163 lines
4.1 KiB
ArmAsm
163 lines
4.1 KiB
ArmAsm
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/* mc68020 rshift -- Shift right a low-level natural-number integer.
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*
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* Copyright (C) 1996, 1998, 2001, 2002 Free Software Foundation, Inc.
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*
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* This file is part of Libgcrypt.
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*
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* Libgcrypt is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Lesser General Public License as
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* published by the Free Software Foundation; either version 2.1 of
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* the License, or (at your option) any later version.
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*
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* Libgcrypt 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 Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
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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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*/
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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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* _gcry_mpih_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(_gcry_mpih_rshift)
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C_SYMBOL_NAME(_gcry_mpih_rshift:)
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PROLOG(_gcry_mpih_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(_gcry_mpih_rshift)
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