-dnl AMD K6 mpn_rshift -- mpn right shift.
-dnl
-dnl K6: 3.0 cycles/limb
-
-
-dnl Copyright (C) 1999, 2000 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 2.1 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
-dnl License along with the GNU MP Library; see the file COPYING.LIB. If
-dnl not, write to the Free Software Foundation, Inc., 59 Temple Place -
-dnl Suite 330, Boston, MA 02111-1307, USA.
-
-
-include(`../config.m4')
-
-
-C mp_limb_t mpn_rshift (mp_ptr dst, mp_srcptr src, mp_size_t size,
-C unsigned shift);
-C
-C The loop runs at 3 cycles/limb, limited by decoding and by having 3 mmx
-C instructions. This is despite every second fetch being unaligned.
-
-
-defframe(PARAM_SHIFT,16)
-defframe(PARAM_SIZE, 12)
-defframe(PARAM_SRC, 8)
-defframe(PARAM_DST, 4)
-deflit(`FRAME',0)
-
- .text
- ALIGN(32)
-
-PROLOGUE(mpn_rshift)
-deflit(`FRAME',0)
-
- C The 1 limb case can be done without the push %ebx, but it's then
- C still the same speed. The push is left as a free helping hand for
- C the two_or_more code.
-
- movl PARAM_SIZE, %eax
- pushl %ebx FRAME_pushl()
-
- movl PARAM_SRC, %ebx
- decl %eax
-
- movl PARAM_SHIFT, %ecx
- jnz L(two_or_more)
-
- movl (%ebx), %edx C src limb
- movl PARAM_DST, %ebx
-
- shrdl( %cl, %edx, %eax) C return value
-
- shrl %cl, %edx
-
- movl %edx, (%ebx) C dst limb
- popl %ebx
-
- ret
-
-
- ALIGN(16) C avoid offset 0x1f
-L(two_or_more):
- C eax size-1
- C ebx src
- C ecx shift
- C edx
-
- movl (%ebx), %edx C src low limb
- negl %ecx
-
- addl $32, %ecx C 32-shift
- movd PARAM_SHIFT, %mm6
-
- shll %cl, %edx C retval
- movl PARAM_DST, %ecx
-
- leal (%ebx,%eax,4), %ebx
-
- leal -4(%ecx,%eax,4), %ecx
- negl %eax
-
-
-L(simple):
- C eax counter (negative)
- C ebx &src[size-1]
- C ecx &dst[size-1]
- C edx retval
- C
- C mm0 scratch
- C mm6 shift
-
-Zdisp( movq, 0,(%ebx,%eax,4), %mm0)
- incl %eax
-
- psrlq %mm6, %mm0
-
-Zdisp( movd, %mm0, 0,(%ecx,%eax,4))
- jnz L(simple)
-
-
- movq %mm0, (%ecx)
- movl %edx, %eax
-
- popl %ebx
-
- emms
- ret
-
-EPILOGUE()