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164 lines
4.1 KiB
ArmAsm
164 lines
4.1 KiB
ArmAsm
/* mc68020 rshift -- Shift right a low-level natural-number integer.
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*
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* Copyright (C) 1996, 1998, 2001 Free Software Foundation, Inc.
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*
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* This file is part of GnuPG.
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*
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* GnuPG is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* GnuPG is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*
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* Note: This code is heavily based on the GNU MP Library.
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* Actually it's the same code with only minor changes in the
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* way the data is stored; this is to support the abstraction
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* of an optional secure memory allocation which may be used
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* to avoid revealing of sensitive data due to paging etc.
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* The GNU MP Library itself is published under the LGPL;
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* however I decided to publish this code under the plain GPL.
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*/
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#include "sysdep.h"
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#include "asm-syntax.h"
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/*******************
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* mpi_limb_t
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* mpihelp_rshift( mpi_ptr_t wp, (sp + 4)
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* mpi_ptr_t up, (sp + 8)
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* mpi_size_t usize, (sp + 12)
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* unsigned cnt) (sp + 16)
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*/
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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(mpihelp_rshift)
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C_SYMBOL_NAME(mpihelp_rshift:)
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PROLOG(mpihelp_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(Rnormal)
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cmpl R(res_ptr),R(s_ptr)
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bls L(Rspecial) /* 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(Rspecial) /* jump if s_ptr >= res_ptr + s_size */
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L(Rnormal:)
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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(Rend)
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lsrl #1,R(s_size)
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bcs L(R1)
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subql #1,R(s_size)
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L(Roop:)
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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(R1:)
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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(Roop)
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subl #0x10000,R(s_size)
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bcc L(Roop)
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L(Rend:)
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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(Rspecial:)
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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(LR1)
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subql #1,R(s_size)
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L(LRoop:)
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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(LR1:)
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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(LRoop)
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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(LRend)
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addl R(d0),R(d0) /* restore cy */
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bra L(LRoop)
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L(LRend:)
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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(mpihelp_rshift)
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