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dnl mc68020 mpn_rshift -- mpn right shift.
dnl Copyright 1996, 1999-2003 Free Software Foundation, Inc.
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 modify
dnl it under the terms of either:
dnl
dnl * the GNU Lesser General Public License as published by the Free
dnl Software Foundation; either version 3 of the License, or (at your
dnl option) any later version.
dnl
dnl or
dnl
dnl * the GNU General Public License as published by the Free Software
dnl Foundation; either version 2 of the License, or (at your option) any
dnl later version.
dnl
dnl or both in parallel, as here.
dnl
dnl The GNU MP Library is distributed in the hope that it will be useful, but
dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
dnl for more details.
dnl
dnl You should have received copies of the GNU General Public License and the
dnl GNU Lesser General Public License along with the GNU MP Library. If not,
dnl see https://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)
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