overlookmotel 66a7a68f9f perf(parser): lexer byte handlers consume ASCII chars faster (#2046) ... In the lexer, most `BYTE_HANDLER`s immediately consume the current char with `lexer.consume_char()`. Byte handlers are only called if there's a certain value (or range of values) for the next char. This is their entire purpose. So in all cases we know for sure that we're not at EOF, and that the next char is a single-byte ASCII character. The compiler, however, doesn't seem to be able to "see through" the `BYTE_HANDLERS[byte](self)` call and understand these invariants. So it produces very verbose ASM for `lexer.consume_char()`. This PR replaces `lexer.consume_char()` in the byte handlers with an unsafe `lexer.consume_ascii_char()` which skips on to next char with a single `inc` instruction. The difference in codegen can be seen here: https://godbolt.org/z/1ha3cr9W5 (compare the 2 x `core::ops::function::FnOnce::call_once` handlers). Downside is that this does introduce a lot of unsafe blocks, but in my opinion they're all pretty trivial to validate. --------- Co-authored-by: Boshen <boshenc@gmail.com>		2024-01-16 12:31:45 +08:00
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examples	chore(clippy): enable undocumented_unsafe_blocks	2023-10-16 15:18:14 +08:00
src	perf(parser): lexer byte handlers consume ASCII chars faster (#2046)	2024-01-16 12:31:45 +08:00
Cargo.toml	perf(parser): lexer byte handlers consume ASCII chars faster (#2046)	2024-01-16 12:31:45 +08:00