This adds a new semantic token type, PreprocessorMacro.
Calls to preprocessor macros will now be highlighted when semantic
highlighting is enabled in Hack Studio.
This is now the source of truth for 'user enabled/disabled scripting',
but it has to ask the window's page, which actually stores the setting.
Also use this new functionality in two places where it was previously
marked as a FIXME.
There's no need to have a custom is_scripting_enabled() for the
Document class, as it (indirectly) inherits from Node.
Also, let's not hardcode false here :^)
This caused a system-wide crash because of a previous bug relating to
non-trivial types in HashTable. Therefore, check that such types
actually work under various workloads.
As seen on TV, HashTable can get "thrashed", i.e. it has a bunch of
deleted buckets that count towards the load factor. This means that hash
tables which are large enough for their contents need to be resized.
This was fixed in 9d8da16 with a workaround that shrinks the HashTable
back down in these cases, as after the resize and re-hash the load
factor is very low again. However, that's not a good solution. If you
insert and remove repeatedly around a size boundary, you might get
frequent resizes, which involve frequent re-allocations.
The new solution is an in-place rehashing algorithm that I came up with.
(Do complain to me, I'm at fault.) Basically, it iterates the buckets
and re-hashes the used buckets while marking the deleted slots empty.
The issue arises with collisions in the re-hash. For this reason, there
are two kinds of used buckets during the re-hashing: the normal "used"
buckets, which are old and are treated as free space, and the
"re-hashed" buckets, which are new and treated as used space, i.e. they
trigger probing. Therefore, the procedure for relocating a bucket's
contents is as follows:
- Locate the "real" bucket of the contents with the hash. That bucket is
the starting point for the target bucket, and the current (old) bucket
is the bucket we want to move.
- While we still need to move the bucket:
- If we're the target, something strange happened last iteration or we
just re-hashed to the same location. We're done.
- If the target is empty or deleted, just move the bucket. We're done.
- If the target is a re-hashed full bucket, we probe by double-hashing
our hash as usual. Henceforth, we move our target for the next
iteration.
- If the target is an old full bucket, we swap the target and to-move
buckets. Therefore, the bucket to move is a the correct location and the
former target, which still needs to find a new place, is now in the
bucket to move. So we can just continue with the loop; the target is
re-obtained from the bucket to move. This happens for each and every
bucket, though some buckets are "coincidentally" moved before their
point of iteration is reached. Either way, this guarantees full in-place
movement (even without stack storage) and therefore space complexity of
O(1). Time complexity is amortized O(2n) asssuming a good hashing
function.
This leads to a performance improvement of ~30% on the benchmark
introduced with the last commit.
Co-authored-by: Hendiadyoin1 <leon.a@serenityos.org>
Thrashing is what I call the situations where a table is mostly filled
with deleted markers, causing an increase in size (at least temporarily)
when a simple re-hash would be enough to get rid of those. This happens
when a hash table (especially with many elements) has a lot of deletes
and re-inserts done to it, which is what this benchmark does.
The hash table buckets had three different state booleans that are in
fact exclusive. In preparation for further states, this commit
consolidates them into one enum. This has the added benefit on not
relying on the compiler's boolean packing anymore; we definitely now
only need one byte for the bucket state.
I noticed that we were populating this StringBuilder and then throwing
away the result while profiling `true` with UserSpace emulator.
Before:
courage:~ $ time -n 1000 true
Timing report: 3454 ms
==============
Command: true
Average time: 3.45 ms (median: 3, stddev: 3.42, min: 0, max:11)
Excluding first: 3.45 ms (median: 3, stddev: 3.42, min: 0, max:11)
After:
courage:~ $ time -n 1000 true
Timing report: 3308 ms
==============
Command: true
Average time: 3.30 ms (median: 3, stddev: 3.28, min: 0, max:12)
Excluding first: 3.30 ms (median: 3, stddev: 3.29, min: 0, max:12)
