blob: 2d35d4f2befd5c0f6bc62e5cc648760e7c26babb [file] [log] [blame]
/*
* 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
/* void *memset(void *s, int c, size_t n); */
.global mymemset
mymemset:
// check for zero length
cmp r2, #0
bxeq lr
// save the original pointer
mov r12, r0
// short memsets aren't worth optimizing
cmp r2, #(32 + 16)
blt .L_bytewise
// fill a 32 bit register with the 8 bit value
and r1, r1, #0xff
orr r1, r1, r1, lsl #8
orr r1, r1, r1, lsl #16
// check for 16 byte alignment
tst r0, #15
bne .L_not16bytealigned
.L_bigset:
// dump some registers to make space for our values
stmfd sp!, { r4-r5 }
// fill a bunch of registers with the set value
mov r3, r1
mov r4, r1
mov r5, r1
// prepare the count register so we can avoid an extra compare
sub r2, r2, #32
// 32 bytes at a time
.L_bigset_loop:
stmia r0!, { r1, r3, r4, r5 }
subs r2, r2, #32
stmia r0!, { r1, r3, r4, r5 }
bge .L_bigset_loop
// restore our dumped registers
ldmfd sp!, { r4-r5 }
// see if we're done
adds r2, r2, #32
beq .L_done
.L_bytewise:
// bytewise memset
subs r2, r2, #1
strb r1, [r0], #1
bgt .L_bytewise
.L_done:
// restore the base pointer as return value
mov r0, r12
bx lr
.L_not16bytealigned:
// dst is not 16 byte aligned, so we will set up to 15 bytes to get it aligned.
// set the condition flags based on the alignment.
lsl r3, r0, #28
rsb r3, r3, #0
msr CPSR_f, r3 // move into NZCV fields in CPSR
// move as many bytes as necessary to get the dst aligned
strvsb r1, [r0], #1 // V set
strcsh r1, [r0], #2 // C set
streq r1, [r0], #4 // Z set
strmi r1, [r0], #4 // N set
strmi r1, [r0], #4 // N set
// fix the remaining len
sub r2, r2, r3, lsr #28
// do the large memset
b .L_bigset