usr/src/lib/libc/i386/gen/ldivide.s

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27         .file   "ldivide.s"
  28
  29 / Double long divide routine.
  30
  31 #include "SYS.h"
  32
  33         .set    lop,16
  34         .set    rop,24
  35         .set    ans,0
  36
  37         ENTRY(ldivide)
  38         popl    %eax
  39         xchgl   %eax,0(%esp)
  40         pushl   %eax
  41
  42         pushl   %esi
  43         pushl   %edi
  44
  45         movl    lop(%esp),%eax
  46         movl    lop+4(%esp),%edx
  47
  48 / the following code is only for compatibility with original ldivide code
  49         orl     %edx,%edx       / force numerator positive
  50         jns     .ldiv1
  51         notl    %edx
  52         negl    %eax
  53         sbbl    $0xffffffff,%edx
  54 .ldiv1:
  55         testl   $0x80000000,rop+4(%esp)
  56         jz      .ldiv2
  57         notl    rop+4(%esp)     / force denominator positive
  58         negl    rop(%esp)
  59         sbbl    $0xffffffff,rop+4(%esp)
  60 .ldiv2:
  61 / end of compatibility code
  62
  63         xorl    %esi,%esi       / initialize remainder to 0
  64         movl    %esi,%edi
  65         movl    $64,%ecx        / initialize counter for 64-bits
  66 .div_mod_loop:
  67         shll    $1,%edi
  68         rcll    $1,%esi         / remainder * 2
  69         shll    $1,%eax
  70         rcll    $1,%edx         / numerator * 2 (also quotient)
  71         adcl    $0,%edi         / add in any carry from the shift
  72         subl    rop(%esp),%edi  / subtract denominator from remainder
  73         sbbl    rop+4(%esp),%esi
  74         incl    %eax            / turn on quotient bit for now
  75         jnc     .inc_remainder  / inc didn't affect carry flag
  76 / can't subtract the denominator from the remainder, add it back
  77         addl    rop(%esp),%edi
  78         adcl    rop+4(%esp),%esi
  79         decl    %eax            / turn quotient bit off
  80 .inc_remainder:
  81         loop    .div_mod_loop
  82
  83 / at this point, %edx:%eax has the quotient and %edi:%esi has the remainder
  84         popl    %edi
  85         popl    %esi
  86         movl    %eax,%ecx
  87         popl    %eax
  88         movl    %ecx,ans(%eax)
  89         movl    %edx,ans+4(%eax)
  90         ret
  91         SET_SIZE(ldivide)