362 lines
9.0 KiB
NASM
362 lines
9.0 KiB
NASM
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; Copyright 2001 Free Software Foundation, Inc.
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;
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; This file is part of the GNU MP Library.
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;
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; The GNU MP Library is free software; you can redistribute it and/or
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; modify it under the terms of the GNU Lesser General Public License as
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; published by the Free Software Foundation; either version 2.1 of the
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; License, or (at your option) any later version.
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;
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; The GNU MP Library is distributed in the hope that it will be useful,
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; but WITHOUT ANY WARRANTY; without even the implied warranty of
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; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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; Lesser General Public License for more details.
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;
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; You should have received a copy of the GNU Lesser General Public
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; License along with the GNU MP Library; see the file COPYING.LIB. If
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; not, write to the Free Software Foundation, Inc., 59 Temple Place -
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; Suite 330, Boston, MA 02111-1307, USA.
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;
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; Translation of AT&T syntax code by Brian Gladman
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%include "..\..\x86i.inc"
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%define PARAM_SHIFT esp+frame+16
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%define PARAM_SIZE esp+frame+12
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%define PARAM_SRC esp+frame+8
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%define PARAM_DST esp+frame+4
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%define frame 8
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; Minimum 5,because the unrolled loop can't handle less.
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%define UNROLL_THRESHOLD 5
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section .text
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global ___gmpn_rshift
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%ifdef DLL
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export ___gmpn_rshift
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%endif
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align 8
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___gmpn_rshift:
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push ebx
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push edi
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mov eax,[PARAM_SIZE]
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mov edx,[PARAM_DST]
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mov ebx,[PARAM_SRC]
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mov ecx,[PARAM_SHIFT]
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cmp eax,UNROLL_THRESHOLD
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jae Lunroll
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dec eax
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mov edi,[ebx] ; src low limb
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jnz Lsimple
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shrd eax,edi,cl
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shr edi,cl
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mov [edx],edi ; dst low limb
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pop edi ; risk of data cache bank clash
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pop ebx
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ret
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; eax size-1
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; ebx src
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; ecx shift
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; edx dst
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; esi
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; edi
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; ebp
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align 8
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Lsimple:
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movd mm5,[ebx] ; src[0]
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lea ebx,[ebx+eax*4] ; &src[size-1]
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movd mm6,ecx ; rshift
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lea edx,[-4+edx+eax*4] ; &dst[size-2]
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psllq mm5,32
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neg eax
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; This loop is 5 or 8 cycles,with every second load unaligned and a wasted
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; cycle waiting for the mm0 result to be ready. For comparison a shrdl is 4
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; cycles and would be 8 in a simple loop. Using mmx helps the return value
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; and last limb calculations too.
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; eax counter,limbs,negative
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; ebx &src[size-1]
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; ecx return value
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; edx &dst[size-2]
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;
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; mm0 scratch
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; mm5 return value
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; mm6 shift
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Lsimple_top:
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movq mm0,[ebx+eax*4]
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inc eax
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psrlq mm0,mm6
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movd [edx+eax*4],mm0
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jnz Lsimple_top
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movd mm0,[ebx]
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psrlq mm5,mm6 ; return value
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psrlq mm0,mm6
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pop edi
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movd eax,mm5
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pop ebx
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movd [4+edx],mm0
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emms
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ret
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; eax size
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; ebx src
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; ecx shift
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; edx dst
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; esi
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; edi
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; ebp
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align 8
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Lunroll:
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movd mm5,[ebx] ; src[0]
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mov edi,4
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movd mm6,ecx ; rshift
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test ebx,edi
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psllq mm5,32
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jz Lstart_src_aligned
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; src isn't aligned,process low limb separately (marked xxx) and
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; step src and dst by one limb,making src aligned.
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;
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; source ebx
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; --+-------+-------+-------+
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; | xxx |
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; --+-------+-------+-------+
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; 4mod8 0mod8 4mod8
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;
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; dest edx
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; --+-------+-------+
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; | | xxx |
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; --+-------+-------+
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movq mm0,[ebx] ; unaligned load
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psrlq mm0,mm6
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add ebx,4
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dec eax
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movd [edx],mm0
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add edx,4
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Lstart_src_aligned:
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movq mm1,[ebx]
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test edx,edi
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psrlq mm5,mm6 ; retval
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jz Lstart_dst_aligned
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; dst isn't aligned,add 4 to make it so,and pretend the shift is
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; 32 bits extra. Low limb of dst (marked xxx) handled here
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; separately.
