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dnl Intel Pentium-4 mpn_addlsh1_n -- mpn x+2*y.
dnl Copyright 2001-2004, 2006 Free Software Foundation, Inc.
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 modify
dnl it under the terms of either:
dnl
dnl * the GNU Lesser General Public License as published by the Free
dnl Software Foundation; either version 3 of the License, or (at your
dnl option) any later version.
dnl
dnl or
dnl
dnl * the GNU General Public License as published by the Free Software
dnl Foundation; either version 2 of the License, or (at your option) any
dnl later version.
dnl
dnl or both in parallel, as here.
dnl
dnl The GNU MP Library is distributed in the hope that it will be useful, but
dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
dnl for more details.
dnl
dnl You should have received copies of the GNU General Public License and the
dnl GNU Lesser General Public License along with the GNU MP Library. If not,
dnl see https://www.gnu.org/licenses/.
include(`../config.m4')
C cycles/limb
C dst!=src1,2 dst==src1 dst==src2
C P6 model 0-8,10-12 -
C P6 model 9 (Banias) ?
C P6 model 13 (Dothan) ?
C P4 model 0-1 (Willamette) ?
C P4 model 2 (Northwood) 4.25 6 6
C P4 model 3-4 (Prescott) 5 8.5 8.5
C The slightly strange combination of indexing and pointer incrementing
C that's used seems to work best. Not sure why, but %ecx,4 with src1 and/or
C src2 is a slowdown.
C
C The dependent chain is simply the paddq of x+2*y to the previous carry,
C then psrlq to get the new carry. That makes 4 c/l the target speed, which
C is almost achieved for separate src/dst but when src==dst the write
C combining anomalies slow it down.
defframe(PARAM_SIZE, 16)
defframe(PARAM_SRC2, 12)
defframe(PARAM_SRC1, 8)
defframe(PARAM_DST, 4)
dnl re-use parameter space
define(SAVE_EBX,`PARAM_SRC1')
TEXT
ALIGN(8)
PROLOGUE(mpn_addlsh1_n)
deflit(`FRAME',0)
mov PARAM_SRC1, %eax
mov %ebx, SAVE_EBX
mov PARAM_SRC2, %ebx
pxor %mm0, %mm0 C initial carry
mov PARAM_DST, %edx
mov PARAM_SIZE, %ecx
lea (%edx,%ecx,4), %edx C dst end
neg %ecx C -size
L(top):
C eax src1 end
C ebx src2 end
C ecx counter, limbs, negative
C edx dst end
C mm0 carry
movd (%ebx), %mm2
movd (%eax), %mm1
psrlq $32, %mm0
lea 4(%eax), %eax
lea 4(%ebx), %ebx
psllq $1, %mm2
paddq %mm2, %mm1
paddq %mm1, %mm0
movd %mm0, (%edx,%ecx,4)
add $1, %ecx
jnz L(top)
psrlq $32, %mm0
mov SAVE_EBX, %ebx
movd %mm0, %eax
emms
ret
EPILOGUE()
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