Update.
[glibc.git] / sysdeps / alpha / rshift.s
blob389054ab0e92a903f2b845e6808ccafa62e059fc
1 # Alpha 21064 __mpn_rshift --
3 # Copyright (C) 1994, 1995 Free Software Foundation, Inc.
5 # This file is part of the GNU MP Library.
7 # The GNU MP Library is free software; you can redistribute it and/or modify
8 # it under the terms of the GNU Library General Public License as published by
9 # the Free Software Foundation; either version 2 of the License, or (at your
10 # option) any later version.
12 # The GNU MP Library is distributed in the hope that it will be useful, but
13 # WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
14 # or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
15 # License for more details.
17 # You should have received a copy of the GNU Library General Public License
18 # along with the GNU MP Library; see the file COPYING.LIB. If not, write to
19 # the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
20 # MA 02111-1307, USA.
23 # INPUT PARAMETERS
24 # res_ptr r16
25 # s1_ptr r17
26 # size r18
27 # cnt r19
29 # This code runs at 4.8 cycles/limb on the 21064. With infinite unrolling,
30 # it would take 4 cycles/limb. It should be possible to get down to 3
31 # cycles/limb since both ldq and stq can be paired with the other used
32 # instructions. But there are many restrictions in the 21064 pipeline that
33 # makes it hard, if not impossible, to get down to 3 cycles/limb:
35 # 1. ldq has a 3 cycle delay, srl and sll have a 2 cycle delay.
36 # 2. Only aligned instruction pairs can be paired.
37 # 3. The store buffer or silo might not be able to deal with the bandwidth.
39 .set noreorder
40 .set noat
41 .text
42 .align 3
43 .globl __mpn_rshift
44 .ent __mpn_rshift
45 __mpn_rshift:
46 .frame $30,0,$26,0
48 ldq $4,0($17) # load first limb
49 addq $17,8,$17
50 subq $31,$19,$7
51 subq $18,1,$18
52 and $18,4-1,$20 # number of limbs in first loop
53 sll $4,$7,$0 # compute function result
55 beq $20,.L0
56 subq $18,$20,$18
58 .align 3
59 .Loop0:
60 ldq $3,0($17)
61 addq $16,8,$16
62 addq $17,8,$17
63 subq $20,1,$20
64 srl $4,$19,$5
65 sll $3,$7,$6
66 bis $3,$3,$4
67 bis $5,$6,$8
68 stq $8,-8($16)
69 bne $20,.Loop0
71 .L0: beq $18,.Lend
73 .align 3
74 .Loop: ldq $3,0($17)
75 addq $16,32,$16
76 subq $18,4,$18
77 srl $4,$19,$5
78 sll $3,$7,$6
80 ldq $4,8($17)
81 srl $3,$19,$1
82 bis $5,$6,$8
83 stq $8,-32($16)
84 sll $4,$7,$2
86 ldq $3,16($17)
87 srl $4,$19,$5
88 bis $1,$2,$8
89 stq $8,-24($16)
90 sll $3,$7,$6
92 ldq $4,24($17)
93 srl $3,$19,$1
94 bis $5,$6,$8
95 stq $8,-16($16)
96 sll $4,$7,$2
98 addq $17,32,$17
99 bis $1,$2,$8
100 stq $8,-8($16)
102 bgt $18,.Loop
104 .Lend: srl $4,$19,$8
105 stq $8,0($16)
106 ret $31,($26),1
107 .end __mpn_rshift