; Copyright 2016 Jens Nurmann and Alexander Kruppa ; This file is part of the MPIR Library. ; The MPIR Library is free software; you can redistribute it and/or modify ; it under the terms of the GNU Lesser General Public License as published ; by the Free Software Foundation; either version 2.1 of the License, or (at ; your option) any later version. ; The MPIR Library is distributed in the hope that it will be useful, but ; WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY ; or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public ; License for more details. ; You should have received a copy of the GNU Lesser General Public License ; along with the MPIR Library; see the file COPYING.LIB. If not, write ; to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, ; Boston, MA 02110-1301, USA. ; mp_limb_t mpn_rshift1(mp_ptr Op2, mp_srcptr Op1, mp_size_t Size1 ) ; Linux RAX RDI RSI RDX ; Win7 RAX RCX RDX R8 ; ; Description: ; The function shifts Op1 right by one bit, stores the result in Op2 (non- ; destructive shr) and hands back the shifted-out least significant bit of Op1. ; The function operates increasing in memory supporting in place shifts. ; ; Caveats: ; - the AVX version uses mnemonics only available on Haswell, Broadwell and ; Skylake cores ; - the behaviour of cache prefetching in combination with AVX shifting seems ; somewhat erratic ; - slight (a few clock cycles) degradation for 1/2 LD1$ sizes ; - slight (a few percent) improvement for full LD1$ sizes ; - substantial (>10%) improvement for 1/2 LD2$ sizes ; - slight (a few percent) improvement for full LD2$ sizes ; - slight (a few percent) degradation for 1/2 LD3$ sizes ; - substantial (around 10%) degradation for full LD3$ sizes ; ; Comments: ; - AVX based version implemented, tested & benched on 21.02.2016 by jn ; - includes cache prefetching %include 'yasm_mac.inc' BITS 64 %ifdef USE_WIN64 %define Op2 RCX %define Op1 RDX %define Size1 R8 %define Limb1 R9 %define Limb2 R10 %define Offs 512 ; used direct def. to stay in Win scratch regs %define ShrDL0 XMM2 ; Attn: this must match ShrQL0 definition %define ShlDL0 XMM3 ; Attn: this must match ShlQL0 definition %define QLimb0 YMM0 %define QLimb1 YMM1 %define ShrQL0 YMM2 %define ShlQL0 YMM3 %define ShrQL1 YMM4 %define ShlQL1 YMM5 %else %define Op2 RDI %define Op1 RSI %define Size1 RDX %define Limb1 R8 %define Limb2 R9 %define Offs 512 ; used direct def. to stay in Win scratch regs %define ShrDL0 XMM2 ; Attn: this must match ShrQL0 definition %define ShlDL0 XMM3 ; Attn: this must match ShlQL0 definition %define QLimb0 YMM0 %define QLimb1 YMM1 %define ShrQL0 YMM2 %define ShlQL0 YMM3 %define ShrQL1 YMM4 %define ShlQL1 YMM5 %endif align 32 GLOBAL_FUNC mpn_rshift1 xor EAX, EAX or Size1, Size1 je .Exit mov RAX, [Op1] mov Limb1, RAX shl RAX, 63 sub Size1, 1 je .lShr1EquPost ; Size1=1 => cmp Size1, 8 jc .lShr1EquFour ; AVX inefficient => ; first align Op2 to 32 bytes test Op2, 8 je .lShr1EquAlign16 mov Limb2, [Op1+8] shrd Limb1, Limb2, 1 mov [Op2], Limb1 mov Limb1, Limb2 add Op1, 8 add Op2, 8 sub Size1, 1 .lShr1EquAlign16: test Op2, 16 je .lShr1EquAVX mov Limb2, [Op1+8] shrd Limb1, Limb2, 1 mov [Op2], Limb1 mov Limb1, [Op1+16] shrd Limb2, Limb1, 1 mov [Op2+8], Limb2 add Op1, 16 add Op2, 16 sub Size1, 2 .lShr1EquAVX: ; pre-fetch first quad-limb vmovdqu QLimb0, [Op1] vpsllq ShlQL0, QLimb0, 63 add Op1, 32 sub Size1, 4 jmp .lShr1EquAVXCheck ; main loop (prefetching enabled, unloaded data cache) ; - 0.60 cycles per limb in LD1$ ; - 0.60-0.75 cycles per limb in LD2$ ; - 0.75-1.00 cycles per limb in LD3$ align 16 .lShr1EquAVXLoop: %ifdef USE_PREFETCH prefetchnta [Op1+Offs] %endif vmovdqu QLimb1, [Op1] vpsrlq ShrQL0, QLimb0, 1 vmovdqu QLimb0, [Op1+32] vpsllq ShlQL1, QLimb1, 63 vpblendd ShlQL0, ShlQL0, ShlQL1, 00000011b vpermq ShlQL0, ShlQL0, 00111001b vpor ShrQL0, ShrQL0, ShlQL0 vpsrlq ShrQL1, QLimb1, 1 vpsllq ShlQL0, QLimb0, 63 vpblendd ShlQL1, ShlQL1, ShlQL0, 00000011b vpermq ShlQL1, ShlQL1, 00111001b vmovdqa [Op2], ShrQL0 vpor ShrQL1, ShrQL1, ShlQL1 vmovdqa [Op2+32], ShrQL1 add Op1, 64 add Op2, 64 .lShr1EquAVXCheck: sub Size1, 8 jnc .lShr1EquAVXLoop mov Limb2, [Op1] mov Limb1, Limb2 shl Limb2, 63 %if 1 vmovq ShrDL0, Limb2 vpblendd ShlQL0, ShlQL0, ShrQL0, 3 %else ; I am mixing in a single SSE4.1 instruction into otherwise pure AVX2 ; this is generating stalls on Haswell & Broadwell architecture (Agner Fog) ; but it is only executed once and there is no AVX2 based alternative pinsrq ShlDL0, Limb2, 0 ; SSE4.1 %endif vpsrlq ShrQL0, QLimb0, 1 vpermq ShlQL0, ShlQL0, 00111001b vpor ShrQL0, ShrQL0, ShlQL0 vmovdqa [Op2], ShrQL0 add Op2, 32 add Size1, 8 ; shift remaining max. 7 limbs with SHRD mnemonic .lShr1EquFour: add Op1, 8 test Size1, 4 je .lShr1EquTwo mov Limb2, [Op1] shrd Limb1, Limb2, 1 mov [Op2], Limb1 mov Limb1, [Op1+8] shrd Limb2, Limb1, 1 mov [Op2+8], Limb2 mov Limb2, [Op1+16] shrd Limb1, Limb2, 1 mov [Op2+16], Limb1 mov Limb1, [Op1+24] shrd Limb2, Limb1, 1 mov [Op2+24], Limb2 add Op1, 32 add Op2, 32 .lShr1EquTwo: test Size1, 2 je .lShr1EquOne mov Limb2, [Op1] shrd Limb1, Limb2, 1 mov [Op2], Limb1 mov Limb1, [Op1+8] shrd Limb2, Limb1, 1 mov [Op2+8], Limb2 add Op1, 16 add Op2, 16 .lShr1EquOne: test Size1, 1 je .lShr1EquPost mov Limb2, [Op1] shrd Limb1, Limb2, 1 mov [Op2], Limb1 mov Limb1, Limb2 add Op2, 8 .lShr1EquPost: shr Limb1, 1 mov [Op2], Limb1 .Exit: vzeroupper ret .end: