1/* Copyright (C) 1996-2021 Free Software Foundation, Inc.
2   This file is part of the GNU C Library.
3
4   The GNU C Library is free software; you can redistribute it and/or
5   modify it under the terms of the GNU Lesser General Public
6   License as published by the Free Software Foundation; either
7   version 2.1 of the License, or (at your option) any later version.
8
9   The GNU C Library is distributed in the hope that it will be useful,
10   but WITHOUT ANY WARRANTY; without even the implied warranty of
11   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
12   Lesser General Public License for more details.
13
14   You should have received a copy of the GNU Lesser General Public
15   License along with the GNU C Library.  If not, see
16   <https://www.gnu.org/licenses/>.  */
17
18/* Fill a block of memory with a character.  Optimized for the Alpha
19   architecture:
20
21   - memory accessed as aligned quadwords only
22   - destination memory not read unless needed for good cache behaviour
23   - basic blocks arranged to optimize branch prediction for full-quadword
24     aligned memory blocks.
25   - partial head and tail quadwords constructed with byte-mask instructions
26
27   This is generally scheduled for the EV5 (got to look out for my own
28   interests :-), but with EV4 needs in mind.  There *should* be no more
29   stalls for the EV4 than there are for the EV5.
30*/
31
32
33#include <sysdep.h>
34
35	.set noat
36	.set noreorder
37
38	.text
39	.type	memset, @function
40	.globl	memset
41	.usepv	memset, USEPV_PROF
42
43	cfi_startproc
44
45	/* On entry to this basic block:
46	   t3 == loop counter
47	   t4 == bytes in partial final word
48	   a0 == possibly misaligned destination pointer
49	   a1 == replicated source character  */
50
51	.align 3
52memset_loop:
53	beq	t3, $tail
54	blbc	t3, 0f		# skip single store if count even
55
56	stq_u	a1, 0(a0)	# e0    : store one word
57	subq	t3, 1, t3	# .. e1 :
58	addq	a0, 8, a0	# e0    :
59	beq	t3, $tail	# .. e1 :
60
610:	stq_u	a1, 0(a0)	# e0    : store two words
62	subq	t3, 2, t3	# .. e1 :
63	stq_u	a1, 8(a0)	# e0    :
64	addq	a0, 16, a0	# .. e1 :
65	bne	t3, 0b		# e1    :
66
67$tail:	bne	t4, 1f		# is there a tail to do?
68	ret			# no
69
70	.align 3
711:	ldq_u	t0, 0(a0)	# e1    : yes, load original data
72	mskql	a1, t4, t1	# .. e0 :
73	mskqh	t0, t4, t0	# e0    :
74	or	t0, t1, t0	# e1 (stall)
75	stq_u	t0, 0(a0)	# e0    :
76	ret			# .. e1 :
77
78memset:
79#ifdef PROF
80	ldgp	gp, 0(pv)
81	lda	AT, _mcount
82	jsr	AT, (AT), _mcount
83#endif
84
85	and	a1, 0xff, a1	# e0    : zero extend input character
86	mov	a0, v0		# .. e1 : move return value in place
87	sll	a1, 8, t0	# e0    : begin replicating the char
88	beq	a2, $done	# .. e1 : early exit for zero-length store
89	or	t0, a1, a1	# e0    :
90	and	a0, 7, t1	# .. e1 : dest misalignment
91	sll	a1, 16, t0	# e0    :
92	addq	a2, t1, a2	# .. e1 : add dest misalignment to count
93	or	t0, a1, a1	# e0    :
94	srl	a2, 3, t3	# .. e1 : loop = count >> 3
95	sll	a1, 32, t0	# e0    :
96	and	a2, 7, t4	# .. e1 : find number of bytes in tail
97	or	t0, a1, a1	# e0    : character replication done
98
99	beq	t1, memset_loop	# .. e1 : aligned head, jump right in
100
101	ldq_u	t0, 0(a0)	# e1    : load original data to mask into
102	mskqh	a1, a0, t1	# .. e0 :
103
104	cmpult	a2, 8, t2	# e0    : is this a sub-word set?
105	bne	t2, $oneq	# .. e1 (zdb)
106
107	mskql	t0, a0, t0	# e0    : we span words.  finish this partial
108	subq	t3, 1, t3	# .. e1 :
109	addq	a0, 8, a0	# e0    :
110	or	t0, t1, t0	# .. e1 :
111	stq_u	t0, -8(a0)	# e0    :
112	br 	memset_loop	# .. e1 :
113
114	.align 3
115$oneq:
116	mskql	t1, a2, t1	# e0    : entire operation within one word
117	mskql	t0, a0, t2	# e0    :
118	mskqh	t0, a2, t3	# e0    :
119	or	t1, t2, t0	# .. e1 :
120	or	t0, t3, t0	# e1    :
121	stq_u	t0, 0(a0)	# e0 (stall)
122
123$done:	ret
124
125	cfi_endproc
126libc_hidden_builtin_def (memset)
127