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

     1  dnl  Alpha ev67 mpn_popcount -- mpn bit population count.
     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: 1.5 cycles/limb
    35  
    36  
    37  C unsigned long mpn_popcount (mp_srcptr src, mp_size_t size);
    38  C
    39  C This schedule seems necessary for the full 1.5 c/l, the IQ can't quite hide
    40  C all latencies, the addq's must be deferred to the next iteration.
    41  C
    42  C Since we need just 3 instructions per limb, further unrolling could approach
    43  C 1.0 c/l.
    44  C
    45  C The main loop processes two limbs at a time.  An odd size is handled by
    46  C processing src[0] at the start.  If the size is even that result is
    47  C discarded, and src[0] is repeated by the main loop.
    48  C
    49  
    50  ASM_START()
    51  PROLOGUE(mpn_popcount)
    52  
    53  	C r16	src
    54  	C r17	size
    55  
    56  	ldq	r0, 0(r16)		C L0  src[0]
    57  	and	r17, 1, r8		C U1  1 if size odd
    58  	srl	r17, 1, r17		C U0  size, limb pairs
    59  
    60  	s8addq	r8, r16, r16		C L1  src++ if size odd
    61  	ctpop	r0, r0			C U0
    62  	beq	r17, L(one)		C U1  if size==1
    63  
    64  	cmoveq	r8, r31, r0		C L   discard first limb if size even
    65  	clr	r3			C L
    66  
    67  	clr	r4			C L
    68  	unop				C U
    69  	unop				C L
    70  	unop				C U
    71  
    72  
    73  	ALIGN(16)
    74  L(top):
    75  	C r0	total accumulating
    76  	C r3	pop 0
    77  	C r4	pop 1
    78  	C r16	src, incrementing
    79  	C r17	size, decrementing
    80  
    81  	ldq	r1, 0(r16)		C L
    82  	ldq	r2, 8(r16)		C L
    83  	lda	r16, 16(r16)		C U
    84  	lda	r17, -1(r17)		C U
    85  
    86  	addq	r0, r3, r0		C L
    87  	addq	r0, r4, r0		C L
    88  	ctpop	r1, r3			C U0
    89  	ctpop	r2, r4			C U0
    90  
    91  	ldl	r31, 512(r16)		C L	prefetch
    92  	bne	r17, L(top)		C U
    93  
    94  
    95  	addq	r0, r3, r0		C L
    96  	addq	r0, r4, r0		C U
    97  L(one):
    98  	ret	r31, (r26), 1		C L0
    99  
   100  EPILOGUE()
   101  ASM_END()