1/* Copyright 2002 Andi Kleen, SuSE Labs */ 2 3#include <linux/linkage.h> 4#include <asm/dwarf2.h> 5#include <asm/cpufeature.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 orignal function as well. 14 * 15 * rdi destination 16 * rsi value (char) 17 * rdx count (bytes) 18 * 19 * rax original destination 20 */ 21ENTRY(memset) 22ENTRY(__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 45ENDPROC(memset) 46ENDPROC(__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 */ 59ENTRY(memset_erms) 60 movq %rdi,%r9 61 movb %sil,%al 62 movq %rdx,%rcx 63 rep stosb 64 movq %r9,%rax 65 ret 66ENDPROC(memset_erms) 67 68ENTRY(memset_orig) 69 CFI_STARTPROC 70 movq %rdi,%r10 71 72 /* expand byte value */ 73 movzbl %sil,%ecx 74 movabs $0x0101010101010101,%rax 75 imulq %rcx,%rax 76 77 /* align dst */ 78 movl %edi,%r9d 79 andl $7,%r9d 80 jnz .Lbad_alignment 81 CFI_REMEMBER_STATE 82.Lafter_bad_alignment: 83 84 movq %rdx,%rcx 85 shrq $6,%rcx 86 jz .Lhandle_tail 87 88 .p2align 4 89.Lloop_64: 90 decq %rcx 91 movq %rax,(%rdi) 92 movq %rax,8(%rdi) 93 movq %rax,16(%rdi) 94 movq %rax,24(%rdi) 95 movq %rax,32(%rdi) 96 movq %rax,40(%rdi) 97 movq %rax,48(%rdi) 98 movq %rax,56(%rdi) 99 leaq 64(%rdi),%rdi 100 jnz .Lloop_64 101 102 /* Handle tail in loops. The loops should be faster than hard 103 to predict jump tables. */ 104 .p2align 4 105.Lhandle_tail: 106 movl %edx,%ecx 107 andl $63&(~7),%ecx 108 jz .Lhandle_7 109 shrl $3,%ecx 110 .p2align 4 111.Lloop_8: 112 decl %ecx 113 movq %rax,(%rdi) 114 leaq 8(%rdi),%rdi 115 jnz .Lloop_8 116 117.Lhandle_7: 118 andl $7,%edx 119 jz .Lende 120 .p2align 4 121.Lloop_1: 122 decl %edx 123 movb %al,(%rdi) 124 leaq 1(%rdi),%rdi 125 jnz .Lloop_1 126 127.Lende: 128 movq %r10,%rax 129 ret 130 131 CFI_RESTORE_STATE 132.Lbad_alignment: 133 cmpq $7,%rdx 134 jbe .Lhandle_7 135 movq %rax,(%rdi) /* unaligned store */ 136 movq $8,%r8 137 subq %r9,%r8 138 addq %r8,%rdi 139 subq %r8,%rdx 140 jmp .Lafter_bad_alignment 141.Lfinal: 142 CFI_ENDPROC 143ENDPROC(memset_orig) 144