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Diffstat (limited to 'library/core/benches/ascii.rs')
| -rw-r--r-- | library/core/benches/ascii.rs | 353 |
1 files changed, 353 insertions, 0 deletions
diff --git a/library/core/benches/ascii.rs b/library/core/benches/ascii.rs new file mode 100644 index 000000000..64938745a --- /dev/null +++ b/library/core/benches/ascii.rs @@ -0,0 +1,353 @@ +mod is_ascii; + +// Lower-case ASCII 'a' is the first byte that has its highest bit set +// after wrap-adding 0x1F: +// +// b'a' + 0x1F == 0x80 == 0b1000_0000 +// b'z' + 0x1F == 0x98 == 0b1001_1000 +// +// Lower-case ASCII 'z' is the last byte that has its highest bit unset +// after wrap-adding 0x05: +// +// b'a' + 0x05 == 0x66 == 0b0110_0110 +// b'z' + 0x05 == 0x7F == 0b0111_1111 +// +// … except for 0xFB to 0xFF, but those are in the range of bytes +// that have the highest bit unset again after adding 0x1F. +// +// So `(byte + 0x1f) & !(byte + 5)` has its highest bit set +// iff `byte` is a lower-case ASCII letter. +// +// Lower-case ASCII letters all have the 0x20 bit set. +// (Two positions right of 0x80, the highest bit.) +// Unsetting that bit produces the same letter, in upper-case. +// +// Therefore: +fn branchless_to_ascii_upper_case(byte: u8) -> u8 { + byte & !((byte.wrapping_add(0x1f) & !byte.wrapping_add(0x05) & 0x80) >> 2) +} + +macro_rules! benches { + ($( fn $name: ident($arg: ident: &mut [u8]) $body: block )+ @iter $( $is_: ident, )+) => { + benches! {@ + $( fn $name($arg: &mut [u8]) $body )+ + $( fn $is_(bytes: &mut [u8]) { bytes.iter().all(u8::$is_) } )+ + } + }; + + (@$( fn $name: ident($arg: ident: &mut [u8]) $body: block )+) => { + benches!(mod short SHORT $($name $arg $body)+); + benches!(mod medium MEDIUM $($name $arg $body)+); + benches!(mod long LONG $($name $arg $body)+); + }; + + (mod $mod_name: ident $input: ident $($name: ident $arg: ident $body: block)+) => { + mod $mod_name { + use super::*; + + $( + #[bench] + fn $name(bencher: &mut Bencher) { + bencher.bytes = $input.len() as u64; + bencher.iter(|| { + let mut vec = $input.as_bytes().to_vec(); + { + let $arg = &mut vec[..]; + black_box($body); + } + vec + }) + } + )+ + } + } +} + +use test::black_box; +use test::Bencher; + +const ASCII_CASE_MASK: u8 = 0b0010_0000; + +benches! { + fn case00_alloc_only(_bytes: &mut [u8]) {} + + fn case01_black_box_read_each_byte(bytes: &mut [u8]) { + for byte in bytes { + black_box(*byte); + } + } + + fn case02_lookup_table(bytes: &mut [u8]) { + for byte in bytes { + *byte = ASCII_UPPERCASE_MAP[*byte as usize] + } + } + + fn case03_branch_and_subtract(bytes: &mut [u8]) { + for byte in bytes { + *byte = if b'a' <= *byte && *byte <= b'z' { + *byte - b'a' + b'A' + } else { + *byte + } + } + } + + fn case04_branch_and_mask(bytes: &mut [u8]) { + for byte in bytes { + *byte = if b'a' <= *byte && *byte <= b'z' { + *byte & !0x20 + } else { + *byte + } + } + } + + fn case05_branchless(bytes: &mut [u8]) { + for byte in bytes { + *byte = branchless_to_ascii_upper_case(*byte) + } + } + + fn case06_libcore(bytes: &mut [u8]) { + bytes.make_ascii_uppercase() + } + + fn case07_fake_simd_u32(bytes: &mut [u8]) { + // SAFETY: transmuting a sequence of `u8` to `u32` is always fine + let (before, aligned, after) = unsafe { + bytes.align_to_mut::<u32>() + }; + for byte in before { + *byte = branchless_to_ascii_upper_case(*byte) + } + for word in aligned { + // FIXME: this is incorrect for some byte values: + // addition within a byte can carry/overflow into the next byte. + // Test case: b"\xFFz " + *word &= !