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dnl AMD K6 mpn_mul_1 -- mpn by limb multiply.
dnl Copyright 1999, 2000, 2002, 2005 Free Software Foundation, Inc.
dnl
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
dnl modify it under the terms of the GNU Lesser General Public License as
dnl published by the Free Software Foundation; either version 3 of the
dnl License, or (at your option) any later version.
dnl
dnl The GNU MP Library is distributed in the hope that it will be useful,
dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
dnl Lesser General Public License for more details.
dnl
dnl You should have received a copy of the GNU Lesser General Public License
dnl along with the GNU MP Library. If not, see http://www.gnu.org/licenses/.
include(`../config.m4')
C cycles/limb
C P5:
C P6 model 0-8,10-12) 5.5
C P6 model 9 (Banias)
C P6 model 13 (Dothan) 4.87
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 K6: 6.25
C K7:
C K8:
C mp_limb_t mpn_mul_1 (mp_ptr dst, mp_srcptr src, mp_size_t size,
C mp_limb_t multiplier);
C mp_limb_t mpn_mul_1c (mp_ptr dst, mp_srcptr src, mp_size_t size,
C mp_limb_t multiplier, mp_limb_t carry);
C
C Multiply src,size by mult and store the result in dst,size.
C Return the carry limb from the top of the result.
C
C mpn_mul_1c() accepts an initial carry for the calculation, it's added into
C the low limb of the result.
defframe(PARAM_CARRY, 20)
defframe(PARAM_MULTIPLIER,16)
defframe(PARAM_SIZE, 12)
defframe(PARAM_SRC, 8)
defframe(PARAM_DST, 4)
dnl minimum 5 because the unrolled code can't handle less
deflit(UNROLL_THRESHOLD, 5)
TEXT
ALIGN(32)
PROLOGUE(mpn_mul_1c)
pushl %esi
deflit(`FRAME',4)
movl PARAM_CARRY, %esi
jmp L(start_nc)
EPILOGUE()
PROLOGUE(mpn_mul_1)
push %esi
deflit(`FRAME',4)
xorl %esi, %esi C initial carry
L(start_nc):
mov PARAM_SIZE, %ecx
push %ebx
FRAME_pushl()
movl PARAM_SRC, %ebx
push %edi
FRAME_pushl()
movl PARAM_DST, %edi
pushl %ebp
FRAME_pushl()
cmpl $UNROLL_THRESHOLD, %ecx
movl PARAM_MULTIPLIER, %ebp
jae L(unroll)
C code offset 0x22 here, close enough to aligned
L(simple):
C eax scratch
C ebx src
C ecx counter
C edx scratch
C esi carry
C edi dst
C ebp multiplier
C
C this loop 8 cycles/limb
movl (%ebx), %eax
addl $4, %ebx
mull %ebp
addl %esi, %eax
movl $0, %esi
adcl %edx, %esi
movl %eax, (%edi)
addl $4, %edi
loop L(simple)
popl %ebp
popl %edi
popl %ebx
movl %esi, %eax
popl %esi
ret
C -----------------------------------------------------------------------------
C The code for each limb is 6 cycles, with instruction decoding being the
C limiting factor. At 4 limbs/loop and 1 cycle/loop of overhead it's 6.25
C cycles/limb in total.
C
C The secret ingredient to get 6.25 is to start the loop with the mul and
C have the load/store pair at the end. Rotating the load/store to the top
C is an 0.5 c/l slowdown. (Some address generation effect probably.)
C
C The whole unrolled loop fits nicely in exactly 80 bytes.
ALIGN(16) C already aligned to 16 here actually
L(unroll):
movl (%ebx), %eax
leal -16(%ebx,%ecx,4), %ebx
leal -16(%edi,%ecx,4), %edi
subl $4, %ecx
negl %ecx
ALIGN(16) C one byte nop for this alignment
L(top):
C eax scratch
C ebx &src[size-4]
C ecx counter
C edx scratch
C esi carry
C edi &dst[size-4]
C ebp multiplier
mull %ebp
addl %esi, %eax
movl $0, %esi
adcl %edx, %esi
movl %eax, (%edi,%ecx,4)
movl 4(%ebx,%ecx,4), %eax
mull %ebp
addl %esi, %eax
movl $0, %esi
adcl %edx, %esi
movl %eax, 4(%edi,%ecx,4)
movl 8(%ebx,%ecx,4), %eax
mull %ebp
addl %esi, %eax
movl $0, %esi
adcl %edx, %esi
movl %eax, 8(%edi,%ecx,4)
movl 12(%ebx,%ecx,4), %eax
mull %ebp
addl %esi, %eax
movl $0, %esi
adcl %edx, %esi
movl %eax, 12(%edi,%ecx,4)
movl 16(%ebx,%ecx,4), %eax
addl $4, %ecx
js L(top)
C eax next src limb
C ebx &src[size-4]
C ecx 0 to 3 representing respectively 4 to 1 further limbs
C edx
C esi carry
C edi &dst[size-4]
testb $2, %cl
jnz L(finish_not_two)
mull %ebp
addl %esi, %eax
movl $0, %esi
adcl %edx, %esi
movl %eax, (%edi,%ecx,4)
movl 4(%ebx,%ecx,4), %eax
mull %ebp
addl %esi, %eax
movl $0, %esi
adcl %edx, %esi
movl %eax, 4(%edi,%ecx,4)
movl 8(%ebx,%ecx,4), %eax
addl $2, %ecx
L(finish_not_two):
testb $1, %cl
jnz L(finish_not_one)
mull %ebp
addl %esi, %eax
movl $0, %esi
adcl %edx, %esi
movl %eax, 8(%edi)
movl 12(%ebx), %eax
L(finish_not_one):
mull %ebp
addl %esi, %eax
popl %ebp
adcl $0, %edx
movl %eax, 12(%edi)
popl %edi
popl %ebx
movl %edx, %eax
popl %esi
ret
EPILOGUE()
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