I was suggesting this because `FloatingPoint` is pretty long. `int` and
`float` should be familiar abbreviations. `unsigned` should be familiar
to developers too, but `UnsignedInt` still feels usefully clearer for
the additional chars.
Specifically, after lexing a comment line, look at the next line and see
if it starts with an identical sequence of indent, comment '/'s and
character after the '/'s. If so, skip it as part of a block of comments.
This skips repeatedly diagnosing the same erroneous comment introducer
after the first one in a block, but that seems like a feature rather
than a bug.
The big motivation is to make sure the lexer is minimally impacted by
the length of comment blocks and skips them as efficiently as possible.
While they aren't exactly common, large block comments do come up and
it'd be unfortunate for those to actually slow down the toolchain.
It also happens that this is particularly easy to do because we're just
looking to see if we see the same prefix byte sequence. With SIMD we can
typically handle the most common indents with just a few instructions.
Because of the diagnostic differences, I've included a scalar fallback
that replicates the functionality but has no limit on indent size or CPU
features. I've also added testing to cover this behavior.
The only non-noise benchmark changes are as expected the comment ones,
with a nice improvement across the board:
```
BM_CommentLines/1/0/0 15.8ms ± 2% 15.6ms ± 2% -0.87% (p=0.004 n=19+19)
BM_CommentLines/4/0/0 20.2ms ± 1% 18.8ms ± 1% -6.75% (p=0.000 n=18+18)
BM_CommentLines/128/0/0 221ms ± 1% 167ms ± 1% -24.44% (p=0.000 n=20+19)
BM_CommentLines/1/30/0 16.6ms ± 3% 16.5ms ± 3% ~ (p=0.175 n=19+20)
BM_CommentLines/4/30/0 26.1ms ± 1% 24.8ms ± 2% -5.05% (p=0.000 n=18+19)
BM_CommentLines/128/30/0 233ms ± 1% 185ms ± 1% -20.38% (p=0.000 n=19+20)
BM_CommentLines/1/70/0 19.2ms ± 1% 19.0ms ± 2% -0.66% (p=0.016 n=19+20)
BM_CommentLines/4/70/0 27.9ms ± 1% 26.6ms ± 1% -4.63% (p=0.000 n=19+19)
BM_CommentLines/128/70/0 251ms ± 1% 213ms ± 1% -15.18% (p=0.000 n=20+18)
BM_CommentLines/1/0/2 15.9ms ± 1% 15.8ms ± 2% ~ (p=0.061 n=19+19)
BM_CommentLines/4/0/2 20.5ms ± 2% 19.0ms ± 2% -7.53% (p=0.000 n=20+20)
BM_CommentLines/128/0/2 213ms ± 1% 153ms ± 1% -28.18% (p=0.000 n=19+20)
BM_CommentLines/1/30/2 16.8ms ± 2% 16.7ms ± 3% ~ (p=0.134 n=20+20)
BM_CommentLines/4/30/2 26.6ms ± 1% 25.2ms ± 3% -5.50% (p=0.000 n=20+20)
BM_CommentLines/128/30/2 238ms ± 1% 187ms ± 2% -21.49% (p=0.000 n=17+19)
BM_CommentLines/1/70/2 19.3ms ± 1% 19.4ms ± 3% ~ (p=0.407 n=17+20)
BM_CommentLines/4/70/2 28.2ms ± 1% 26.9ms ± 2% -4.70% (p=0.000 n=19+19)
BM_CommentLines/128/70/2 257ms ± 2% 214ms ± 1% -16.52% (p=0.000 n=20+18)
BM_CommentLines/1/0/8 16.3ms ± 2% 16.1ms ± 2% -1.22% (p=0.001 n=20+20)
BM_CommentLines/4/0/8 22.7ms ± 2% 20.4ms ± 2% -10.20% (p=0.000 n=20+20)
BM_CommentLines/128/0/8 244ms ± 1% 153ms ± 1% -37.26% (p=0.000 n=20+18)
BM_CommentLines/1/30/8 17.3ms ± 2% 17.2ms ± 3% ~ (p=0.192 n=20+20)
BM_CommentLines/4/30/8 28.0ms ± 2% 25.6ms ± 3% -8.46% (p=0.000 n=19+18)
BM_CommentLines/128/30/8 272ms ± 1% 196ms ± 2% -27.90% (p=0.000 n=18+20)
BM_CommentLines/1/70/8 19.9ms ± 2% 19.9ms ± 2% ~ (p=0.531 n=20+19)
BM_CommentLines/4/70/8 29.3ms ± 1% 27.3ms ± 1% -6.87% (p=0.000 n=19+19)
BM_CommentLines/128/70/8 292ms ± 1% 228ms ± 1% -21.97% (p=0.000 n=20+19)
```
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Jon Ross-Perkins
Chandler CarruthandRichard Smith