194 lines
5.0 KiB
Plaintext
194 lines
5.0 KiB
Plaintext
.\" -*- nroff -*-
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.\"
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.\" 62bit.tmac
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.\"
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.\" Copyright (C) 2003-2014 Free Software Foundation, Inc.
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.\" Written by Werner Lemberg (wl@gnu.org)
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.\"
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.\" This file is part of groff.
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.\"
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.\" groff is free software; you can redistribute it and/or modify it under
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.\" the terms of the GNU General Public License as published by the Free
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.\" Software Foundation, either version 3 of the License, or
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.\" (at your option) any later version.
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.\"
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.\" groff is distributed in the hope that it will be useful, but WITHOUT ANY
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.\" WARRANTY; without even the implied warranty of MERCHANTABILITY or
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.\" FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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.\" for more details.
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.\"
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.\" You should have received a copy of the GNU General Public License
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.\" along with this program. If not, see <http://www.gnu.org/licenses/>.
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.\"
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.\"
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.\"
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.\" This file provides macros for addition, multiplication, and division of
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.\" 62bit signed integers. Its main application is to `scale' 31bit values,
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.\" namely, to perform the operation `a * b / c' accurately.
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.\"
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.\" Note that it is the duty of the user to check whether the input values
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.\" fit within 31 bits (this is the range [-1073741824,1073741823]).
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.\"
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.
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.if d add31to62 \
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. nx
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.
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.
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.\" .add31to62 <x> <y> <z>
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.\"
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.\" Add a 31bit signed integer to a signed 62bit integer. Result is a
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.\" signed 62bit integer:
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.\"
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.\" <x> + (<y>h * 2^30 + <y>l) = <z>h * 2^30 + <z>l
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.\"
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.\"
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.\" in: \n[<x>], \n[<y>h], \n[<y>l]
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.\"
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.\" out: \n[<z>h], \n[<z>l]
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.\"
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.\" Example: .add31to62 p q r
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.\"
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.\" -> input registers: \n[p], \n[qh], \n[ql]
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.\" output registers: \n[rh], \n[rl]
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.\"
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.de1 add31to62
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. nr 62bit-lo2 (\\n[\\$2l])
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. nr 62bit-hi2 (\\n[\\$2h])
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.
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. nr 62bit-i ((\\n[\\$1] + \\n[62bit-lo2]) / 1073741824)
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. nr \\$3l ((\\n[\\$1] + \\n[62bit-lo2]) % 1073741824)
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.
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. ie ((\\n[62bit-lo2] > 0) & (\\n[\\$3l] < 0)) \{\
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. nr \\$3l +1073741824
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. nr 62bit-i -1
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. \}
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. el \
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. if ((\\n[62bit-lo2] < 0) & (\\n[\\$3l] > 0)) \{\
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. nr \\$3l -1073741824
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. nr 62bit-i +1
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. \}
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.
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. nr \\$3h (\\n[62bit-hi2] + \\n[62bit-i])
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..
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.
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.
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.\" .mult31by31 <x> <y> <z>
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.\"
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.\" Multiply two 31bit signed integers. Result is a 62bit signed
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.\" integer:
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.\"
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.\" <x> * <y> = <z>h * 2^30 + <z>l
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.\"
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.\"
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.\" in: \n[<x>], \n[<y>]
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.\"
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.\" out: \n[<z>h], \n[<z>l]
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.\"
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.\" Example: .mult31by31 a b c
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.\"
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.\" -> input registers: \n[a], \n[b]
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.\" output registers: \n[ch], \n[cl]
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.\"
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.de1 mult31by31
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. nr 62bit-1 (\\n[\\$1])
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. nr 62bit-2 (\\n[\\$2])
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.
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. nr 62bit-sign 1
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. if !\\n[62bit-1] \{\
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. nr 62bit-sign -(\\n[62bit-sign])
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. nr 62bit-1 -(\\n[62bit-1])
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. \}
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. if !\\n[62bit-2] \{\
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. nr 62bit-sign -(\\n[62bit-sign])
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. nr 62bit-2 -(\\n[62bit-2])
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. \}
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.
