/* * Normally compiler builtins are used, but sometimes the compiler calls out * of line code. Based on asm-i386/string.h. * * This assembly file is re-written from memmove_64.c file. * - Copyright 2011 Fenghua Yu <fenghua.yu@intel.com> */ #define _STRING_C #include <linux/linkage.h> #include <asm/dwarf2.h> #include <asm/cpufeature.h> #include <asm/alternative-asm.h> #undef memmove /* * Implement memmove(). This can handle overlap between src and dst. * * Input: * rdi: dest * rsi: src * rdx: count * * Output: * rax: dest */ ENTRY(memmove) CFI_STARTPROC /* Handle more 32 bytes in loop */ mov %rdi, %rax cmp $0x20, %rdx jb 1f /* Decide forward/backward copy mode */ cmp %rdi, %rsi jge .Lmemmove_begin_forward mov %rsi, %r8 add %rdx, %r8 cmp %rdi, %r8 jg 2f .Lmemmove_begin_forward: /* * movsq instruction have many startup latency * so we handle small size by general register. */ cmp $680, %rdx jb 3f /* * movsq instruction is only good for aligned case. */ cmpb %dil, %sil je 4f 3: sub $0x20, %rdx /* * We gobble 32 bytes forward in each loop. */ 5: sub $0x20, %rdx movq 0*8(%rsi), %r11 movq 1*8(%rsi), %r10 movq 2*8(%rsi), %r9 movq 3*8(%rsi), %r8 leaq 4*8(%rsi), %rsi movq %r11, 0*8(%rdi) movq %r10, 1*8(%rdi) movq %r9, 2*8(%rdi) movq %r8, 3*8(%rdi) leaq 4*8(%rdi), %rdi jae 5b addq $0x20, %rdx jmp 1f /* * Handle data forward by movsq. */ .p2align 4 4: movq %rdx, %rcx movq -8(%rsi, %rdx), %r11 lea -8(%rdi, %rdx), %r10 shrq $3, %rcx rep movsq movq %r11, (%r10) jmp 13f .Lmemmove_end_forward: /* * Handle data backward by movsq. */ .p2align 4 7: movq %rdx, %rcx movq (%rsi), %r11 movq %rdi, %r10 leaq -8(%rsi, %rdx), %rsi leaq -8(%rdi, %rdx), %rdi shrq $3, %rcx std rep movsq cld movq %r11, (%r10) jmp 13f /* * Start to prepare for backward copy. */ .p2align 4 2: cmp $680, %rdx jb 6f cmp %dil, %sil je 7b 6: /* * Calculate copy position to tail. */ addq %rdx, %rsi addq %rdx, %rdi subq $0x20, %rdx /* * We gobble 32 bytes backward in each loop. */ 8: subq $0x20, %rdx movq -1*8(%rsi), %r11 movq -2*8(%rsi), %r10 movq -3*8(%rsi), %r9 movq -4*8(%rsi), %r8 leaq -4*8(%rsi), %rsi movq %r11, -1*8(%rdi) movq %r10, -2*8(%rdi) movq %r9, -3*8(%rdi) movq %r8, -4*8(%rdi) leaq -4*8(%rdi), %rdi jae 8b /* * Calculate copy position to head. */ addq $0x20, %rdx subq %rdx, %rsi subq %rdx, %rdi 1: cmpq $16, %rdx jb 9f /* * Move data from 16 bytes to 31 bytes. */ movq 0*8(%rsi), %r11 movq 1*8(%rsi), %r10 movq -2*8(%rsi, %rdx), %r9 movq -1*8(%rsi, %rdx), %r8 movq %r11, 0*8(%rdi) movq %r10, 1*8(%rdi) movq %r9, -2*8(%rdi, %rdx) movq %r8, -1*8(%rdi, %rdx) jmp 13f .p2align 4 9: cmpq $8, %rdx jb 10f /* * Move data from 8 bytes to 15 bytes. */ movq 0*8(%rsi), %r11 movq -1*8(%rsi, %rdx), %r10 movq %r11, 0*8(%rdi) movq %r10, -1*8(%rdi, %rdx) jmp 13f 10: cmpq $4, %rdx jb 11f /* * Move data from 4 bytes to 7 bytes. */ movl (%rsi), %r11d movl -4(%rsi, %rdx), %r10d movl %r11d, (%rdi) movl %r10d, -4(%rdi, %rdx) jmp 13f 11: cmp $2, %rdx jb 12f /* * Move data from 2 bytes to 3 bytes. */ movw (%rsi), %r11w movw -2(%rsi, %rdx), %r10w movw %r11w, (%rdi) movw %r10w, -2(%rdi, %rdx) jmp 13f 12: cmp $1, %rdx jb 13f /* * Move data for 1 byte. */ movb (%rsi), %r11b movb %r11b, (%rdi) 13: retq CFI_ENDPROC .section .altinstr_replacement,"ax" .Lmemmove_begin_forward_efs: /* Forward moving data. */ movq %rdx, %rcx rep movsb retq .Lmemmove_end_forward_efs: .previous .section .altinstructions,"a" altinstruction_entry .Lmemmove_begin_forward, \ .Lmemmove_begin_forward_efs,X86_FEATURE_ERMS, \ .Lmemmove_end_forward-.Lmemmove_begin_forward, \ .Lmemmove_end_forward_efs-.Lmemmove_begin_forward_efs .previous ENDPROC(memmove)