/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
* or http://www.opensolaris.org/os/licensing.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information: Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*/
/*
* Copyright 2003 Sun Microsystems, Inc. All rights reserved.
* Use is subject to license terms.
*/
#pragma ident "%Z%%M% %I% %E% SMI"
/*
* _D_cplx_div_ix(b, w) returns (I * b) / w with infinities handled
* according to C99.
*
* If b and w are both finite and w is nonzero, _D_cplx_div_ix(b, w)
* delivers the complex quotient q according to the usual formula:
* let c = Re(w), and d = Im(w); then q = x + I * y where x = (b * d)
* / r and y = (b * c) / r with r = c * c + d * d. This implementa-
* tion scales to avoid premature underflow or overflow.
*
* If b is neither NaN nor zero and w is zero, or if b is infinite
* and w is finite and nonzero, _D_cplx_div_ix delivers an infinite
* result. If b is finite and w is infinite, _D_cplx_div_ix delivers
* a zero result.
*
* If b and w are both zero or both infinite, or if either b or w is
* NaN, _D_cplx_div_ix delivers NaN + I * NaN. C99 doesn't specify
* these cases.
*
* This implementation can raise spurious underflow, overflow, in-
* valid operation, inexact, and division-by-zero exceptions. C99
* allows this.
*
* Warning: Do not attempt to "optimize" this code by removing multi-
* plications by zero.
*/
#if !defined(sparc) && !defined(__sparc)
#error This code is for SPARC only
#endif
/*
* scl[i].d = 2^(250*(4-i)) for i = 0, ..., 9
*/
static const union {
int i[2];
double d;
} scl[9] = {
{ 0x7e700000, 0 },
{ 0x6ed00000, 0 },
{ 0x5f300000, 0 },
{ 0x4f900000, 0 },
{ 0x3ff00000, 0 },
{ 0x30500000, 0 },
{ 0x20b00000, 0 },
{ 0x11100000, 0 },
{ 0x01700000, 0 }
};
/*
* Return +1 if x is +Inf, -1 if x is -Inf, and 0 otherwise
*/
static int
testinf(double x)
{
union {
int i[2];
double d;
} xx;
xx.d = x;
return (((((xx.i[0] << 1) - 0xffe00000) | xx.i[1]) == 0)?
(1 | (xx.i[0] >> 31)) : 0);
}
double _Complex
_D_cplx_div_ix(double b, double _Complex w)
{
double _Complex v;
union {
int i[2];
double d;
} bb, cc, dd;
double c, d, sc, sd, r;
int hb, hc, hd, hw, i, j;
/*
* The following is equivalent to
*
* c = creal(w); d = cimag(w);
*/
c = ((double *)&w)[0];
d = ((double *)&w)[1];
/* extract high-order words to estimate |b| and |w| */
bb.d = b;
hb = bb.i[0] & ~0x80000000;
cc.d = c;
dd.d = d;
hc = cc.i[0] & ~0x80000000;
hd = dd.i[0] & ~0x80000000;
hw = (hc > hd)? hc : hd;
/* check for special cases */
if (hw >= 0x7ff00000) { /* w is inf or nan */
i = testinf(c);
j = testinf(d);
if (i | j) { /* w is infinite */
c = (cc.i[0] < 0)? -0.0 : 0.0;
d = (dd.i[0] < 0)? -0.0 : 0.0;
} else /* w is nan */
b *= c * d;
((double *)&v)[0] = b * d;
((double *)&v)[1] = b * c;
return (v);
}
if (hw < 0x00100000) {
/*
* This nonsense is needed to work around some SPARC
* implementations of nonstandard mode; if both parts
* of w are subnormal, multiply them by one to force
* them to be flushed to zero when nonstandard mode
* is enabled. Sheesh.
*/
cc.d = c = c * 1.0;
dd.d = d = d * 1.0;
hc = cc.i[0] & ~0x80000000;
hd = dd.i[0] & ~0x80000000;
hw = (hc > hd)? hc : hd;
}
if (hw == 0 && (cc.i[1] | dd.i[1]) == 0) {
/* w is zero; multiply b by 1/Re(w) - I * Im(w) */
c = 1.0 / c;
j = testinf(b);
if (j) { /* b is infinite */
b = j;
}
((double *)&v)[0] = (b == 0.0)? b * c : b * d;
((double *)&v)[1] = b * c;
return (v);
}
if (hb >= 0x7ff00000) { /* a is inf or nan */
((double *)&v)[0] = b * d;
((double *)&v)[1] = b * c;
return (v);
}
/*
* Compute the real and imaginary parts of the quotient,
* scaling to avoid overflow or underflow.
*/
hw = (hw - 0x38000000) >> 28;
sc = c * scl[hw + 4].d;
sd = d * scl[hw + 4].d;
r = sc * sc + sd * sd;
hb = (hb - 0x38000000) >> 28;
b = (b * scl[hb + 4].d) / r;
hb -= (hw + hw);
hc = (hc - 0x38000000) >> 28;
c = (c * scl[hc + 4].d) * b;
hc += hb;
hd = (hd - 0x38000000) >> 28;
d = (d * scl[hd + 4].d) * b;
hd += hb;
/* compensate for scaling */
sc = scl[3].d; /* 2^250 */
if (hc < 0) {
hc = -hc;
sc = scl[5].d; /* 2^-250 */
}
while (hc--)
c *= sc;
sd = scl[3].d;
if (hd < 0) {
hd = -hd;
sd = scl[5].d;
}
while (hd--)
d *= sd;
((double *)&v)[0] = d;
((double *)&v)[1] = c;
return (v);
}