1 dnl IBM POWER mpn_submul_1 -- Multiply a limb vector with a limb and subtract
2 dnl the result from a second limb vector.
4 dnl Copyright 1992, 1994, 1999-2001 Free Software Foundation, Inc.
6 dnl This file is part of the GNU MP Library.
8 dnl The GNU MP Library is free software; you can redistribute it and/or modify
9 dnl it under the terms of either:
11 dnl * the GNU Lesser General Public License as published by the Free
12 dnl Software Foundation; either version 3 of the License, or (at your
13 dnl option) any later version.
17 dnl * the GNU General Public License as published by the Free Software
18 dnl Foundation; either version 2 of the License, or (at your option) any
21 dnl or both in parallel, as here.
23 dnl The GNU MP Library is distributed in the hope that it will be useful, but
24 dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
25 dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
28 dnl You should have received copies of the GNU General Public License and the
29 dnl GNU Lesser General Public License along with the GNU MP Library. If not,
30 dnl see https://www.gnu.org/licenses/.
39 dnl The POWER architecture has no unsigned 32x32->64 bit multiplication
40 dnl instruction. To obtain that operation, we have to use the 32x32->64
41 dnl signed multiplication instruction, and add the appropriate compensation to
42 dnl the high limb of the result. We add the multiplicand if the multiplier
43 dnl has its most significant bit set, and we add the multiplier if the
44 dnl multiplicand has its most significant bit set. We need to preserve the
45 dnl carry flag between each iteration, so we have to compute the compensation
46 dnl carefully (the natural, srai+and doesn't work). Since all POWER can
47 dnl branch in zero cycles, we use conditional branches for the compensation.
49 include(`../config.m4')
52 PROLOGUE(mpn_submul_1)
63 sf 8,11,7 C add res_limb
64 a 11,8,11 C invert cy (r11 is junk)
73 ae 11,0,9 C low limb + old_cy_limb + old cy
75 aze 10,10 C propagate cy to new cy_limb
76 sf 8,11,7 C add res_limb
77 a 11,8,11 C invert cy (r11 is junk)
79 cax 10,10,6 C adjust high limb for negative limb from s1
90 a 11,8,11 C invert cy (r11 is junk)
92 cax 9,9,6 C adjust high limb for negative limb from s1
106 ae 10,10,0 C propagate cy to new cy_limb
107 sf 8,11,7 C add res_limb
108 a 11,8,11 C invert cy (r11 is junk)
110 cax 10,10,6 C adjust high limb for negative limb from s1
119 ae 9,9,0 C propagate cy to new cy_limb
120 sf 8,11,7 C add res_limb
121 a 11,8,11 C invert cy (r11 is junk)
123 cax 9,9,6 C adjust high limb for negative limb from s1
131 EPILOGUE(mpn_submul_1)