| /* 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_WEAK(memset) |
| 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) |
| SYM_FUNC_END_ALIAS(memset) |
| EXPORT_SYMBOL(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) |
