1/*
  2 *  arch/xtensa/lib/memset.S
  3 *
  4 *  ANSI C standard library function memset
  5 *  (Well, almost.  .fixup code might return zero.)
  6 *
  7 *  This file is subject to the terms and conditions of the GNU General
  8 *  Public License.  See the file "COPYING" in the main directory of
  9 *  this archive for more details.
 10 *
 11 *  Copyright (C) 2002 Tensilica Inc.
 12 */
 13
 14#include <linux/linkage.h>
 15#include <variant/core.h>
 16#include <asm/asmmacro.h>
 17
 18/*
 19 * void *memset(void *dst, int c, size_t length)
 20 *
 21 * The algorithm is as follows:
 22 *   Create a word with c in all byte positions
 23 *   If the destination is aligned,
 24 *     do 16B chucks with a loop, and then finish up with
 25 *     8B, 4B, 2B, and 1B stores conditional on the length.
 26 *   If destination is unaligned, align it by conditionally
 27 *     setting 1B and 2B and then go to aligned case.
 28 *   This code tries to use fall-through branches for the common
 29 *     case of an aligned destination (except for the branches to
 30 *     the alignment labels).
 31 */
 32
 33.text
 34ENTRY(__memset)
 35WEAK(memset)
 36
 37	entry	sp, 16		# minimal stack frame
 38	# a2/ dst, a3/ c, a4/ length
 39	extui	a3, a3, 0, 8	# mask to just 8 bits
 40	slli	a7, a3, 8	# duplicate character in all bytes of word
 41	or	a3, a3, a7	# ...
 42	slli	a7, a3, 16	# ...
 43	or	a3, a3, a7	# ...
 44	mov	a5, a2		# copy dst so that a2 is return value
 45	movi	a6, 3		# for alignment tests
 46	bany	a2, a6, .Ldstunaligned # if dst is unaligned
 47.L0:	# return here from .Ldstunaligned when dst is aligned
 48	srli	a7, a4, 4	# number of loop iterations with 16B
 49				# per iteration
 50	bnez	a4, .Laligned
 51	retw
 52
 53/*
 54 * Destination is word-aligned.
 55 */
 56	# set 16 bytes per iteration for word-aligned dst
 57	.align	4		# 1 mod 4 alignment for LOOPNEZ
 58	.byte	0		# (0 mod 4 alignment for LBEG)
 59.Laligned:
 60#if XCHAL_HAVE_LOOPS
 61	loopnez	a7, .Loop1done
 62#else /* !XCHAL_HAVE_LOOPS */
 63	beqz	a7, .Loop1done
 64	slli	a6, a7, 4
 65	add	a6, a6, a5	# a6 = end of last 16B chunk
 66#endif /* !XCHAL_HAVE_LOOPS */
 67.Loop1:
 68EX(10f) s32i	a3, a5,  0
 69EX(10f) s32i	a3, a5,  4
 70EX(10f) s32i	a3, a5,  8
 71EX(10f) s32i	a3, a5, 12
 72	addi	a5, a5, 16
 73#if !XCHAL_HAVE_LOOPS
 74	blt	a5, a6, .Loop1
 75#endif /* !XCHAL_HAVE_LOOPS */
 76.Loop1done:
 77	bbci.l	a4, 3, .L2
 78	# set 8 bytes
 79EX(10f) s32i	a3, a5,  0
 80EX(10f) s32i	a3, a5,  4
 81	addi	a5, a5,  8
 82.L2:
 83	bbci.l	a4, 2, .L3
 84	# set 4 bytes
 85EX(10f) s32i	a3, a5,  0
 86	addi	a5, a5,  4
 87.L3:
 88	bbci.l	a4, 1, .L4
 89	# set 2 bytes
 90EX(10f) s16i	a3, a5,  0
 91	addi	a5, a5,  2
 92.L4:
 93	bbci.l	a4, 0, .L5
 94	# set 1 byte
 95EX(10f) s8i	a3, a5,  0
 96.L5:
 97.Lret1:
 98	retw
 99
100/*
101 * Destination is unaligned
102 */
103
104.Ldstunaligned:
105	bltui	a4, 8, .Lbyteset	# do short copies byte by byte
106	bbci.l	a5, 0, .L20		# branch if dst alignment half-aligned
107	# dst is only byte aligned
108	# set 1 byte
109EX(10f) s8i	a3, a5,  0
110	addi	a5, a5,  1
111	addi	a4, a4, -1
112	# now retest if dst aligned
113	bbci.l	a5, 1, .L0	# if now aligned, return to main algorithm
114.L20:
115	# dst half-aligned
116	# set 2 bytes
117EX(10f) s16i	a3, a5,  0
118	addi	a5, a5,  2
119	addi	a4, a4, -2
120	j	.L0		# dst is now aligned, return to main algorithm
121
122/*
123 * Byte by byte set
124 */
125	.align	4
126	.byte	0		# 1 mod 4 alignment for LOOPNEZ
127				# (0 mod 4 alignment for LBEG)
128.Lbyteset:
129#if XCHAL_HAVE_LOOPS
130	loopnez	a4, .Lbytesetdone
131#else /* !XCHAL_HAVE_LOOPS */
132	beqz	a4, .Lbytesetdone
133	add	a6, a5, a4	# a6 = ending address
134#endif /* !XCHAL_HAVE_LOOPS */
135.Lbyteloop:
136EX(10f) s8i	a3, a5, 0
137	addi	a5, a5, 1
138#if !XCHAL_HAVE_LOOPS
139	blt	a5, a6, .Lbyteloop
140#endif /* !XCHAL_HAVE_LOOPS */
141.Lbytesetdone:
142	retw
143
144ENDPROC(__memset)
145
146	.section .fixup, "ax"
147	.align	4
148
149/* We return zero if a failure occurred. */
150
15110:
152	movi	a2, 0
153	retw