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

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