEnvironment will get their `this`
value from the ExecutionContext. This patch stops generating
ResolveThisBinding instructions at all for functions like that, and
instead pre-populates the `this` register when entering a new bytecode
executable.
We already have a dedicated register slot for `this`, so instead of
having ResolveThisBinding take a `dst` operand, just write the value
directly into the `this` register every time.
...that maintains a list of allocated execution contexts so malloc()
does not have to be called every time we need to get a new one.
20% improvement in Octane/typescript.js
16% improvement in Kraken/imaging-darkroom.js
By using separate struct we can avoid updating AST node and
ECMAScriptFunctionObject constructors every time there is a need to
add or remove some additional information colllected during parsing.
Allows to skip function environment allocation for non-arrow functions
if the only reason it is needed is to hold `this` binding.
The parser is changed to do following:
- If a function is an arrow function and uses `this` then all functions
in a scope chain are marked to allocate function environment for
`this` binding.
- If a function uses `new.target` then all functions in a scope chain
are marked to allocate function environment.
`ordinary_call_bind_this()` is changed to put `this` value in execution
context when function environment allocation is skipped.
35% improvement in Octane/typescript.js
50% improvement in Octane/deltablue.js
19% improvement in Octane/raytrace.js
This allows us to skip allocating a function environment in cases where
it was previously impossible because the arguments object needed a
binding.
This change does not bring visible improvement in Kraken or Octane
benchmarks but seems useful to have anyway.
By doing this, we can remove all the special-case checks for `length`
from the generic GetById and GetByIdWithThis code paths, making every
other property lookup a bit faster.
Small progressions on most benchmarks, and some larger progressions:
- 12% on Octane/crypto.js
- 6% on Kraken/ai-astar.js
The VERIFY assumed that we either have a finally block which we already
visited through a previous boundary or have no finally block what so
ever; But since 301a1fc763 we propagate
finalizers through unwind scopes breaking that assumption.
It wasn't safe to use addition_would_overflow(a, -b) to check if
subtraction (a - b) would overflow, since it doesn't cover this case.
I don't know why we didn't have subtraction_would_overflow(), so this
patch adds it. :^)
With this only `ContinuePendingUnwind` needs to dynamically check if a
scheduled return needs to go through a `finally` block, making the
interpreter loop a bit nicer
Instead of SetVariable having 2x2 modes for variable/lexical and
initialize/set, those 4 modes are now separate instructions, which
makes each instruction much less branchy.
The last completion value in a function is not exposed to the language,
since functions always either return something, or undefined.
Given this, we can avoid emitting code that propagates the completion
value from various statements, as long as we know we're generating code
for a context where the completion value is not accessible. In practical
terms, this means that function code gets to do less completion
shuffling, while global and eval code has to keep doing it.
This means that SetVariable instructions will now remember which
(relative) environment contains the targeted binding, letting it bypass
the full binding resolution machinery on subsequent accesses.
Merging registers, constants and locals into single vector means:
- Better data locality
- No need to check type in Interpreter::get() and Interpreter::set()
which are very hot functions
Performance improvement is visible in almost all Octane and Kraken
tests.
Filling a typed array with an integer shouldn't have to go through the
generic Set for every element.
This knocks a 7% item down to <1% in profiles of Another World JS at
https://cyxx.github.io/another_js/
When comparing two numbers, we can avoid a lot of implicit type
conversion nonsense and go straight to comparison, saving time in the
most common case.
These were out-of-line because we had some ideas about marking
instruction streams PROT_READ only, but that seems pretty arbitrary and
there's a lot of performance to be gained by putting these inline.
Instead, generate bytecode to execute their AST nodes and save the
resulting operands inside the NewClass instruction.
Moving property expression evaluation to happen before NewClass
execution also moves along creation of new private environment and
its population with private members (private members should be visible
during property evaluation).
Before:
- NewClass
After:
- CreatePrivateEnvironment
- AddPrivateName
- ...
- AddPrivateName
- NewClass
- LeavePrivateEnvironment
