-
Notifications
You must be signed in to change notification settings - Fork 12.5k
/
ascii.rs
206 lines (185 loc) · 6.46 KB
/
ascii.rs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
// See comments in `u8::to_ascii_uppercase` in `src/libcore/num/mod.rs`.
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 )+) => {
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[..];
$body
}
vec
})
}
)+
}
}
}
use test::black_box;
use test::Bencher;
benches! {
fn bench00_alloc_only(_bytes: &mut [u8]) {}
fn bench01_black_box_read_each_byte(bytes: &mut [u8]) {
for byte in bytes {
black_box(*byte);
}
}
fn bench02_lookup(bytes: &mut [u8]) {
for byte in bytes {
*byte = ASCII_UPPERCASE_MAP[*byte as usize]
}
}
fn bench03_branch_and_subtract(bytes: &mut [u8]) {
for byte in bytes {
*byte = if b'a' <= *byte && *byte <= b'z' {
*byte - b'a' + b'A'
} else {
*byte
}
}
}
fn bench04_branch_and_mask(bytes: &mut [u8]) {
for byte in bytes {
*byte = if b'a' <= *byte && *byte <= b'z' {
*byte & !0x20
} else {
*byte
}
}
}
fn bench05_branchless(bytes: &mut [u8]) {
for byte in bytes {
*byte = branchless_to_ascii_upper_case(*byte)
}
}
fn bench05_multiply_by_bool(bytes: &mut [u8]) {
for byte in bytes {
*byte &= !(0x20 * (b'a' <= *byte && *byte <= b'z') as u8)
}
}
fn bench06_libcore(bytes: &mut [u8]) {
bytes.make_ascii_uppercase()
}
fn bench07_fake_simd_u32(bytes: &mut [u8]) {
let (before, aligned, after) = unsafe {
bytes.align_to_mut::<u32>()
};
for byte in before {
*byte = branchless_to_ascii_upper_case(*byte)
}
for word in aligned {
// FIXME: this is incorrect for some byte values:
// addition within a byte can carry/overflow into the next byte.
// Test case: b"\xFFz "
*word &= !(
(
word.wrapping_add(0x1f1f1f1f) &
!word.wrapping_add(0x05050505) &
0x80808080
) >> 2
)
}
for byte in after {
*byte = branchless_to_ascii_upper_case(*byte)
}
}
fn bench08_fake_simd_u64(bytes: &mut [u8]) {
let (before, aligned, after) = unsafe {
bytes.align_to_mut::<u64>()
};
for byte in before {
*byte = branchless_to_ascii_upper_case(*byte)
}
for word in aligned {
// FIXME: like above, this is incorrect for some byte values.
*word &= !(
(
word.wrapping_add(0x1f1f1f1f_1f1f1f1f) &
!word.wrapping_add(0x05050505_05050505) &
0x80808080_80808080
) >> 2
)
}
for byte in after {
*byte = branchless_to_ascii_upper_case(*byte)
}
}
}
macro_rules! repeat {
($s: expr) => { concat!($s, $s, $s, $s, $s, $s, $s, $s, $s, $s) }
}
const SHORT: &'static str = "Alice's";
const MEDIUM: &'static str = "Alice's Adventures in Wonderland";
const LONG: &'static str = repeat!(r#"
La Guida di Bragia, a Ballad Opera for the Marionette Theatre (around 1850)
Alice's Adventures in Wonderland (1865)
Phantasmagoria and Other Poems (1869)
Through the Looking-Glass, and What Alice Found There
(includes "Jabberwocky" and "The Walrus and the Carpenter") (1871)
The Hunting of the Snark (1876)
Rhyme? And Reason? (1883) – shares some contents with the 1869 collection,
including the long poem "Phantasmagoria"
A Tangled Tale (1885)
Sylvie and Bruno (1889)
Sylvie and Bruno Concluded (1893)
Pillow Problems (1893)
What the Tortoise Said to Achilles (1895)
Three Sunsets and Other Poems (1898)
The Manlet (1903)[106]
"#);
const ASCII_UPPERCASE_MAP: [u8; 256] = [
0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
b' ', b'!', b'"', b'#', b'$', 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,
];