diff options
Diffstat (limited to 'arch/x86/lib/memset_64.S')
| -rw-r--r-- | arch/x86/lib/memset_64.S | 85 |
1 files changed, 56 insertions, 29 deletions
diff --git a/arch/x86/lib/memset_64.S b/arch/x86/lib/memset_64.S index 09d34426965..2dcb3808cbd 100644 --- a/arch/x86/lib/memset_64.S +++ b/arch/x86/lib/memset_64.S @@ -2,9 +2,13 @@ #include <linux/linkage.h> #include <asm/dwarf2.h> +#include <asm/cpufeature.h> +#include <asm/alternative-asm.h> /* - * ISO C memset - set a memory block to a byte value. + * 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 orignal function as well. * * rdi destination * rsi value (char) @@ -15,32 +19,52 @@ .section .altinstr_replacement, "ax", @progbits .Lmemset_c: movq %rdi,%r9 - movl %edx,%r8d - andl $7,%r8d - movl %edx,%ecx - shrl $3,%ecx + movq %rdx,%rcx + andl $7,%edx + shrq $3,%rcx /* expand byte value */ movzbl %sil,%esi movabs $0x0101010101010101,%rax - mulq %rsi /* with rax, clobbers rdx */ + imulq %rsi,%rax rep stosq - movl %r8d,%ecx + movl %edx,%ecx rep stosb movq %r9,%rax ret .Lmemset_e: .previous +/* + * 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 + */ + .section .altinstr_replacement, "ax", @progbits +.Lmemset_c_e: + movq %rdi,%r9 + movb %sil,%al + movq %rdx,%rcx + rep stosb + movq %r9,%rax + ret +.Lmemset_e_e: + .previous + ENTRY(memset) ENTRY(__memset) CFI_STARTPROC movq %rdi,%r10 - movq %rdx,%r11 /* expand byte value */ movzbl %sil,%ecx movabs $0x0101010101010101,%rax - mul %rcx /* with rax, clobbers rdx */ + imulq %rcx,%rax /* align dst */ movl %edi,%r9d @@ -49,13 +73,13 @@ ENTRY(__memset) CFI_REMEMBER_STATE .Lafter_bad_alignment: - movl %r11d,%ecx - shrl $6,%ecx + movq %rdx,%rcx + shrq $6,%rcx jz .Lhandle_tail .p2align 4 .Lloop_64: - decl %ecx + decq %rcx movq %rax,(%rdi) movq %rax,8(%rdi) movq %rax,16(%rdi) @@ -71,7 +95,7 @@ ENTRY(__memset) to predict jump tables. */ .p2align 4 .Lhandle_tail: - movl %r11d,%ecx + movl %edx,%ecx andl $63&(~7),%ecx jz .Lhandle_7 shrl $3,%ecx @@ -83,12 +107,11 @@ ENTRY(__memset) jnz .Lloop_8 .Lhandle_7: - movl %r11d,%ecx - andl $7,%ecx + andl $7,%edx jz .Lende .p2align 4 .Lloop_1: - decl %ecx + decl %edx movb %al,(%rdi) leaq 1(%rdi),%rdi jnz .Lloop_1 @@ -99,29 +122,33 @@ ENTRY(__memset) CFI_RESTORE_STATE .Lbad_alignment: - cmpq $7,%r11 + cmpq $7,%rdx jbe .Lhandle_7 movq %rax,(%rdi) /* unaligned store */ movq $8,%r8 subq %r9,%r8 addq %r8,%rdi - subq %r8,%r11 + subq %r8,%rdx jmp .Lafter_bad_alignment .Lfinal: CFI_ENDPROC ENDPROC(memset) ENDPROC(__memset) - /* Some CPUs run faster using the string instructions. - It is also a lot simpler. Use this when possible */ - -#include <asm/cpufeature.h> - + /* Some CPUs support enhanced REP MOVSB/STOSB feature. + * It is recommended to use this when possible. + * + * If enhanced REP MOVSB/STOSB feature is not available, use fast string + * instructions. + * + * Otherwise, use original memset function. + * + * In .altinstructions section, ERMS feature is placed after REG_GOOD + * feature to implement the right patch order. + */ .section .altinstructions,"a" - .align 8 - .quad memset - .quad .Lmemset_c - .word X86_FEATURE_REP_GOOD - .byte .Lfinal - memset - .byte .Lmemset_e - .Lmemset_c + altinstruction_entry memset,.Lmemset_c,X86_FEATURE_REP_GOOD,\ + .Lfinal-memset,.Lmemset_e-.Lmemset_c + altinstruction_entry memset,.Lmemset_c_e,X86_FEATURE_ERMS, \ + .Lfinal-memset,.Lmemset_e_e-.Lmemset_c_e .previous |