github.com/aergoio/aergo@v1.3.1/libtool/src/gmp-6.1.2/mpn/x86/k6/k62mmx/copyd.asm (about)

     1  dnl  AMD K6-2 mpn_copyd -- copy limb vector, decrementing.
     2  
     3  dnl  Copyright 2001, 2002 Free Software Foundation, Inc.
     4  
     5  dnl  This file is part of the GNU MP Library.
     6  dnl
     7  dnl  The GNU MP Library is free software; you can redistribute it and/or modify
     8  dnl  it under the terms of either:
     9  dnl
    10  dnl    * the GNU Lesser General Public License as published by the Free
    11  dnl      Software Foundation; either version 3 of the License, or (at your
    12  dnl      option) any later version.
    13  dnl
    14  dnl  or
    15  dnl
    16  dnl    * the GNU General Public License as published by the Free Software
    17  dnl      Foundation; either version 2 of the License, or (at your option) any
    18  dnl      later version.
    19  dnl
    20  dnl  or both in parallel, as here.
    21  dnl
    22  dnl  The GNU MP Library is distributed in the hope that it will be useful, but
    23  dnl  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
    24  dnl  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
    25  dnl  for more details.
    26  dnl
    27  dnl  You should have received copies of the GNU General Public License and the
    28  dnl  GNU Lesser General Public License along with the GNU MP Library.  If not,
    29  dnl  see https://www.gnu.org/licenses/.
    30  
    31  include(`../config.m4')
    32  
    33  
    34  C K6-2: 1.0 cycles/limb
    35  
    36  
    37  C void mpn_copyd (mp_ptr dst, mp_srcptr src, mp_size_t size);
    38  C
    39  C The loop here is no faster than a rep movsl at 1.0 c/l, but it avoids a 30
    40  C cycle startup time, which amounts for instance to a 2x speedup at 15
    41  C limbs.
    42  C
    43  C If dst is 4mod8 the loop would be 1.17 c/l, but that's avoided by
    44  C processing one limb separately to make it aligned.  This and a final odd
    45  C limb are handled in a branch-free fashion, ending up re-copying if the
    46  C special case isn't needed.
    47  C
    48  C Alternatives:
    49  C
    50  C There used to be a big unrolled version of this, running at 0.56 c/l if
    51  C the destination was aligned, but that seemed rather excessive for the
    52  C relative importance of copyd.
    53  C
    54  C If the destination alignment is ignored and just left to run at 1.17 c/l
    55  C some code size and a fixed few cycles can be saved.  Considering how few
    56  C uses copyd finds perhaps that should be favoured.  The current code has
    57  C the attraction of being no slower than a basic rep movsl though.
    58  
    59  defframe(PARAM_SIZE,12)
    60  defframe(PARAM_SRC, 8)
    61  defframe(PARAM_DST, 4)
    62  
    63  dnl  re-using parameter space
    64  define(SAVE_EBX,`PARAM_SIZE')
    65  
    66  	TEXT
    67  	ALIGN(16)
    68  
    69  PROLOGUE(mpn_copyd)
    70  deflit(`FRAME',0)
    71  
    72  	movl	PARAM_SIZE, %ecx
    73  	movl	%ebx, SAVE_EBX
    74  
    75  	movl	PARAM_SRC, %eax
    76  	movl	PARAM_DST, %edx
    77  
    78  	subl	$1, %ecx		C better code alignment than decl
    79  	jb	L(zero)
    80  
    81  	jz	L(one_more)
    82  	leal	4(%edx,%ecx,4), %ebx
    83  
    84  Zdisp(	movd,	0,(%eax,%ecx,4), %mm0)	C high limb
    85  Zdisp(	movd,	%mm0, 0,(%edx,%ecx,4))	C Zdisp for good code alignment
    86  
    87  	cmpl	$1, %ecx
    88  	je	L(one_more)
    89  
    90  	shrl	$2, %ebx
    91  	andl	$1, %ebx		C 1 if dst[size-2] unaligned
    92  
    93  	subl	%ebx, %ecx
    94  	nop				C code alignment
    95  
    96  L(top):
    97  	C eax	src
    98  	C ebx
    99  	C ecx	counter
   100  	C edx	dst
   101  
   102  	movq	-4(%eax,%ecx,4), %mm0
   103  	subl	$2, %ecx
   104  
   105  	movq	%mm0, 4(%edx,%ecx,4)
   106  	ja	L(top)
   107  
   108  
   109  L(one_more):
   110  	movd	(%eax), %mm0
   111  	movd	%mm0, (%edx)
   112  
   113  	movl	SAVE_EBX, %ebx
   114  	emms_or_femms
   115  L(zero):
   116  	ret
   117  
   118  EPILOGUE()