1 /* Optimized strcmp implementation for PowerPC.
2 Copyright (C) 1997-2023 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 <https://www.gnu.org/licenses/>. */
21 /* See strlen.s for comments on how the end-of-string testing works. */
23 /* int [r3] strcmp (const char *s1 [r3], const char *s2 [r4]) */
29 #define rSTR1 r3 /* first string arg */
30 #define rSTR2 r4 /* second string arg */
31 #define rWORD1 r5 /* current word in s1 */
32 #define rWORD2 r6 /* current word in s2 */
33 #define rFEFE r7 /* constant 0xfefefeff (-0x01010101) */
34 #define r7F7F r8 /* constant 0x7f7f7f7f */
35 #define rNEG r9 /* ~(word in s1 | 0x7f7f7f7f) */
36 #define rBITDIF r10 /* bits that differ in s1 & s2 words */
41 clrlwi. rTMP, rTMP, 30
48 addi rFEFE, rFEFE, -0x101
49 addi r7F7F, r7F7F, 0x7f7f
52 L(g0): lwzu rWORD1, 4(rSTR1)
55 L(g1): add rTMP, rFEFE, rWORD1
56 nor rNEG, r7F7F, rWORD1
58 cmpw cr1, rWORD1, rWORD2
61 /* OK. We've hit the end of the string. We need to be careful that
62 we don't compare two strings as different because of gunk beyond
63 the end of the strings... */
64 #ifdef __LITTLE_ENDIAN__
67 andc rTMP2, rTMP2, rTMP
68 rlwimi rTMP2, rTMP2, 1, 0, 30
69 and rWORD2, rWORD2, rTMP2 /* Mask off gunk. */
70 and rWORD1, rWORD1, rTMP2
71 rlwinm rTMP2, rWORD2, 8, 0xffffffff /* Byte reverse word. */
72 rlwinm rTMP, rWORD1, 8, 0xffffffff
73 rlwimi rTMP2, rWORD2, 24, 0, 7
74 rlwimi rTMP, rWORD1, 24, 0, 7
75 rlwimi rTMP2, rWORD2, 24, 16, 23
76 rlwimi rTMP, rWORD1, 24, 16, 23
77 xor. rBITDIF, rTMP, rTMP2
85 rlwinm rTMP2, rWORD2, 8, 0xffffffff /* Byte reverse word. */
86 rlwinm rTMP, rWORD1, 8, 0xffffffff
87 rlwimi rTMP2, rWORD2, 24, 0, 7
88 rlwimi rTMP, rWORD1, 24, 0, 7
89 rlwimi rTMP2, rWORD2, 24, 16, 23
90 rlwimi rTMP, rWORD1, 24, 16, 23
91 xor. rBITDIF, rTMP, rTMP2
99 and rTMP, r7F7F, rWORD1
101 add rTMP, rTMP, r7F7F
102 xor. rBITDIF, rWORD1, rWORD2
103 andc rNEG, rNEG, rTMP
105 cntlzw rBITDIF, rBITDIF
108 cmpw cr1, rNEG, rBITDIF
109 sub rRTN, rWORD1, rWORD2
116 lwz rWORD1, -4(rSTR1)
117 xor. rBITDIF, rWORD1, rWORD2
118 sub rRTN, rWORD1, rWORD2
125 /* Oh well. In this case, we just do a byte-by-byte comparison. */
132 L(u0): lbzu rWORD1, 1(rSTR1)
134 lbzu rWORD2, 1(rSTR2)
135 L(u1): cmpwi cr1, rWORD1, 0
139 lbzu rWORD1, 1(rSTR1)
140 lbzu rWORD2, 1(rSTR2)
144 L(u3): sub rRTN, rWORD1, rWORD2
146 L(u4): lbz rWORD1, -1(rSTR1)
147 sub rRTN, rWORD1, rWORD2
150 libc_hidden_builtin_def (strcmp)