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

   1// SPDX-License-Identifier: GPL-2.0
   2/*---------------------------------------------------------------------------+
   3 |  fpu_etc.c                                                                |
   4 |                                                                           |
   5 | Implement a few FPU instructions.                                         |
   6 |                                                                           |
   7 | Copyright (C) 1992,1993,1994,1997                                         |
   8 |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
   9 |                       Australia.  E-mail   billm@suburbia.net             |
  10 |                                                                           |
  11 |                                                                           |
  12 +---------------------------------------------------------------------------*/
  13
  14#include "fpu_system.h"
  15#include "exception.h"
  16#include "fpu_emu.h"
  17#include "status_w.h"
  18#include "reg_constant.h"
  19
  20static void fchs(FPU_REG *st0_ptr, u_char st0tag)
  21{
  22        if (st0tag ^ TAG_Empty) {
  23                signbyte(st0_ptr) ^= SIGN_NEG;
  24                clear_C1();
  25        } else
  26                FPU_stack_underflow();
  27}
  28
  29static void fabs(FPU_REG *st0_ptr, u_char st0tag)
  30{
  31        if (st0tag ^ TAG_Empty) {
  32                setpositive(st0_ptr);
  33                clear_C1();
  34        } else
  35                FPU_stack_underflow();
  36}
  37
  38static void ftst_(FPU_REG *st0_ptr, u_char st0tag)
  39{
  40        switch (st0tag) {
  41        case TAG_Zero:
  42                setcc(SW_C3);
  43                break;
  44        case TAG_Valid:
  45                if (getsign(st0_ptr) == SIGN_POS)
  46                        setcc(0);
  47                else
  48                        setcc(SW_C0);
  49                break;
  50        case TAG_Special:
  51                switch (FPU_Special(st0_ptr)) {
  52                case TW_Denormal:
  53                        if (getsign(st0_ptr) == SIGN_POS)
  54                                setcc(0);
  55                        else
  56                                setcc(SW_C0);
  57                        if (denormal_operand() < 0) {
  58#ifdef PECULIAR_486
  59                                /* This is weird! */
  60                                if (getsign(st0_ptr) == SIGN_POS)
  61                                        setcc(SW_C3);
  62#endif /* PECULIAR_486 */
  63                                return;
  64                        }
  65                        break;
  66                case TW_NaN:
  67                        setcc(SW_C0 | SW_C2 | SW_C3);   /* Operand is not comparable */
  68                        EXCEPTION(EX_Invalid);
  69                        break;
  70                case TW_Infinity:
  71                        if (getsign(st0_ptr) == SIGN_POS)
  72                                setcc(0);
  73                        else
  74                                setcc(SW_C0);
  75                        break;
  76                default:
  77                        setcc(SW_C0 | SW_C2 | SW_C3);   /* Operand is not comparable */
  78                        EXCEPTION(EX_INTERNAL | 0x14);
  79                        break;
  80                }
  81                break;
  82        case TAG_Empty:
  83                setcc(SW_C0 | SW_C2 | SW_C3);
  84                EXCEPTION(EX_StackUnder);
  85                break;
  86        }
  87}
  88
  89static void fxam(FPU_REG *st0_ptr, u_char st0tag)
  90{
  91        int c = 0;
  92        switch (st0tag) {
  93        case TAG_Empty:
  94                c = SW_C3 | SW_C0;
  95                break;
  96        case TAG_Zero:
  97                c = SW_C3;
  98                break;
  99        case TAG_Valid:
 100                c = SW_C2;
 101                break;
 102        case TAG_Special:
 103                switch (FPU_Special(st0_ptr)) {
 104                case TW_Denormal:
 105                        c = SW_C2 | SW_C3;      /* Denormal */
 106                        break;
 107                case TW_NaN:
 108                        /* We also use NaN for unsupported types. */
 109                        if ((st0_ptr->sigh & 0x80000000)
 110                            && (exponent(st0_ptr) == EXP_OVER))
 111                                c = SW_C0;
 112                        break;
 113                case TW_Infinity:
 114                        c = SW_C2 | SW_C0;
 115                        break;
 116                }
 117        }
 118        if (getsign(st0_ptr) == SIGN_NEG)
 119                c |= SW_C1;
 120        setcc(c);
 121}
 122
 123static FUNC_ST0 const fp_etc_table[] = {
 124        fchs, fabs, (FUNC_ST0) FPU_illegal, (FUNC_ST0) FPU_illegal,
 125        ftst_, fxam, (FUNC_ST0) FPU_illegal, (FUNC_ST0) FPU_illegal
 126};
 127
 128void FPU_etc(void)
 129{
 130        (fp_etc_table[FPU_rm]) (&st(0), FPU_gettag0());
 131}
 132