관리-도구

편집 파일: memset_64.S

/* SPDX-License-Identifier: GPL-2.0 */ /* Copyright 2002 Andi Kleen, SuSE Labs */ #include <linux/linkage.h> #include <asm/cpufeatures.h> #include <asm/alternative.h> #include <asm/export.h> /* * ISO C memset - set a memory block to a byte value. This function uses fast * string to get better performance than the original function. The code is * simpler and shorter than the original function as well. * * rdi destination * rsi value (char) * rdx count (bytes) * * rax original destination */ SYM_FUNC_START(__memset) /* * Some CPUs support enhanced REP MOVSB/STOSB feature. It is recommended * to use it when possible. If not available, use fast string instructions. * * Otherwise, use original memset function. */ ALTERNATIVE_2 "jmp memset_orig", "", X86_FEATURE_REP_GOOD, \ "jmp memset_erms", X86_FEATURE_ERMS movq %rdi,%r9 movq %rdx,%rcx andl $7,%edx shrq $3,%rcx /* expand byte value */ movzbl %sil,%esi movabs $0x0101010101010101,%rax imulq %rsi,%rax rep stosq movl %edx,%ecx rep stosb movq %r9,%rax RET SYM_FUNC_END(__memset) EXPORT_SYMBOL(__memset) SYM_FUNC_ALIAS_WEAK(memset, __memset) EXPORT_SYMBOL(memset) /* * ISO C memset - set a memory block to a byte value. This function uses * enhanced rep stosb to override the fast string function. * The code is simpler and shorter than the fast string function as well. * * rdi destination * rsi value (char) * rdx count (bytes) * * rax original destination */ SYM_FUNC_START_LOCAL(memset_erms) movq %rdi,%r9 movb %sil,%al movq %rdx,%rcx rep stosb movq %r9,%rax RET SYM_FUNC_END(memset_erms) SYM_FUNC_START_LOCAL(memset_orig) movq %rdi,%r10 /* expand byte value */ movzbl %sil,%ecx movabs $0x0101010101010101,%rax imulq %rcx,%rax /* align dst */ movl %edi,%r9d andl $7,%r9d jnz .Lbad_alignment .Lafter_bad_alignment: movq %rdx,%rcx shrq $6,%rcx jz .Lhandle_tail .p2align 4 .Lloop_64: decq %rcx 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 %edx,%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: andl $7,%edx jz .Lende .p2align 4 .Lloop_1: decl %edx movb %al,(%rdi) leaq 1(%rdi),%rdi jnz .Lloop_1 .Lende: movq %r10,%rax RET .Lbad_alignment: cmpq $7,%rdx jbe .Lhandle_7 movq %rax,(%rdi) /* unaligned store */ movq $8,%r8 subq %r9,%r8 addq %r8,%rdi subq %r8,%rdx jmp .Lafter_bad_alignment .Lfinal: SYM_FUNC_END(memset_orig)