1 # Alpha 21064 __mpn_rshift -- 2 3 # Copyright (C) 1994-2022 Free Software Foundation, Inc. 4 5 # This file is part of the GNU MP Library. 6 7 # The GNU MP Library is free software; you can redistribute it and/or modify 8 # it under the terms of the GNU Lesser General Public License as published by 9 # the Free Software Foundation; either version 2.1 of the License, or (at your 10 # option) any later version. 11 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 Lesser General Public 15 # License for more details. 16 17 # You should have received a copy of the GNU Lesser General Public License 18 # along with the GNU MP Library. If not, see <https://www.gnu.org/licenses/>. 19 20 21 # INPUT PARAMETERS 22 # res_ptr r16 23 # s1_ptr r17 24 # size r18 25 # cnt r19 26 27 # This code runs at 4.8 cycles/limb on the 21064. With infinite unrolling, 28 # it would take 4 cycles/limb. It should be possible to get down to 3 29 # cycles/limb since both ldq and stq can be paired with the other used 30 # instructions. But there are many restrictions in the 21064 pipeline that 31 # makes it hard, if not impossible, to get down to 3 cycles/limb: 32 33 # 1. ldq has a 3 cycle delay, srl and sll have a 2 cycle delay. 34 # 2. Only aligned instruction pairs can be paired. 35 # 3. The store buffer or silo might not be able to deal with the bandwidth. 36 37 .set noreorder 38 .set noat 39.text 40 .align 3 41 .globl __mpn_rshift 42 .ent __mpn_rshift 43__mpn_rshift: 44 .frame $30,0,$26,0 45 46 ldq $4,0($17) # load first limb 47 addq $17,8,$17 48 subq $31,$19,$7 49 subq $18,1,$18 50 and $18,4-1,$20 # number of limbs in first loop 51 sll $4,$7,$0 # compute function result 52 53 beq $20,.L0 54 subq $18,$20,$18 55 56 .align 3 57.Loop0: 58 ldq $3,0($17) 59 addq $16,8,$16 60 addq $17,8,$17 61 subq $20,1,$20 62 srl $4,$19,$5 63 sll $3,$7,$6 64 bis $3,$3,$4 65 bis $5,$6,$8 66 stq $8,-8($16) 67 bne $20,.Loop0 68 69.L0: beq $18,.Lend 70 71 .align 3 72.Loop: ldq $3,0($17) 73 addq $16,32,$16 74 subq $18,4,$18 75 srl $4,$19,$5 76 sll $3,$7,$6 77 78 ldq $4,8($17) 79 srl $3,$19,$1 80 bis $5,$6,$8 81 stq $8,-32($16) 82 sll $4,$7,$2 83 84 ldq $3,16($17) 85 srl $4,$19,$5 86 bis $1,$2,$8 87 stq $8,-24($16) 88 sll $3,$7,$6 89 90 ldq $4,24($17) 91 srl $3,$19,$1 92 bis $5,$6,$8 93 stq $8,-16($16) 94 sll $4,$7,$2 95 96 addq $17,32,$17 97 bis $1,$2,$8 98 stq $8,-8($16) 99 100 bgt $18,.Loop 101 102.Lend: srl $4,$19,$8 103 stq $8,0($16) 104 ret $31,($26),1 105 .end __mpn_rshift 106