1 /* Optimized strcmp implementation for PowerPC32.
2 Copyright (C) 2003-2013 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/>. */
23 /* See strlen.s for comments on how the end-of-string testing works. */
25 /* int [r3] strncmp (const char *s1 [r3], const char *s2 [r4], size_t size [r5]) */
27 EALIGN (BP_SYM(strncmp), 4, 0)
31 #define rSTR1 r3 /* first string arg */
32 #define rSTR2 r4 /* second string arg */
33 #define rN r5 /* max string length */
34 /* Note: The Bounded pointer support in this code is broken. This code
35 was inherited from PPC32 and that support was never completed.
36 Current PPC gcc does not support -fbounds-check or -fbounded-pointers. */
37 #define rWORD1 r6 /* current word in s1 */
38 #define rWORD2 r7 /* current word in s2 */
41 #define rFEFE r8 /* constant 0xfefefeff (-0x01010101) */
42 #define r7F7F r9 /* constant 0x7f7f7f7f */
43 #define rNEG r10 /* ~(word in s1 | 0x7f7f7f7f) */
44 #define rBITDIF r11 /* bits that differ in s1 & s2 words */
50 clrlwi. rTMP, rTMP, 30
54 /* We are word aligned so set up for two loops. first a word
55 loop, then fall into the byte loop if any residual. */
58 addi rFEFE, rFEFE, -0x101
59 addi r7F7F, r7F7F, 0x7f7f
63 mtctr rTMP /* Power4 wants mtctr 1st in dispatch group. */
70 bne- cr1, L(different)
72 L(g1): add rTMP, rFEFE, rWORD1
73 nor rNEG, r7F7F, rWORD1
76 cmpw cr1, rWORD1, rWORD2
79 /* OK. We've hit the end of the string. We need to be careful that
80 we don't compare two strings as different because of gunk beyond
81 the end of the strings... */
84 and rTMP, r7F7F, rWORD1
87 xor. rBITDIF, rWORD1, rWORD2
91 cntlzw rBITDIF, rBITDIF
94 cmpw cr1, rNEG, rBITDIF
95 sub rRTN, rWORD1, rWORD2
105 lwzu rWORD1, -4(rSTR1)
106 xor. rBITDIF, rWORD1, rWORD2
107 sub rRTN, rWORD1, rWORD2
113 srwi rWORD2, rWORD2, 24
114 srwi rWORD1, rWORD1, 24
115 sub rRTN, rWORD1, rWORD2
119 /* Oh well. In this case, we just do a byte-by-byte comparison. */
122 and. rTMP, rTMP, rNEG
123 cmpw cr1, rWORD1, rWORD2
126 bne- cr1, L(different)
130 mtctr rN /* Power4 wants mtctr 1st in dispatch group */
142 lbzu rWORD3, 1(rSTR1)
143 lbzu rWORD4, 1(rSTR2)
149 lbzu rWORD1, 1(rSTR1)
150 lbzu rWORD2, 1(rSTR2)
156 lbzu rWORD3, 1(rSTR1)
157 lbzu rWORD4, 1(rSTR2)
163 lbzu rWORD1, 1(rSTR1)
164 lbzu rWORD2, 1(rSTR2)
167 L(u3): sub rRTN, rWORD3, rWORD4
169 L(u4): sub rRTN, rWORD1, rWORD2
174 END (BP_SYM (strncmp))
175 libc_hidden_builtin_def (strncmp)