1 | /* strlen/wcslen optimized with 256/512-bit EVEX instructions. |
2 | Copyright (C) 2021-2024 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | |
5 | The GNU C Library is free software; you can redistribute it and/or |
6 | modify it under the terms of the GNU Lesser General Public |
7 | License as published by the Free Software Foundation; either |
8 | version 2.1 of the License, or (at your option) any later version. |
9 | |
10 | The GNU C Library is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
13 | Lesser General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU Lesser General Public |
16 | License along with the GNU C Library; if not, see |
17 | <https://www.gnu.org/licenses/>. */ |
18 | |
19 | |
20 | #include <isa-level.h> |
21 | |
22 | #if ISA_SHOULD_BUILD (4) |
23 | |
24 | # include <sysdep.h> |
25 | |
26 | # ifdef USE_AS_WCSLEN |
27 | # define VPCMPEQ vpcmpeqd |
28 | # define VPCMPNEQ vpcmpneqd |
29 | # define VPTESTN vptestnmd |
30 | # define VPTEST vptestmd |
31 | # define VPMINU vpminud |
32 | # define CHAR_SIZE 4 |
33 | # define CHAR_SIZE_SHIFT_REG(reg) sar $2, %reg |
34 | # else |
35 | # define VPCMPEQ vpcmpeqb |
36 | # define VPCMPNEQ vpcmpneqb |
37 | # define VPTESTN vptestnmb |
38 | # define VPTEST vptestmb |
39 | # define VPMINU vpminub |
40 | # define CHAR_SIZE 1 |
41 | # define CHAR_SIZE_SHIFT_REG(reg) |
42 | |
43 | # define REG_WIDTH VEC_SIZE |
44 | # endif |
45 | |
46 | # define CHAR_PER_VEC (VEC_SIZE / CHAR_SIZE) |
47 | |
48 | # include "reg-macros.h" |
49 | |
50 | # if CHAR_PER_VEC == 64 |
51 | |
52 | # define TAIL_RETURN_LBL first_vec_x2 |
53 | # define TAIL_RETURN_OFFSET (CHAR_PER_VEC * 2) |
54 | |
55 | # define FALLTHROUGH_RETURN_LBL first_vec_x3 |
56 | # define FALLTHROUGH_RETURN_OFFSET (CHAR_PER_VEC * 3) |
57 | |
58 | # else |
59 | |
60 | # define TAIL_RETURN_LBL first_vec_x3 |
61 | # define TAIL_RETURN_OFFSET (CHAR_PER_VEC * 3) |
62 | |
63 | # define FALLTHROUGH_RETURN_LBL first_vec_x2 |
64 | # define FALLTHROUGH_RETURN_OFFSET (CHAR_PER_VEC * 2) |
65 | # endif |
66 | |
67 | # define XZERO VMM_128(0) |
68 | # define VZERO VMM(0) |
69 | # define PAGE_SIZE 4096 |
70 | |
71 | .section SECTION(.text), "ax" , @progbits |
72 | ENTRY_P2ALIGN(STRLEN, 6) |
73 | movl %edi, %eax |
74 | vpxorq %XZERO, %XZERO, %XZERO |
75 | andl $(PAGE_SIZE - 1), %eax |
76 | cmpl $(PAGE_SIZE - VEC_SIZE), %eax |
77 | ja L(cross_page_boundary) |
78 | |
79 | /* Check the first VEC_SIZE bytes. Each bit in K0 represents a |
80 | null byte. */ |
81 | VPCMPEQ (%rdi), %VZERO, %k0 |
82 | KMOV %k0, %VRAX |
83 | test %VRAX, %VRAX |
84 | jz L(aligned_more) |
85 | bsf %VRAX, %VRAX |
86 | ret |
87 | |
88 | .p2align 4,, 8 |
89 | L(first_vec_x4): |
90 | bsf %VRAX, %VRAX |
91 | subl %ecx, %edi |
92 | CHAR_SIZE_SHIFT_REG (edi) |
93 | leal (CHAR_PER_VEC * 4)(%rdi, %rax), %eax |
94 | ret |
95 | |
96 | |
97 | |
98 | /* Aligned more for strnlen compares remaining length vs 2 * |
99 | CHAR_PER_VEC, 4 * CHAR_PER_VEC, and 8 * CHAR_PER_VEC before |
100 | going to the loop. */ |
101 | .p2align 4,, 10 |
102 | L(aligned_more): |
103 | movq %rdi, %rcx |
104 | andq $(VEC_SIZE * -1), %rdi |
105 | L(cross_page_continue): |
106 | /* Remaining length >= 2 * CHAR_PER_VEC so do VEC0/VEC1 without |
107 | rechecking bounds. */ |
108 | VPCMPEQ (VEC_SIZE * 1)(%rdi), %VZERO, %k0 |
109 | KMOV %k0, %VRAX |
