lib/libm/rint.c


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#include <float.h>
#include <math.h>
#include <stdint.h>

#if FLT_EVAL_METHOD == 0 || FLT_EVAL_METHOD == 1
#define EPS DBL_EPSILON
#elif FLT_EVAL_METHOD == 2
#define EPS LDBL_EPSILON
#endif
static const double_t toint = 1 / EPS;

double rint(double x)
{
	union {
		double f;
		uint64_t i;
	} u = { x };
	int e = u.i >> 52 & 0x7ff;
	int s = u.i >> 63;
	double_t y;

	if (e >= 0x3ff + 52)
		return x;
	if (s)
		y = x - toint + toint;
	else
		y = x + toint - toint;
	if (y == 0)
		return s ? -0.0 : 0;
	return y;
}