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

   1/*---------------------------------------------------------------------------+
   2 |  reg_divide.c                                                             |
   3 |                                                                           |
   4 | Divide one FPU_REG by another and put the result in a destination FPU_REG.|
   5 |                                                                           |
   6 | Copyright (C) 1996                                                        |
   7 |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
   8 |                  E-mail   billm@jacobi.maths.monash.edu.au                |
   9 |                                                                           |
  10 |    Return value is the tag of the answer, or-ed with FPU_Exception if     |
  11 |    one was raised, or -1 on internal error.                               |
  12 |                                                                           |
  13 +---------------------------------------------------------------------------*/
  14
  15/*---------------------------------------------------------------------------+
  16 | The destination may be any FPU_REG, including one of the source FPU_REGs. |
  17 +---------------------------------------------------------------------------*/
  18
  19#include "exception.h"
  20#include "reg_constant.h"
  21#include "fpu_emu.h"
  22#include "fpu_system.h"
  23
  24/*
  25  Divide one register by another and put the result into a third register.
  26  */
  27int FPU_div(int flags, int rm, int control_w)
  28{
  29        FPU_REG x, y;
  30        FPU_REG const *a, *b, *st0_ptr, *st_ptr;
  31        FPU_REG *dest;
  32        u_char taga, tagb, signa, signb, sign, saved_sign;
  33        int tag, deststnr;
  34
  35        if (flags & DEST_RM)
  36                deststnr = rm;
  37        else
  38                deststnr = 0;
  39
  40        if (flags & REV) {
  41                b = &st(0);
  42                st0_ptr = b;
  43                tagb = FPU_gettag0();
  44                if (flags & LOADED) {
  45                        a = (FPU_REG *) rm;
  46                        taga = flags & 0x0f;
  47                } else {
  48                        a = &st(rm);
  49                        st_ptr = a;
  50                        taga = FPU_gettagi(rm);
  51                }
  52        } else {
  53                a = &st(0);
  54                st0_ptr = a;
  55                taga = FPU_gettag0();
  56                if (flags & LOADED) {
  57                        b = (FPU_REG *) rm;
  58                        tagb = flags & 0x0f;
  59                } else {
  60                        b = &st(rm);
  61                        st_ptr = b;
  62                        tagb = FPU_gettagi(rm);
  63                }
  64        }
  65
  66        signa = getsign(a);
  67        signb = getsign(b);
  68
  69        sign = signa ^ signb;
  70
  71        dest = &st(deststnr);
  72        saved_sign = getsign(dest);
  73
  74        if (!(taga | tagb)) {
  75                /* Both regs Valid, this should be the most common case. */
  76                reg_copy(a, &x);
  77                reg_copy(b, &y);
  78                setpositive(&x);
  79                setpositive(&y);
  80                tag = FPU_u_div(&x, &y, dest, control_w, sign);
  81
  82                if (tag < 0)
  83                        return tag;
  84
  85                FPU_settagi(deststnr, tag);
  86                return tag;
  87        }
  88
  89        if (taga == TAG_Special)
  90                taga = FPU_Special(a);
  91        if (tagb == TAG_Special)
  92                tagb = FPU_Special(b);
  93
  94        if (((taga == TAG_Valid) && (tagb == TW_Denormal))
  95            || ((taga == TW_Denormal) && (tagb == TAG_Valid))
  96            || ((taga == TW_Denormal) && (tagb == TW_Denormal))) {
  97                if (denormal_operand() < 0)
  98                        return FPU_Exception;
  99
 100                FPU_to_exp16(a, &x);
 101                FPU_to_exp16(b, &y);
 102                tag = FPU_u_div(&x, &y, dest, control_w, sign);
 103                if (tag < 0)
 104                        return tag;
 105
 106                FPU_settagi(deststnr, tag);
 107                return tag;
 108        } else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) {
 109                if (tagb != TAG_Zero) {
 110                        /* Want to find Zero/Valid */
 111                        if (tagb == TW_Denormal) {
 112                                if (denormal_operand() < 0)
 113                                        return FPU_Exception;
 114                        }
 115
 116                        /* The result is zero. */
 117                        FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
 118                        setsign(dest, sign);
 119                        return TAG_Zero;
 120                }
 121                /* We have an exception condition, either 0/0 or Valid/Zero. */
 122                if (taga == TAG_Zero) {
 123                        /* 0/0 */
 124                        return arith_invalid(deststnr);
 125                }
 126                /* Valid/Zero */
 127                return FPU_divide_by_zero(deststnr, sign);
 128        }
 129        /* Must have infinities, NaNs, etc */
 130        else if ((taga == TW_NaN) || (tagb == TW_NaN)) {
 131                if (flags & LOADED)
 132                        return real_2op_NaN((FPU_REG *) rm, flags & 0x0f, 0,
 133                                            st0_ptr);
 134
 135                if (flags & DEST_RM) {
 136                        int tag;
 137                        tag = FPU_gettag0();
 138                        if (tag == TAG_Special)
 139                                tag = FPU_Special(st0_ptr);
 140                        return real_2op_NaN(st0_ptr, tag, rm,
 141                                            (flags & REV) ? st0_ptr : &st(rm));
 142                } else {
 143                        int tag;
 144                        tag = FPU_gettagi(rm);
 145                        if (tag == TAG_Special)
 146                                tag = FPU_Special(&st(rm));
 147                        return real_2op_NaN(&st(rm), tag, 0,
 148                                            (flags & REV) ? st0_ptr : &st(rm));
 149                }
 150        } else if (taga == TW_Infinity) {
 151                if (tagb == TW_Infinity) {
 152                        /* infinity/infinity */
 153                        return arith_invalid(deststnr);
 154                } else {
 155                        /* tagb must be Valid or Zero */
 156                        if ((tagb == TW_Denormal) && (denormal_operand() < 0))
 157                                return FPU_Exception;
 158
 159                        /* Infinity divided by Zero or Valid does
 160                           not raise and exception, but returns Infinity */
 161                        FPU_copy_to_regi(a, TAG_Special, deststnr);
 162                        setsign(dest, sign);
 163                        return taga;
 164                }
 165        } else if (tagb == TW_Infinity) {
 166                if ((taga == TW_Denormal) && (denormal_operand() < 0))
 167                        return FPU_Exception;
 168
 169                /* The result is zero. */
 170                FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
 171                setsign(dest, sign);
 172                return TAG_Zero;
 173        }
 174#ifdef PARANOID
 175        else {
 176                EXCEPTION(EX_INTERNAL | 0x102);
 177                return FPU_Exception;
 178        }
 179#endif /* PARANOID */
 180
 181        return 0;
 182}
 183