Instead of displaying locals as "locN", we now show them as "name~N".
This makes it a lot easier to follow bytecode dumps, especially in
longer functions.
Note that we keep displaying the local index, to avoid confusion in case
there are multiple separate locals with the same name in one executable.
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.
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
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.
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.
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
If the minimal amount of required bindings is known in advance, it could
be used to ensure capacity to avoid resizing the internal vector that
holds bindings.
By doing that all instructions required for instantiation are emitted
once in compilation and then reused for subsequent calls, instead of
running generic instantiation process for each call.
We now fuse sequences like [LessThan, JumpIf] to JumpLessThan.
This is only allowed for temporaries (i.e VM registers) with no other
references to them.
This removes a layer of indirection in the bytecode where we had to make
sure all the initializer elements were laid out in sequential registers.
Array expressions no longer clobber registers permanently, and they can
be reused immediately afterwards.
If we don't have enough stack space, throw an exception while we still
can, and give the caller a chance to recover.
This particular problem will go away once we make calls non-recursive.
This means inlining all the things. This yields a 40% speedup on the for
loop microbenchmark, and everything else gets faster as well. :^)
This makes compilation take foreeeever with GCC, so I'm only enabling it
for Clang in this commit. We should figure out how to make GCC compile
this without timing out CI, since the speedup is amazing.
This commit converts the main loop in Bytecode::Interpreter to use a
label table and computed goto for fast instruction dispatch.
This yields roughly 35% speedup on the for loop microbenchmark,
and makes everything else faster as well. :^)
This commit adds a HANDLE_INSTRUCTION macro that expands to everything
needed to handle a single instruction (invoking the handler function,
checking for exceptions, and advancing the program counter).
This gives a ~15% speed-up on a for loop microbenchmark, and makes
basically everything faster.
Instead of keeping bytecode as a set of disjoint basic blocks on the
malloc heap, bytecode is now a contiguous sequence of bytes(!)
The transformation happens at the end of Bytecode::Generator::generate()
and the only really hairy part is rerouting jump labels.
This required solving a few problems:
- The interpreter execution loop had to change quite a bit, since we
were storing BasicBlock pointers all over the place, and control
transfer was done by redirecting the interpreter's current block.
- Exception handlers & finalizers are now stored per-bytecode-range
in a side table in Executable.
- The interpreter now has a plain program counter instead of a stream
iterator. This actually makes error stack generation a bit nicer
since we just have to deal with a number instead of reaching into
the iterator.
This yields a 25% performance improvement on this microbenchmark:
for (let i = 0; i < 1_000_000; ++i) { }
But basically everything gets faster. :^)
Before this change, all JumpFoo instructions inherited from Jump, which
forced the unconditional Jump to have an unusued "false target" member.
Also, labels were unnecessarily wrapped in Optional<>.
By defining each jump instruction separately, they all shrink in size,
and all ambiguity is removed.
This does two things:
* Clear exceptions when transferring control out of a finalizer
Otherwise they would resurface at the end of the next finalizer
(see test the new test case), or at the end of a function
* Pop one scheduled jump when transferring control out of a finalizer
This removes one old FIXME
