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dnl AMD K7 mpn_addlsh1_n -- rp[] = up[] + (vp[] << 1)
dnl Copyright 2011 Free Software Foundation, Inc.
dnl Contributed to the GNU project by Torbjorn Granlund and Marco Bodrato.
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 This is an attempt at an addlsh1_n for x86-32, not relying on sse2 insns.
C The innerloop is 2*3-way unrolled, which is best we can do with the available
C registers. It seems tricky to use the same structure for rsblsh1_n, since we
C cannot feed carry between operations there.
C cycles/limb
C P5
C P6 model 0-8,10-12
C P6 model 9 (Banias)
C P6 model 13 (Dothan) 5.4 (worse than add_n + lshift)
C P4 model 0 (Willamette)
C P4 model 1 (?)
C P4 model 2 (Northwood)
C P4 model 3 (Prescott)
C P4 model 4 (Nocona)
C Intel Atom 6
C AMD K6 ?
C AMD K7 2.5
C AMD K8
C This is a basic addlsh1_n for k7, atom, and perhaps some other x86-32
C processors. It uses 2*3-way unrolling, for good reasons. Unfortunately,
C that means we need an initial magic multiply.
C
C It is not clear how to do sublsh1_n or rsblsh1_n using the same pattern. We
C cannot do rsblsh1_n since we feed carry from the shift blocks to the
C add/subtract blocks, which is right for addition but reversed for
C subtraction. We could perhaps do sublsh1_n, with some extra move insns,
C without losing any time, since we're not issue limited but carry recurrency
C latency.
C
C Breaking carry recurrency might be a good idea. We would then need separate
C registers for the shift carry and add/subtract carry, which in turn would
C force us to 2*2-way unrolling.
defframe(PARAM_SIZE, 16)
defframe(PARAM_DBLD, 12)
defframe(PARAM_SRC, 8)
defframe(PARAM_DST, 4)
dnl re-use parameter space
define(VAR_COUNT,`PARAM_DST')
define(VAR_TMP,`PARAM_DBLD')
ASM_START()
TEXT
ALIGN(8)
PROLOGUE(mpn_addlsh1_n)
deflit(`FRAME',0)
define(`rp', `%edi')
define(`up', `%esi')
define(`vp', `%ebp')
mov $0x2aaaaaab, %eax
push %ebx FRAME_pushl()
mov PARAM_SIZE, %ebx C size
push rp FRAME_pushl()
mov PARAM_DST, rp
mul %ebx
push up FRAME_pushl()
mov PARAM_SRC, up
not %edx C count = -(size\8)-1
mov %edx, VAR_COUNT
push vp FRAME_pushl()
mov PARAM_DBLD, vp
lea 3(%edx,%edx,2), %ecx C count*3+3 = -(size\6)*3
xor %edx, %edx
lea (%ebx,%ecx,2), %ebx C size + (count*3+3)*2 = size % 6
or %ebx, %ebx
jz L(exact)
L(oop):
ifdef(`CPU_P6',`
shr %edx ') C restore 2nd saved carry bit
mov (vp), %eax
adc %eax, %eax
rcr %edx C restore 1st saved carry bit
lea 4(vp), vp
adc (up), %eax
lea 4(up), up
adc %edx, %edx C save a carry bit in edx
ifdef(`CPU_P6',`
adc %edx, %edx ') C save another carry bit in edx
dec %ebx
mov %eax, (rp)
lea 4(rp), rp
jnz L(oop)
mov vp, VAR_TMP
L(exact):
incl VAR_COUNT
jz L(end)
ALIGN(16)
L(top):
ifdef(`CPU_P6',`
shr %edx ') C restore 2nd saved carry bit
mov (vp), %eax
adc %eax, %eax
mov 4(vp), %ebx
adc %ebx, %ebx
mov 8(vp), %ecx
adc %ecx, %ecx
rcr %edx C restore 1st saved carry bit
adc (up), %eax
mov %eax, (rp)
adc 4(up), %ebx
mov %ebx, 4(rp)
adc 8(up), %ecx
mov %ecx, 8(rp)
mov 12(vp), %eax
adc %eax, %eax
mov 16(vp), %ebx
adc %ebx, %ebx
mov 20(vp), %ecx
adc %ecx, %ecx
lea 24(vp), vp
adc %edx, %edx C save a carry bit in edx
adc 12(up), %eax
mov %eax, 12(rp)
adc 16(up), %ebx
mov %ebx, 16(rp)
adc 20(up), %ecx
lea 24(up), up
ifdef(`CPU_P6',`
adc %edx, %edx ') C save another carry bit in edx
mov %ecx, 20(rp)
incl VAR_COUNT
lea 24(rp), rp
jne L(top)
L(end):
pop vp FRAME_popl()
pop up FRAME_popl()
ifdef(`CPU_P6',`
xor %eax, %eax
shr $1, %edx
adc %edx, %eax
',`
adc $0, %edx
mov %edx, %eax
')
pop rp FRAME_popl()
pop %ebx FRAME_popl()
ret
EPILOGUE()
ASM_END()
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