--- /dev/null
+dnl AMD K6 mpn_mod_34lsub1 -- mpn remainder modulo 2**24-1.
+
+dnl Copyright 2000, 2001, 2002 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 K6: 2.66 cycles/limb
+
+
+C mp_limb_t mpn_mod_34lsub1 (mp_srcptr src, mp_size_t size)
+C
+C An attempt was made to use a loop like
+C
+C L(top):
+C adcl (%edx), %eax
+C adcl 4(%edx), %ebx
+C adcl 8(%edx), %esi
+C leal 12(%edx), %edx
+C loop L(top)
+C
+C with %ecx starting from floor(size/3), but it still measured 2.66 c/l.
+C The form used instead can save about 6 cycles by not dividing by 3.
+C
+C In the code used, putting the "leal"s at the top of the loop is necessary
+C for the claimed speed, anywhere else costs an extra cycle per loop.
+C Perhaps a tight loop like this needs short decode instructions at the
+C branch target, which would explain the leal/loop form above taking 8
+C cycles instead of 7 too.
+
+defframe(PARAM_SIZE, 8)
+defframe(PARAM_SRC, 4)
+
+dnl re-use parameter space
+define(SAVE_EBX, `PARAM_SIZE')
+define(SAVE_ESI, `PARAM_SRC')
+
+ TEXT
+ ALIGN(16)
+PROLOGUE(mpn_mod_34lsub1)
+deflit(`FRAME',0)
+
+ movl PARAM_SIZE, %eax
+ movl PARAM_SRC, %edx
+
+ subl $2, %eax
+ ja L(three_or_more)
+
+Zdisp( movl, 0,(%edx), %eax) C avoid code cache line boundary
+ jne L(one)
+
+ movl %eax, %ecx
+ movl 4(%edx), %edx
+
+ shrl $24, %eax C src[0] high
+ andl $0x00FFFFFF, %ecx C src[0] low
+
+ addl %ecx, %eax
+ movl %edx, %ecx
+
+ shll $8, %edx
+ andl $0x00FFFF00, %edx C src[1] high
+
+ shrl $16, %ecx C src[1] low
+ addl %ecx, %eax
+
+ addl %edx, %eax
+
+L(one):
+ ret
+
+
+L(three_or_more):
+ C eax size-2
+ C ebx
+ C ecx
+ C edx src
+
+ movl %ebx, SAVE_EBX
+ xorl %ebx, %ebx
+
+ movl %esi, SAVE_ESI
+ pushl %edi FRAME_pushl()
+
+ xorl %esi, %esi
+ xorl %edi, %edi C and clear carry flag
+
+L(top):
+ C eax counter, limbs
+ C ebx acc 0mod3
+ C ecx
+ C edx src, incrementing
+ C esi acc 1mod3
+ C edi acc 2mod3
+ C ebp
+
+ leal -2(%eax), %eax
+ leal 12(%edx), %edx
+
+ adcl -12(%edx), %ebx
+ adcl -8(%edx), %esi
+ adcl -4(%edx), %edi
+
+ decl %eax
+ jg L(top)
+
+
+ C ecx is -3, -2 or -1 representing 0, 1 or 2 more limbs, respectively
+
+ movb $0, %cl
+ incl %eax
+
+ js L(combine) C 0 more
+
+Zdisp( adcl, 0,(%edx), %ebx) C avoid code cache line crossings
+
+ movb $8, %cl
+ decl %eax
+
+ js L(combine) C 1 more
+
+ adcl 4(%edx), %esi
+
+ movb $16, %cl
+
+
+L(combine):
+ sbbl %edx, %edx
+
+ shll %cl, %edx C carry
+ movl %ebx, %eax C 0mod3
+
+ shrl $24, %eax C 0mod3 high
+ andl $0x00FFFFFF, %ebx C 0mod3 low
+
+ subl %edx, %eax C apply carry
+ movl %esi, %ecx C 1mod3
+
+ shrl $16, %esi C 1mod3 high
+ addl %ebx, %eax C apply 0mod3 low
+
+ andl $0x0000FFFF, %ecx
+ addl %esi, %eax C apply 1mod3 high
+
+ shll $8, %ecx C 1mod3 low
+ movl %edi, %edx C 2mod3
+
+ shrl $8, %edx C 2mod3 high
+ addl %ecx, %eax C apply 1mod3 low
+
+ addl %edx, %eax C apply 2mod3 high
+ andl $0x000000FF, %edi
+
+ shll $16, %edi C 2mod3 low
+ movl SAVE_EBX, %ebx
+
+ addl %edi, %eax C apply 2mod3 low
+ movl SAVE_ESI, %esi
+
+ popl %edi
+
+ ret
+
+EPILOGUE()
projects / msp430-gcc.git / blobdiff