/*
 *  linux/arch/arm/vfp/vfpdouble.c
 *
 * This code is derived in part from John R. Housers softfloat library, which
 * carries the following notice:
 *
 * ===========================================================================
 * This C source file is part of the SoftFloat IEC/IEEE Floating-point
 * Arithmetic Package, Release 2.
 *
 * Written by John R. Hauser.  This work was made possible in part by the
 * International Computer Science Institute, located at Suite 600, 1947 Center
 * Street, Berkeley, California 94704.  Funding was partially provided by the
 * National Science Foundation under grant MIP-9311980.  The original version
 * of this code was written as part of a project to build a fixed-point vector
 * processor in collaboration with the University of California at Berkeley,
 * overseen by Profs. Nelson Morgan and John Wawrzynek.  More information
 * is available through the web page `http://HTTP.CS.Berkeley.EDU/~jhauser/
 * arithmetic/softfloat.html'.
 *
 * THIS SOFTWARE IS DISTRIBUTED AS IS, FOR FREE.  Although reasonable effort
 * has been made to avoid it, THIS SOFTWARE MAY CONTAIN FAULTS THAT WILL AT
 * TIMES RESULT IN INCORRECT BEHAVIOR.  USE OF THIS SOFTWARE IS RESTRICTED TO
 * PERSONS AND ORGANIZATIONS WHO CAN AND WILL TAKE FULL RESPONSIBILITY FOR ANY
 * AND ALL LOSSES, COSTS, OR OTHER PROBLEMS ARISING FROM ITS USE.
 *
 * Derivative works are acceptable, even for commercial purposes, so long as
 * (1) they include prominent notice that the work is derivative, and (2) they
 * include prominent notice akin to these three paragraphs for those parts of
 * this code that are retained.
 * ===========================================================================
 */
#include <linux/kernel.h>
#include <linux/bitops.h>

#include <asm/div64.h>
#include <asm/vfp.h>

#include "vfpinstr.h"
#include "vfp.h"

static struct vfp_double vfp_double_default_qnan = {
	.exponent	= 2047,
	.sign		= 0,
	.significand	= VFP_DOUBLE_SIGNIFICAND_QNAN,
};

static void vfp_double_dump(const char *str, struct vfp_double *d)
{
	pr_debug("VFP: %s: sign=%d exponent=%d significand=%016llx\n",
		 str, d->sign != 0, d->exponent, d->significand);
}

static void vfp_double_normalise_denormal(struct vfp_double *vd)
{
	int bits = 31 - fls(vd->significand >> 32);
	if (bits == 31)
		bits = 63 - fls(vd->significand);

	vfp_double_dump("normalise_denormal: in", vd);

	if (bits) {
		vd->exponent -= bits - 1;
		vd->significand <<= bits;
	}

	vfp_double_dump("normalise_denormal: out", vd);
}

u32 vfp_double_normaliseround(int dd, struct vfp_double *vd, u32 fpscr, u32 exceptions, const char *func)
{
	u64 significand, incr;
	int exponent, shift, underflow;
	u32 rmode;

	vfp_double_dump("pack: in", vd);

	/*
	 * Infinities and NaNs are a special case.
	 */
	if (vd->exponent == 2047 && (vd->significand == 0 || exceptions))
		goto pack;

	/*
	 * Special-case zero.
	 */
	if (vd->significand == 0) {
		vd->exponent = 0;
		goto pack;
	}

	exponent = vd->exponent;
	significand = vd->significand;

	shift = 32 - fls(significand >> 32);
	if (shift == 32)
		shift = 64 - fls(significand);
	if (shift) {
		exponent -= shift;
		significand <<= shift;
	}

#ifdef DEBUG
	vd->exponent = exponent;
	vd->significand = significand;
	vfp_double_dump("pack: normalised", vd);
#endif

	/*
	 * Tiny number?
	 */
	underflow = exponent < 0;
	if (underflow) {
		significand = vfp_shiftright64jamming(significand, -exponent);
		exponent = 0;
#ifdef DEBUG
		vd->exponent = exponent;
		vd->significand = significand;
		vfp_double_dump("pack: tiny number", vd);
#endif
		if (!(significand & ((1ULL << (VFP_DOUBLE_LOW_BITS + 1)) - 1)))
			underflow = 0;
	}

