201 lines
3.8 KiB
ArmAsm
201 lines
3.8 KiB
ArmAsm
/* SPDX-License-Identifier: GPL-2.0 */
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#include <linux/linkage.h>
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#include <asm/export.h>
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SYM_FUNC_START(memmove)
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/*
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* void *memmove(void *dest_in, const void *src_in, size_t n)
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* -mregparm=3 passes these in registers:
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* dest_in: %eax
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* src_in: %edx
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* n: %ecx
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* See also: arch/x86/entry/calling.h for description of the calling convention.
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*
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* n can remain in %ecx, but for `rep movsl`, we'll need dest in %edi and src
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* in %esi.
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*/
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.set dest_in, %eax
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.set dest, %edi
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.set src_in, %edx
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.set src, %esi
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.set n, %ecx
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.set tmp0, %edx
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.set tmp0w, %dx
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.set tmp1, %ebx
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.set tmp1w, %bx
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.set tmp2, %eax
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.set tmp3b, %cl
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/*
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* Save all callee-saved registers, because this function is going to clobber
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* all of them:
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*/
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pushl %ebp
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movl %esp, %ebp // set standard frame pointer
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pushl %ebx
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pushl %edi
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pushl %esi
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pushl %eax // save 'dest_in' parameter [eax] as the return value
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movl src_in, src
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movl dest_in, dest
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/* Handle more 16 bytes in loop */
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cmpl $0x10, n
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jb .Lmove_16B
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/* Decide forward/backward copy mode */
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cmpl dest, src
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jb .Lbackwards_header
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/*
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* movs instruction have many startup latency
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* so we handle small size by general register.
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*/
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cmpl $680, n
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jb .Ltoo_small_forwards
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/* movs instruction is only good for aligned case. */
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movl src, tmp0
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xorl dest, tmp0
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andl $0xff, tmp0
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jz .Lforward_movs
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.Ltoo_small_forwards:
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subl $0x10, n
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/* We gobble 16 bytes forward in each loop. */
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.Lmove_16B_forwards_loop:
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subl $0x10, n
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movl 0*4(src), tmp0
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movl 1*4(src), tmp1
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movl tmp0, 0*4(dest)
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movl tmp1, 1*4(dest)
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movl 2*4(src), tmp0
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movl 3*4(src), tmp1
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movl tmp0, 2*4(dest)
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movl tmp1, 3*4(dest)
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leal 0x10(src), src
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leal 0x10(dest), dest
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jae .Lmove_16B_forwards_loop
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addl $0x10, n
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jmp .Lmove_16B
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/* Handle data forward by movs. */
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.p2align 4
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.Lforward_movs:
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movl -4(src, n), tmp0
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leal -4(dest, n), tmp1
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shrl $2, n
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rep movsl
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movl tmp0, (tmp1)
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jmp .Ldone
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/* Handle data backward by movs. */
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.p2align 4
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.Lbackwards_movs:
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movl (src), tmp0
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movl dest, tmp1
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leal -4(src, n), src
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leal -4(dest, n), dest
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shrl $2, n
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std
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rep movsl
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movl tmp0,(tmp1)
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cld
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jmp .Ldone
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/* Start to prepare for backward copy. */
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.p2align 4
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.Lbackwards_header:
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cmpl $680, n
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jb .Ltoo_small_backwards
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movl src, tmp0
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xorl dest, tmp0
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andl $0xff, tmp0
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jz .Lbackwards_movs
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/* Calculate copy position to tail. */
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.Ltoo_small_backwards:
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addl n, src
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addl n, dest
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subl $0x10, n
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/* We gobble 16 bytes backward in each loop. */
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.Lmove_16B_backwards_loop:
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subl $0x10, n
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movl -1*4(src), tmp0
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movl -2*4(src), tmp1
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movl tmp0, -1*4(dest)
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movl tmp1, -2*4(dest)
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movl -3*4(src), tmp0
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movl -4*4(src), tmp1
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movl tmp0, -3*4(dest)
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movl tmp1, -4*4(dest)
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leal -0x10(src), src
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leal -0x10(dest), dest
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jae .Lmove_16B_backwards_loop
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/* Calculate copy position to head. */
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addl $0x10, n
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subl n, src
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subl n, dest
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/* Move data from 8 bytes to 15 bytes. */
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.p2align 4
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.Lmove_16B:
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cmpl $8, n
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jb .Lmove_8B
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movl 0*4(src), tmp0
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movl 1*4(src), tmp1
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movl -2*4(src, n), tmp2
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movl -1*4(src, n), src
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movl tmp0, 0*4(dest)
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movl tmp1, 1*4(dest)
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movl tmp2, -2*4(dest, n)
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movl src, -1*4(dest, n)
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jmp .Ldone
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/* Move data from 4 bytes to 7 bytes. */
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.p2align 4
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.Lmove_8B:
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cmpl $4, n
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jb .Lmove_4B
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movl 0*4(src), tmp0
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movl -1*4(src, n), tmp1
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movl tmp0, 0*4(dest)
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movl tmp1, -1*4(dest, n)
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jmp .Ldone
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/* Move data from 2 bytes to 3 bytes. */
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.p2align 4
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.Lmove_4B:
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cmpl $2, n
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jb .Lmove_1B
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movw 0*2(src), tmp0w
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movw -1*2(src, n), tmp1w
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movw tmp0w, 0*2(dest)
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movw tmp1w, -1*2(dest, n)
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jmp .Ldone
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/* Move data for 1 byte. */
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.p2align 4
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.Lmove_1B:
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cmpl $1, n
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jb .Ldone
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movb (src), tmp3b
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movb tmp3b, (dest)
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.p2align 4
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.Ldone:
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popl dest_in // restore 'dest_in' [eax] as the return value
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/* Restore all callee-saved registers: */
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popl %esi
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popl %edi
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popl %ebx
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popl %ebp
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RET
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SYM_FUNC_END(memmove)
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EXPORT_SYMBOL(memmove)
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