rshift.asm
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- dnl mc68020 mpn_rshift -- mpn right shift.
- dnl Copyright 1996, 1999, 2000, 2001, 2002, 2003 Free Software Foundation,
- dnl 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 shift==1 shift>1
- C 68040: 9 12
- C mp_limb_t mpn_rshift (mp_ptr res_ptr, mp_srcptr s_ptr, mp_size_t s_size,
- C unsigned cnt);
- C
- C The "cnt" parameter is either 16 bits or 32 bits depending on
- C SIZEOF_UNSIGNED (see ABI notes in mpn/m68k/README). The value is of
- C course only 1 to 31. When loaded as 16 bits there's garbage in the upper
- C half, hence the use of cmpw. The shift instructions take the their count
- C modulo 64, so the upper part doesn't matter to them either.
- C
- C INPUT PARAMETERS
- C res_ptr (sp + 4)
- C s_ptr (sp + 8)
- C s_size (sp + 12)
- C cnt (sp + 16)
- define(res_ptr, `a1')
- define(s_ptr, `a0')
- define(s_size, `d6')
- define(cnt, `d4')
- ifdef(`SIZEOF_UNSIGNED',,
- `m4_error(`SIZEOF_UNSIGNED not defined, should be in config.m4
- ')')
- PROLOGUE(mpn_rshift)
- C Save used registers on the stack.
- moveml d2-d6/a2, M(-,sp)
- C Copy the arguments to registers.
- movel M(sp,28), res_ptr
- movel M(sp,32), s_ptr
- movel M(sp,36), s_size
- ifelse(SIZEOF_UNSIGNED,2,
- ` movew M(sp,40), cnt',
- ` movel M(sp,40), cnt')
- moveql #1, d5
- cmpw d5, cnt
- bne L(Lnormal)
- cmpl res_ptr, s_ptr
- bls L(Lspecial) C jump if res_ptr >= s_ptr
- ifelse(scale_available_p,1,`
- lea M(res_ptr,s_size,l,4), a2
- ',`
- movel s_size, d0
- asll #2, d0
- lea M(res_ptr,d0,l), a2
- ')
- cmpl s_ptr, a2
- bls L(Lspecial) C jump if s_ptr >= res_ptr + s_size
- L(Lnormal:)
- moveql #32, d5
- subl cnt, d5
- movel M(s_ptr,+), d2
- movel d2, d0
- lsll d5, d0 C compute carry limb
- lsrl cnt, d2
- movel d2, d1
- subql #1, s_size
- beq L(Lend)
- lsrl #1, s_size
- bcs L(L1)
- subql #1, s_size
- L(Loop:)
- movel M(s_ptr,+), d2
- movel d2, d3
- lsll d5, d3
- orl d3, d1
- movel d1, M(res_ptr,+)
- lsrl cnt, d2
- L(L1:)
- movel M(s_ptr,+), d1
- movel d1, d3
- lsll d5, d3
- orl d3, d2
- movel d2, M(res_ptr,+)
- lsrl cnt, d1
- dbf s_size, L(Loop)
- subl #0x10000, s_size
- bcc L(Loop)
- L(Lend:)
- movel d1, M(res_ptr) C store most significant limb
- C Restore used registers from stack frame.
- moveml M(sp,+), d2-d6/a2
- rts
- C We loop from most significant end of the arrays, which is only permissable
- C if the source and destination don't overlap, since the function is
- C documented to work for overlapping source and destination.
- L(Lspecial:)
- ifelse(scale_available_p,1,`
- lea M(s_ptr,s_size,l,4), s_ptr
- lea M(res_ptr,s_size,l,4), res_ptr
- ',`
- movel s_size, d0
- asll #2, d0
- addl d0, s_ptr
- addl d0, res_ptr
- ')
- clrl d0 C initialize carry
- eorw #1, s_size
- lsrl #1, s_size
- bcc L(LL1)
- subql #1, s_size
- L(LLoop:)
- movel M(-,s_ptr), d2
- roxrl #1, d2
- movel d2, M(-,res_ptr)
- L(LL1:)
- movel M(-,s_ptr), d2
- roxrl #1, d2
- movel d2, M(-,res_ptr)
- dbf s_size, L(LLoop)
- roxrl #1, d0 C save cy in msb
- subl #0x10000, s_size
- bcs L(LLend)
- addl d0, d0 C restore cy
- bra L(LLoop)
- L(LLend:)
- C Restore used registers from stack frame.
- moveml M(sp,+), d2-d6/a2
- rts
- EPILOGUE(mpn_rshift)