dnl AMD64 mpn_modexact_1_odd -- exact division style remainder. dnl Copyright 2000, 2001, 2002, 2003, 2004, 2005, 2006 Free Software dnl Foundation, Inc. dnl 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 dnl modify it under the terms of the GNU Lesser General Public License as dnl published by the Free Software Foundation; either version 3 of the dnl License, or (at your option) any later version. dnl dnl The GNU MP Library is distributed in the hope that it will be useful, dnl but WITHOUT ANY WARRANTY; without even the implied warranty of dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU dnl Lesser General Public License for more details. dnl 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 cycles/limb C K8,K9: 10 C K10: 10 C P4: 33 C P6-15 (Core2):13 C P6-28 (Atom): 35 C mp_limb_t mpn_modexact_1_odd (mp_srcptr src, mp_size_t size, C mp_limb_t divisor); C mp_limb_t mpn_modexact_1c_odd (mp_srcptr src, mp_size_t size, C mp_limb_t divisor, mp_limb_t carry); C C C The dependent chain in the main loop is C C cycles C subq %rdx, %rax 1 C imulq %r9, %rax 4 C mulq %r8 5 C ---- C total 10 C C The movq load from src seems to need to be scheduled back before the jz to C achieve this speed, out-of-order execution apparently can't completely C hide the latency otherwise. C C The l=src[i]-cbit step is rotated back too, since that allows us to avoid C it for the first iteration (where there's no cbit). C C The code alignment used (32-byte) for the loop also seems necessary. C Without that the non-PIC case has adcq crossing the 0x60 offset, C apparently making it run at 11 cycles instead of 10. C C Not done: C C divq for size==1 was measured at about 79 cycles, compared to the inverse C at about 25 cycles (both including function call overheads), so that's not C used. C C Enhancements: C C For PIC, we shouldn't really need the GOT fetch for binvert_limb_table, C it'll be in rodata or text in libgmp.so and can be accessed directly %rip C relative. This would be for small model only (something we don't C presently detect, but which is all that gcc 3.3.3 supports), since 8-byte C PC-relative relocations are apparently not available. Some rough C experiments with binutils 2.13 looked worrylingly like it might come out C with an unwanted text segment relocation though, even with ".protected". ASM_START() TEXT ALIGN(32) PROLOGUE(mpn_modexact_1_odd) movl $0, %ecx PROLOGUE(mpn_modexact_1c_odd) C rdi src C rsi size C rdx divisor C rcx carry movq %rdx, %r8 C d shrl %edx C d/2 ifdef(`PIC',` movq binvert_limb_table@GOTPCREL(%rip), %r9 ',` movabsq $binvert_limb_table, %r9 ') andl $127, %edx movq %rcx, %r10 C initial carry movzbl (%r9,%rdx), %edx C inv 8 bits movq (%rdi), %rax C src[0] leaq (%rdi,%rsi,8), %r11 C src end movq %r8, %rdi C d, made available to imull leal (%rdx,%rdx), %ecx C 2*inv imull %edx, %edx C inv*inv negq %rsi C -size imull %edi, %edx C inv*inv*d subl %edx, %ecx C inv = 2*inv - inv*inv*d, 16 bits leal (%rcx,%rcx), %edx C 2*inv imull %ecx, %ecx C inv*inv imull %edi, %ecx C inv*inv*d subl %ecx, %edx C inv = 2*inv - inv*inv*d, 32 bits xorl %ecx, %ecx C initial cbit leaq (%rdx,%rdx), %r9 C 2*inv imulq %rdx, %rdx C inv*inv imulq %r8, %rdx C inv*inv*d subq %rdx, %r9 C inv = 2*inv - inv*inv*d, 64 bits movq %r10, %rdx C initial climb ASSERT(e,` C d*inv == 1 mod 2^64 movq %r8, %r10 imulq %r9, %r10 cmpq $1, %r10') incq %rsi jz L(one) ALIGN(16) L(top): C rax l = src[i]-cbit C rcx new cbit, 0 or 1 C rdx climb, high of last product C rsi counter, limbs, negative C rdi C r8 divisor C r9 inverse C r11 src end ptr subq %rdx, %rax C l = src[i]-cbit - climb adcq $0, %rcx C more cbit imulq %r9, %rax C q = l * inverse mulq %r8 C climb = high (q * d) movq (%r11,%rsi,8), %rax C src[i+1] subq %rcx, %rax C next l = src[i+1] - cbit setc %cl C new cbit incq %rsi jnz L(top) L(one): subq %rdx, %rax C l = src[i]-cbit - climb adcq $0, %rcx C more cbit imulq %r9, %rax C q = l * inverse mulq %r8 C climb = high (q * d) leaq (%rcx,%rdx), %rax C climb+cbit ret EPILOGUE(mpn_modexact_1c_odd) EPILOGUE(mpn_modexact_1_odd)