1/* SPDX-License-Identifier: GPL-2.0 */ 2/* Copyright 2002 Andi Kleen, SuSE Labs */ 3 4#include <linux/linkage.h> 5#include <asm/cpufeatures.h> 6#include <asm/alternative-asm.h> 7 8.weak memset 9 10/* 11 * ISO C memset - set a memory block to a byte value. This function uses fast 12 * string to get better performance than the original function. The code is 13 * simpler and shorter than the original function as well. 14 * 15 * rdi destination 16 * rsi value (char) 17 * rdx count (bytes) 18 * 19 * rax original destination 20 */ 21SYM_FUNC_START_ALIAS(memset) 22SYM_FUNC_START(__memset) 23 /* 24 * Some CPUs support enhanced REP MOVSB/STOSB feature. It is recommended 25 * to use it when possible. If not available, use fast string instructions. 26 * 27 * Otherwise, use original memset function. 28 */ 29 ALTERNATIVE_2 "jmp memset_orig", "", X86_FEATURE_REP_GOOD, \ 30 "jmp memset_erms", X86_FEATURE_ERMS 31 32 movq %rdi,%r9 33 movq %rdx,%rcx 34 andl $7,%edx 35 shrq $3,%rcx 36 /* expand byte value */ 37 movzbl %sil,%esi 38 movabs $0x0101010101010101,%rax 39 imulq %rsi,%rax 40 rep stosq 41 movl %edx,%ecx 42 rep stosb 43 movq %r9,%rax 44 ret 45SYM_FUNC_END(__memset) 46SYM_FUNC_END_ALIAS(memset) 47 48/* 49 * ISO C memset - set a memory block to a byte value. This function uses 50 * enhanced rep stosb to override the fast string function. 51 * The code is simpler and shorter than the fast string function as well. 52 * 53 * rdi destination 54 * rsi value (char) 55 * rdx count (bytes) 56 * 57 * rax original destination 58 */ 59SYM_FUNC_START(memset_erms) 60 movq %rdi,%r9 61 movb %sil,%al 62 movq %rdx,%rcx 63 rep stosb 64 movq %r9,%rax 65 ret 66SYM_FUNC_END(memset_erms) 67 68SYM_FUNC_START(memset_orig) 69 movq %rdi,%r10 70 71 /* expand byte value */ 72 movzbl %sil,%ecx 73 movabs $0x0101010101010101,%rax 74 imulq %rcx,%rax 75 76 /* align dst */ 77 movl %edi,%r9d 78 andl $7,%r9d 79 jnz .Lbad_alignment 80.Lafter_bad_alignment: 81 82 movq %rdx,%rcx 83 shrq $6,%rcx 84 jz .Lhandle_tail 85 86 .p2align 4 87.Lloop_64: 88 decq %rcx 89 movq %rax,(%rdi) 90 movq %rax,8(%rdi) 91 movq %rax,16(%rdi) 92 movq %rax,24(%rdi) 93 movq %rax,32(%rdi) 94 movq %rax,40(%rdi) 95 movq %rax,48(%rdi) 96 movq %rax,56(%rdi) 97 leaq 64(%rdi),%rdi 98 jnz .Lloop_64 99 100 /* Handle tail in loops. The loops should be faster than hard 101 to predict jump tables. */ 102 .p2align 4 103.Lhandle_tail: 104 movl %edx,%ecx 105 andl $63&(~7),%ecx 106 jz .Lhandle_7 107 shrl $3,%ecx 108 .p2align 4 109.Lloop_8: 110 decl %ecx 111 movq %rax,(%rdi) 112 leaq 8(%rdi),%rdi 113 jnz .Lloop_8 114 115.Lhandle_7: 116 andl $7,%edx 117 jz .Lende 118 .p2align 4 119.Lloop_1: 120 decl %edx 121 movb %al,(%rdi) 122 leaq 1(%rdi),%rdi 123 jnz .Lloop_1 124 125.Lende: 126 movq %r10,%rax 127 ret 128 129.Lbad_alignment: 130 cmpq $7,%rdx 131 jbe .Lhandle_7 132 movq %rax,(%rdi) /* unaligned store */ 133 movq $8,%r8 134 subq %r9,%r8 135 addq %r8,%rdi 136 subq %r8,%rdx 137 jmp .Lafter_bad_alignment 138.Lfinal: 139SYM_FUNC_END(memset_orig) 140