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 */
39 #define rFEFE r8 /* constant 0xfefefeff (-0x01010101) */
40 #define r7F7F r9 /* constant 0x7f7f7f7f */
41 #define rNEG r10 /* ~(word in s1 | 0x7f7f7f7f) */
42 #define rBITDIF r11 /* bits that differ in s1 & s2 words */
48 clrlwi. rTMP, rTMP, 30
52 /* We are word aligned so set up for two loops. first a word
53 loop, then fall into the byte loop if any residual. */
56 addi rFEFE, rFEFE, -0x101
57 addi r7F7F, r7F7F, 0x7f7f
61 mtctr rTMP /* Power4 wants mtctr 1st in dispatch group. */
68 bne- cr1, L(different)
70 L(g1): add rTMP, rFEFE, rWORD1
71 nor rNEG, r7F7F, rWORD1
74 cmpw cr1, rWORD1, rWORD2
77 /* OK. We've hit the end of the string. We need to be careful that
78 we don't compare two strings as different because of gunk beyond
79 the end of the strings... */
82 and rTMP, r7F7F, rWORD1
85 xor. rBITDIF, rWORD1, rWORD2
89 cntlzw rBITDIF, rBITDIF
92 cmpw cr1, rNEG, rBITDIF
93 sub rRTN, rWORD1, rWORD2
103 lwzu rWORD1, -4(rSTR1)
104 xor. rBITDIF, rWORD1, rWORD2
105 sub rRTN, rWORD1, rWORD2
111 srwi rWORD2, rWORD2, 24
112 srwi rWORD1, rWORD1, 24
113 sub rRTN, rWORD1, rWORD2
117 /* Oh well. In this case, we just do a byte-by-byte comparison. */
120 and. rTMP, rTMP, rNEG
121 cmpw cr1, rWORD1, rWORD2
124 bne- cr1, L(different)
128 mtctr rN /* Power4 wants mtctr 1st in dispatch group */
140 lbzu rWORD2, 1(rSTR2)
146 lbzu rWORD1, 1(rSTR1)
148 lbzu rWORD2, 1(rSTR2)
153 lbzu rWORD1, 1(rSTR1)
156 L(u2): lbzu rWORD1, -1(rSTR1)
157 L(u3): sub rRTN, rWORD1, rWORD2
159 END (BP_SYM (strncmp))
160 libc_hidden_builtin_def (strncmp)