110 lines
2.8 KiB
NASM
110 lines
2.8 KiB
NASM
dnl AMD K6-2 mpn_copyd -- copy limb vector, decrementing.
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dnl Copyright 2001, 2002 Free Software Foundation, Inc.
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dnl
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dnl This file is part of the GNU MP Library.
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dnl
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dnl The GNU MP Library is free software; you can redistribute it and/or
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dnl modify it under the terms of the GNU Lesser General Public License as
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dnl published by the Free Software Foundation; either version 2.1 of the
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dnl License, or (at your option) any later version.
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dnl
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dnl The GNU MP Library is distributed in the hope that it will be useful,
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dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
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dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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dnl Lesser General Public License for more details.
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dnl
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dnl You should have received a copy of the GNU Lesser General Public
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dnl License along with the GNU MP Library; see the file COPYING.LIB. If
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dnl not, write to the Free Software Foundation, Inc., 51 Franklin Street,
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dnl Fifth Floor, Boston, MA 02110-1301, USA.
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include(`../config.m4')
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C K6-2: 1.0 cycles/limb
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C void mpn_copyd (mp_ptr dst, mp_srcptr src, mp_size_t size);
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C
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C The loop here is no faster than a rep movsl at 1.0 c/l, but it avoids a 30
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C cycle startup time, which amounts for instance to a 2x speedup at 15
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C limbs.
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C
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C If dst is 4mod8 the loop would be 1.17 c/l, but that's avoided by
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C processing one limb separately to make it aligned. This and a final odd
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C limb are handled in a branch-free fashion, ending up re-copying if the
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C special case isn't needed.
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C
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C Alternatives:
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C
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C There used to be a big unrolled version of this, running at 0.56 c/l if
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C the destination was aligned, but that seemed rather excessive for the
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C relative importance of copyd.
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C
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C If the destination alignment is ignored and just left to run at 1.17 c/l
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C some code size and a fixed few cycles can be saved. Considering how few
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C uses copyd finds perhaps that should be favoured. The current code has
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C the attraction of being no slower than a basic rep movsl though.
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defframe(PARAM_SIZE,12)
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defframe(PARAM_SRC, 8)
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defframe(PARAM_DST, 4)
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dnl re-using parameter space
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define(SAVE_EBX,`PARAM_SIZE')
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TEXT
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ALIGN(16)
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PROLOGUE(mpn_copyd)
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deflit(`FRAME',0)
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movl PARAM_SIZE, %ecx
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movl %ebx, SAVE_EBX
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movl PARAM_SRC, %eax
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movl PARAM_DST, %edx
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subl $1, %ecx C better code alignment than decl
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jb L(zero)
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jz L(one_more)
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leal 4(%edx,%ecx,4), %ebx
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Zdisp( movd, 0,(%eax,%ecx,4), %mm0) C high limb
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Zdisp( movd, %mm0, 0,(%edx,%ecx,4)) C Zdisp for good code alignment
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cmpl $1, %ecx
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je L(one_more)
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shrl $2, %ebx
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andl $1, %ebx C 1 if dst[size-2] unaligned
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subl %ebx, %ecx
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nop C code alignment
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L(top):
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C eax src
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C ebx
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C ecx counter
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C edx dst
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movq -4(%eax,%ecx,4), %mm0
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subl $2, %ecx
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movq %mm0, 4(%edx,%ecx,4)
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ja L(top)
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L(one_more):
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movd (%eax), %mm0
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movd %mm0, (%edx)
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movl SAVE_EBX, %ebx
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emms_or_femms
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L(zero):
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ret
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EPILOGUE()
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