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1 | /* |
2 | * arch/xtensa/lib/memset.S | |
3 | * | |
4 | * ANSI C standard library function memset | |
5 | * (Well, almost. .fixup code might return zero.) | |
6 | * | |
7 | * This file is subject to the terms and conditions of the GNU General | |
8 | * Public License. See the file "COPYING" in the main directory of | |
9 | * this archive for more details. | |
10 | * | |
11 | * Copyright (C) 2002 Tensilica Inc. | |
12 | */ | |
13 | ||
173d6681 | 14 | #include <asm/variant/core.h> |
249ac17e CZ |
15 | |
16 | /* | |
17 | * void *memset(void *dst, int c, size_t length) | |
18 | * | |
19 | * The algorithm is as follows: | |
20 | * Create a word with c in all byte positions | |
21 | * If the destination is aligned, | |
22 | * do 16B chucks with a loop, and then finish up with | |
23 | * 8B, 4B, 2B, and 1B stores conditional on the length. | |
24 | * If destination is unaligned, align it by conditionally | |
25 | * setting 1B and 2B and then go to aligned case. | |
26 | * This code tries to use fall-through branches for the common | |
27 | * case of an aligned destination (except for the branches to | |
28 | * the alignment labels). | |
29 | */ | |
30 | ||
31 | /* Load or store instructions that may cause exceptions use the EX macro. */ | |
32 | ||
33 | #define EX(insn,reg1,reg2,offset,handler) \ | |
34 | 9: insn reg1, reg2, offset; \ | |
35 | .section __ex_table, "a"; \ | |
36 | .word 9b, handler; \ | |
37 | .previous | |
38 | ||
39 | ||
40 | .text | |
41 | .align 4 | |
42 | .global memset | |
43 | .type memset,@function | |
44 | memset: | |
45 | entry sp, 16 # minimal stack frame | |
46 | # a2/ dst, a3/ c, a4/ length | |
47 | extui a3, a3, 0, 8 # mask to just 8 bits | |
48 | slli a7, a3, 8 # duplicate character in all bytes of word | |
49 | or a3, a3, a7 # ... | |
50 | slli a7, a3, 16 # ... | |
51 | or a3, a3, a7 # ... | |
52 | mov a5, a2 # copy dst so that a2 is return value | |
53 | movi a6, 3 # for alignment tests | |
54 | bany a2, a6, .Ldstunaligned # if dst is unaligned | |
55 | .L0: # return here from .Ldstunaligned when dst is aligned | |
56 | srli a7, a4, 4 # number of loop iterations with 16B | |
57 | # per iteration | |
58 | bnez a4, .Laligned | |
59 | retw | |
60 | ||
61 | /* | |
62 | * Destination is word-aligned. | |
63 | */ | |
64 | # set 16 bytes per iteration for word-aligned dst | |
65 | .align 4 # 1 mod 4 alignment for LOOPNEZ | |
66 | .byte 0 # (0 mod 4 alignment for LBEG) | |
67 | .Laligned: | |
68 | #if XCHAL_HAVE_LOOPS | |
69 | loopnez a7, .Loop1done | |
70 | #else /* !XCHAL_HAVE_LOOPS */ | |
71 | beqz a7, .Loop1done | |
72 | slli a6, a7, 4 | |
73 | add a6, a6, a5 # a6 = end of last 16B chunk | |
74 | #endif /* !XCHAL_HAVE_LOOPS */ | |
75 | .Loop1: | |
76 | EX(s32i, a3, a5, 0, memset_fixup) | |
77 | EX(s32i, a3, a5, 4, memset_fixup) | |
78 | EX(s32i, a3, a5, 8, memset_fixup) | |
79 | EX(s32i, a3, a5, 12, memset_fixup) | |
80 | addi a5, a5, 16 | |
81 | #if !XCHAL_HAVE_LOOPS | |
82 | blt a5, a6, .Loop1 | |
83 | #endif /* !XCHAL_HAVE_LOOPS */ | |
84 | .Loop1done: | |
85 | bbci.l a4, 3, .L2 | |
86 | # set 8 bytes | |
87 | EX(s32i, a3, a5, 0, memset_fixup) | |
88 | EX(s32i, a3, a5, 4, memset_fixup) | |
89 | addi a5, a5, 8 | |
90 | .L2: | |
91 | bbci.l a4, 2, .L3 | |
92 | # set 4 bytes | |
93 | EX(s32i, a3, a5, 0, memset_fixup) | |
94 | addi a5, a5, 4 | |
95 | .L3: | |
96 | bbci.l a4, 1, .L4 | |
97 | # set 2 bytes | |
98 | EX(s16i, a3, a5, 0, memset_fixup) | |
99 | addi a5, a5, 2 | |
100 | .L4: | |
101 | bbci.l a4, 0, .L5 | |
102 | # set 1 byte | |
103 | EX(s8i, a3, a5, 0, memset_fixup) | |
104 | .L5: | |
105 | .Lret1: | |
106 | retw | |
107 | ||
108 | /* | |
109 | * Destination is unaligned | |
110 | */ | |
111 | ||
112 | .Ldstunaligned: | |
113 | bltui a4, 8, .Lbyteset # do short copies byte by byte | |
114 | bbci.l a5, 0, .L20 # branch if dst alignment half-aligned | |
115 | # dst is only byte aligned | |
116 | # set 1 byte | |
117 | EX(s8i, a3, a5, 0, memset_fixup) | |
118 | addi a5, a5, 1 | |
119 | addi a4, a4, -1 | |
120 | # now retest if dst aligned | |
121 | bbci.l a5, 1, .L0 # if now aligned, return to main algorithm | |
122 | .L20: | |
123 | # dst half-aligned | |
124 | # set 2 bytes | |
125 | EX(s16i, a3, a5, 0, memset_fixup) | |
126 | addi a5, a5, 2 | |
127 | addi a4, a4, -2 | |
128 | j .L0 # dst is now aligned, return to main algorithm | |
129 | ||
130 | /* | |
131 | * Byte by byte set | |
132 | */ | |
133 | .align 4 | |
134 | .byte 0 # 1 mod 4 alignment for LOOPNEZ | |
135 | # (0 mod 4 alignment for LBEG) | |
136 | .Lbyteset: | |
137 | #if XCHAL_HAVE_LOOPS | |
138 | loopnez a4, .Lbytesetdone | |
139 | #else /* !XCHAL_HAVE_LOOPS */ | |
140 | beqz a4, .Lbytesetdone | |
141 | add a6, a5, a4 # a6 = ending address | |
142 | #endif /* !XCHAL_HAVE_LOOPS */ | |
143 | .Lbyteloop: | |
144 | EX(s8i, a3, a5, 0, memset_fixup) | |
145 | addi a5, a5, 1 | |
146 | #if !XCHAL_HAVE_LOOPS | |
147 | blt a5, a6, .Lbyteloop | |
148 | #endif /* !XCHAL_HAVE_LOOPS */ | |
149 | .Lbytesetdone: | |
150 | retw | |
151 | ||
152 | ||
153 | .section .fixup, "ax" | |
154 | .align 4 | |
155 | ||
156 | /* We return zero if a failure occurred. */ | |
157 | ||
158 | memset_fixup: | |
159 | movi a2, 0 | |
160 | retw |