LXR linux/arch/x86/math-emu/reg_u

   1/* SPDX-License-Identifier: GPL-2.0 */
   2        .file   "reg_u_add.S"
   3/*---------------------------------------------------------------------------+
   4 |  reg_u_add.S                                                              |
   5 |                                                                           |
   6 | Add two valid (TAG_Valid) FPU_REG numbers, of the same sign, and put the  |
   7 |   result in a destination FPU_REG.                                        |
   8 |                                                                           |
   9 | Copyright (C) 1992,1993,1995,1997                                         |
  10 |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
  11 |                  E-mail   billm@suburbia.net                              |
  12 |                                                                           |
  13 | Call from C as:                                                           |
  14 |   int  FPU_u_add(FPU_REG *arg1, FPU_REG *arg2, FPU_REG *answ,             |
  15 |                                                int control_w)             |
  16 |    Return value is the tag of the answer, or-ed with FPU_Exception if     |
  17 |    one was raised, or -1 on internal error.                               |
  18 |                                                                           |
  19 +---------------------------------------------------------------------------*/
  20
  21/*
  22 |    Kernel addition routine FPU_u_add(reg *arg1, reg *arg2, reg *answ).
  23 |    Takes two valid reg f.p. numbers (TAG_Valid), which are
  24 |    treated as unsigned numbers,
  25 |    and returns their sum as a TAG_Valid or TAG_Special f.p. number.
  26 |    The returned number is normalized.
  27 |    Basic checks are performed if PARANOID is defined.
  28 */
  29
  30#include "exception.h"
  31#include "fpu_emu.h"
  32#include "control_w.h"
  33
  34.text
  35SYM_FUNC_START(FPU_u_add)
  36        pushl   %ebp
  37        movl    %esp,%ebp
  38        pushl   %esi
  39        pushl   %edi
  40        pushl   %ebx
  41
  42        movl    PARAM1,%esi             /* source 1 */
  43        movl    PARAM2,%edi             /* source 2 */
  44
  45        movl    PARAM6,%ecx
  46        movl    %ecx,%edx
  47        subl    PARAM7,%ecx                     /* exp1 - exp2 */
  48        jge     L_arg1_larger
  49
  50        /* num1 is smaller */
  51        movl    SIGL(%esi),%ebx
  52        movl    SIGH(%esi),%eax
  53
  54        movl    %edi,%esi
  55        movl    PARAM7,%edx
  56        negw    %cx
  57        jmp     L_accum_loaded
  58
  59L_arg1_larger:
  60        /* num1 has larger or equal exponent */
  61        movl    SIGL(%edi),%ebx
  62        movl    SIGH(%edi),%eax
  63
  64L_accum_loaded:
  65        movl    PARAM3,%edi             /* destination */
  66        movw    %dx,EXP(%edi)           /* Copy exponent to destination */
  67
  68        xorl    %edx,%edx               /* clear the extension */
  69
  70#ifdef PARANOID
  71        testl   $0x80000000,%eax
  72        je      L_bugged
  73
  74        testl   $0x80000000,SIGH(%esi)
  75        je      L_bugged
  76#endif /* PARANOID */
  77
  78/* The number to be shifted is in %eax:%ebx:%edx */
  79        cmpw    $32,%cx         /* shrd only works for 0..31 bits */
  80        jnc     L_more_than_31
  81
  82/* less than 32 bits */
  83        shrd    %cl,%ebx,%edx
  84        shrd    %cl,%eax,%ebx
  85        shr     %cl,%eax
  86        jmp     L_shift_done
  87
  88L_more_than_31:
  89        cmpw    $64,%cx
  90        jnc     L_more_than_63
  91
  92        subb    $32,%cl
  93        jz      L_exactly_32
  94
  95        shrd    %cl,%eax,%edx
  96        shr     %cl,%eax
  97        orl     %ebx,%ebx
  98        jz      L_more_31_no_low        /* none of the lowest bits is set */
  99
 100        orl     $1,%edx                 /* record the fact in the extension */
 101
 102L_more_31_no_low:
 103        movl    %eax,%ebx
 104        xorl    %eax,%eax
 105        jmp     L_shift_done
 106
 107L_exactly_32:
 108        movl    %ebx,%edx
 109        movl    %eax,%ebx
 110        xorl    %eax,%eax
 111        jmp     L_shift_done
 112
 113L_more_than_63:
 114        cmpw    $65,%cx
 115        jnc     L_more_than_64
 116
 117        movl    %eax,%edx
 118        orl     %ebx,%ebx
 119        jz      L_more_63_no_low
 120
 121        orl     $1,%edx
 122        jmp     L_more_63_no_low
 123
 124L_more_than_64:
 125        movl    $1,%edx         /* The shifted nr always at least one '1' */
 126
 127L_more_63_no_low:
 128        xorl    %ebx,%ebx
 129        xorl    %eax,%eax
 130
 131L_shift_done:
 132        /* Now do the addition */
 133        addl    SIGL(%esi),%ebx
 134        adcl    SIGH(%esi),%eax
 135        jnc     L_round_the_result
 136
 137        /* Overflow, adjust the result */
 138        rcrl    $1,%eax
 139        rcrl    $1,%ebx
 140        rcrl    $1,%edx
 141        jnc     L_no_bit_lost
 142
 143        orl     $1,%edx
 144
 145L_no_bit_lost:
 146        incw    EXP(%edi)
 147
 148L_round_the_result:
 149        jmp     fpu_reg_round   /* Round the result */
 150
 151
 152
 153#ifdef PARANOID
 154/* If we ever get here then we have problems! */
 155L_bugged:
 156        pushl   EX_INTERNAL|0x201
 157        call    EXCEPTION
 158        pop     %ebx
 159        movl    $-1,%eax
 160        jmp     L_exit
 161
 162L_exit:
 163        popl    %ebx
 164        popl    %edi
 165        popl    %esi
 166        leave
 167        ret
 168#endif /* PARANOID */
 169SYM_FUNC_END(FPU_u_add)
 170