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. nr 62bit-lo1 (\\n[62bit-1] % 32768)
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. nr 62bit-hi1 (\\n[62bit-1] / 32768)
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. nr 62bit-lo2 (\\n[62bit-2] % 32768)
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. nr 62bit-hi2 (\\n[62bit-2] / 32768)
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.
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. nr 62bit-lo3 (\\n[62bit-lo1] * \\n[62bit-lo2] % 1073741824)
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. nr 62bit-i1 (\\n[62bit-lo1] * \\n[62bit-hi2] % 1073741824)
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. nr 62bit-i2 (\\n[62bit-lo2] * \\n[62bit-hi1] % 1073741824)
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. nr 62bit-hi3 (\\n[62bit-hi1] * \\n[62bit-hi2] % 1073741824)
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.
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. nr 62bit-i1 (\\n[62bit-i1] + \\n[62bit-i2] % 1073741824)
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. \" check carry overflow of 62bit-i1 + 62bit-i2
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. if (\\n[62bit-i1] < \\n[62bit-i2]) \
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. nr 62bit-hi3 +32768
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.
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. nr 62bit-hi3 +(\\n[62bit-i1] / 32768)
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. \" multiply by 32768 in small steps to avoid overflow
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. nr 62bit-i 16 1
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. while \\n-[62bit-i] \
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. nr 62bit-i1 (\\n[62bit-i1] * 2 % 1073741824)
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.
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. nr 62bit-lo3 (\\n[62bit-lo3] + \\n[62bit-i1] % 1073741824)
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. \" check carry overflow of 62bit-i1 + lo
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. if (\\n[62bit-lo3] < \\n[62bit-i1]) \
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. nr 62bit-hi3 +1
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.
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. if !\\n[62bit-sign] \{\
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. nr 62bit-lo3 -(\\n[62bit-lo3])
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. nr 62bit-hi3 -(\\n[62bit-hi3])
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. \}
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. nr \\$3l \\n[62bit-lo3]
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. nr \\$3h \\n[62bit-hi3]
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..
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.
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.
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.\" .div62by31 <x> <y> <z>
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.\"
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.\" Divide a signed 62bit integer by a 31bit integer. Result is a
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.\" 31bit signed integer:
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.\"
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.\" (<x>h * 2^30 + <x>l) / <y> = <z>
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.\"
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.\"
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.\" in: \n[<x>h], \n[<x>l], \n[<y>]
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.\"
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.\" out: \n[<z>]
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.\"
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.\" Example: .div62by31 foo bar baz
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.\"
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.\" -> input registers: \n[fooh] \n[fool] \n[bar]
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.\" output register: \n[baz]
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.\"
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.de1 div62by31
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. nr 62bit-lo1 \\n[\\$1l]
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. nr 62bit-hi1 \\n[\\$1h]
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. nr 62bit-2 \\n[\\$2]
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. nr 62bit-3 0
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.
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. nr 62bit-sign 1
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. if ((\\n[62bit-lo1] < 0) : (\\n[62bit-hi1] < 0)) \{\
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. nr 62bit-sign -(\\n[62bit-sign])
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. nr 62bit-lo1 -(\\n[62bit-lo1])
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. nr 62bit-hi1 -(\\n[62bit-hi1])
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. \}
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. if !\\n[62bit-2] \{\
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. nr 62bit-sign -(\\n[62bit-sign])
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. nr 62bit-2 -(\\n[62bit-2])
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. \}
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.
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. nr 62bit-i 31 1
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. while \\n-[62bit-i] \{\
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. nr 62bit-hi1 (\\n[62bit-hi1] * 2 % 1073741824)
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. nr 62bit-3 (\\n[62bit-3] * 2)
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. nr 62bit-hi1 +(\\n[62bit-lo1] / 536870912)
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.
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. if (\\n[62bit-hi1] >= \\n[62bit-2]) \{\
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. nr 62bit-hi1 -\\n[62bit-2]
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. nr 62bit-3 +1
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. \}
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. nr 62bit-lo1 (\\n[62bit-lo1] * 2 % 1073741824)
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. \}
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.
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. if !\\n[62bit-sign] \
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. nr 62bit-3 -(\\n[62bit-3])
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. nr \\$3 \\n[62bit-3]
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..
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.
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.\" EOF
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