( + ( + word.wrapping_add(0x1f1f1f1f) & + !word.wrapping_add(0x05050505) & + 0x80808080 + ) >> 2 + ) + } + for byte in after { + *byte = branchless_to_ascii_upper_case(*byte) + } + } + + fn case08_fake_simd_u64(bytes: &mut [u8]) { + // SAFETY: transmuting a sequence of `u8` to `u64` is always fine + let (before, aligned, after) = unsafe { + bytes.align_to_mut::<u64>() + }; + for byte in before { + *byte = branchless_to_ascii_upper_case(*byte) + } + for word in aligned { + // FIXME: like above, this is incorrect for some byte values. + *word &= !( + ( + word.wrapping_add(0x1f1f1f1f_1f1f1f1f) & + !word.wrapping_add(0x05050505_05050505) & + 0x80808080_80808080 + ) >> 2 + ) + } + for byte in after { + *byte = branchless_to_ascii_upper_case(*byte) + } + } + + fn case09_mask_mult_bool_branchy_lookup_table(bytes: &mut [u8]) { + fn is_ascii_lowercase(b: u8) -> bool { + if b >= 0x80 { return false } + match ASCII_CHARACTER_CLASS[b as usize] { + L | Lx => true, + _ => false, + } + } + for byte in bytes { + *byte &= !(0x20 * (is_ascii_lowercase(*byte) as u8)) + } + } + + fn case10_mask_mult_bool_lookup_table(bytes: &mut [u8]) { + fn is_ascii_lowercase(b: u8) -> bool { + match ASCII_CHARACTER_CLASS[b as usize] { + L | Lx => true, + _ => false + } + } + for byte in bytes { + *byte &= !(0x20 * (is_ascii_lowercase(*byte) as u8)) + } + } + + fn case11_mask_mult_bool_match_range(bytes: &mut [u8]) { + fn is_ascii_lowercase(b: u8) -> bool { + match b { + b'a'..=b'z' => true, + _ => false + } + } + for byte in bytes { + *byte &= !(0x20 * (is_ascii_lowercase(*byte) as u8)) + } + } + + fn case12_mask_shifted_bool_match_range(bytes: &mut [u8]) { + fn is_ascii_lowercase(b: u8) -> bool { + match b { + b'a'..=b'z' => true, + _ => false + } + } + for byte in bytes { + *byte &= !((is_ascii_lowercase(*byte) as u8) * ASCII_CASE_MASK) + } + } + + fn case13_subtract_shifted_bool_match_range(bytes: &mut [u8]) { + fn is_ascii_lowercase(b: u8) -> bool { + match b { + b'a'..=b'z' => true, + _ => false + } + } + for byte in bytes { + *byte -= (is_ascii_lowercase(*byte) as u8) * ASCII_CASE_MASK + } + } + + fn case14_subtract_multiplied_bool_match_range(bytes: &mut [u8]) { + fn is_ascii_lowercase(b: u8) -> bool { + match b { + b'a'..=b'z' => true, + _ => false + } + } + for byte in bytes { + *byte -= (b'a' - b'A') * is_ascii_lowercase(*byte) as u8 + } + } + + @iter + + is_ascii, + is_ascii_alphabetic, + is_ascii_uppercase, + is_ascii_lowercase, + is_ascii_alphanumeric, + is_ascii_digit, + is_ascii_hexdigit, + is_ascii_punctuation, + is_ascii_graphic, + is_ascii_whitespace, + is_ascii_control, +} + +macro_rules! repeat { + ($s: expr) => { + concat!($s, $s, $s, $s, $s, $s, $s, $s, $s, $s) + }; +} + +const SHORT: &str = "Alice's"; +const MEDIUM: &str = "Alice's Adventures in Wonderland"; +const LONG: &str = repeat!