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Chris Zankel249ac172005-06-23 22:01:20 -07001/*
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
Chris Zankel367b8112008-11-06 06:40:46 -080014#include <variant/core.h>
Chris Zankel249ac172005-06-23 22:01:20 -070015
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) \
349: 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
44memset:
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
158memset_fixup:
159 movi a2, 0
160 retw