168 lines
3.8 KiB
NASM
168 lines
3.8 KiB
NASM
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dnl mc68020 mpn_rshift -- mpn right shift.
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dnl Copyright 1996, 1999, 2000, 2001, 2002, 2003 Free Software Foundation,
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dnl Inc.
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dnl
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dnl This file is part of the GNU MP Library.
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dnl
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dnl The GNU MP Library is free software; you can redistribute it and/or
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dnl modify it under the terms of the GNU Lesser General Public License as
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dnl published by the Free Software Foundation; either version 2.1 of the
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dnl License, or (at your option) any later version.
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dnl
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dnl The GNU MP Library is distributed in the hope that it will be useful,
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dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
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dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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dnl Lesser General Public License for more details.
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dnl
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dnl You should have received a copy of the GNU Lesser General Public
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dnl License along with the GNU MP Library; see the file COPYING.LIB. If
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dnl not, write to the Free Software Foundation, Inc., 51 Franklin Street,
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dnl Fifth Floor, Boston, MA 02110-1301, USA.
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include(`../config.m4')
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C cycles/limb
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C shift==1 shift>1
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C 68040: 9 12
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C mp_limb_t mpn_rshift (mp_ptr res_ptr, mp_srcptr s_ptr, mp_size_t s_size,
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C unsigned cnt);
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C
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C The "cnt" parameter is either 16 bits or 32 bits depending on
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C SIZEOF_UNSIGNED (see ABI notes in mpn/m68k/README). The value is of
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C course only 1 to 31. When loaded as 16 bits there's garbage in the upper
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C half, hence the use of cmpw. The shift instructions take the their count
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C modulo 64, so the upper part doesn't matter to them either.
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C
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C INPUT PARAMETERS
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C res_ptr (sp + 4)
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C s_ptr (sp + 8)
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C s_size (sp + 12)
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C cnt (sp + 16)
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define(res_ptr, `a1')
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define(s_ptr, `a0')
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define(s_size, `d6')
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define(cnt, `d4')
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ifdef(`SIZEOF_UNSIGNED',,
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`m4_error(`SIZEOF_UNSIGNED not defined, should be in config.m4
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')')
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PROLOGUE(mpn_rshift)
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C Save used registers on the stack.
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moveml d2-d6/a2, M(-,sp)
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C Copy the arguments to registers.
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movel M(sp,28), res_ptr
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movel M(sp,32), s_ptr
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movel M(sp,36), s_size
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ifelse(SIZEOF_UNSIGNED,2,
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` movew M(sp,40), cnt',
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` movel M(sp,40), cnt')
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moveql #1, d5
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cmpw d5, cnt
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bne L(Lnormal)
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cmpl res_ptr, s_ptr
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bls L(Lspecial) C jump if res_ptr >= s_ptr
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ifelse(scale_available_p,1,`
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lea M(res_ptr,s_size,l,4), a2
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',`
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movel s_size, d0
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asll #2, d0
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lea M(res_ptr,d0,l), a2
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')
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cmpl s_ptr, a2
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bls L(Lspecial) C jump if s_ptr >= res_ptr + s_size
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L(Lnormal:)
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moveql #32, d5
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subl cnt, d5
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movel M(s_ptr,+), d2
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movel d2, d0
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lsll d5, d0 C compute carry limb
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lsrl cnt, d2
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movel d2, d1
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subql #1, s_size
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beq L(Lend)
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lsrl #1, s_size
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bcs L(L1)
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subql #1, s_size
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L(Loop:)
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movel M(s_ptr,+), d2
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movel d2, d3
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lsll d5, d3
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orl d3, d1
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movel d1, M(res_ptr,+)
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lsrl cnt, d2
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L(L1:)
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movel M(s_ptr,+), d1
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movel d1, d3
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lsll d5, d3
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orl d3, d2
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movel d2, M(res_ptr,+)
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lsrl cnt, d1
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dbf s_size, L(Loop)
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subl #0x10000, s_size
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bcc L(Loop)
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L(Lend:)
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movel d1, M(res_ptr) C store most significant limb
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C Restore used registers from stack frame.
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moveml M(sp,+), d2-d6/a2
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rts
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C We loop from most significant end of the arrays, which is only permissable
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C if the source and destination don't overlap, since the function is
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C documented to work for overlapping source and destination.
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L(Lspecial:)
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ifelse(scale_available_p,1,`
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lea M(s_ptr,s_size,l,4), s_ptr
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lea M(res_ptr,s_size,l,4), res_ptr
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',`
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movel s_size, d0
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asll #2, d0
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addl d0, s_ptr
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addl d0, res_ptr
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')
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clrl d0 C initialize carry
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eorw #1, s_size
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lsrl #1, s_size
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bcc L(LL1)
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subql #1, s_size
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L(LLoop:)
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movel M(-,s_ptr), d2
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roxrl #1, d2
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movel d2, M(-,res_ptr)
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L(LL1:)
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movel M(-,s_ptr), d2
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roxrl #1, d2
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movel d2, M(-,res_ptr)
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dbf s_size, L(LLoop)
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roxrl #1, d0 C save cy in msb
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subl #0x10000, s_size
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bcs L(LLend)
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addl d0, d0 C restore cy
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bra L(LLoop)
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L(LLend:)
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C Restore used registers from stack frame.
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moveml M(sp,+), d2-d6/a2
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rts
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EPILOGUE(mpn_rshift)
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