glibc/sysdeps/m68k/rshift.S

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/* mc68020 __mpn_rshift -- Shift right a low-level natural-number integer.
Copyright (C) 1996, 1998 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
The GNU MP Library is free software; you can redistribute it and/or modify
it under the terms of the GNU Library General Public License as published by
the Free Software Foundation; either version 2 of the License, or (at your
option) any later version.
The GNU MP Library is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
License for more details.
You should have received a copy of the GNU Library General Public License
along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
MA 02111-1307, USA. */
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/*
INPUT PARAMETERS
res_ptr (sp + 4)
s_ptr (sp + 8)
s_size (sp + 16)
cnt (sp + 12)
*/
#include "sysdep.h"
#include "asm-syntax.h"
#define res_ptr a1
#define s_ptr a0
#define s_size d6
#define cnt d4
TEXT
ENTRY(__mpn_rshift)
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/* Save used registers on the stack. */
moveml R(d2)-R(d6)/R(a2),MEM_PREDEC(sp)
/* Copy the arguments to registers. */
movel MEM_DISP(sp,28),R(res_ptr)
movel MEM_DISP(sp,32),R(s_ptr)
movel MEM_DISP(sp,36),R(s_size)
movel MEM_DISP(sp,40),R(cnt)
moveql #1,R(d5)
cmpl R(d5),R(cnt)
bne L(Lnormal)
cmpl R(res_ptr),R(s_ptr)
bls L(Lspecial) /* jump if res_ptr >= s_ptr */
#if (defined (__mc68020__) || defined (__NeXT__) || defined(mc68020))
lea MEM_INDX1(res_ptr,s_size,l,4),R(a2)
#else /* not mc68020 */
movel R(s_size),R(d0)
asll #2,R(d0)
lea MEM_INDX(res_ptr,d0,l),R(a2)
#endif
cmpl R(s_ptr),R(a2)
bls L(Lspecial) /* jump if s_ptr >= res_ptr + s_size */
L(Lnormal:)
moveql #32,R(d5)
subl R(cnt),R(d5)
movel MEM_POSTINC(s_ptr),R(d2)
movel R(d2),R(d0)
lsll R(d5),R(d0) /* compute carry limb */
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lsrl R(cnt),R(d2)
movel R(d2),R(d1)
subql #1,R(s_size)
beq L(Lend)
lsrl #1,R(s_size)
bcs L(L1)
subql #1,R(s_size)
L(Loop:)
movel MEM_POSTINC(s_ptr),R(d2)
movel R(d2),R(d3)
lsll R(d5),R(d3)
orl R(d3),R(d1)
movel R(d1),MEM_POSTINC(res_ptr)
lsrl R(cnt),R(d2)
L(L1:)
movel MEM_POSTINC(s_ptr),R(d1)
movel R(d1),R(d3)
lsll R(d5),R(d3)
orl R(d3),R(d2)
movel R(d2),MEM_POSTINC(res_ptr)
lsrl R(cnt),R(d1)
dbf R(s_size),L(Loop)
subl #0x10000,R(s_size)
bcc L(Loop)
L(Lend:)
movel R(d1),MEM(res_ptr) /* store most significant limb */
/* Restore used registers from stack frame. */
moveml MEM_POSTINC(sp),R(d2)-R(d6)/R(a2)
rts
/* We loop from most significant end of the arrays, which is only
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permissible if the source and destination don't overlap, since the
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function is documented to work for overlapping source and destination. */
L(Lspecial:)
#if (defined (__mc68020__) || defined (__NeXT__) || defined(mc68020))
lea MEM_INDX1(s_ptr,s_size,l,4),R(s_ptr)
lea MEM_INDX1(res_ptr,s_size,l,4),R(res_ptr)
#else /* not mc68000 */
movel R(s_size),R(d0)
asll #2,R(d0)
addl R(s_size),R(s_ptr)
addl R(s_size),R(res_ptr)
#endif
clrl R(d0) /* initialize carry */
eorw #1,R(s_size)
lsrl #1,R(s_size)
bcc L(LL1)
subql #1,R(s_size)
L(LLoop:)
movel MEM_PREDEC(s_ptr),R(d2)
roxrl #1,R(d2)
movel R(d2),MEM_PREDEC(res_ptr)
L(LL1:)
movel MEM_PREDEC(s_ptr),R(d2)
roxrl #1,R(d2)
movel R(d2),MEM_PREDEC(res_ptr)
dbf R(s_size),L(LLoop)
roxrl #1,R(d0) /* save cy in msb */
subl #0x10000,R(s_size)
bcs L(LLend)
addl R(d0),R(d0) /* restore cy */
bra L(LLoop)
L(LLend:)
/* Restore used registers from stack frame. */
moveml MEM_POSTINC(sp),R(d2)-R(d6)/R(a2)
rts
END(__mpn_rshift)