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/*
* Copyright (c) 2008 Travis Geiselbrecht
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files
* (the "Software"), to deal in the Software without restriction,
* including without limitation the rights to use, copy, modify, merge,
* publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include <asm.h>
#include <arch/arm/cores.h>
.text
.align 2
.global mymemcpy
mymemcpy:
// check for zero length copy or the same pointer
cmp r2, #0
cmpne r1, r0
bxeq lr
// save a few registers for use and the return code (input dst)
stmfd sp!, {r0, r4, r5, lr}
// check for forwards overlap (src > dst, distance < len)
subs r3, r0, r1
cmpgt r2, r3
bgt .L_forwardoverlap
// check for a short copy len.
// 20 bytes is enough so that if a 16 byte alignment needs to happen there is at least a
// wordwise copy worth of work to be done.
cmp r2, #(16+4)
blt .L_bytewise
// see if they are similarly aligned on 4 byte boundaries
eor r3, r0, r1
tst r3, #3
bne .L_bytewise // dissimilarly aligned, nothing we can do (for now)
// check for 16 byte alignment on dst.
// this will also catch src being not 4 byte aligned, since it is similarly 4 byte
// aligned with dst at this point.
tst r0, #15
bne .L_not16bytealigned
// check to see if we have at least 32 bytes of data to copy.
// if not, just revert to wordwise copy
cmp r2, #32
blt .L_wordwise
.L_bigcopy:
// copy 32 bytes at a time. src & dst need to be at least 4 byte aligned,
// and we need at least 32 bytes remaining to copy
// save r6-r7 for use in the big copy
stmfd sp!, {r6-r7}
sub r2, r2, #32 // subtract an extra 32 to the len so we can avoid an extra compare
.L_bigcopy_loop:
ldmia r1!, {r4, r5, r6, r7}
stmia r0!, {r4, r5, r6, r7}
ldmia r1!, {r4, r5, r6, r7}
subs r2, r2, #32
stmia r0!, {r4, r5, r6, r7}
bge .L_bigcopy_loop
// restore r6-r7
ldmfd sp!, {r6-r7}
// see if we are done
adds r2, r2, #32
beq .L_done
// less then 4 bytes left?
cmp r2, #4
blt .L_bytewise
.L_wordwise:
// copy 4 bytes at a time.
// src & dst are guaranteed to be word aligned, and at least 4 bytes are left to copy.
subs r2, r2, #4
.L_wordwise_loop:
ldr r3, [r1], #4
subs r2, r2, #4
str r3, [r0], #4
bge .L_wordwise_loop
// correct the remaining len and test for completion
adds r2, r2, #4
beq .L_done
.L_bytewise:
// simple bytewise copy
ldrb r3, [r1], #1
subs r2, r2, #1
strb r3, [r0], #1
bgt .L_bytewise
.L_done:
// load dst for return and restore r4,r5
#if ARM_ARCH_LEVEL >= 5
ldmfd sp!, {r0, r4, r5, pc}
#else
ldmfd sp!, {r0, r4, r5, lr}
bx lr
#endif
.L_not16bytealigned:
// dst is not 16 byte aligned, so we will copy up to 15 bytes to get it aligned.
// src is guaranteed to be similarly word aligned with dst.
// set the condition flags based on the alignment.
lsl r12, r0, #28
rsb r12, r12, #0
msr CPSR_f, r12 // move into NZCV fields in CPSR
// move as many bytes as necessary to get the dst aligned
ldrvsb r3, [r1], #1 // V set
ldrcsh r4, [r1], #2 // C set
ldreq r5, [r1], #4 // Z set
strvsb r3, [r0], #1
strcsh r4, [r0], #2
streq r5, [r0], #4
ldmmiia r1!, {r3-r4} // N set
stmmiia r0!, {r3-r4}
// fix the remaining len
sub r2, r2, r12, lsr #28
// test to see what we should do now
cmp r2, #32
bge .L_bigcopy
b .L_wordwise
// src and dest overlap 'forwards' or dst > src
.L_forwardoverlap:
// do a bytewise reverse copy for now
add r1, r1, r2
add r0, r0, r2
.L_bytewisereverse:
// simple bytewise reverse copy
ldrb r3, [r1], #-1
subs r2, r2, #1
strb r3, [r0], #-1
bgt .L_bytewisereverse
b .L_done