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   1         .file   "reg_u_add.S"
   2 /*---------------------------------------------------------------------------+
   3  |  reg_u_add.S                                                              |
   4  |                                                                           |
   5  | Add two valid (TAG_Valid) FPU_REG numbers, of the same sign, and put the  |
   6  |   result in a destination FPU_REG.                                        |
   7  |                                                                           |
   8  | Copyright (C) 1992,1993,1995,1997                                         |
   9  |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
  10  |                  E-mail   billm@suburbia.net                              |
  11  |                                                                           |
  12  | Call from C as:                                                           |
  13  |   int  FPU_u_add(FPU_REG *arg1, FPU_REG *arg2, FPU_REG *answ,             |
  14  |                                                int control_w)             |
  15  |    Return value is the tag of the answer, or-ed with FPU_Exception if     |
  16  |    one was raised, or -1 on internal error.                               |
  17  |                                                                           |
  18  +---------------------------------------------------------------------------*/
  19
  20 /*
  21  |    Kernel addition routine FPU_u_add(reg *arg1, reg *arg2, reg *answ).
  22  |    Takes two valid reg f.p. numbers (TAG_Valid), which are
  23  |    treated as unsigned numbers,
  24  |    and returns their sum as a TAG_Valid or TAG_Special f.p. number.
  25  |    The returned number is normalized.
  26  |    Basic checks are performed if PARANOID is defined.
  27  */
  28
  29 #include "exception.h"
  30 #include "fpu_emu.h"
  31 #include "control_w.h"
  32
  33 .text
  34 ENTRY(FPU_u_add)
  35         pushl   %ebp
  36         movl    %esp,%ebp
  37         pushl   %esi
  38         pushl   %edi
  39         pushl   %ebx
  40
  41         movl    PARAM1,%esi             /* source 1 */
  42         movl    PARAM2,%edi             /* source 2 */
  43
  44         movl    PARAM6,%ecx
  45         movl    %ecx,%edx
  46         subl    PARAM7,%ecx                     /* exp1 - exp2 */
  47         jge     L_arg1_larger
  48
  49         /* num1 is smaller */
  50         movl    SIGL(%esi),%ebx
  51         movl    SIGH(%esi),%eax
  52
  53         movl    %edi,%esi
  54         movl    PARAM7,%edx
  55         negw    %cx
  56         jmp     L_accum_loaded
  57
  58 L_arg1_larger:
  59         /* num1 has larger or equal exponent */
  60         movl    SIGL(%edi),%ebx
  61         movl    SIGH(%edi),%eax
  62
  63 L_accum_loaded:
  64         movl    PARAM3,%edi             /* destination */
  65         movw    %dx,EXP(%edi)           /* Copy exponent to destination */
  66
  67         xorl    %edx,%edx               /* clear the extension */
  68
  69 #ifdef PARANOID
  70         testl   $0x80000000,%eax
  71         je      L_bugged
  72
  73         testl   $0x80000000,SIGH(%esi)
  74         je      L_bugged
  75 #endif /* PARANOID */
  76
  77 /* The number to be shifted is in %eax:%ebx:%edx */
  78         cmpw    $32,%cx         /* shrd only works for 0..31 bits */
  79         jnc     L_more_than_31
  80
  81 /* less than 32 bits */
  82         shrd    %cl,%ebx,%edx
  83         shrd    %cl,%eax,%ebx
  84         shr     %cl,%eax
  85         jmp     L_shift_done
  86
  87 L_more_than_31:
  88         cmpw    $64,%cx
  89         jnc     L_more_than_63
  90
  91         subb    $32,%cl
  92         jz      L_exactly_32
  93
  94         shrd    %cl,%eax,%edx
  95         shr     %cl,%eax
  96         orl     %ebx,%ebx
  97         jz      L_more_31_no_low        /* none of the lowest bits is set */
  98
  99         orl     $1,%edx                 /* record the fact in the extension */
 100
 101 L_more_31_no_low:
 102         movl    %eax,%ebx
 103         xorl    %eax,%eax
 104         jmp     L_shift_done
 105
 106 L_exactly_32:
 107         movl    %ebx,%edx
 108         movl    %eax,%ebx
 109         xorl    %eax,%eax
 110         jmp     L_shift_done
 111
 112 L_more_than_63:
 113         cmpw    $65,%cx
 114         jnc     L_more_than_64
 115
 116         movl    %eax,%edx
 117         orl     %ebx,%ebx
 118         jz      L_more_63_no_low
 119
 120         orl     $1,%edx
 121         jmp     L_more_63_no_low
 122
 123 L_more_than_64:
 124         movl    $1,%edx         /* The shifted nr always at least one '1' */
 125
 126 L_more_63_no_low:
 127         xorl    %ebx,%ebx
 128         xorl    %eax,%eax
 129
 130 L_shift_done:
 131         /* Now do the addition */
 132         addl    SIGL(%esi),%ebx
 133         adcl    SIGH(%esi),%eax
 134         jnc     L_round_the_result
 135
 136         /* Overflow, adjust the result */
 137         rcrl    $1,%eax
 138         rcrl    $1,%ebx
 139         rcrl    $1,%edx
 140         jnc     L_no_bit_lost
 141
 142         orl     $1,%edx
 143
 144 L_no_bit_lost:
 145         incw    EXP(%edi)
 146
 147 L_round_the_result:
 148         jmp     fpu_reg_round   /* Round the result */
 149
 150
 151
 152 #ifdef PARANOID
 153 /* If we ever get here then we have problems! */
 154 L_bugged:
 155         pushl   EX_INTERNAL|0x201
 156         call    EXCEPTION
 157         pop     %ebx
 158         movl    $-1,%eax
 159         jmp     L_exit
 160
 161 L_exit:
 162         popl    %ebx
 163         popl    %edi
 164         popl    %esi
 165         leave
 166         ret
 167 #endif /* PARANOID */