| /* Copyright 2002 Andi Kleen */ |
| |
| #include <linux/linkage.h> |
| |
| #include <asm/cpufeature.h> |
| #include <asm/dwarf2.h> |
| #include <asm/alternative-asm.h> |
| |
| /* |
| * memcpy - Copy a memory block. |
| * |
| * Input: |
| * rdi destination |
| * rsi source |
| * rdx count |
| * |
| * Output: |
| * rax original destination |
| */ |
| |
| /* |
| * memcpy_c() - fast string ops (REP MOVSQ) based variant. |
| * |
| * This gets patched over the unrolled variant (below) via the |
| * alternative instructions framework: |
| */ |
| .section .altinstr_replacement, "ax", @progbits |
| .Lmemcpy_c: |
| movq %rdi, %rax |
| movq %rdx, %rcx |
| shrq $3, %rcx |
| andl $7, %edx |
| rep movsq |
| movl %edx, %ecx |
| rep movsb |
| ret |
| .Lmemcpy_e: |
| .previous |
| |
| /* |
| * memcpy_c_e() - enhanced fast string memcpy. This is faster and simpler than |
| * memcpy_c. Use memcpy_c_e when possible. |
| * |
| * This gets patched over the unrolled variant (below) via the |
| * alternative instructions framework: |
| */ |
| .section .altinstr_replacement, "ax", @progbits |
| .Lmemcpy_c_e: |
| movq %rdi, %rax |
| movq %rdx, %rcx |
| rep movsb |
| ret |
| .Lmemcpy_e_e: |
| .previous |
| |
| ENTRY(__memcpy) |
| ENTRY(memcpy) |
| CFI_STARTPROC |
| movq %rdi, %rax |
| |
| cmpq $0x20, %rdx |
| jb .Lhandle_tail |
| |
| /* |
| * We check whether memory false dependence could occur, |
| * then jump to corresponding copy mode. |
| */ |
| cmp %dil, %sil |
| jl .Lcopy_backward |
| subq $0x20, %rdx |
| .Lcopy_forward_loop: |
| subq $0x20, %rdx |
| |
| /* |
| * Move in blocks of 4x8 bytes: |
| */ |
| movq 0*8(%rsi), %r8 |
| movq 1*8(%rsi), %r9 |
| movq 2*8(%rsi), %r10 |
| movq 3*8(%rsi), %r11 |
| leaq 4*8(%rsi), %rsi |
| |
| movq %r8, 0*8(%rdi) |
| movq %r9, 1*8(%rdi) |
| movq %r10, 2*8(%rdi) |
| movq %r11, 3*8(%rdi) |
| leaq 4*8(%rdi), %rdi |
| jae .Lcopy_forward_loop |
| addl $0x20, %edx |
| jmp .Lhandle_tail |
| |
| .Lcopy_backward: |
| /* |
| * Calculate copy position to tail. |
| */ |
| addq %rdx, %rsi |
| addq %rdx, %rdi |
| subq $0x20, %rdx |
| /* |
| * At most 3 ALU operations in one cycle, |
| * so append NOPS in the same 16 bytes trunk. |
| */ |
| .p2align 4 |
| .Lcopy_backward_loop: |
| subq $0x20, %rdx |
| movq -1*8(%rsi), %r8 |
| movq -2*8(%rsi), %r9 |
| movq -3*8(%rsi), %r10 |
| movq -4*8(%rsi), %r11 |
| leaq -4*8(%rsi), %rsi |
| movq %r8, -1*8(%rdi) |
| movq %r9, -2*8(%rdi) |
| movq %r10, -3*8(%rdi) |
| movq %r11, -4*8(%rdi) |
| leaq -4*8(%rdi), %rdi |
| jae .Lcopy_backward_loop |
| |
| /* |
| * Calculate copy position to head. |
| */ |
| addl $0x20, %edx |
| subq %rdx, %rsi |
| subq %rdx, %rdi |
| .Lhandle_tail: |
| cmpl $16, %edx |
| jb .Lless_16bytes |
| |
| /* |
| * Move data from 16 bytes to 31 bytes. |
| */ |
| movq 0*8(%rsi), %r8 |
| movq 1*8(%rsi), %r9 |
| movq -2*8(%rsi, %rdx), %r10 |
| movq -1*8(%rsi, %rdx), %r11 |
| movq %r8, 0*8(%rdi) |
| movq %r9, 1*8(%rdi) |
| movq %r10, -2*8(%rdi, %rdx) |
| movq %r11, -1*8(%rdi, %rdx) |
| retq |
| .p2align 4 |
| .Lless_16bytes: |
| cmpl $8, %edx |
| jb .Lless_8bytes |
| /* |
| * Move data from 8 bytes to 15 bytes. |
| */ |
| movq 0*8(%rsi), %r8 |
| movq -1*8(%rsi, %rdx), %r9 |
| movq %r8, 0*8(%rdi) |
| movq %r9, -1*8(%rdi, %rdx) |
| retq |
| .p2align 4 |
| .Lless_8bytes: |
| cmpl $4, %edx |
| jb .Lless_3bytes |
| |
| /* |
| * Move data from 4 bytes to 7 bytes. |
| */ |
| movl (%rsi), %ecx |
| movl -4(%rsi, %rdx), %r8d |
| movl %ecx, (%rdi) |
| movl %r8d, -4(%rdi, %rdx) |
| retq |
| .p2align 4 |
| .Lless_3bytes: |
| subl $1, %edx |
| jb .Lend |
| /* |
| * Move data from 1 bytes to 3 bytes. |
| */ |
| movzbl (%rsi), %ecx |
| jz .Lstore_1byte |
| movzbq 1(%rsi), %r8 |
| movzbq (%rsi, %rdx), %r9 |
| movb %r8b, 1(%rdi) |
| movb %r9b, (%rdi, %rdx) |
| .Lstore_1byte: |
| movb %cl, (%rdi) |
| |
| .Lend: |
| retq |
| CFI_ENDPROC |
| ENDPROC(memcpy) |
| ENDPROC(__memcpy) |
| |
| /* |
| * Some CPUs are adding enhanced REP MOVSB/STOSB feature |
| * If the feature is supported, memcpy_c_e() is the first choice. |
| * If enhanced rep movsb copy is not available, use fast string copy |
| * memcpy_c() when possible. This is faster and code is simpler than |
| * original memcpy(). |
| * Otherwise, original memcpy() is used. |
| * In .altinstructions section, ERMS feature is placed after REG_GOOD |
| * feature to implement the right patch order. |
| * |
| * Replace only beginning, memcpy is used to apply alternatives, |
| * so it is silly to overwrite itself with nops - reboot is the |
| * only outcome... |
| */ |
| .section .altinstructions, "a" |
| altinstruction_entry memcpy,.Lmemcpy_c,X86_FEATURE_REP_GOOD,\ |
| .Lmemcpy_e-.Lmemcpy_c,.Lmemcpy_e-.Lmemcpy_c |
| altinstruction_entry memcpy,.Lmemcpy_c_e,X86_FEATURE_ERMS, \ |
| .Lmemcpy_e_e-.Lmemcpy_c_e,.Lmemcpy_e_e-.Lmemcpy_c_e |
| .previous |
