1 /* Optimized strcmp for Xtensa.
2 Copyright (C) 2001, 2007 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
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.
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.
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 <http://www.gnu.org/licenses/>. */
20 #include <bits/xtensa-config.h>
24 #define MASK0 0xff000000
25 #define MASK1 0x00ff0000
26 #define MASK2 0x0000ff00
27 #define MASK3 0x000000ff
29 #define MASK0 0x000000ff
30 #define MASK1 0x0000ff00
31 #define MASK2 0x00ff0000
32 #define MASK3 0xff000000
35 #define MASK4 0x40404040
40 .literal .Lmask0, MASK0
41 .literal .Lmask1, MASK1
42 .literal .Lmask2, MASK2
43 .literal .Lmask3, MASK3
44 .literal .Lmask4, MASK4
46 /* a2 = s1, a3 = s2 */
48 l8ui a8, a2, 0 /* byte 0 from s1 */
49 l8ui a9, a3, 0 /* byte 0 from s2 */
50 movi a10, 3 /* mask */
54 bnone a11, a10, .Laligned
56 xor a11, a2, a3 /* compare low two bits of s1 and s2 */
57 bany a11, a10, .Lunaligned /* if they have different alignment */
59 /* s1/s2 are not word-aligned. */
60 addi a2, a2, 1 /* advance s1 */
61 beqz a8, .Leq /* bytes equal, if zero, strings are equal */
62 addi a3, a3, 1 /* advance s2 */
63 bnone a2, a10, .Laligned /* if s1/s2 now aligned */
64 l8ui a8, a2, 0 /* byte 1 from s1 */
65 l8ui a9, a3, 0 /* byte 1 from s2 */
66 addi a2, a2, 1 /* advance s1 */
67 bne a8, a9, .Lretdiff /* if different, return difference */
68 beqz a8, .Leq /* bytes equal, if zero, strings are equal */
69 addi a3, a3, 1 /* advance s2 */
70 bnone a2, a10, .Laligned /* if s1/s2 now aligned */
71 l8ui a8, a2, 0 /* byte 2 from s1 */
72 l8ui a9, a3, 0 /* byte 2 from s2 */
73 addi a2, a2, 1 /* advance s1 */
74 bne a8, a9, .Lretdiff /* if different, return difference */
75 beqz a8, .Leq /* bytes equal, if zero, strings are equal */
76 addi a3, a3, 1 /* advance s2 */
79 /* s1 and s2 have different alignment.
81 If the zero-overhead loop option is available, use an (almost)
82 infinite zero-overhead loop with conditional exits so we only pay
83 for taken branches when exiting the loop.
85 Note: It is important for this unaligned case to come before the
86 code for aligned strings, because otherwise some of the branches
87 above cannot reach and have to be transformed to branches around
88 jumps. The unaligned code is smaller and the branches can reach
92 /* (2 mod 4) alignment for loop instruction */
95 _movi.n a8, 0 /* set up for the maximum loop count */
96 loop a8, .Lretdiff /* loop forever (almost anyway) */
102 bne a8, a9, .Lretdiff
113 /* s1 is word-aligned; s2 is word-aligned.
115 If the zero-overhead loop option is available, use an (almost)
116 infinite zero-overhead loop with conditional exits so we only pay
117 for taken branches when exiting the loop. */
119 /* New algorithm, relying on the fact that all normal ASCII is between
122 Rather than check all bytes for zero:
123 Take one word (4 bytes). Call it w1.
124 Shift w1 left by one into w1'.
125 Or w1 and w1'. For all normal ASCII bit 6 will be 1; for zero it won't.
126 Check that all 4 bit 6's (one for each byte) are one:
127 If they are, we are definitely not done.
128 If they are not, we are probably done, but need to check for zero. */
134 l32r a4, .Lmask0 /* mask for byte 0 */
136 /* Loop forever. (a4 is more than than the maximum number
138 loop a4, .Laligned_done
140 /* First unrolled loop body. */
141 l32i a8, a2, 0 /* get word from s1 */
142 l32i a9, a3, 0 /* get word from s2 */
146 bnall a9, a7, .Lprobeq
148 /* Second unrolled loop body. */
149 l32i a8, a2, 4 /* get word from s1+4 */
150 l32i a9, a3, 4 /* get word from s2+4 */
154 bnall a9, a7, .Lprobeq2
156 addi a2, a2, 8 /* advance s1 pointer */
157 addi a3, a3, 8 /* advance s2 pointer */
159 or a1, a1, a1 /* nop */
162 /* Adjust pointers to account for the loop unrolling. */
166 #else /* !XCHAL_HAVE_LOOPS */
169 movi a4, MASK0 /* mask for byte 0 */
173 addi a2, a2, 4 /* advance s1 pointer */
174 addi a3, a3, 4 /* advance s2 pointer */
176 l32i a8, a2, 0 /* get word from s1 */
177 l32i a9, a3, 0 /* get word from s2 */
181 ball a9, a7, .Lnextword
182 #endif /* !XCHAL_HAVE_LOOPS */
184 /* align (0 mod 4) */
186 /* Words are probably equal, but check for sure.
