aboutsummaryrefslogtreecommitdiffstats
path: root/arch/x86_64/lib/memset.S
blob: 09ed1f6b0eaa2c9037abb072db6bd4684d8bb6c2 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
/* Copyright 2002 Andi Kleen, SuSE Labs */

#include <linux/config.h>
#include <linux/linkage.h>
#include <asm/dwarf2.h>

/*
 * ISO C memset - set a memory block to a byte value.
 *	
 * rdi   destination
 * rsi   value (char) 
 * rdx   count (bytes) 
 * 
 * rax   original destination
 */	
	ALIGN
memset_c:
	CFI_STARTPROC
	movq %rdi,%r9
	movl %edx,%r8d
	andl $7,%r8d
	movl %edx,%ecx
	shrl $3,%ecx
	/* expand byte value  */
	movzbl %sil,%esi
	movabs $0x0101010101010101,%rax
	mulq %rsi		/* with rax, clobbers rdx */
	rep stosq
	movl %r8d,%ecx
	rep stosb
	movq %r9,%rax
	ret
	CFI_ENDPROC
ENDPROC(memset_c)

ENTRY(memset)
ENTRY(__memset)
	CFI_STARTPROC
	movq %rdi,%r10
	movq %rdx,%r11

	/* expand byte value  */
	movzbl %sil,%ecx
	movabs $0x0101010101010101,%rax
	mul    %rcx		/* with rax, clobbers rdx */

	/* align dst */
	movl  %edi,%r9d
	andl  $7,%r9d
	jnz  .Lbad_alignment
	CFI_REMEMBER_STATE
.Lafter_bad_alignment:

	movl %r11d,%ecx
	shrl $6,%ecx
	jz	 .Lhandle_tail

	.p2align 4
.Lloop_64:
	decl   %ecx
	movq  %rax,(%rdi)
	movq  %rax,8(%rdi)
	movq  %rax,16(%rdi)
	movq  %rax,24(%rdi)
	movq  %rax,32(%rdi)
	movq  %rax,40(%rdi)
	movq  %rax,48(%rdi)
	movq  %rax,56(%rdi)
	leaq  64(%rdi),%rdi
	jnz    .Lloop_64

	/* Handle tail in loops. The loops should be faster than hard
	   to predict jump tables. */
	.p2align 4
.Lhandle_tail:
	movl	%r11d,%ecx
	andl    $63&(~7),%ecx
	jz 		.Lhandle_7
	shrl	$3,%ecx
	.p2align 4
.Lloop_8:
	decl   %ecx
	movq  %rax,(%rdi)
	leaq  8(%rdi),%rdi
	jnz    .Lloop_8

.Lhandle_7:
	movl	%r11d,%ecx
	andl	$7,%ecx
	jz      .Lende
	.p2align 4
.Lloop_1:
	decl    %ecx
	movb 	%al,(%rdi)
	leaq	1(%rdi),%rdi
	jnz     .Lloop_1

.Lende:
	movq	%r10,%rax
	ret

	CFI_RESTORE_STATE
.Lbad_alignment:
	cmpq $7,%r11
	jbe	.Lhandle_7
	movq %rax,(%rdi)	/* unaligned store */
	movq $8,%r8
	subq %r9,%r8
	addq %r8,%rdi
	subq %r8,%r11
	jmp .Lafter_bad_alignment
.Lfinal:
	CFI_ENDPROC
ENDPROC(memset)
ENDPROC(__memset)

	/* Some CPUs run faster using the string instructions.
	   It is also a lot simpler. Use this when possible */

#include <asm/cpufeature.h>

	.section .altinstr_replacement,"ax"
1:	.byte 0xeb				/* jmp <disp8> */
	.byte (memset_c - memset) - (2f - 1b)	/* offset */
2:
	.previous
	.section .altinstructions,"a"
	.align 8
	.quad memset
	.quad 1b
	.byte X86_FEATURE_REP_GOOD
	.byte .Lfinal - memset
	.byte 2b - 1b
	.previous