copyd.asm
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上传日期:2022-08-06
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- dnl AMD K6-2 mpn_copyd -- copy limb vector, decrementing.
- dnl Copyright 2001, 2002 Free Software 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 K6-2: 1.0 cycles/limb
- C void mpn_copyd (mp_ptr dst, mp_srcptr src, mp_size_t size);
- C
- C The loop here is no faster than a rep movsl at 1.0 c/l, but it avoids a 30
- C cycle startup time, which amounts for instance to a 2x speedup at 15
- C limbs.
- C
- C If dst is 4mod8 the loop would be 1.17 c/l, but that's avoided by
- C processing one limb separately to make it aligned. This and a final odd
- C limb are handled in a branch-free fashion, ending up re-copying if the
- C special case isn't needed.
- C
- C Alternatives:
- C
- C There used to be a big unrolled version of this, running at 0.56 c/l if
- C the destination was aligned, but that seemed rather excessive for the
- C relative importance of copyd.
- C
- C If the destination alignment is ignored and just left to run at 1.17 c/l
- C some code size and a fixed few cycles can be saved. Considering how few
- C uses copyd finds perhaps that should be favoured. The current code has
- C the attraction of being no slower than a basic rep movsl though.
- defframe(PARAM_SIZE,12)
- defframe(PARAM_SRC, 8)
- defframe(PARAM_DST, 4)
- dnl re-using parameter space
- define(SAVE_EBX,`PARAM_SIZE')
- TEXT
- ALIGN(16)
- PROLOGUE(mpn_copyd)
- deflit(`FRAME',0)
- movl PARAM_SIZE, %ecx
- movl %ebx, SAVE_EBX
- movl PARAM_SRC, %eax
- movl PARAM_DST, %edx
- subl $1, %ecx C better code alignment than decl
- jb L(zero)
- jz L(one_more)
- leal 4(%edx,%ecx,4), %ebx
- Zdisp( movd, 0,(%eax,%ecx,4), %mm0) C high limb
- Zdisp( movd, %mm0, 0,(%edx,%ecx,4)) C Zdisp for good code alignment
- cmpl $1, %ecx
- je L(one_more)
- shrl $2, %ebx
- andl $1, %ebx C 1 if dst[size-2] unaligned
- subl %ebx, %ecx
- nop C code alignment
- L(top):
- C eax src
- C ebx
- C ecx counter
- C edx dst
- movq -4(%eax,%ecx,4), %mm0
- subl $2, %ecx
- movq %mm0, 4(%edx,%ecx,4)
- ja L(top)
- L(one_more):
- movd (%eax), %mm0
- movd %mm0, (%edx)
- movl SAVE_EBX, %ebx
- emms_or_femms
- L(zero):
- ret
- EPILOGUE()