summary refs log tree commit diff
path: root/sysdeps/alpha/memset.S
blob: d621aeed19ec3f7a908caceab5d255ea1a8352b2 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
/* Copyright (C) 1996, 1997 Free Software Foundation, Inc.
   Contributed by Richard Henderson (rth@tamu.edu)
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

/* Fill a block of memory with a character.  Optimized for the Alpha
   architecture:

   - memory accessed as aligned quadwords only
   - destination memory not read unless needed for good cache behaviour
   - basic blocks arranged to optimize branch prediction for full-quadword
     aligned memory blocks.
   - partial head and tail quadwords constructed with byte-mask instructions

   This is generally scheduled for the EV5 (got to look out for my own
   interests :-), but with EV4 needs in mind.  There *should* be no more
   stalls for the EV4 than there are for the EV5.
*/


#include <sysdep.h>

	.set noat
	.set noreorder

	.text

/* There is a problem with either gdb (as of 4.16) or gas (as of 2.7) that
   doesn't like putting the entry point for a procedure somewhere in the
   middle of the procedure descriptor.  Work around this by putting the main
   loop in its own procedure descriptor.  */

	/* On entry to this basic block:
	   t3 == loop counter
	   t4 == bytes in partial final word
	   a0 == possibly misaligned destination pointer
	   a1 == replicated source character  */

	.ent memset_loop
	.align 3
memset_loop:
	.frame sp, 0, ra, 0
	.prologue 0

	beq	t3, $tail
	blbc	t3, 0f		# skip single store if count even

	stq_u	a1, 0(a0)	# e0    : store one word
	subq	t3, 1, t3	# .. e1 :
	addq	a0, 8, a0	# e0    :
	beq	t3, $tail	# .. e1 :

0:	stq_u	a1, 0(a0)	# e0    : store two words
	subq	t3, 2, t3	# .. e1 :
	stq_u	a1, 8(a0)	# e0    :
	addq	a0, 16, a0	# .. e1 :
	bne	t3, 0b		# e1    :

$tail:	bne	t4, 1f		# is there a tail to do?
	ret			# no

	.align 3
1:	ldq_u	t0, 0(a0)	# e1    : yes, load original data
	mskql	a1, t4, t1	# .. e0 :
	mskqh	t0, t4, t0	# e0    :
	or	t0, t1, t0	# e1 (stall)
	stq_u	t0, 0(a0)	# e0    :
	ret			# .. e1 :

	.end memset_loop

ENTRY(memset)
#ifdef PROF
	ldgp	gp, 0(pv)
	lda	AT, _mcount
	jsr	AT, (AT), _mcount
	.prologue 1
#else
	.prologue 0
#endif

	zapnot	a1, 1, a1	# e0    : zero extend input character
	mov	a0, v0		# .. e1 : move return value in place
	sll	a1, 8, t0	# e0    : begin replicating the char
	beq	a2, $done	# .. e1 : early exit for zero-length store
	or	t0, a1, a1	# e0    :
	and	a0, 7, t1	# .. e1 : dest misalignment
	sll	a1, 16, t0	# e0    :
	addq	a2, t1, a2	# .. e1 : add dest misalignment to count
	or	t0, a1, a1	# e0    :
	srl	a2, 3, t3	# .. e1 : loop = count >> 3
	sll	a1, 32, t0	# e0    :
	and	a2, 7, t4	# .. e1 : find number of bytes in tail
	or	t0, a1, a1	# e0    : character replication done

	beq	t1, memset_loop	# .. e1 : aligned head, jump right in

	ldq_u	t0, 0(a0)	# e1    : load original data to mask into
	mskqh	a1, a0, t1	# .. e0 :

	cmpult	a2, 8, t2	# e0    : is this a sub-word set?
	bne	t2, $oneq	# .. e1 (zdb)

	mskql	t0, a0, t0	# e0    : we span words.  finish this partial
	subq	t3, 1, t3	# .. e1 :
	addq	a0, 8, a0	# e0    :
	or	t0, t1, t0	# .. e1 :
	stq_u	t0, -8(a0)	# e0    :
	br 	memset_loop	# .. e1 :

	.align 3
$oneq:
	mskql	t1, a2, t1	# e0    : entire operation within one word
	mskql	t0, a0, t2	# e0    :
	mskqh	t0, a2, t3	# e0    :
	or	t1, t2, t0	# .. e1 :
	or	t0, t3, t0	# e1    :
	stq_u	t0, 0(a0)	# e0 (stall)

$done:	ret

	END(memset)