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/*
* arch/xtensa/lib/memset.S
*
* ANSI C standard library function memset
* (Well, almost. .fixup code might return zero.)
*
* This file is subject to the terms and conditions of the GNU General
* Public License. See the file "COPYING" in the main directory of
* this archive for more details.
*
* Copyright (C) 2002 Tensilica Inc.
*/
#include <asm/variant/core.h>
/*
* void *memset(void *dst, int c, size_t length)
*
* The algorithm is as follows:
* Create a word with c in all byte positions
* If the destination is aligned,
* do 16B chucks with a loop, and then finish up with
* 8B, 4B, 2B, and 1B stores conditional on the length.
* If destination is unaligned, align it by conditionally
* setting 1B and 2B and then go to aligned case.
* This code tries to use fall-through branches for the common
* case of an aligned destination (except for the branches to
* the alignment labels).
*/
/* Load or store instructions that may cause exceptions use the EX macro. */
#define EX(insn,reg1,reg2,offset,handler) \
9: insn reg1, reg2, offset; \
.section __ex_table, "a"; \
.word 9b, handler; \
.previous
.text
.align 4
.global memset
.type memset,@function
memset:
entry sp, 16 # minimal stack frame
# a2/ dst, a3/ c, a4/ length
extui a3, a3, 0, 8 # mask to just 8 bits
slli a7, a3, 8 # duplicate character in all bytes of word
or a3, a3, a7 # ...
slli a7, a3, 16 # ...
or a3, a3, a7 # ...
mov a5, a2 # copy dst so that a2 is return value
movi a6, 3 # for alignment tests
bany a2, a6, .Ldstunaligned # if dst is unaligned
.L0: # return here from .Ldstunaligned when dst is aligned
srli a7, a4, 4 # number of loop iterations with 16B
# per iteration
bnez a4, .Laligned
retw
/*
* Destination is word-aligned.
*/
# set 16 bytes per iteration for word-aligned dst
.align 4 # 1 mod 4 alignment for LOOPNEZ
.byte 0 # (0 mod 4 alignment for LBEG)
.Laligned:
#if XCHAL_HAVE_LOOPS
loopnez a7, .Loop1done
#else /* !XCHAL_HAVE_LOOPS */
beqz a7, .Loop1done
slli a6, a7, 4
add a6, a6, a5 # a6 = end of last 16B chunk
#endif /* !XCHAL_HAVE_LOOPS */
.Loop1:
EX(s32i, a3, a5, 0, memset_fixup)
EX(s32i, a3, a5, 4, memset_fixup)
EX(s32i, a3, a5, 8, memset_fixup)
EX(s32i, a3, a5, 12, memset_fixup)
addi a5, a5, 16
#if !XCHAL_HAVE_LOOPS
blt a5, a6, .Loop1
#endif /* !XCHAL_HAVE_LOOPS */
.Loop1done:
bbci.l a4, 3, .L2
# set 8 bytes
EX(s32i, a3, a5, 0, memset_fixup)
EX(s32i, a3, a5, 4, memset_fixup)
addi a5, a5, 8
.L2:
bbci.l a4, 2, .L3
# set 4 bytes
EX(s32i, a3, a5, 0, memset_fixup)
addi a5, a5, 4
.L3:
bbci.l a4, 1, .L4
# set 2 bytes
EX(s16i, a3, a5, 0, memset_fixup)
addi a5, a5, 2
.L4:
bbci.l a4, 0, .L5
# set 1 byte
EX(s8i, a3, a5, 0, memset_fixup)
.L5:
.Lret1:
retw
/*
* Destination is unaligned
*/
.Ldstunaligned:
bltui a4, 8, .Lbyteset # do short copies byte by byte
bbci.l a5, 0, .L20 # branch if dst alignment half-aligned
# dst is only byte aligned
# set 1 byte
EX(s8i, a3, a5, 0, memset_fixup)
addi a5, a5, 1
addi a4, a4, -1
# now retest if dst aligned
bbci.l a5, 1, .L0 # if now aligned, return to main algorithm
.L20:
# dst half-aligned
# set 2 bytes
EX(s16i, a3, a5, 0, memset_fixup)
addi a5, a5, 2
addi a4, a4, -2
j .L0 # dst is now aligned, return to main algorithm
/*
* Byte by byte set
*/
.align 4
.byte 0 # 1 mod 4 alignment for LOOPNEZ
# (0 mod 4 alignment for LBEG)
.Lbyteset:
#if XCHAL_HAVE_LOOPS
loopnez a4, .Lbytesetdone
#else /* !XCHAL_HAVE_LOOPS */
beqz a4, .Lbytesetdone
add a6, a5, a4 # a6 = ending address
#endif /* !XCHAL_HAVE_LOOPS */
.Lbyteloop:
EX(s8i, a3, a5, 0, memset_fixup)
addi a5, a5, 1
#if !XCHAL_HAVE_LOOPS
blt a5, a6, .Lbyteloop
#endif /* !XCHAL_HAVE_LOOPS */
.Lbytesetdone:
retw
.section .fixup, "ax"
.align 4
/* We return zero if a failure occurred. */
memset_fixup:
movi a2, 0
retw
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