	/*
	 * Select rounding increment.
	 */
	incr = 0;
	rmode = fpscr & FPSCR_RMODE_MASK;

	if (rmode == FPSCR_ROUND_NEAREST) {
		incr = 1ULL << VFP_DOUBLE_LOW_BITS;
		if ((significand & (1ULL << (VFP_DOUBLE_LOW_BITS + 1))) == 0)
			incr -= 1;
	} else if (rmode == FPSCR_ROUND_TOZERO) {
		incr = 0;
	} else if ((rmode == FPSCR_ROUND_PLUSINF) ^ (vd->sign != 0))
		incr = (1ULL << (VFP_DOUBLE_LOW_BITS + 1)) - 1;

	pr_debug("VFP: rounding increment = 0x%08llx\n", incr);

	/*
	 * Is our rounding going to overflow?
	 */
	if ((significand + incr) < significand) {
		exponent += 1;
		significand = (significand >> 1) | (significand & 1);
		incr >>= 1;
#ifdef DEBUG
		vd->exponent = exponent;
		vd->significand = significand;
		vfp_double_dump("pack: overflow", vd);
#endif
	}

	/*
	 * If any of the low bits (which will be shifted out of the
	 * number) are non-zero, the result is inexact.
	 */
	if (significand & ((1 << (VFP_DOUBLE_LOW_BITS + 1)) - 1))
		exceptions |= FPSCR_IXC;

	/*
	 * Do our rounding.
	 */
	significand += incr;

	/*
	 * Infinity?
	 */
	if (exponent >= 2046) {
		exceptions |= FPSCR_OFC | FPSCR_IXC;
		if (incr == 0) {
			vd->exponent = 2045;
			vd->significand = 0x7fffffffffffffffULL;
		} else {
			vd->exponent = 2047;		/* infinity */
			vd->significand = 0;
		}
	} else {
		if (significand >> (VFP_DOUBLE_LOW_BITS + 1) == 0)
			exponent = 0;
		if (exponent || significand > 0x8000000000000000ULL)
			underflow = 0;
		if (underflow)
			exceptions |= FPSCR_UFC;
		vd->exponent = exponent;
		vd->significand = significand >> 1;
	}

 pack:
	vfp_double_dump("pack: final", vd);
	{
		s64 d = vfp_double_pack(vd);
		pr_debug("VFP: %s: d(d%d)=%016llx exceptions=%08x\n", func,
			 dd, d, exceptions);
		vfp_put_double(d, dd);
	}
	return exceptions;
}

/*
 * Propagate the NaN, setting exceptions if it is signalling.
 * 'n' is always a NaN.  'm' may be a number, NaN or infinity.
 */
static u32
vfp_propagate_nan(struct vfp_double *vdd, struct vfp_double *vdn,
		  struct vfp_double *vdm, u32 fpscr)
{
	struct vfp_double *nan;
	int tn, tm = 0;

	tn = vfp_double_type(vdn);

	if (vdm)
		tm = vfp_double_type(vdm);

	if (fpscr & FPSCR_DEFAULT_NAN)
		/*
		 * Default NaN mode - always returns a quiet NaN
		 */
		nan = &vfp_double_default_qnan;
	else {
		/*
		 * Contemporary mode - select the first signalling
		 * NAN, or if neither are signalling, the first
		 * quiet NAN.
		 */
		if (tn == VFP_SNAN || (tm != VFP_SNAN && tn == VFP_QNAN))
			nan = vdn;
		else
			nan = vdm;
		/*
		 * Make the NaN quiet.
		 */
		nan->significand |= VFP_DOUBLE_SIGNIFICAND_QNAN;
	}

	*vdd = *nan;

	/*
	 * If one was a signalling NAN, raise invalid operation.
	 */
	return tn == VFP_SNAN || tm == VFP_SNAN ? FPSCR_IOC : VFP_NAN_FLAG;
}

/*
 * Extended operations
 */
static u32 vfp_double_fabs(int dd, int unused, int dm, u32 fpscr)
{
	vfp_put_double(vfp_double_packed_abs(vfp_get_double(dm)), dd);
	return 0;
}

static u32 vfp_double_fcpy(int dd, int unused, int dm, u32 fpscr)