( + r#" + La Guida di Bragia, a Ballad Opera for the Marionette Theatre (around 1850) + Alice's Adventures in Wonderland (1865) + Phantasmagoria and Other Poems (1869) + Through the Looking-Glass, and What Alice Found There + (includes "Jabberwocky" and "The Walrus and the Carpenter") (1871) + The Hunting of the Snark (1876) + Rhyme? And Reason? (1883) – shares some contents with the 1869 collection, + including the long poem "Phantasmagoria" + A Tangled Tale (1885) + Sylvie and Bruno (1889) + Sylvie and Bruno Concluded (1893) + Pillow Problems (1893) + What the Tortoise Said to Achilles (1895) + Three Sunsets and Other Poems (1898) + The Manlet (1903)[106] +"# +); + +#[rustfmt::skip] +const ASCII_UPPERCASE_MAP: [u8; 256] = [ + 0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, + 0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, + 0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, + 0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, + b' ', b'!', b'"', b'#', b'$', b'%', b'&', b'\'', + b'(', b')', b'*', b'+', b',', b'-', b'.', b'/', + b'0', b'1', b'2', b'3', b'4', b'5', b'6', b'7', + b'8', b'9', b':', b';', b'<', b'=', b'>', b'?', + b'@', b'A', b'B', b'C', b'D', b'E', b'F', b'G', + b'H', b'I', b'J', b'K', b'L', b'M', b'N', b'O', + b'P', b'Q', b'R', b'S', b'T', b'U', b'V', b'W', + b'X', b'Y', b'Z', b'[', b'\\', b']', b'^', b'_', + b'`', + + b'A', b'B', b'C', b'D', b'E', b'F', b'G', + b'H', b'I', b'J', b'K', b'L', b'M', b'N', b'O', + b'P', b'Q', b'R', b'S', b'T', b'U', b'V', b'W', + b'X', b'Y', b'Z', + + b'{', b'|', b'}', b'~', 0x7f, + 0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, + 0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f, + 0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, + 0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f, + 0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7, + 0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf, + 0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7, + 0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf, + 0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7, + 0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf, + 0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7, + 0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf, + 0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7, + 0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef, + 0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7, + 0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff, +]; + +enum AsciiCharacterClass { + C, // control + Cw, // control whitespace + W, // whitespace + D, // digit + L, // lowercase + Lx, // lowercase hex digit + U, // uppercase + Ux, // uppercase hex digit + P, // punctuation + N, // Non-ASCII +} +use self::AsciiCharacterClass::*; + +#[rustfmt::skip] +static ASCII_CHARACTER_CLASS: [AsciiCharacterClass; 256] = [ +// _0 _1 _2 _3 _4 _5 _6 _7 _8 _9 _a _b _c _d _e _f + C, C, C, C, C, C, C, C, C, Cw,Cw,C, Cw,Cw,C, C, // 0_ + C, C, C, C, C, C, C, C, C, C, C, C, C, C, C, C, // 1_ + W, P, P, P, P, P, P, P, P, P, P, P, P, P, P, P, // 2_ + D, D, D, D, D, D, D, D, D, D, P, P, P, P, P, P, // 3_ + P, Ux,Ux,Ux,Ux,Ux,Ux,U, U, U, U, U, U, U, U, U, // 4_ + U, U, U, U, U, U, U, U, U, U, U, P, P, P, P, P, // 5_ + P, Lx,Lx,Lx,Lx,Lx,Lx,L, L, L, L, L, L, L, L, L, // 6_ + L, L, L, L, L, L, L, L, L, L, L, P, P, P, P, C, // 7_ + N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, + N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, + N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, + N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, + N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, + N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, + N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, + N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, N, +]; |