1 /* Optimized strcmp implementation for PowerPC32.
2 Copyright (C) 2003-2017 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/>. */
21 /* See strlen.s for comments on how the end-of-string testing works. */
23 /* int [r3] strncmp (const char *s1 [r3], const char *s2 [r4], size_t size [r5]) */
25 EALIGN (strncmp, 4, 0)
29 #define rSTR1 r3 /* first string arg */
30 #define rSTR2 r4 /* second string arg */
31 #define rN r5 /* max string length */
32 #define rWORD1 r6 /* current word in s1 */
33 #define rWORD2 r7 /* current word in s2 */
34 #define rFEFE r8 /* constant 0xfefefeff (-0x01010101) */
35 #define r7F7F r9 /* constant 0x7f7f7f7f */
36 #define rNEG r10 /* ~(word in s1 | 0x7f7f7f7f) */
37 #define rBITDIF r11 /* bits that differ in s1 & s2 words */
44 clrlwi. rTMP, rTMP, 30
48 /* We are word aligned so set up for two loops. first a word
49 loop, then fall into the byte loop if any residual. */
52 addi rFEFE, rFEFE, -0x101
53 addi r7F7F, r7F7F, 0x7f7f
57 mtctr rTMP /* Power4 wants mtctr 1st in dispatch group. */
64 bne- cr1, L(different)
66 L(g1): add rTMP, rFEFE, rWORD1
67 nor rNEG, r7F7F, rWORD1
70 cmpw cr1, rWORD1, rWORD2
73 /* OK. We've hit the end of the string. We need to be careful that
74 we don't compare two strings as different because of gunk beyond
75 the end of the strings... */
77 #ifdef __LITTLE_ENDIAN__
81 andc rTMP2, rTMP2, rTMP
82 and rWORD2, rWORD2, rTMP2 /* Mask off gunk. */
83 and rWORD1, rWORD1, rTMP2
84 rlwinm rTMP2, rWORD2, 8, 0xffffffff /* Byte reverse word. */
85 rlwinm rTMP, rWORD1, 8, 0xffffffff
86 rlwimi rTMP2, rWORD2, 24, 0, 7
87 rlwimi rTMP, rWORD1, 24, 0, 7
88 rlwimi rTMP2, rWORD2, 24, 16, 23
89 rlwimi rTMP, rWORD1, 24, 16, 23
90 xor. rBITDIF, rTMP, rTMP2
98 rlwinm rTMP2, rWORD2, 8, 0xffffffff /* Byte reverse word. */
99 rlwinm rTMP, rWORD1, 8, 0xffffffff
100 rlwimi rTMP2, rWORD2, 24, 0, 7
101 rlwimi rTMP, rWORD1, 24, 0, 7
102 rlwimi rTMP2, rWORD2, 24, 16, 23
103 rlwimi rTMP, rWORD1, 24, 16, 23
104 xor. rBITDIF, rTMP, rTMP2
105 sub rRTN, rTMP, rTMP2
112 and rTMP, r7F7F, rWORD1
114 add rTMP, rTMP, r7F7F
115 xor. rBITDIF, rWORD1, rWORD2
116 andc rNEG, rNEG, rTMP
118 cntlzw rBITDIF, rBITDIF
121 cmpw cr1, rNEG, rBITDIF
122 sub rRTN, rWORD1, rWORD2
129 lwz rWORD1, -4(rSTR1)
130 xor. rBITDIF, rWORD1, rWORD2
131 sub rRTN, rWORD1, rWORD2
138 /* Oh well. In this case, we just do a byte-by-byte comparison. */
141 and. rTMP, rTMP, rNEG
142 cmpw cr1, rWORD1, rWORD2
145 bne- cr1, L(different)
149 mtctr rN /* Power4 wants mtctr 1st in dispatch group */
161 lbzu rWORD2, 1(rSTR2)
167 lbzu rWORD1, 1(rSTR1)
169 lbzu rWORD2, 1(rSTR2)
174 lbzu rWORD1, 1(rSTR1)
177 L(u2): lbzu rWORD1, -1(rSTR1)
178 L(u3): sub rRTN, rWORD1, rWORD2
181 libc_hidden_builtin_def (strncmp)