int FPU_store_single()

in math-emu/reg_ld_str.c [564:750]

• 151 lines of code
• 41 McCabe index (conditional complexity)

int FPU_store_single(FPU_REG *st0_ptr, u_char st0_tag, float __user *single)
{
	long templ = 0;
	unsigned long increment = 0;	/* avoid gcc warnings */
	int precision_loss;
	int exp;
	FPU_REG tmp;

	if (st0_tag == TAG_Valid) {

		reg_copy(st0_ptr, &tmp);
		exp = exponent(&tmp);

		if (exp < SINGLE_Emin) {
			addexponent(&tmp, -SINGLE_Emin + 23);	/* largest exp to be 22 */

		      denormal_arg:

			if ((precision_loss = FPU_round_to_int(&tmp, st0_tag))) {
#ifdef PECULIAR_486
				/* Did it round to a non-denormal ? */
				/* This behaviour might be regarded as peculiar, it appears
				   that the 80486 rounds to the dest precision, then
				   converts to decide underflow. */
				if (!((tmp.sigl == 0x00800000) &&
				      ((st0_ptr->sigh & 0x000000ff)
				       || st0_ptr->sigl)))
#endif /* PECULIAR_486 */
				{
					EXCEPTION(EX_Underflow);
					/* This is a special case: see sec 16.2.5.1 of
					   the 80486 book */
					if (!(control_word & CW_Underflow))
						return 0;
				}
				EXCEPTION(precision_loss);
				if (!(control_word & CW_Precision))
					return 0;
			}
			templ = tmp.sigl;
		} else {
			if (tmp.sigl | (tmp.sigh & 0x000000ff)) {
				unsigned long sigh = tmp.sigh;
				unsigned long sigl = tmp.sigl;

				precision_loss = 1;
				switch (control_word & CW_RC) {
				case RC_RND:
					increment = ((sigh & 0xff) > 0x80)	/* more than half */
					    ||(((sigh & 0xff) == 0x80) && sigl)	/* more than half */
					    ||((sigh & 0x180) == 0x180);	/* round to even */
					break;
				case RC_DOWN:	/* towards -infinity */
					increment = signpositive(&tmp)
					    ? 0 : (sigl | (sigh & 0xff));
					break;
				case RC_UP:	/* towards +infinity */
					increment = signpositive(&tmp)
					    ? (sigl | (sigh & 0xff)) : 0;
					break;
				case RC_CHOP:
					increment = 0;
					break;
				}

				/* Truncate part of the mantissa */
				tmp.sigl = 0;

				if (increment) {
					if (sigh >= 0xffffff00) {
						/* The sigh part overflows */
						tmp.sigh = 0x80000000;
						exp++;
						if (exp >= EXP_OVER)
							goto overflow;
					} else {
						tmp.sigh &= 0xffffff00;
						tmp.sigh += 0x100;
					}
				} else {
					tmp.sigh &= 0xffffff00;	/* Finish the truncation */
				}
			} else
				precision_loss = 0;

			templ = (tmp.sigh >> 8) & 0x007fffff;

			if (exp > SINGLE_Emax) {
			      overflow:
				EXCEPTION(EX_Overflow);
				if (!(control_word & CW_Overflow))
					return 0;
				set_precision_flag_up();
				if (!(control_word & CW_Precision))
					return 0;

				/* This is a special case: see sec 16.2.5.1 of the 80486 book. */
				/* Masked response is overflow to infinity. */
				templ = 0x7f800000;
			} else {
				if (precision_loss) {
					if (increment)
						set_precision_flag_up();
					else
						set_precision_flag_down();
				}
				/* Add the exponent */
				templ |= ((exp + SINGLE_Ebias) & 0xff) << 23;
			}
		}
	} else if (st0_tag == TAG_Zero) {
		templ = 0;
	} else if (st0_tag == TAG_Special) {
		st0_tag = FPU_Special(st0_ptr);
		if (st0_tag == TW_Denormal) {
			reg_copy(st0_ptr, &tmp);

			/* A denormal will always underflow. */
#ifndef PECULIAR_486
			/* An 80486 is supposed to be able to generate
			   a denormal exception here, but... */
			/* Underflow has priority. */
			if (control_word & CW_Underflow)
				denormal_operand();
#endif /* PECULIAR_486 */
			goto denormal_arg;
		} else if (st0_tag == TW_Infinity) {
			templ = 0x7f800000;
		} else if (st0_tag == TW_NaN) {
			/* Is it really a NaN ? */
			if ((exponent(st0_ptr) == EXP_OVER)
			    && (st0_ptr->sigh & 0x80000000)) {
				/* See if we can get a valid NaN from the FPU_REG */
				templ = st0_ptr->sigh >> 8;
				if (!(st0_ptr->sigh & 0x40000000)) {
					/* It is a signalling NaN */
					EXCEPTION(EX_Invalid);
					if (!(control_word & CW_Invalid))
						return 0;
					templ |= (0x40000000 >> 8);
				}
				templ |= 0x7f800000;
			} else {
				/* It is an unsupported data type */
				EXCEPTION(EX_Invalid);
				if (!(control_word & CW_Invalid))
					return 0;
				templ = 0xffc00000;
			}
		}
#ifdef PARANOID
		else {
			EXCEPTION(EX_INTERNAL | 0x164);
			return 0;
		}
#endif
	} else if (st0_tag == TAG_Empty) {
		/* Empty register (stack underflow) */
		EXCEPTION(EX_StackUnder);
		if (control_word & EX_Invalid) {
			/* The masked response */
			/* Put out the QNaN indefinite */
			RE_ENTRANT_CHECK_OFF;
			FPU_access_ok(single, 4);
			FPU_put_user(0xffc00000,
				     (unsigned long __user *)single);
			RE_ENTRANT_CHECK_ON;
			return 1;
		} else
			return 0;
	}
#ifdef PARANOID
	else {
		EXCEPTION(EX_INTERNAL | 0x163);
		return 0;
	}
#endif
	if (getsign(st0_ptr))
		templ |= 0x80000000;

	RE_ENTRANT_CHECK_OFF;
	FPU_access_ok(single, 4);
	FPU_put_user(templ, (unsigned long __user *)single);
	RE_ENTRANT_CHECK_ON;

	return 1;
}