root/arch/x86/math-emu/fpu_etc.c

DEFINITIONS

1. fchs
2. fabs
3. ftst_
4. fxam
5. FPU_etc

/*---------------------------------------------------------------------------+
 |  fpu_etc.c                                                                |
 |                                                                           |
 | Implement a few FPU instructions.                                         |
 |                                                                           |
 | Copyright (C) 1992,1993,1994,1997                                         |
 |                       W. Metzenthen, 22 Parker St, Ormond, Vic 3163,      |
 |                       Australia.  E-mail   billm@suburbia.net             |
 |                                                                           |
 |                                                                           |
 +---------------------------------------------------------------------------*/

#include "fpu_system.h"
#include "exception.h"
#include "fpu_emu.h"
#include "status_w.h"
#include "reg_constant.h"

static void fchs(FPU_REG *st0_ptr, u_char st0tag)
{
        if (st0tag ^ TAG_Empty) {
                signbyte(st0_ptr) ^= SIGN_NEG;
                clear_C1();
        } else
                FPU_stack_underflow();
}

static void fabs(FPU_REG *st0_ptr, u_char st0tag)
{
        if (st0tag ^ TAG_Empty) {
                setpositive(st0_ptr);
                clear_C1();
        } else
                FPU_stack_underflow();
}

static void ftst_(FPU_REG *st0_ptr, u_char st0tag)
{
        switch (st0tag) {
        case TAG_Zero:
                setcc(SW_C3);
                break;
        case TAG_Valid:
                if (getsign(st0_ptr) == SIGN_POS)
                        setcc(0);
                else
                        setcc(SW_C0);
                break;
        case TAG_Special:
                switch (FPU_Special(st0_ptr)) {
                case TW_Denormal:
                        if (getsign(st0_ptr) == SIGN_POS)
                                setcc(0);
                        else
                                setcc(SW_C0);
                        if (denormal_operand() < 0) {
#ifdef PECULIAR_486
                                /* This is weird! */
                                if (getsign(st0_ptr) == SIGN_POS)
                                        setcc(SW_C3);
#endif /* PECULIAR_486 */
                                return;
                        }
                        break;
                case TW_NaN:
                        setcc(SW_C0 | SW_C2 | SW_C3);   /* Operand is not comparable */
                        EXCEPTION(EX_Invalid);
                        break;
                case TW_Infinity:
                        if (getsign(st0_ptr) == SIGN_POS)
                                setcc(0);
                        else
                                setcc(SW_C0);
                        break;
                default:
                        setcc(SW_C0 | SW_C2 | SW_C3);   /* Operand is not comparable */
                        EXCEPTION(EX_INTERNAL | 0x14);
                        break;
                }
                break;
        case TAG_Empty:
                setcc(SW_C0 | SW_C2 | SW_C3);
                EXCEPTION(EX_StackUnder);
                break;
        }
}

static void fxam(FPU_REG *st0_ptr, u_char st0tag)
{
        int c = 0;
        switch (st0tag) {
        case TAG_Empty:
                c = SW_C3 | SW_C0;
                break;
        case TAG_Zero:
                c = SW_C3;
                break;
        case TAG_Valid:
                c = SW_C2;
                break;
        case TAG_Special:
                switch (FPU_Special(st0_ptr)) {
                case TW_Denormal:
                        c = SW_C2 | SW_C3;      /* Denormal */
                        break;
                case TW_NaN:
                        /* We also use NaN for unsupported types. */
                        if ((st0_ptr->sigh & 0x80000000)
                            && (exponent(st0_ptr) == EXP_OVER))
                                c = SW_C0;
                        break;
                case TW_Infinity:
                        c = SW_C2 | SW_C0;
                        break;
                }
        }
        if (getsign(st0_ptr) == SIGN_NEG)
                c |= SW_C1;
        setcc(c);
}

static FUNC_ST0 const fp_etc_table[] = {
        fchs, fabs, (FUNC_ST0) FPU_illegal, (FUNC_ST0) FPU_illegal,
        ftst_, fxam, (FUNC_ST0) FPU_illegal, (FUNC_ST0) FPU_illegal
};

void FPU_etc(void)
{
        (fp_etc_table[FPU_rm]) (&st(0), FPU_gettag0());
}