| dnl ARM mpn_invert_limb -- Invert a normalized limb. |
| |
| dnl Copyright 2001 Free Software Foundation, Inc. |
| |
| dnl This file is part of the GNU MP Library. |
| |
| dnl The GNU MP Library is free software; you can redistribute it and/or modify |
| dnl it under the terms of the GNU Lesser General Public License as published |
| dnl by the Free Software Foundation; either version 3 of the License, or (at |
| dnl your option) any later version. |
| |
| dnl The GNU MP Library is distributed in the hope that it will be useful, but |
| dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY |
| dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public |
| dnl License for more details. |
| |
| dnl You should have received a copy of the GNU Lesser General Public License |
| dnl along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. |
| |
| include(`../config.m4') |
| |
| C INPUT PARAMETERS |
| define(`d',`r0') C number to be inverted |
| |
| |
| PROLOGUE(mpn_invert_limb) |
| stmfd sp!, {r4, lr} |
| mov r3, d, lsr #23 |
| sub r3, r3, #256 |
| add r2, pc, #invtab-.-8 |
| mov r3, r3, lsl #1 |
| ldrh r1, [r2, r3] C get initial approximation from table |
| mov r2, r1, lsl #6 C start iteration 1 |
| mul ip, r2, r2 |
| umull lr, r4, ip, d |
| mov r2, r4, lsl #1 |
| rsb r2, r2, r1, lsl #23 C iteration 1 complete |
| umull ip, r3, r2, r2 C start iteration 2 |
| umull lr, r4, r3, d |
| umull r3, r1, ip, d |
| adds lr, lr, r1 |
| addcs r4, r4, #1 |
| mov r3, lr, lsr #30 |
| orr r4, r3, r4, lsl #2 |
| mov lr, lr, lsl #2 |
| cmn lr, #1 |
| rsc r2, r4, r2, lsl #2 C iteration 2 complete |
| umull ip, r1, d, r2 C start adjustment step |
| add r1, r1, d |
| cmn r1, #1 |
| beq L(1) |
| adds ip, ip, d |
| adc r1, r1, #0 |
| add r2, r2, #1 |
| L(1): |
| adds r3, ip, d |
| adcs r1, r1, #0 |
| moveq r0, r2 |
| addne r0, r2, #1 |
| ldmfd sp!, {r4, pc} |
| |
| invtab: |
| .short 1023,1020,1016,1012,1008,1004,1000,996 |
| .short 992,989,985,981,978,974,970,967 |
| .short 963,960,956,953,949,946,942,939 |
| .short 936,932,929,926,923,919,916,913 |
| .short 910,907,903,900,897,894,891,888 |
| .short 885,882,879,876,873,870,868,865 |
| .short 862,859,856,853,851,848,845,842 |
| .short 840,837,834,832,829,826,824,821 |
| .short 819,816,814,811,809,806,804,801 |
| .short 799,796,794,791,789,787,784,782 |
| .short 780,777,775,773,771,768,766,764 |
| .short 762,759,757,755,753,751,748,746 |
| .short 744,742,740,738,736,734,732,730 |
| .short 728,726,724,722,720,718,716,714 |
| .short 712,710,708,706,704,702,700,699 |
| .short 697,695,693,691,689,688,686,684 |
| .short 682,680,679,677,675,673,672,670 |
| .short 668,667,665,663,661,660,658,657 |
| .short 655,653,652,650,648,647,645,644 |
| .short 642,640,639,637,636,634,633,631 |
| .short 630,628,627,625,624,622,621,619 |
| .short 618,616,615,613,612,611,609,608 |
| .short 606,605,604,602,601,599,598,597 |
| .short 595,594,593,591,590,589,587,586 |
| .short 585,583,582,581,579,578,577,576 |
| .short 574,573,572,571,569,568,567,566 |
| .short 564,563,562,561,560,558,557,556 |
| .short 555,554,553,551,550,549,548,547 |
| .short 546,544,543,542,541,540,539,538 |
| .short 537,536,534,533,532,531,530,529 |
| .short 528,527,526,525,524,523,522,521 |
| .short 520,519,518,517,516,515,514,513 |
| EPILOGUE(mpn_invert_limb) |
