fpu_etc.c

// SPDX-License-Identifier: GPL-2.0
/*---------------------------------------------------------------------------+
 |  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());
}