Optimized rint implementation for x86-64.

ChangeLog

@@ -1,5 +1,7 @@
 2009-08-25  Ulrich Drepper  <drepper@redhat.com>
 
+	* sysdeps/ieee754/dbl-64/wordsize-64/s_rint.c: New file.
+
 	* sysdeps/ieee754/dbl-64/wordsize-64/s_round.c: New file.
 
 2009-08-25  Joseph Myers  <joseph@codesourcery.com>

sysdeps/ieee754/dbl-64/wordsize-64/s_rint.c

@@ -0,0 +1,79 @@
+/* @(#)s_rint.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+
+/*
+ * rint(x)
+ * Return x rounded to integral value according to the prevailing
+ * rounding mode.
+ * Method:
+ *	Using floating addition.
+ * Exception:
+ *	Inexact flag raised if x not equal to rint(x).
+ */
+
+#include "math.h"
+#include "math_private.h"
+
+#ifdef __STDC__
+static const double
+#else
+static double
+#endif
+TWO52[2]={
+  4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
+ -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
+};
+
+#ifdef __STDC__
+	double __rint(double x)
+#else
+	double __rint(x)
+	double x;
+#endif
+{
+	int64_t i0,sx;
+	int32_t j0;
+	EXTRACT_WORDS64(i0,x);
+	sx = (i0>>63)&1;
+	j0 = ((i0>>52)&0x7ff)-0x3ff;
+	if(j0<52) {
+	    if(j0<0) {
+		if((i0 & UINT64_C(0x7fffffffffffffff))==0) return x;
+		uint64_t i = i0 & UINT64_C(0xfffffffffffff);
+		i0 &= UINT64_C(0xfffe000000000000);
+		i0 |= (((i|-i) >> 12) & UINT64_C(0x8000000000000));
+		INSERT_WORDS64(x,i0);
+		double w = TWO52[sx]+x;
+		double t =  w-TWO52[sx];
+		EXTRACT_WORDS64(i0,t);
+		INSERT_WORDS64(t,(i0&UINT64_C(0x7fffffffffffffff))|(sx<<63));
+		return t;
+	    } else {
+		uint64_t i = UINT64_C(0x000fffffffffffff)>>j0;
+		if((i0&i)==0) return x; /* x is integral */
+		i>>=1;
+		if((i0&i)!=0)
+		    i0 = (i0&(~i))|(UINT64_C(0x4000000000000)>>j0);
+	    }
+	} else {
+	    if(j0==0x400) return x+x;	/* inf or NaN */
+	    else return x;		/* x is integral */
+	}
+	INSERT_WORDS64(x,i0);
+	double w = TWO52[sx]+x;
+	return w-TWO52[sx];
+}
+weak_alias (__rint, rint)
+#ifdef NO_LONG_DOUBLE
+strong_alias (__rint, __rintl)
+weak_alias (__rint, rintl)
+#endif