Implement fmodl.

Document fmodl and fix some errors in the fmod manpage.

2 files changed, 149 insertions, 2 deletions

diff --git a/lib/msun/src/e_fmodl.c b/lib/msun/src/e_fmodl.c
new file mode 100644
index 0000000..c983000
--- /dev/null
+++ b/lib/msun/src/e_fmodl.c
@@ -0,0 +1,149 @@
+/* @(#)e_fmod.c 1.3 95/01/18 */
+/*-
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunSoft, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice 
+ * is preserved.
+ * ====================================================
+ */
+
+#include <sys/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <float.h>
+#include <stdint.h>
+
+#include "fpmath.h"
+#include "math.h"
+#include "math_private.h"
+
+#define	BIAS (LDBL_MAX_EXP - 1)
+
+#if LDBL_MANL_SIZE > 32
+typedef	uint64_t manl_t;
+#else
+typedef	uint32_t manl_t;
+#endif
+
+#if LDBL_MANH_SIZE > 32
+typedef	uint64_t manh_t;
+#else
+typedef	uint32_t manh_t;
+#endif
+
+/*
+ * These macros add and remove an explicit integer bit in front of the
+ * fractional mantissa, if the architecture doesn't have such a bit by
+ * default already.
+ */
+#ifdef LDBL_IMPLICIT_NBIT
+#define	SET_NBIT(hx)	((hx) | (1ULL << LDBL_MANH_SIZE))
+#define	HFRAC_BITS	LDBL_MANH_SIZE
+#else
+#define	SET_NBIT(hx)	(hx)
+#define	HFRAC_BITS	(LDBL_MANH_SIZE - 1)
+#endif
+
+#define	MANL_SHIFT	(LDBL_MANL_SIZE - 1)
+
+static const long double one = 1.0, Zero[] = {0.0, -0.0,};
+
+/*
+ * fmodl(x,y)
+ * Return x mod y in exact arithmetic
+ * Method: shift and subtract
+ *
+ * Assumptions:
+ * - The low part of the mantissa fits in a manl_t exactly.
+ * - The high part of the mantissa fits in an int64_t with enough room
+ *   for an explicit integer bit in front of the fractional bits.
+ */
+long double
+fmodl(long double x, long double y)
+{
+	union IEEEl2bits ux, uy;
+	int64_t hx,hz;	/* We need a carry bit even if LDBL_MANH_SIZE is 32. */
+	manh_t hy;
+	manl_t lx,ly,lz;
+	int ix,iy,n,sx;
+
+	ux.e = x;
+	uy.e = y;
+	sx = ux.bits.sign;
+
+    /* purge off exception values */
+	if((uy.bits.exp|uy.bits.manh|uy.bits.manl)==0 || /* y=0 */
+	   (ux.bits.exp == BIAS + LDBL_MAX_EXP) ||	 /* or x not finite */
+	   (uy.bits.exp == BIAS + LDBL_MAX_EXP &&
+	    ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl)!=0)) /* or y is NaN */
+	    return (x*y)/(x*y);
+	if(ux.bits.exp<=uy.bits.exp) {
+	    if((ux.bits.exp<uy.bits.exp) ||
+	       (ux.bits.manh<=uy.bits.manh &&
+		(ux.bits.manh<uy.bits.manh ||
+		 ux.bits.manl<uy.bits.manl))) {
+		return x;		/* |x|<|y| return x or x-y */
+	    }
+	    if(ux.bits.manh==uy.bits.manh && ux.bits.manl==uy.bits.manl) {
+		return Zero[sx];	/* |x|=|y| return x*0*/
+	    }
+	}
+
+    /* determine ix = ilogb(x) */
+	if(ux.bits.exp == 0) {	/* subnormal x */
+	    ux.e *= 0x1.0p512;
+	    ix = ux.bits.exp - (BIAS + 512);
+	} else {
+	    ix = ux.bits.exp - BIAS;
+	}
+
+    /* determine iy = ilogb(y) */
+	if(uy.bits.exp == 0) {	/* subnormal y */
+	    uy.e *= 0x1.0p512;
+	    iy = uy.bits.exp - (BIAS + 512);
+	} else {
+	    iy = uy.bits.exp - BIAS;
+	}
+
+    /* set up {hx,lx}, {hy,ly} and align y to x */
+	hx = SET_NBIT(ux.bits.manh);
+	hy = SET_NBIT(uy.bits.manh);
+	lx = ux.bits.manl;
+	ly = uy.bits.manl;
+
+    /* fix point fmod */
+	n = ix - iy;
+
+	while(n--) {
+	    hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
+	    if(hz<0){hx = hx+hx+(lx>>MANL_SHIFT); lx = lx+lx;}
+	    else {
+		if ((hz|lz)==0)		/* return sign(x)*0 */
+		    return Zero[sx];
+		hx = hz+hz+(lz>>MANL_SHIFT); lx = lz+lz;
+	    }
+	}
+	hz=hx-hy;lz=lx-ly; if(lx<ly) hz -= 1;
+	if(hz>=0) {hx=hz;lx=lz;}
+
+    /* convert back to floating value and restore the sign */
+	if((hx|lx)==0)			/* return sign(x)*0 */
+	    return Zero[sx];
+	while(hx<(1U<<HFRAC_BITS)) {	/* normalize x */
+	    hx = hx+hx+(lx>>MANL_SHIFT); lx = lx+lx;
+	    iy -= 1;
+	}
+	ux.bits.manh = hx; /* The mantissa is truncated here if needed. */
+	ux.bits.manl = lx;
+	if (iy < LDBL_MIN_EXP) {
+	    ux.bits.exp = iy + (BIAS + 512);
+	    ux.e *= 0x1p-512;
+	} else {
+	    ux.bits.exp = iy + BIAS;
+	}
+	x = ux.e * one;		/* create necessary signal */
+	return x;		/* exact output */
+}
diff --git a/lib/msun/src/math.h b/lib/msun/src/math.h
index c27a2be..97d1a58 100644
--- a/lib/msun/src/math.h
+++ b/lib/msun/src/math.h
@@ -423,9 +423,7 @@ long double	floorl(long double);
 long double	fmal(long double, long double, long double);
 long double	fmaxl(long double, long double) __pure2;
 long double	fminl(long double, long double) __pure2;
-#if 0
 long double	fmodl(long double, long double);
-#endif
 long double	frexpl(long double value, int *); /* fundamentally !__pure2 */
 long double	hypotl(long double, long double);
 int		ilogbl(long double) __pure2;