xref: /openbmc/linux/arch/microblaze/lib/memmove.c (revision 82ced6fd)
1 /*
2  * Copyright (C) 2008-2009 Michal Simek <monstr@monstr.eu>
3  * Copyright (C) 2008-2009 PetaLogix
4  * Copyright (C) 2007 John Williams
5  *
6  * Reasonably optimised generic C-code for memcpy on Microblaze
7  * This is generic C code to do efficient, alignment-aware memmove.
8  *
9  * It is based on demo code originally Copyright 2001 by Intel Corp, taken from
10  * http://www.embedded.com/showArticle.jhtml?articleID=19205567
11  *
12  * Attempts were made, unsuccesfully, to contact the original
13  * author of this code (Michael Morrow, Intel).  Below is the original
14  * copyright notice.
15  *
16  * This software has been developed by Intel Corporation.
17  * Intel specifically disclaims all warranties, express or
18  * implied, and all liability, including consequential and
19  * other indirect damages, for the use of this program, including
20  * liability for infringement of any proprietary rights,
21  * and including the warranties of merchantability and fitness
22  * for a particular purpose. Intel does not assume any
23  * responsibility for and errors which may appear in this program
24  * not any responsibility to update it.
25  */
26 
27 #include <linux/types.h>
28 #include <linux/stddef.h>
29 #include <linux/compiler.h>
30 #include <linux/module.h>
31 #include <linux/string.h>
32 
33 #ifdef __HAVE_ARCH_MEMMOVE
34 void *memmove(void *v_dst, const void *v_src, __kernel_size_t c)
35 {
36 	const char *src = v_src;
37 	char *dst = v_dst;
38 
39 #ifdef CONFIG_OPT_LIB_FUNCTION
40 	const uint32_t *i_src;
41 	uint32_t *i_dst;
42 #endif
43 
44 	if (!c)
45 		return v_dst;
46 
47 	/* Use memcpy when source is higher than dest */
48 	if (v_dst <= v_src)
49 		return memcpy(v_dst, v_src, c);
50 
51 #ifndef CONFIG_OPT_LIB_FUNCTION
52 	/* copy backwards, from end to beginning */
53 	src += c;
54 	dst += c;
55 
56 	/* Simple, byte oriented memmove. */
57 	while (c--)
58 		*--dst = *--src;
59 
60 	return v_dst;
61 #else
62 	/* The following code tries to optimize the copy by using unsigned
63 	 * alignment. This will work fine if both source and destination are
64 	 * aligned on the same boundary. However, if they are aligned on
65 	 * different boundaries shifts will be necessary. This might result in
66 	 * bad performance on MicroBlaze systems without a barrel shifter.
67 	 */
68 	/* FIXME this part needs more test */
69 	/* Do a descending copy - this is a bit trickier! */
70 	dst += c;
71 	src += c;
72 
73 	if (c >= 4) {
74 		unsigned  value, buf_hold;
75 
76 		/* Align the destination to a word boundry. */
77 		/* This is done in an endian independant manner. */
78 
79 		switch ((unsigned long)dst & 3) {
80 		case 3:
81 			*--dst = *--src;
82 			--c;
83 		case 2:
84 			*--dst = *--src;
85 			--c;
86 		case 1:
87 			*--dst = *--src;
88 			--c;
89 		}
90 
91 		i_dst = (void *)dst;
92 		/* Choose a copy scheme based on the source */
93 		/* alignment relative to dstination. */
94 		switch ((unsigned long)src & 3) {
95 		case 0x0:	/* Both byte offsets are aligned */
96 
97 			i_src  = (const void *)src;
98 
99 			for (; c >= 4; c -= 4)
100 				*--i_dst = *--i_src;
101 
102 			src  = (const void *)i_src;
103 			break;
104 		case 0x1:	/* Unaligned - Off by 1 */
105 			/* Word align the source */
106 			i_src = (const void *) (((unsigned)src + 4) & ~3);
107 
108 			/* Load the holding buffer */
109 			buf_hold = *--i_src >> 24;
110 
111 			for (; c >= 4; c -= 4) {
112 				value = *--i_src;
113 				*--i_dst = buf_hold << 8 | value;
114 				buf_hold = value >> 24;
115 			}
116 
117 			/* Realign the source */
118 			src = (const void *)i_src;
119 			src += 1;
120 			break;
121 		case 0x2:	/* Unaligned - Off by 2 */
122 			/* Word align the source */
123 			i_src = (const void *) (((unsigned)src + 4) & ~3);
124 
125 			/* Load the holding buffer */
126 			buf_hold = *--i_src >> 16;
127 
128 			for (; c >= 4; c -= 4) {
129 				value = *--i_src;
130 				*--i_dst = buf_hold << 16 | value;
131 				buf_hold = value >> 16;
132 			}
133 
134 			/* Realign the source */
135 			src = (const void *)i_src;
136 			src += 2;
137 			break;
138 		case 0x3:	/* Unaligned - Off by 3 */
139 			/* Word align the source */
140 			i_src = (const void *) (((unsigned)src + 4) & ~3);
141 
142 			/* Load the holding buffer */
143 			buf_hold = *--i_src >> 8;
144 
145 			for (; c >= 4; c -= 4) {
146 				value = *--i_src;
147 				*--i_dst = buf_hold << 24 | value;
148 				buf_hold = value >> 8;
149 			}
150 
151 			/* Realign the source */
152 			src = (const void *)i_src;
153 			src += 3;
154 			break;
155 		}
156 		dst = (void *)i_dst;
157 	}
158 
159 	/* simple fast copy, ... unless a cache boundry is crossed */
160 	/* Finish off any remaining bytes */
161 	switch (c) {
162 	case 4:
163 		*--dst = *--src;
164 	case 3:
165 		*--dst = *--src;
166 	case 2:
167 		*--dst = *--src;
168 	case 1:
169 		*--dst = *--src;
170 	}
171 	return v_dst;
172 #endif
173 }
174 EXPORT_SYMBOL(memmove);
175 #endif /* __HAVE_ARCH_MEMMOVE */
176