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bfff8b1b | 1 | /* Copyright (C) 1996-2017 Free Software Foundation, Inc. |
cf182b58 | 2 | Contributed by Richard Henderson (rth@tamu.edu) |
db31c863 | 3 | This file is part of the GNU C Library. |
cf182b58 | 4 | |
db31c863 | 5 | The GNU C Library is free software; you can redistribute it and/or |
3214b89b AJ |
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. | |
cf182b58 | 9 | |
db31c863 UD |
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 | |
3214b89b | 13 | Lesser General Public License for more details. |
cf182b58 | 14 | |
3214b89b | 15 | You should have received a copy of the GNU Lesser General Public |
ab84e3ff PE |
16 | License along with the GNU C Library. If not, see |
17 | <http://www.gnu.org/licenses/>. */ | |
cf182b58 UD |
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 | |
b2afe910 RH |
39 | .type __bzero, @function |
40 | .globl __bzero | |
41 | .usepv __bzero, USEPV_PROF | |
cf182b58 | 42 | |
b2afe910 | 43 | cfi_startproc |
cf182b58 UD |
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 | ||
cf182b58 UD |
50 | .align 3 |
51 | bzero_loop: | |
cf182b58 UD |
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 | ||
60 | 0: 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 | ||
69 | 1: ldq_u t0, 0(a0) # yes, load original data | |
70 | mskqh t0, t4, t0 # | |
71 | stq_u t0, 0(a0) # | |
72 | ret # | |
73 | ||
b2afe910 | 74 | __bzero: |
60c74cf0 UD |
75 | #ifdef PROF |
76 | ldgp gp, 0(pv) | |
77 | lda AT, _mcount | |
78 | jsr AT, (AT), _mcount | |
60c74cf0 | 79 | #endif |
cf182b58 UD |
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 | ||
b2afe910 | 109 | cfi_endproc |
384cd03a | 110 | weak_alias (__bzero, bzero) |