/* $Id: fcalc.c,v 1.2 2010/03/21 19:36:47 kostik Exp $ */

#include <sys/types.h>
#include <err.h>
#include <fcntl.h>
#include <math.h>
#include <stdio.h>
#include <unistd.h>

double
calc1(double x)
{

	return (x + 1.0);
}

static void fadd1(void *p) __attribute((noinline));
void
fadd1(void *p)
{
	static const double one = 1.0;

	__asm volatile(
	      "movsd	%1,%%xmm0\n\t"
	      "movsd	(%2),%%xmm1\n\t"
	      "addsd	%%xmm0,%%xmm1\n\t"
	      "movsd	%%xmm1,(%0)"
	      : "=r" (p)
	      : "m" (one), "r" (p)
	      : "memory", "xmm0", "xmm1");
}

double calc2(double x) __attribute((noinline));
double
calc2(double x)
{

	fadd1(&x);
	return (x);
}

double
calc3(double x)
{
	int fd;
	int res;

	fd = open("/dev/kernfpu", O_RDWR);
	if (fd == -1)
		err(1, "open /dev/kernfpu");
	res = write(fd, &x, sizeof(x));
	if (res == -1)
		err(1, "write to kernfpu");
	else if (res != sizeof(x))
		errx(1, "short write");
	res = read(fd, &x, sizeof(x));
	if (res == -1)
		err(1, "read from kernfpu");
	else if (res != sizeof(x))
		errx(1, "short read");

	return (x);
}

int
main(int argc, char *argv[])
{
	double b, c1, c2, c3;

	b = 2.0;
	c1 = calc1(b);
	printf("%e\n", c1);
	c2 = calc2(b);
	printf("%e\n", c2);
	c3 = calc3(b);
	printf("%e\n", c3);

	return (0);
}