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;
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; source ebx
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; --+-------+-------+
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; | mm1 |
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; --+-------+-------+
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; 4mod8 0mod8
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;
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; dest edx
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; --+-------+-------+-------+
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; | xxx |
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; --+-------+-------+-------+
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; 4mod8 0mod8 4mod8
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movq mm0,mm1
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add ecx,32 ; new shift
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psrlq mm0,mm6
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movd mm6,ecx
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movd [edx],mm0
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add edx,4
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Lstart_dst_aligned:
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movq mm3,[8+ebx]
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neg ecx
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movq mm2,mm3 ; mm2 src qword
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add ecx,64
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movd mm7,ecx
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psrlq mm1,mm6
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lea ebx,[-12+ebx+eax*4]
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lea edx,[-20+edx+eax*4]
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psllq mm3,mm7
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sub eax,7 ; size-7
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por mm3,mm1 ; mm3 ready to store
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neg eax ; -(size-7)
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jns Lfinish
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; This loop is the important bit,the rest is just support. Careful
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; instruction scheduling achieves the claimed 1.75 c/l. The
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; relevant parts of the pairing rules are:
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;
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; - mmx loads and stores execute only in the U pipe
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; - only one mmx shift in a pair
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; - wait one cycle before storing an mmx register result
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; - the usual address generation interlock
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;
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; Two qword calculations are slightly interleaved. The instructions
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; marked "C" belong to the second qword,and the "C prev" one is for
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; the second qword from the previous iteration.
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; eax counter,limbs,negative
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; ebx &src[size-12]
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; ecx
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; edx &dst[size-12]
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; esi
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; edi
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;
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; mm0
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; mm1
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; mm2 src qword from -8(%ebx,%eax,4)
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; mm3 dst qword ready to store to -8(%edx,%eax,4)
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;
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; mm5 return value
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; mm6 rshift
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; mm7 lshift
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align 8
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Lunroll_loop:
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movq mm0,[ebx+eax*4]
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psrlq mm2,mm6
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movq mm1,mm0
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psllq mm0,mm7
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movq [-8+edx+eax*4],mm3
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por mm0,mm2
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movq mm3,[ebx+eax*4+8]
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psrlq mm1,mm6
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movq [edx+eax*4],mm0
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movq mm2,mm3
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psllq mm3,mm7
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add eax,4
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por mm3,mm1
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js Lunroll_loop
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Lfinish:
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; eax 0 to 3 representing respectively 3 to 0 limbs remaining
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test al,2
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jnz Lfinish_no_two
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movq mm0,[ebx+eax*4]
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psrlq mm2,mm6
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movq mm1,mm0
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psllq mm0,mm7
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movq [-8+edx+eax*4],mm3 ; prev
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por mm0,mm2
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movq mm2,mm1
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movq mm3,mm0
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add eax,2
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Lfinish_no_two:
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; eax 2 or 3 representing respectively 1 or 0 limbs remaining
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;
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; mm2 src prev qword,from -8(%ebx,%eax,4)
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; mm3 dst qword,for -8(%edx,%eax,4)
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test al,1
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pop edi
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movd eax,mm5 ; retval
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jnz Lfinish_zero
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; One extra limb,destination was aligned.
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;
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; source ebx
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; +-------+---------------+--
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; | | mm2 |
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; +-------+---------------+--
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;
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; dest edx
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; +-------+---------------+---------------+--
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; | | | mm3 |
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; +-------+---------------+---------------+--
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;
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; mm6 = shift
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; mm7 = ecx = 64-shift
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; One extra limb,destination was unaligned.
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;
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; source ebx
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; +-------+---------------+--
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; | | mm2 |
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; +-------+---------------+--
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;
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; dest edx
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; +---------------+---------------+--
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; | | mm3 |
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; +---------------+---------------+--
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;
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; mm6 = shift+32
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; mm7 = ecx = 64-(shift+32)
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; In both cases there's one extra limb of src to fetch and combine
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; with mm2 to make a qword at 8(%edx),and in the aligned case
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; there's a further extra limb of dst to be formed.
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movd mm0,[8+ebx]
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psrlq mm2,mm6
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movq mm1,mm0
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psllq mm0,mm7
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movq [edx],mm3
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por mm0,mm2
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psrlq mm1,mm6
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and ecx,32
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pop ebx
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jz Lfinish_one_unaligned
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; dst was aligned,must store one extra limb
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movd [16+edx],mm1
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Lfinish_one_unaligned:
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movq [8+edx],mm0
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emms
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ret
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Lfinish_zero:
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; No extra limbs,destination was aligned.
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;
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; source ebx
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; +---------------+--
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; | mm2 |
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; +---------------+--
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;
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; dest edx+4
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; +---------------+---------------+--
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; | | mm3 |
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; +---------------+---------------+--
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;
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; mm6 = shift
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; mm7 = ecx = 64-shift
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; No extra limbs,destination was unaligned.
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;
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; source ebx
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; +---------------+--
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; | mm2 |
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; +---------------+--
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;
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; dest edx+4
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; +-------+---------------+--
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; | | mm3 |
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; +-------+---------------+--
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;
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; mm6 = shift+32
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; mm7 = 64-(shift+32)
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; The movd for the unaligned case is clearly the same data as the
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; movq for the aligned case,it's just a choice between whether one
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; or two limbs should be written.
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movq [4+edx],mm3
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psrlq mm2,mm6
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movd [12+edx],mm2
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and ecx,32
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pop ebx
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jz Lfinish_zero_unaligned
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movq [12+edx],mm2
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Lfinish_zero_unaligned:
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emms
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ret
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end
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