This was quite straightforward using the same label/jump machinery that
we added for while statements.
The main addition here is a new JumpIfTrue bytecode instruction.
This introduces two new instructions: Jump and JumpIfFalse.
Jumps are made to a Bytecode::Label, which is a simple object that
represents a location in the bytecode stream.
Note that you may not always know the target of a jump when adding the
jump instruction itself, but we can just update the instruction later
on during codegen once we know where the jump target is.
The Bytecode::Interpreter now implements jumping via a jump slot that
gets checked after each instruction to see if a jump is pending.
If not, we just increment the PC as usual.
- NewString (allocates a new PrimitiveString from the GC heap)
- GetVariable (retrieves a variable in the current scope)
- SetVariable (assigns a variable in the current scope)
This patch begins the work of implementing JavaScript execution in a
bytecode VM instead of an AST tree-walk interpreter.
It's probably quite naive, but we have to start somewhere.
The basic idea is that you call Bytecode::Generator::generate() on an
AST node and it hands you back a Bytecode::Block filled with
instructions that can then be interpreted by a Bytecode::Interpreter.
This first version only implements two instructions: Load and Add. :^)
Each bytecode block has infinity registers, and the interpreter resizes
its register file to fit the block being executed.
Two new `js` options are added in this patch as well:
`-d` will dump the generated bytecode
`-b` will execute the generated bytecode
Note that unless `-d` and/or `-b` are specified, none of the bytecode
related stuff in LibJS runs at all. This is implemented in parallel
with the existing AST interpreter. :^)
And use them to highlight javascript in HTML source.
This commit also changes how TextDocumentSpan::data is interpreted,
as it used to be an opaque pointer, but everyone stuffed an enum value
inside it, which made the values not unique to each highlighter;
that field is now a u64 serial id.
The syntax highlighters don't need to change their ways of stuffing
token types into that field, but a highlighter that calls another
nested highlighter needs to register the nested types for use with
token pairs.
This is just a simple helper that dumps the current VM call stack
to the debug console. I find myself rewriting this function over and
over, so let's just have it in the tree.
This is now a bit closer to the spec's 10.4.2.2 ArrayCreate - it will
throw a RangeError if the requested length exceeds 2^32 - 1, so anyone
passing in a custom value (defaults to zero for same behaviour as
before) will need an exception check at the call site.
Since DateTime stores months as 1 to 12, while JS accepts months as
0 to 11, we have to account for the difference (by subtracting or
adding 1) where appropriate.
Since theres no way to drop the arguments before the call to the
constructor (or to signal to the constructor that it was not called
directly), we simply reuse the code for the no arguments provided
special case. (And to prevent code duplication, the code was extracted
into the separate static function Date::now(GlobalObject&).
When using Core::DateTime::from_timestamp(0) the resulting Date is
1970-01-01 00:00:00 in UTC, which might be something different in local
time - this is incorrect and relevant as invalid Dates can be made valid
later on.
This is now about as close to the spec as it gets - instead of querying
the |this| value inside of the function, we now pass it in from the
outside.
Also get rid of the oddly specific error messages, they're nice but
pretty inconsistent with most others. Let's prefer consistency and
simplicity for now.
Other than that, no functionality change.
Throws an exception if the given value is nullish, returns it otherwise.
We can now gradually replace such manual checks with this function where
applicable.
This also has the advantage that the somewhat useless "ToObject on null
or undefined" will be replaced with "null cannot be converted to an
object" or "undefined cannot be converted to an object". :^)
