static void fscale()

in math-emu/fpu_trig.c [1486:1628]

• 113 lines of code
• 38 McCabe index (conditional complexity)

static void fscale(FPU_REG *st0_ptr, u_char st0_tag)
{
	FPU_REG *st1_ptr = &st(1);
	u_char st1_tag = FPU_gettagi(1);
	int old_cw = control_word;
	u_char sign = getsign(st0_ptr);

	clear_C1();
	if (!((st0_tag ^ TAG_Valid) | (st1_tag ^ TAG_Valid))) {
		long scale;
		FPU_REG tmp;

		/* Convert register for internal use. */
		setexponent16(st0_ptr, exponent(st0_ptr));

	      valid_scale:

		if (exponent(st1_ptr) > 30) {
			/* 2^31 is far too large, would require 2^(2^30) or 2^(-2^30) */

			if (signpositive(st1_ptr)) {
				EXCEPTION(EX_Overflow);
				FPU_copy_to_reg0(&CONST_INF, TAG_Special);
			} else {
				EXCEPTION(EX_Underflow);
				FPU_copy_to_reg0(&CONST_Z, TAG_Zero);
			}
			setsign(st0_ptr, sign);
			return;
		}

		control_word &= ~CW_RC;
		control_word |= RC_CHOP;
		reg_copy(st1_ptr, &tmp);
		FPU_round_to_int(&tmp, st1_tag);	/* This can never overflow here */
		control_word = old_cw;
		scale = signnegative(st1_ptr) ? -tmp.sigl : tmp.sigl;
		scale += exponent16(st0_ptr);

		setexponent16(st0_ptr, scale);

		/* Use FPU_round() to properly detect under/overflow etc */
		FPU_round(st0_ptr, 0, 0, control_word, sign);

		return;
	}

	if (st0_tag == TAG_Special)
		st0_tag = FPU_Special(st0_ptr);
	if (st1_tag == TAG_Special)
		st1_tag = FPU_Special(st1_ptr);

	if ((st0_tag == TAG_Valid) || (st0_tag == TW_Denormal)) {
		switch (st1_tag) {
		case TAG_Valid:
			/* st(0) must be a denormal */
			if ((st0_tag == TW_Denormal)
			    && (denormal_operand() < 0))
				return;

			FPU_to_exp16(st0_ptr, st0_ptr);	/* Will not be left on stack */
			goto valid_scale;

		case TAG_Zero:
			if (st0_tag == TW_Denormal)
				denormal_operand();
			return;

		case TW_Denormal:
			denormal_operand();
			return;

		case TW_Infinity:
			if ((st0_tag == TW_Denormal)
			    && (denormal_operand() < 0))
				return;

			if (signpositive(st1_ptr))
				FPU_copy_to_reg0(&CONST_INF, TAG_Special);
			else
				FPU_copy_to_reg0(&CONST_Z, TAG_Zero);
			setsign(st0_ptr, sign);
			return;

		case TW_NaN:
			real_2op_NaN(st1_ptr, st1_tag, 0, st0_ptr);
			return;
		}
	} else if (st0_tag == TAG_Zero) {
		switch (st1_tag) {
		case TAG_Valid:
		case TAG_Zero:
			return;

		case TW_Denormal:
			denormal_operand();
			return;

		case TW_Infinity:
			if (signpositive(st1_ptr))
				arith_invalid(0);	/* Zero scaled by +Infinity */
			return;

		case TW_NaN:
			real_2op_NaN(st1_ptr, st1_tag, 0, st0_ptr);
			return;
		}
	} else if (st0_tag == TW_Infinity) {
		switch (st1_tag) {
		case TAG_Valid:
		case TAG_Zero:
			return;

		case TW_Denormal:
			denormal_operand();
			return;

		case TW_Infinity:
			if (signnegative(st1_ptr))
				arith_invalid(0);	/* Infinity scaled by -Infinity */
			return;

		case TW_NaN:
			real_2op_NaN(st1_ptr, st1_tag, 0, st0_ptr);
			return;
		}
	} else if (st0_tag == TW_NaN) {
		if (st1_tag != TAG_Empty) {
			real_2op_NaN(st1_ptr, st1_tag, 0, st0_ptr);
			return;
		}
	}
#ifdef PARANOID
	if (!((st0_tag == TAG_Empty) || (st1_tag == TAG_Empty))) {
		EXCEPTION(EX_INTERNAL | 0x115);
		return;
	}
#endif

	/* At least one of st(0), st(1) must be empty */
	FPU_stack_underflow();

}