arch/i386/math-emu/wm_shrx.S

   1         .file   "wm_shrx.S"
   2 /*---------------------------------------------------------------------------+
   3  |  wm_shrx.S                                                                |
   4  |                                                                           |
   5  | 64 bit right shift functions                                              |
   6  |                                                                           |
   7  | Copyright (C) 1992,1995                                                   |
   8  |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
   9  |                       Australia.  E-mail billm@jacobi.maths.monash.edu.au |
  10  |                                                                           |
  11  | Call from C as:                                                           |
  12  |   unsigned FPU_shrx(void *arg1, unsigned arg2)                            |
  13  | and                                                                       |
  14  |   unsigned FPU_shrxs(void *arg1, unsigned arg2)                           |
  15  |                                                                           |
  16  +---------------------------------------------------------------------------*/
  17
  18 #include "fpu_emu.h"
  19
  20 .text
  21 /*---------------------------------------------------------------------------+
  22  |   unsigned FPU_shrx(void *arg1, unsigned arg2)                            |
  23  |                                                                           |
  24  |   Extended shift right function.                                          |
  25  |   Fastest for small shifts.                                               |
  26  |   Shifts the 64 bit quantity pointed to by the first arg (arg1)           |
  27  |   right by the number of bits specified by the second arg (arg2).         |
  28  |   Forms a 96 bit quantity from the 64 bit arg and eax:                    |
  29  |                [  64 bit arg ][ eax ]                                     |
  30  |            shift right  --------->                                        |
  31  |   The eax register is initialized to 0 before the shifting.               |
  32  |   Results returned in the 64 bit arg and eax.                             |
  33  +---------------------------------------------------------------------------*/
  34
  35 ENTRY(FPU_shrx)
  36         push    %ebp
  37         movl    %esp,%ebp
  38         pushl   %esi
  39         movl    PARAM2,%ecx
  40         movl    PARAM1,%esi
  41         cmpl    $32,%ecx        /* shrd only works for 0..31 bits */
  42         jnc     L_more_than_31
  43
  44 /* less than 32 bits */
  45         pushl   %ebx
  46         movl    (%esi),%ebx     /* lsl */
  47         movl    4(%esi),%edx    /* msl */
  48         xorl    %eax,%eax       /* extension */
  49         shrd    %cl,%ebx,%eax
  50         shrd    %cl,%edx,%ebx
  51         shr     %cl,%edx
  52         movl    %ebx,(%esi)
  53         movl    %edx,4(%esi)
  54         popl    %ebx
  55         popl    %esi
  56         leave
  57         ret
  58
  59 L_more_than_31:
  60         cmpl    $64,%ecx
  61         jnc     L_more_than_63
  62
  63         subb    $32,%cl
  64         movl    (%esi),%eax     /* lsl */
  65         movl    4(%esi),%edx    /* msl */
  66         shrd    %cl,%edx,%eax
  67         shr     %cl,%edx
  68         movl    %edx,(%esi)
  69         movl    $0,4(%esi)
  70         popl    %esi
  71         leave
  72         ret
  73
  74 L_more_than_63:
  75         cmpl    $96,%ecx
  76         jnc     L_more_than_95
  77
  78         subb    $64,%cl
  79         movl    4(%esi),%eax    /* msl */
  80         shr     %cl,%eax
  81         xorl    %edx,%edx
  82         movl    %edx,(%esi)
  83         movl    %edx,4(%esi)
  84         popl    %esi
  85         leave
  86         ret
  87
  88 L_more_than_95:
  89         xorl    %eax,%eax
  90         movl    %eax,(%esi)
  91         movl    %eax,4(%esi)
  92         popl    %esi
  93         leave
  94         ret
  95
  96
  97 /*---------------------------------------------------------------------------+
