-/* origin: FreeBSD /usr/src/lib/msun/src/s_floor.c */
-/*
- * ====================================================
- * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
- *
- * Developed at SunPro, a Sun Microsystems, Inc. business.
- * Permission to use, copy, modify, and distribute this
- * software is freely granted, provided that this notice
- * is preserved.
- * ====================================================
- */
-/*
- * floor(x)
- * Return x rounded toward -inf to integral value
- * Method:
- * Bit twiddling.
- * Exception:
- * Inexact flag raised if x not equal to floor(x).
- */
-
#include "libm.h"
-static const double huge = 1.0e300;
+#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 floor(double x)
{
- int32_t i0,i1,j0;
- uint32_t i,j;
+ union {double f; uint64_t i;} u = {x};
+ int e = u.i >> 52 & 0x7ff;
+ double_t y;
- EXTRACT_WORDS(i0, i1, x);
- // FIXME: signed shift
- j0 = ((i0>>20)&0x7ff) - 0x3ff;
- if (j0 < 20) {
- if (j0 < 0) { /* |x| < 1 */
- /* raise inexact if x != 0 */
- if (huge+x > 0.0) {
- if (i0 >= 0) { /* x >= 0 */
- i0 = i1 = 0;
- } else if (((i0&0x7fffffff)|i1) != 0) {
- i0 = 0xbff00000;
- i1 = 0;
- }
- }
- } else {
- i = 0x000fffff>>j0;
- if (((i0&i)|i1) == 0)
- return x; /* x is integral */
- /* raise inexact flag */
- if (huge+x > 0.0) {
- if (i0 < 0)
- i0 += 0x00100000>>j0;
- i0 &= ~i;
- i1=0;
- }
- }
- } else if (j0 > 51) {
- if (j0 == 0x400)
- return x+x; /* inf or NaN */
- else
- return x; /* x is integral */
- } else {
- i = ((uint32_t)(0xffffffff))>>(j0-20);
- if ((i1&i) == 0)
- return x; /* x is integral */
- /* raise inexact flag */
- if (huge+x > 0.0) {
- if (i0 < 0) {
- if (j0 == 20)
- i0+=1;
- else {
- j = i1+(1<<(52-j0));
- if (j < i1)
- i0 += 1; /* got a carry */
- i1 = j;
- }
- }
- i1 &= ~i;
- }
+ if (e >= 0x3ff+52 || x == 0)
+ return x;
+ /* y = int(x) - x, where int(x) is an integer neighbor of x */
+ if (u.i >> 63)
+ y = x - toint + toint - x;
+ else
+ y = x + toint - toint - x;
+ /* special case because of non-nearest rounding modes */
+ if (e <= 0x3ff-1) {
+ FORCE_EVAL(y);
+ return u.i >> 63 ? -1 : 0;
}
- INSERT_WORDS(x, i0, i1);
- return x;
+ if (y > 0)
+ return x + y - 1;
+ return x + y;
}