github.com/aergoio/aergo@v1.3.1/libtool/src/gmp-6.1.2/mpn/alpha/ev67/hamdist.asm (about)

     1  dnl  Alpha ev67 mpn_hamdist -- mpn hamming distance.
     2  
     3  dnl  Copyright 2003, 2005 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 ev67: 2.5 cycles/limb
    35  
    36  
    37  C unsigned long mpn_hamdist (mp_srcptr xp, mp_srcptr yp, mp_size_t size);
    38  C
    39  C The hope was for 2.0 c/l here, but that isn't achieved.  We're limited by
    40  C renaming register shortage.  Since we need 5 instructions per limb, further
    41  C unrolling could approach 1.5 c/l.
    42  C
    43  C The main loop processes two limbs from each operand on each iteration.  An
    44  C odd size is handled by processing xp[0]^yp[0] at the start.  If the size
    45  C is even that result is discarded, and is repeated by the main loop.
    46  C
    47  
    48  ASM_START()
    49  PROLOGUE(mpn_hamdist)
    50  
    51  	C r16	xp
    52  	C r17	yp
    53  	C r18	size
    54  
    55  	ldq	r1, 0(r16)		C L0  xp[0]
    56  	ldq	r2, 0(r17)		C L1  yp[0]
    57  	and	r18, 1, r8		C U1  1 if size odd
    58  	srl	r18, 1, r18		C U0  size, limb pairs
    59  
    60  	clr	r0			C L0  initial total
    61  	s8addq	r8, r17, r17		C U1  yp++ if size odd
    62  	s8addq	r8, r16, r16		C L1  xp++ if size odd
    63  	clr	r6			C U0  dummy initial xor 1
    64  
    65  	xor	r1, r2, r5		C L   initial xor 0
    66  	beq	r18, L(one)		C U   if size==1
    67  
    68  	cmoveq	r8, r31, r5		C L   discard first limb if size even
    69  	unop				C U
    70  
    71  
    72  	ALIGN(16)
    73  L(top):
    74  	C r0	total accumulating
    75  	C r7	xor 0
    76  	C r8	xor 1
    77  	C r16	xp, incrementing
    78  	C r17	yp, incrementing
    79  	C r18	size, limb pairs, decrementing
    80  
    81  	ldq	r1, 0(r16)		C L
    82  	ldq	r2, 0(r17)		C L
    83  	ctpop	r5, r7			C U0
    84  	lda	r16, 16(r16)		C U
    85  
    86  	ldq	r3, -8(r16)		C L
    87  	ldq	r4, 8(r17)		C L
    88  	ctpop	r6, r8			C U0
    89  	lda	r17, 16(r17)		C U
    90  
    91  	ldl	r31, 256(r16)		C L	prefetch
    92  	ldl	r31, 256(r17)		C L	prefetch
    93  	xor	r1, r2, r5		C U
    94  	lda	r18, -1(r18)		C U
    95  
    96  	xor	r3, r4, r6		C U
    97  	addq	r0, r7, r0		C L
    98  	addq	r0, r8, r0		C L
    99  	bne	r18, L(top)		C U
   100  
   101  
   102  	ctpop	r6, r8			C U0
   103  	addq	r0, r8, r0		C L
   104  L(one):
   105  	ctpop	r5, r7			C U0
   106  	addq	r0, r7, r0		C L
   107  
   108  	ret	r31, (r26), 1		C L0
   109  
   110  EPILOGUE()
   111  ASM_END()