187 If not, loop over the rest of string using normal algorithm. */
189 bnone a8, a4, .Leq /* if byte 0 is zero */
190 l32r a5, .Lmask1 /* mask for byte 1 */
191 l32r a6, .Lmask2 /* mask for byte 2 */
192 bnone a8, a5, .Leq /* if byte 1 is zero */
193 l32r a7, .Lmask3 /* mask for byte 3 */
194 bnone a8, a6, .Leq /* if byte 2 is zero */
195 bnone a8, a7, .Leq /* if byte 3 is zero */
196 addi.n a2, a2, 4 /* advance s1 pointer */
197 addi.n a3, a3, 4 /* advance s2 pointer */
200 /* align (1 mod 4) */
201 loop a4, .Leq /* loop forever (a4 is bigger than max iters) */
204 l32i a8, a2, 0 /* get word from s1 */
205 l32i a9, a3, 0 /* get word from s2 */
206 addi a2, a2, 4 /* advance s1 pointer */
208 bnone a8, a4, .Leq /* if byte 0 is zero */
209 bnone a8, a5, .Leq /* if byte 1 is zero */
210 bnone a8, a6, .Leq /* if byte 2 is zero */
211 bnone a8, a7, .Leq /* if byte 3 is zero */
212 addi a3, a3, 4 /* advance s2 pointer */
214 #else /* !XCHAL_HAVE_LOOPS */
218 addi a3, a3, 4 /* advance s2 pointer */
220 l32i a8, a2, 0 /* get word from s1 */
221 l32i a9, a3, 0 /* get word from s2 */
222 addi a2, a2, 4 /* advance s1 pointer */
224 bnone a8, a4, .Leq /* if byte 0 is zero */
225 bnone a8, a5, .Leq /* if byte 1 is zero */
226 bnone a8, a6, .Leq /* if byte 2 is zero */
227 bany a8, a7, .Lnextword2 /* if byte 3 is zero */
228 #endif /* !XCHAL_HAVE_LOOPS */
230 /* Words are equal; some byte is zero. */
231 .Leq: movi a2, 0 /* return equal */
234 .Lwne2: /* Words are not equal. On big-endian processors, if none of the
235 bytes are zero, the return value can be determined by a simple
239 bnall a10, a7, .Lsomezero
240 bgeu a8, a9, .Lposreturn
246 .Lsomezero: /* There is probably some zero byte. */
247 #endif /* __XTENSA_EB__ */
248 .Lwne: /* Words are not equal. */
249 xor a2, a8, a9 /* get word with nonzero in byte that differs */
250 bany a2, a4, .Ldiff0 /* if byte 0 differs */
251 movi a5, MASK1 /* mask for byte 1 */
252 bnone a8, a4, .Leq /* if byte 0 is zero */
253 bany a2, a5, .Ldiff1 /* if byte 1 differs */
254 movi a6, MASK2 /* mask for byte 2 */
255 bnone a8, a5, .Leq /* if byte 1 is zero */
256 bany a2, a6, .Ldiff2 /* if byte 2 differs */
257 bnone a8, a6, .Leq /* if byte 2 is zero */
262 /* Byte 0 is equal (at least) and there is a difference before a zero
263 byte. Just subtract words to get the return value.
264 The high order equal bytes cancel, leaving room for the sign. */
269 /* Need to make room for the sign, so can't subtract whole words. */
275 #else /* !__XTENSA_EB__ */
276 /* Little-endian is a little more difficult because can't subtract
279 /* Bytes 0-2 are equal; byte 3 is different.
280 For little-endian need to have a sign bit for the difference. */
287 /* Byte 0 is different. */
294 /* Byte 0 is equal; byte 1 is different. */
301 /* Bytes 0-1 are equal; byte 2 is different. */
307 #endif /* !__XTENSA_EB */
309 libc_hidden_def (strcmp)
311 #ifndef __UCLIBC_HAS_LOCALE__
312 strong_alias (strcmp, strcoll)
313 libc_hidden_def (strcoll)