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1/* SPDX-License-Identifier: GPL-2.0 */
2/* Copyright 2002 Andi Kleen, SuSE Labs */
3
4#include <linux/export.h>
5#include <linux/linkage.h>
6#include <asm/cpufeatures.h>
7#include <asm/alternative.h>
8
9.section .noinstr.text, "ax"
10
11/*
12 * ISO C memset - set a memory block to a byte value. This function uses fast
13 * string to get better performance than the original function. The code is
14 * simpler and shorter than the original function as well.
15 *
16 * rdi destination
17 * rsi value (char)
18 * rdx count (bytes)
19 *
20 * rax original destination
21 *
22 * The FSRS alternative should be done inline (avoiding the call and
23 * the disgusting return handling), but that would require some help
24 * from the compiler for better calling conventions.
25 *
26 * The 'rep stosb' itself is small enough to replace the call, but all
27 * the register moves blow up the code. And two of them are "needed"
28 * only for the return value that is the same as the source input,
29 * which the compiler could/should do much better anyway.
30 */
31SYM_FUNC_START(__memset)
32 ALTERNATIVE "jmp memset_orig", "", X86_FEATURE_FSRS
33
34 movq %rdi,%r9
35 movb %sil,%al
36 movq %rdx,%rcx
37 rep stosb
38 movq %r9,%rax
39 RET
40SYM_FUNC_END(__memset)
41EXPORT_SYMBOL(__memset)
42
43SYM_FUNC_ALIAS_MEMFUNC(memset, __memset)
44EXPORT_SYMBOL(memset)
45
46SYM_FUNC_START_LOCAL(memset_orig)
47 movq %rdi,%r10
48
49 /* expand byte value */
50 movzbl %sil,%ecx
51 movabs $0x0101010101010101,%rax
52 imulq %rcx,%rax
53
54 /* align dst */
55 movl %edi,%r9d
56 andl $7,%r9d
57 jnz .Lbad_alignment
58.Lafter_bad_alignment:
59
60 movq %rdx,%rcx
61 shrq $6,%rcx
62 jz .Lhandle_tail
63
64 .p2align 4
65.Lloop_64:
66 decq %rcx
67 movq %rax,(%rdi)
68 movq %rax,8(%rdi)
69 movq %rax,16(%rdi)
70 movq %rax,24(%rdi)
71 movq %rax,32(%rdi)
72 movq %rax,40(%rdi)
73 movq %rax,48(%rdi)
74 movq %rax,56(%rdi)
75 leaq 64(%rdi),%rdi
76 jnz .Lloop_64
77
78 /* Handle tail in loops. The loops should be faster than hard
79 to predict jump tables. */
80 .p2align 4
81.Lhandle_tail:
82 movl %edx,%ecx
83 andl $63&(~7),%ecx
84 jz .Lhandle_7
85 shrl $3,%ecx
86 .p2align 4
87.Lloop_8:
88 decl %ecx
89 movq %rax,(%rdi)
90 leaq 8(%rdi),%rdi
91 jnz .Lloop_8
92
93.Lhandle_7:
94 andl $7,%edx
95 jz .Lende
96 .p2align 4
97.Lloop_1:
98 decl %edx
99 movb %al,(%rdi)
100 leaq 1(%rdi),%rdi
101 jnz .Lloop_1
102
103.Lende:
104 movq %r10,%rax
105 RET
106
107.Lbad_alignment:
108 cmpq $7,%rdx
109 jbe .Lhandle_7
110 movq %rax,(%rdi) /* unaligned store */
111 movq $8,%r8
112 subq %r9,%r8
113 addq %r8,%rdi
114 subq %r8,%rdx
115 jmp .Lafter_bad_alignment
116.Lfinal:
117SYM_FUNC_END(memset_orig)
1/* SPDX-License-Identifier: GPL-2.0 */
2/* Copyright 2002 Andi Kleen, SuSE Labs */
3
4#include <linux/export.h>
5#include <linux/linkage.h>
6#include <asm/cpufeatures.h>
7#include <asm/alternative.h>
8
9.section .noinstr.text, "ax"
10
11/*
12 * ISO C memset - set a memory block to a byte value. This function uses fast
13 * string to get better performance than the original function. The code is
14 * simpler and shorter than the original function as well.
15 *
16 * rdi destination
17 * rsi value (char)
18 * rdx count (bytes)
19 *
20 * rax original destination
21 *
22 * The FSRS alternative should be done inline (avoiding the call and
23 * the disgusting return handling), but that would require some help
24 * from the compiler for better calling conventions.
25 *
26 * The 'rep stosb' itself is small enough to replace the call, but all
27 * the register moves blow up the code. And two of them are "needed"
28 * only for the return value that is the same as the source input,
29 * which the compiler could/should do much better anyway.
30 */
31SYM_FUNC_START(__memset)
32 ALTERNATIVE "jmp memset_orig", "", X86_FEATURE_FSRS
33
34 movq %rdi,%r9
35 movb %sil,%al
36 movq %rdx,%rcx
37 rep stosb
38 movq %r9,%rax
39 RET
40SYM_FUNC_END(__memset)
41EXPORT_SYMBOL(__memset)
42
43SYM_FUNC_ALIAS_MEMFUNC(memset, __memset)
44EXPORT_SYMBOL(memset)
45
46SYM_FUNC_START_LOCAL(memset_orig)
47 movq %rdi,%r10
48
49 /* expand byte value */
50 movzbl %sil,%ecx
51 movabs $0x0101010101010101,%rax
52 imulq %rcx,%rax
53
54 /* align dst */
55 movl %edi,%r9d
56 andl $7,%r9d
57 jnz .Lbad_alignment
58.Lafter_bad_alignment:
59
60 movq %rdx,%rcx
61 shrq $6,%rcx
62 jz .Lhandle_tail
63
64 .p2align 4
65.Lloop_64:
66 decq %rcx
67 movq %rax,(%rdi)
68 movq %rax,8(%rdi)
69 movq %rax,16(%rdi)
70 movq %rax,24(%rdi)
71 movq %rax,32(%rdi)
72 movq %rax,40(%rdi)
73 movq %rax,48(%rdi)
74 movq %rax,56(%rdi)
75 leaq 64(%rdi),%rdi
76 jnz .Lloop_64
77
78 /* Handle tail in loops. The loops should be faster than hard
79 to predict jump tables. */
80 .p2align 4
81.Lhandle_tail:
82 movl %edx,%ecx
83 andl $63&(~7),%ecx
84 jz .Lhandle_7
85 shrl $3,%ecx
86 .p2align 4
87.Lloop_8:
88 decl %ecx
89 movq %rax,(%rdi)
90 leaq 8(%rdi),%rdi
91 jnz .Lloop_8
92
93.Lhandle_7:
94 andl $7,%edx
95 jz .Lende
96 .p2align 4
97.Lloop_1:
98 decl %edx
99 movb %al,(%rdi)
100 leaq 1(%rdi),%rdi
101 jnz .Lloop_1
102
103.Lende:
104 movq %r10,%rax
105 RET
106
107.Lbad_alignment:
108 cmpq $7,%rdx
109 jbe .Lhandle_7
110 movq %rax,(%rdi) /* unaligned store */
111 movq $8,%r8
112 subq %r9,%r8
113 addq %r8,%rdi
114 subq %r8,%rdx
115 jmp .Lafter_bad_alignment
116.Lfinal:
117SYM_FUNC_END(memset_orig)