| dnl PowerPC-32 mpn_divexact_by3 -- mpn by 3 exact division |
| |
| dnl Copyright 2002, 2003, 2005, 2006 Free Software Foundation, Inc. |
| |
| dnl This file is part of the GNU MP Library. |
| dnl |
| dnl The GNU MP Library is free software; you can redistribute it and/or modify |
| dnl it under the terms of either: |
| dnl |
| dnl * the GNU Lesser General Public License as published by the Free |
| dnl Software Foundation; either version 3 of the License, or (at your |
| dnl option) any later version. |
| dnl |
| dnl or |
| dnl |
| dnl * the GNU General Public License as published by the Free Software |
| dnl Foundation; either version 2 of the License, or (at your option) any |
| dnl later version. |
| dnl |
| dnl or both in parallel, as here. |
| dnl |
| 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 General Public License |
| dnl for more details. |
| dnl |
| dnl You should have received copies of the GNU General Public License and the |
| dnl GNU Lesser General Public License along with the GNU MP Library. If not, |
| dnl see https://www.gnu.org/licenses/. |
| |
| include(`../config.m4') |
| |
| C cycles/limb |
| C 603e: ? |
| C 604e: 5 |
| C 75x (G3): ? |
| C 7400,7410 (G4): 8 |
| C 744x,745x (G4+): 6 |
| C power4/ppc970: 12 |
| C power5: ? |
| |
| C void mpn_divexact_by3 (mp_ptr dst, mp_srcptr src, mp_size_t size); |
| C |
| C We avoid the slow subfe instruction and instead rely on an extremely unlikely |
| C branch. |
| C |
| C The mullw has the inverse in the first operand, since 0xAA..AB won't allow |
| C any early-out. The src[] data normally won't either, but there's at least |
| C a chance, whereas 0xAA..AB never will. If, for instance, src[] is all |
| C zeros (not a sensible input of course) we run at 7.0 c/l on ppc750. |
| C |
| C The mulhwu has the "3" multiplier in the second operand, which lets 750 and |
| C 7400 use an early-out. |
| |
| C INPUT PARAMETERS |
| define(`rp', `r3') |
| define(`up', `r4') |
| define(`n', `r5') |
| define(`cy', `r6') |
| |
| ASM_START() |
| PROLOGUE(mpn_divexact_by3c) |
| lwz r11, 0(up) |
| mtctr n |
| lis r12, 0xAAAA |
| ori r12, r12, 0xAAAB |
| li r10, 3 |
| |
| cmplw cr7, cy, r11 |
| subf r11, cy, r11 |
| |
| mullw r0, r11, r12 |
| stw r0, 0(rp) |
| bdz L(one) |
| |
| L(top): lwzu r9, 4(up) |
| mulhwu r7, r0, r10 |
| bgt- cr7, L(adj) C very unlikely branch |
| L(bko): cmplw cr7, r7, r9 |
| subf r0, r7, r9 |
| mullw r0, r12, r0 |
| stwu r0, 4(rp) |
| bdnz L(top) |
| |
| L(one): mulhwu r3, r0, r10 |
| blelr+ cr7 |
| addi r3, r3, 1 |
| blr |
| |
| L(adj): addi r7, r7, 1 |
| b L(bko) |
| EPILOGUE() |
| ASM_END() |