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[glibc.git] / sysdeps / alpha / lshift.s
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1 # Alpha 21064 __mpn_lshift --
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_lshift
44 .ent __mpn_lshift
45 __mpn_lshift:
46 .frame $30,0,$26,0
48 s8addq $18,$17,$17 # make r17 point at end of s1
49 ldq $4,-8($17) # load first limb
50 subq $17,8,$17
51 subq $31,$19,$7
52 s8addq $18,$16,$16 # make r16 point at end of RES
53 subq $18,1,$18
54 and $18,4-1,$20 # number of limbs in first loop
55 srl $4,$7,$0 # compute function result
57 beq $20,.L0
58 subq $18,$20,$18
60 .align 3
61 .Loop0:
62 ldq $3,-8($17)
63 subq $16,8,$16
64 subq $17,8,$17
65 subq $20,1,$20
66 sll $4,$19,$5
67 srl $3,$7,$6
68 bis $3,$3,$4
69 bis $5,$6,$8
70 stq $8,0($16)
71 bne $20,.Loop0
73 .L0: beq $18,.Lend
75 .align 3
76 .Loop: ldq $3,-8($17)
77 subq $16,32,$16
78 subq $18,4,$18
79 sll $4,$19,$5
80 srl $3,$7,$6
82 ldq $4,-16($17)
83 sll $3,$19,$1
84 bis $5,$6,$8
85 stq $8,24($16)
86 srl $4,$7,$2
88 ldq $3,-24($17)
89 sll $4,$19,$5
90 bis $1,$2,$8
91 stq $8,16($16)
92 srl $3,$7,$6
94 ldq $4,-32($17)
95 sll $3,$19,$1
96 bis $5,$6,$8
97 stq $8,8($16)
98 srl $4,$7,$2
100 subq $17,32,$17
101 bis $1,$2,$8
102 stq $8,0($16)
104 bgt $18,.Loop
106 .Lend: sll $4,$19,$8
107 stq $8,-8($16)
108 ret $31,($26),1
109 .end __mpn_lshift