110 | test %VRAX, %VRAX |
111 | jnz L(first_vec_x1) |
112 | |
113 | VPCMPEQ (VEC_SIZE * 2)(%rdi), %VZERO, %k0 |
114 | KMOV %k0, %VRAX |
115 | test %VRAX, %VRAX |
116 | jnz L(first_vec_x2) |
117 | |
118 | VPCMPEQ (VEC_SIZE * 3)(%rdi), %VZERO, %k0 |
119 | KMOV %k0, %VRAX |
120 | test %VRAX, %VRAX |
121 | jnz L(first_vec_x3) |
122 | |
123 | VPCMPEQ (VEC_SIZE * 4)(%rdi), %VZERO, %k0 |
124 | KMOV %k0, %VRAX |
125 | test %VRAX, %VRAX |
126 | jnz L(first_vec_x4) |
127 | |
128 | subq $(VEC_SIZE * -1), %rdi |
129 | |
130 | # if CHAR_PER_VEC == 64 |
131 | /* No partial register stalls on processors that we use evex512 |
132 | on and this saves code size. */ |
133 | xorb %dil, %dil |
134 | # else |
135 | andq $-(VEC_SIZE * 4), %rdi |
136 | # endif |
137 | |
138 | |
139 | |
140 | /* Compare 4 * VEC at a time forward. */ |
141 | .p2align 4 |
142 | L(loop_4x_vec): |
143 | VMOVA (VEC_SIZE * 4)(%rdi), %VMM(1) |
144 | VPMINU (VEC_SIZE * 5)(%rdi), %VMM(1), %VMM(2) |
145 | VMOVA (VEC_SIZE * 6)(%rdi), %VMM(3) |
146 | VPMINU (VEC_SIZE * 7)(%rdi), %VMM(3), %VMM(4) |
147 | VPTESTN %VMM(2), %VMM(2), %k0 |
148 | VPTESTN %VMM(4), %VMM(4), %k2 |
149 | |
150 | subq $-(VEC_SIZE * 4), %rdi |
151 | KORTEST %k0, %k2 |
152 | jz L(loop_4x_vec) |
153 | |
154 | VPTESTN %VMM(1), %VMM(1), %k1 |
155 | KMOV %k1, %VRAX |
156 | test %VRAX, %VRAX |
157 | jnz L(first_vec_x0) |
158 | |
159 | KMOV %k0, %VRAX |
160 | test %VRAX, %VRAX |
161 | jnz L(first_vec_x1) |
162 | |
163 | VPTESTN %VMM(3), %VMM(3), %k0 |
164 | |
165 | # if CHAR_PER_VEC == 64 |
166 | KMOV %k0, %VRAX |
167 | test %VRAX, %VRAX |
168 | jnz L(first_vec_x2) |
169 | KMOV %k2, %VRAX |
170 | # else |
171 | /* We can only combine last 2x VEC masks if CHAR_PER_VEC <= 32. */ |
172 | kmovd %k2, %edx |
173 | kmovd %k0, %eax |
174 | salq $CHAR_PER_VEC, %rdx |
175 | orq %rdx, %rax |
176 | # endif |
177 | |
178 | /* first_vec_x3 for strlen-ZMM and first_vec_x2 for strlen-YMM. */ |
179 | .p2align 4,, 2 |
180 | L(FALLTHROUGH_RETURN_LBL): |
181 | bsfq %rax, %rax |
182 | subq %rcx, %rdi |
183 | CHAR_SIZE_SHIFT_REG (rdi) |
184 | leaq (FALLTHROUGH_RETURN_OFFSET)(%rdi, %rax), %rax |
185 | ret |
186 | |
187 | .p2align 4,, 8 |
188 | L(first_vec_x0): |
189 | bsf %VRAX, %VRAX |
190 | sub %rcx, %rdi |
191 | CHAR_SIZE_SHIFT_REG (rdi) |
192 | addq %rdi, %rax |
193 | ret |
194 | |
195 | .p2align 4,, 10 |
196 | L(first_vec_x1): |
197 | bsf %VRAX, %VRAX |
198 | sub %rcx, %rdi |
199 | CHAR_SIZE_SHIFT_REG (rdi) |
200 | leaq (CHAR_PER_VEC)(%rdi, %rax), %rax |
201 | ret |
202 | |
203 | .p2align 4,, 10 |
204 | /* first_vec_x2 for strlen-ZMM and first_vec_x3 for strlen-YMM. */ |
205 | L(TAIL_RETURN_LBL): |
206 | bsf %VRAX, %VRAX |
207 | sub %VRCX, %VRDI |
208 | CHAR_SIZE_SHIFT_REG (VRDI) |
209 | lea (TAIL_RETURN_OFFSET)(%rdi, %rax), %VRAX |
210 | ret |
211 | |
212 | .p2align 4,, 8 |
213 | L(cross_page_boundary): |
214 | movq %rdi, %rcx |
215 | /* Align data to VEC_SIZE. */ |
216 | andq $-VEC_SIZE, %rdi |
217 | |
218 | VPCMPEQ (%rdi), %VZERO, %k0 |
219 | |
220 | KMOV %k0, %VRAX |
221 | # ifdef USE_AS_WCSLEN |
222 | movl %ecx, %edx |
223 | shrl $2, %edx |
224 | andl $(CHAR_PER_VEC - 1), %edx |
225 | shrx %edx, %eax, %eax |
226 | testl %eax, %eax |
227 | # else |
228 | shr %cl, %VRAX |
229 | # endif |
230 | jz L(cross_page_continue) |
231 | bsf %VRAX, %VRAX |
232 | ret |
233 | |
234 | END(STRLEN) |
235 | #endif |
236 | |