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

   1// SPDX-License-Identifier: GPL-2.0
   2/*---------------------------------------------------------------------------+
   3 |  reg_mul.c                                                                |
   4 |                                                                           |
   5 | Multiply one FPU_REG by another, put the result in a destination FPU_REG. |
   6 |                                                                           |
   7 | Copyright (C) 1992,1993,1997                                              |
   8 |                  W. Metzenthen, 22 Parker St, Ormond, Vic 3163, Australia |
   9 |                  E-mail   billm@suburbia.net                              |
  10 |                                                                           |
  11 | Returns the tag of the result if no exceptions or errors occurred.        |
  12 |                                                                           |
  13 +---------------------------------------------------------------------------*/
  14
  15/*---------------------------------------------------------------------------+
  16 | The destination may be any FPU_REG, including one of the source FPU_REGs. |
  17 +---------------------------------------------------------------------------*/
  18
  19#include "fpu_emu.h"
  20#include "exception.h"
  21#include "reg_constant.h"
  22#include "fpu_system.h"
  23
  24/*
  25  Multiply two registers to give a register result.
  26  The sources are st(deststnr) and (b,tagb,signb).
  27  The destination is st(deststnr).
  28  */
  29/* This routine must be called with non-empty source registers */
  30int FPU_mul(FPU_REG const *b, u_char tagb, int deststnr, int control_w)
  31{
  32        FPU_REG *a = &st(deststnr);
  33        FPU_REG *dest = a;
  34        u_char taga = FPU_gettagi(deststnr);
  35        u_char saved_sign = getsign(dest);
  36        u_char sign = (getsign(a) ^ getsign(b));
  37        int tag;
  38
  39        if (!(taga | tagb)) {
  40                /* Both regs Valid, this should be the most common case. */
  41
  42                tag =
  43                    FPU_u_mul(a, b, dest, control_w, sign,
  44                              exponent(a) + exponent(b));
  45                if (tag < 0) {
  46                        setsign(dest, saved_sign);
  47                        return tag;
  48                }
  49                FPU_settagi(deststnr, tag);
  50                return tag;
  51        }
  52
  53        if (taga == TAG_Special)
  54                taga = FPU_Special(a);
  55        if (tagb == TAG_Special)
  56                tagb = FPU_Special(b);
  57
  58        if (((taga == TAG_Valid) && (tagb == TW_Denormal))
  59            || ((taga == TW_Denormal) && (tagb == TAG_Valid))
  60            || ((taga == TW_Denormal) && (tagb == TW_Denormal))) {
  61                FPU_REG x, y;
  62                if (denormal_operand() < 0)
  63                        return FPU_Exception;
  64
  65                FPU_to_exp16(a, &x);
  66                FPU_to_exp16(b, &y);
  67                tag = FPU_u_mul(&x, &y, dest, control_w, sign,
  68                                exponent16(&x) + exponent16(&y));
  69                if (tag < 0) {
  70                        setsign(dest, saved_sign);
  71                        return tag;
  72                }
  73                FPU_settagi(deststnr, tag);
  74                return tag;
  75        } else if ((taga <= TW_Denormal) && (tagb <= TW_Denormal)) {
  76                if (((tagb == TW_Denormal) || (taga == TW_Denormal))
  77                    && (denormal_operand() < 0))
  78                        return FPU_Exception;
  79
  80                /* Must have either both arguments == zero, or
  81                   one valid and the other zero.
  82                   The result is therefore zero. */
  83                FPU_copy_to_regi(&CONST_Z, TAG_Zero, deststnr);
  84                /* The 80486 book says that the answer is +0, but a real
  85                   80486 behaves this way.
  86                   IEEE-754 apparently says it should be this way. */
  87                setsign(dest, sign);
  88                return TAG_Zero;
  89        }
  90        /* Must have infinities, NaNs, etc */
  91        else if ((taga == TW_NaN) || (tagb == TW_NaN)) {
  92                return real_2op_NaN(b, tagb, deststnr, &st(0));
  93        } else if (((taga == TW_Infinity) && (tagb == TAG_Zero))
  94                   || ((tagb == TW_Infinity) && (taga == TAG_Zero))) {
  95                return arith_invalid(deststnr); /* Zero*Infinity is invalid */
  96        } else if (((taga == TW_Denormal) || (tagb == TW_Denormal))
  97                   && (denormal_operand() < 0)) {
  98                return FPU_Exception;
  99        } else if (taga == TW_Infinity) {
 100                FPU_copy_to_regi(a, TAG_Special, deststnr);
 101                setsign(dest, sign);
 102                return TAG_Special;
 103        } else if (tagb == TW_Infinity) {
 104                FPU_copy_to_regi(b, TAG_Special, deststnr);
 105                setsign(dest, sign);
 106                return TAG_Special;
 107        }
 108#ifdef PARANOID
 109        else {
 110                EXCEPTION(EX_INTERNAL | 0x102);
 111                return FPU_Exception;
 112        }
 113#endif /* PARANOID */
 114
 115        return 0;
 116}
 117