mul.c

操作系统SunOS 4.1.3版本的源码

#ifdef sccsid
static char     sccsid[] = "@(#)mul.c 1.1 92/07/30 SMI";
#endif

/*
 * Copyright (c) 1988 by Sun Microsystems, Inc.
 */

#include <machine/fpu/fpu_simulator.h>
#include <machine/fpu/globals.h>

void
_fp_mul(pfpsd, px, py, pz)
	fp_simd_type	*pfpsd;
	unpacked	*px, *py, *pz;

{
	unpacked	*pt;
	unsigned	acc[4];		/* Product accumulator. */
	unsigned	j, y, *x, s, r, c;

	if ((int) px->fpclass < (int) py->fpclass) {
		pt = px;
		px = py;
		py = pt;
	}
	/* Now class(x) >= class(y).  */

	*pz = *px;
	if ((int)pz->fpclass < (int)fp_quiet) pz->sign = px->sign ^ py->sign;

	switch (px->fpclass) {
	case fp_quiet:
	case fp_signaling:
	case fp_zero:
		return;
	case fp_infinity:
		if (py->fpclass == fp_zero) {
			fpu_error_nan(pfpsd, pz);
			pz->fpclass = fp_quiet;
		}
		return;
	case fp_normal:
		if (py->fpclass == fp_zero) {
			pz->fpclass = fp_zero;
			return;
		}
	}

	/* Now x and y are both normal or subnormal. */

	x = px->significand;	/* save typing */

	s=r=acc[0]=acc[1]=acc[2]=acc[3]=0;	/* intialize acc to zero */

	y = py->significand[3];		/* py->significand[3] * x */
	if (y!=0) {
	    j=1;
	    do {
		s |= r;		/* shift acc right one bit */
		r  = acc[3]&1;
		acc[3] = ((acc[2]&1)<<31)|(acc[3]>>1);
		acc[2] = ((acc[1]&1)<<31)|(acc[2]>>1);
		acc[1] = ((acc[0]&1)<<31)|(acc[1]>>1);
		acc[0] = (acc[0]>>1);
		if (j&y) {		/* bit i of y != 0, add x to acc */
			c = 0;
			c = fpu_add3wc(&acc[3], acc[3], x[3], c);
			c = fpu_add3wc(&acc[2], acc[2], x[2], c);
			c = fpu_add3wc(&acc[1], acc[1], x[1], c);
			c = fpu_add3wc(&acc[0], acc[0], x[0], c);
		}
		j += j;
	    } while (j!=0);
	}

	y = py->significand[2];		/* py->significand[2] * x */
	if (y!=0) {
	    j=1;
	    do {
		s |= r;		/* shift acc right one bit */
		r  = acc[3]&1;
		acc[3] = ((acc[2]&1)<<31)|(acc[3]>>1);
		acc[2] = ((acc[1]&1)<<31)|(acc[2]>>1);
		acc[1] = ((acc[0]&1)<<31)|(acc[1]>>1);
		acc[0] = (acc[0]>>1);
		if (j&y) {		/* bit i of y != 0, add x to acc */
			c = 0;
			c = fpu_add3wc(&acc[3], acc[3], x[3], c);
			c = fpu_add3wc(&acc[2], acc[2], x[2], c);
			c = fpu_add3wc(&acc[1], acc[1], x[1], c);
			c = fpu_add3wc(&acc[0], acc[0], x[0], c);
		}
		j += j;
	    } while (j!=0);
	} else {
		s |= r|(acc[3]&0x7fffffff);
		r  = (acc[3]&0x80000000)>>31;
		acc[3]=acc[2]; acc[2]=acc[1]; acc[1]=acc[0]; acc[0]=0;
	}

	y = py->significand[1];		/* py->significand[1] * x */
	if (y!=0) {
	    j=1;
	    do {
		s |= r;		/* shift acc right one bit */
		r  = acc[3]&1;
		acc[3] = ((acc[2]&1)<<31)|(acc[3]>>1);
		acc[2] = ((acc[1]&1)<<31)|(acc[2]>>1);
		acc[1] = ((acc[0]&1)<<31)|(acc[1]>>1);
		acc[0] = (acc[0]>>1);
		if (j&y) {		/* bit i of y != 0, add x to acc */
			c = 0;
			c = fpu_add3wc(&acc[3], acc[3], x[3], c);
			c = fpu_add3wc(&acc[2], acc[2], x[2], c);
			c = fpu_add3wc(&acc[1], acc[1], x[1], c);
			c = fpu_add3wc(&acc[0], acc[0], x[0], c);
		}
		j += j;
	    } while (j!=0);
	} else {
		s |= r|(acc[3]&0x7fffffff);
		r  = (acc[3]&0x80000000)>>31;
		acc[3]=acc[2]; acc[2]=acc[1]; acc[1]=acc[0]; acc[0]=0;
	}

					/* py->significand[0] * x */
	y = py->significand[0];		/* y is of form 0x0001???? */
	j=1;
	do {
		s |= r;		/* shift acc right one bit */
		r  = acc[3]&1;
		acc[3] = ((acc[2]&1)<<31)|(acc[3]>>1);
		acc[2] = ((acc[1]&1)<<31)|(acc[2]>>1);
		acc[1] = ((acc[0]&1)<<31)|(acc[1]>>1);
		acc[0] = (acc[0]>>1);
		if (j&y) {		/* bit i of y != 0, add x to acc */
			c = 0;
			c = fpu_add3wc(&acc[3], acc[3], x[3], c);
			c = fpu_add3wc(&acc[2], acc[2], x[2], c);
			c = fpu_add3wc(&acc[1], acc[1], x[1], c);
			c = fpu_add3wc(&acc[0], acc[0], x[0], c);
		}
		j += j;
	} while (j<=y);

	if (acc[0]>=0x20000) {	/* right shift one bit to normalize */
		pz->exponent = px->exponent + py->exponent + 1;
		pz->sticky = s|r;
		pz->rounded = acc[3]&1;
		pz->significand[3]=((acc[2]&1)<<31)|(acc[3]>>1);
		pz->significand[2]=((acc[1]&1)<<31)|(acc[2]>>1);
		pz->significand[1]=((acc[0]&1)<<31)|(acc[1]>>1);
		pz->significand[0]=(acc[0]>>1);
	} else {
		pz->exponent = px->exponent + py->exponent;
		pz->sticky = s;
		pz->rounded = r;
		pz->significand[3]=acc[3];
		pz->significand[2]=acc[2];
		pz->significand[1]=acc[1];
		pz->significand[0]=acc[0];
	}
}