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150 lines
3.7 KiB
ArmAsm
150 lines
3.7 KiB
ArmAsm
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/* mc68020 __mpn_rshift -- Shift right a low-level natural-number integer.
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Copyright (C) 1996 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Library General Public License as published by
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the Free Software Foundation; either version 2 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public
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License for more details.
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You should have received a copy of the GNU Library General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */
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/*
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INPUT PARAMETERS
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res_ptr (sp + 4)
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s_ptr (sp + 8)
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s_size (sp + 16)
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cnt (sp + 12)
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*/
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#include "sysdep.h"
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#include "asm-syntax.h"
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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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TEXT
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ALIGN
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GLOBL C_SYMBOL_NAME(__mpn_rshift)
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C_SYMBOL_NAME(__mpn_rshift:)
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PROLOG(__mpn_rshift)
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/* Save used registers on the stack. */
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moveml R(d2)-R(d6)/R(a2),MEM_PREDEC(sp)
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/* Copy the arguments to registers. */
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movel MEM_DISP(sp,28),R(res_ptr)
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movel MEM_DISP(sp,32),R(s_ptr)
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movel MEM_DISP(sp,36),R(s_size)
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movel MEM_DISP(sp,40),R(cnt)
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moveql #1,R(d5)
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cmpl R(d5),R(cnt)
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bne L(Lnormal)
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cmpl R(res_ptr),R(s_ptr)
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bls L(Lspecial) /* jump if res_ptr >= s_ptr */
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#if (defined (__mc68020__) || defined (__NeXT__) || defined(mc68020))
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lea MEM_INDX1(res_ptr,s_size,l,4),R(a2)
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#else /* not mc68020 */
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movel R(s_size),R(d0)
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asll #2,R(d0)
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lea MEM_INDX(res_ptr,d0,l),R(a2)
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#endif
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cmpl R(s_ptr),R(a2)
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bls L(Lspecial) /* jump if s_ptr >= res_ptr + s_size */
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L(Lnormal:)
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moveql #32,R(d5)
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subl R(cnt),R(d5)
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movel MEM_POSTINC(s_ptr),R(d2)
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movel R(d2),R(d0)
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lsll R(d5),R(d0) /* compute carry limb */
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lsrl R(cnt),R(d2)
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movel R(d2),R(d1)
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subql #1,R(s_size)
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beq L(Lend)
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lsrl #1,R(s_size)
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bcs L(L1)
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subql #1,R(s_size)
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L(Loop:)
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movel MEM_POSTINC(s_ptr),R(d2)
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movel R(d2),R(d3)
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lsll R(d5),R(d3)
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orl R(d3),R(d1)
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movel R(d1),MEM_POSTINC(res_ptr)
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lsrl R(cnt),R(d2)
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L(L1:)
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movel MEM_POSTINC(s_ptr),R(d1)
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movel R(d1),R(d3)
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lsll R(d5),R(d3)
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orl R(d3),R(d2)
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movel R(d2),MEM_POSTINC(res_ptr)
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lsrl R(cnt),R(d1)
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dbf R(s_size),L(Loop)
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subl #0x10000,R(s_size)
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bcc L(Loop)
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L(Lend:)
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movel R(d1),MEM(res_ptr) /* store most significant limb */
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/* Restore used registers from stack frame. */
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moveml MEM_POSTINC(sp),R(d2)-R(d6)/R(a2)
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rts
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/* We loop from most significant end of the arrays, which is only
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permissable if the source and destination don't overlap, since the
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function is documented to work for overlapping source and destination. */
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L(Lspecial:)
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#if (defined (__mc68020__) || defined (__NeXT__) || defined(mc68020))
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lea MEM_INDX1(s_ptr,s_size,l,4),R(s_ptr)
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lea MEM_INDX1(res_ptr,s_size,l,4),R(res_ptr)
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#else /* not mc68000 */
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movel R(s_size),R(d0)
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asll #2,R(d0)
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addl R(s_size),R(s_ptr)
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addl R(s_size),R(res_ptr)
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#endif
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clrl R(d0) /* initialize carry */
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eorw #1,R(s_size)
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lsrl #1,R(s_size)
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bcc L(LL1)
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subql #1,R(s_size)
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L(LLoop:)
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movel MEM_PREDEC(s_ptr),R(d2)
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roxrl #1,R(d2)
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movel R(d2),MEM_PREDEC(res_ptr)
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L(LL1:)
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movel MEM_PREDEC(s_ptr),R(d2)
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roxrl #1,R(d2)
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movel R(d2),MEM_PREDEC(res_ptr)
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dbf R(s_size),L(LLoop)
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roxrl #1,R(d0) /* save cy in msb */
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subl #0x10000,R(s_size)
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bcs L(LLend)
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addl R(d0),R(d0) /* restore cy */
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bra L(LLoop)
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L(LLend:)
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/* Restore used registers from stack frame. */
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moveml MEM_POSTINC(sp),R(d2)-R(d6)/R(a2)
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rts
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EPILOG(__mpn_rshift)
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