xref: /linux/arch/riscv/lib/memset.S (revision ae99fb8baafc881b35aa0b79d7ac0178a7c40c89) 
1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 * Copyright (C) 2013 Regents of the University of California
4 */
5
6
7#include <linux/linkage.h>
8#include <asm/asm.h>
9
10/* void *memset(void *, int, size_t) */
11ENTRY(__memset)
12WEAK(memset)
13	move t0, a0  /* Preserve return value */
14
15	/* Defer to byte-oriented fill for small sizes */
16	sltiu a3, a2, 16
17	bnez a3, 4f
18
19	/*
20	 * Round to nearest XLEN-aligned address
21	 * greater than or equal to start address
22	 */
23	addi a3, t0, SZREG-1
24	andi a3, a3, ~(SZREG-1)
25	beq a3, t0, 2f  /* Skip if already aligned */
26	/* Handle initial misalignment */
27	sub a4, a3, t0
281:
29	sb a1, 0(t0)
30	addi t0, t0, 1
31	bltu t0, a3, 1b
32	sub a2, a2, a4  /* Update count */
33
342: /* Duff's device with 32 XLEN stores per iteration */
35	/* Broadcast value into all bytes */
36	andi a1, a1, 0xff
37	slli a3, a1, 8
38	or a1, a3, a1
39	slli a3, a1, 16
40	or a1, a3, a1
41#ifdef CONFIG_64BIT
42	slli a3, a1, 32
43	or a1, a3, a1
44#endif
45
46	/* Calculate end address */
47	andi a4, a2, ~(SZREG-1)
48	add a3, t0, a4
49
50	andi a4, a4, 31*SZREG  /* Calculate remainder */
51	beqz a4, 3f            /* Shortcut if no remainder */
52	neg a4, a4
53	addi a4, a4, 32*SZREG  /* Calculate initial offset */
54
55	/* Adjust start address with offset */
56	sub t0, t0, a4
57
58	/* Jump into loop body */
59	/* Assumes 32-bit instruction lengths */
60	la a5, 3f
61#ifdef CONFIG_64BIT
62	srli a4, a4, 1
63#endif
64	add a5, a5, a4
65	jr a5
663:
67	REG_S a1,        0(t0)
68	REG_S a1,    SZREG(t0)
69	REG_S a1,  2*SZREG(t0)
70	REG_S a1,  3*SZREG(t0)
71	REG_S a1,  4*SZREG(t0)
72	REG_S a1,  5*SZREG(t0)
73	REG_S a1,  6*SZREG(t0)
74	REG_S a1,  7*SZREG(t0)
75	REG_S a1,  8*SZREG(t0)
76	REG_S a1,  9*SZREG(t0)
77	REG_S a1, 10*SZREG(t0)
78	REG_S a1, 11*SZREG(t0)
79	REG_S a1, 12*SZREG(t0)
80	REG_S a1, 13*SZREG(t0)
81	REG_S a1, 14*SZREG(t0)
82	REG_S a1, 15*SZREG(t0)
83	REG_S a1, 16*SZREG(t0)
84	REG_S a1, 17*SZREG(t0)
85	REG_S a1, 18*SZREG(t0)
86	REG_S a1, 19*SZREG(t0)
87	REG_S a1, 20*SZREG(t0)
88	REG_S a1, 21*SZREG(t0)
89	REG_S a1, 22*SZREG(t0)
90	REG_S a1, 23*SZREG(t0)
91	REG_S a1, 24*SZREG(t0)
92	REG_S a1, 25*SZREG(t0)
93	REG_S a1, 26*SZREG(t0)
94	REG_S a1, 27*SZREG(t0)
95	REG_S a1, 28*SZREG(t0)
96	REG_S a1, 29*SZREG(t0)
97	REG_S a1, 30*SZREG(t0)
98	REG_S a1, 31*SZREG(t0)
99	addi t0, t0, 32*SZREG
100	bltu t0, a3, 3b
101	andi a2, a2, SZREG-1  /* Update count */
102
1034:
104	/* Handle trailing misalignment */
105	beqz a2, 6f
106	add a3, t0, a2
1075:
108	sb a1, 0(t0)
109	addi t0, t0, 1
110	bltu t0, a3, 5b
1116:
112	ret
113END(__memset)
114