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1/* Copyright (C) 1996-2019 Free Software Foundation, Inc.
2 Contributed by Richard Henderson (rth@tamu.edu)
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library. If not, see
17 <http://www.gnu.org/licenses/>. */
18
19/* Fill a block of memory with zeros. Optimized for the Alpha 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 __bzero, @function
40 .globl __bzero
41 .usepv __bzero, 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
50 .align 3
51bzero_loop:
52 beq t3, $tail #
53 blbc t3, 0f # skip single store if count even
54
55 stq_u zero, 0(a0) # e0 : store one word
56 subq t3, 1, t3 # .. e1 :
57 addq a0, 8, a0 # e0 :
58 beq t3, $tail # .. e1 :
59
600: stq_u zero, 0(a0) # e0 : store two words
61 subq t3, 2, t3 # .. e1 :
62 stq_u zero, 8(a0) # e0 :
63 addq a0, 16, a0 # .. e1 :
64 bne t3, 0b # e1 :
65
66$tail: bne t4, 1f # is there a tail to do?
67 ret # no
68
691: ldq_u t0, 0(a0) # yes, load original data
70 mskqh t0, t4, t0 #
71 stq_u t0, 0(a0) #
72 ret #
73
74__bzero:
75#ifdef PROF
76 ldgp gp, 0(pv)
77 lda AT, _mcount
78 jsr AT, (AT), _mcount
79#endif
80
81 mov a0, v0 # e0 : move return value in place
82 beq a1, $done # .. e1 : early exit for zero-length store
83 and a0, 7, t1 # e0 :
84 addq a1, t1, a1 # e1 : add dest misalignment to count
85 srl a1, 3, t3 # e0 : loop = count >> 3
86 and a1, 7, t4 # .. e1 : find number of bytes in tail
87 unop # :
88 beq t1, bzero_loop # e1 : aligned head, jump right in
89
90 ldq_u t0, 0(a0) # e0 : load original data to mask into
91 cmpult a1, 8, t2 # .. e1 : is this a sub-word set?
92 bne t2, $oneq # e1 :
93
94 mskql t0, a0, t0 # e0 : we span words. finish this partial
95 subq t3, 1, t3 # e0 :
96 addq a0, 8, a0 # .. e1 :
97 stq_u t0, -8(a0) # e0 :
98 br bzero_loop # .. e1 :
99
100 .align 3
101$oneq:
102 mskql t0, a0, t2 # e0 :
103 mskqh t0, a1, t3 # e0 :
104 or t2, t3, t0 # e1 :
105 stq_u t0, 0(a0) # e0 :
106
107$done: ret
108
109 cfi_endproc
110weak_alias (__bzero, bzero)
111

Warning: That file was not part of the compilation database. It may have many parsing errors.