  98  |   unsigned FPU_shrxs(void *arg1, unsigned arg2)                           |
  99  |                                                                           |
 100  |   Extended shift right function (optimized for small floating point       |
 101  |   integers).                                                              |
 102  |   Shifts the 64 bit quantity pointed to by the first arg (arg1)           |
 103  |   right by the number of bits specified by the second arg (arg2).         |
 104  |   Forms a 96 bit quantity from the 64 bit arg and eax:                    |
 105  |                [  64 bit arg ][ eax ]                                     |
 106  |            shift right  --------->                                        |
 107  |   The eax register is initialized to 0 before the shifting.               |
 108  |   The lower 8 bits of eax are lost and replaced by a flag which is        |
 109  |   set (to 0x01) if any bit, apart from the first one, is set in the       |
 110  |   part which has been shifted out of the arg.                             |
 111  |   Results returned in the 64 bit arg and eax.                             |
 112  +---------------------------------------------------------------------------*/
 113 ENTRY(FPU_shrxs)
 114         push    %ebp
 115         movl    %esp,%ebp
 116         pushl   %esi
 117         pushl   %ebx
 118         movl    PARAM2,%ecx
 119         movl    PARAM1,%esi
 120         cmpl    $64,%ecx        /* shrd only works for 0..31 bits */
 121         jnc     Ls_more_than_63
 122
 123         cmpl    $32,%ecx        /* shrd only works for 0..31 bits */
 124         jc      Ls_less_than_32
 125
 126 /* We got here without jumps by assuming that the most common requirement
 127    is for small integers */
 128 /* Shift by [32..63] bits */
 129         subb    $32,%cl
 130         movl    (%esi),%eax     /* lsl */
 131         movl    4(%esi),%edx    /* msl */
 132         xorl    %ebx,%ebx
 133         shrd    %cl,%eax,%ebx
 134         shrd    %cl,%edx,%eax
 135         shr     %cl,%edx
 136         orl     %ebx,%ebx               /* test these 32 bits */
 137         setne   %bl
 138         test    $0x7fffffff,%eax        /* and 31 bits here */
 139         setne   %bh
 140         orw     %bx,%bx                 /* Any of the 63 bit set ? */
 141         setne   %al
 142         movl    %edx,(%esi)
 143         movl    $0,4(%esi)
 144         popl    %ebx
 145         popl    %esi
 146         leave
 147         ret
 148
 149 /* Shift by [0..31] bits */
 150 Ls_less_than_32:
 151         movl    (%esi),%ebx     /* lsl */
 152         movl    4(%esi),%edx    /* msl */
 153         xorl    %eax,%eax       /* extension */
 154         shrd    %cl,%ebx,%eax
 155         shrd    %cl,%edx,%ebx
 156         shr     %cl,%edx
 157         test    $0x7fffffff,%eax        /* only need to look at eax here */
 158         setne   %al
 159         movl    %ebx,(%esi)
 160         movl    %edx,4(%esi)
 161         popl    %ebx
 162         popl    %esi
 163         leave
 164         ret
 165
 166 /* Shift by [64..95] bits */
 167 Ls_more_than_63:
 168         cmpl    $96,%ecx
 169         jnc     Ls_more_than_95
 170
 171         subb    $64,%cl
 172         movl    (%esi),%ebx     /* lsl */
 173         movl    4(%esi),%eax    /* msl */
 174         xorl    %edx,%edx       /* extension */
 175         shrd    %cl,%ebx,%edx
 176         shrd    %cl,%eax,%ebx
 177         shr     %cl,%eax
 178         orl     %ebx,%edx
 179         setne   %bl
 180         test    $0x7fffffff,%eax        /* only need to look at eax here */
 181         setne   %bh
 182         orw     %bx,%bx
 183         setne   %al
 184         xorl    %edx,%edx
 185         movl    %edx,(%esi)     /* set to zero */
 186         movl    %edx,4(%esi)    /* set to zero */
 187         popl    %ebx
 188         popl    %esi
 189         leave
 190         ret
 191
 192 Ls_more_than_95:
 193 /* Shift by [96..inf) bits */
 194         xorl    %eax,%eax
 195         movl    (%esi),%ebx
 196         orl     4(%esi),%ebx
 197         setne   %al
 198         xorl    %ebx,%ebx
 199         movl    %ebx,(%esi)
 200         movl    %ebx,4(%esi)
 201         popl    %ebx
 202         popl    %esi
 203         leave
 204         ret