Floating point libc functions traditionally written in ASM.

AMD64 does away with the x87 in 64-bit long mode, so we have to play the
SSE/SSE2 game now.

Obtained from:	NetBSD/x86-64

lib/libc/amd64/gen/fabs.S

@@ -0,0 +1,18 @@
+#include <machine/asm.h>
+#if defined(LIBC_SCCS)
+	RCSID("$NetBSD: fabs.S,v 1.4 1997/07/16 14:37:16 christos Exp $")
+#endif
+__FBSDID("$FreeBSD$");
+
+/*
+ * Ok, this sucks. Is there really no way to push an xmm register onto
+ * the FP stack directly?
+ */
+
+ENTRY(fabs)
+	movsd	%xmm0, -8(%rsp)
+	fldl	-8(%rsp)
+	fabs
+	fstp	-8(%rsp)
+	movsd	-8(%rsp),%xmm0
+	ret

lib/libc/amd64/gen/modf.S

@@ -0,0 +1,95 @@
+/*-
+ * Copyright (c) 1990 The Regents of the University of California.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to Berkeley by
+ * Sean Eric Fagan.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	from: @(#)modf.s	5.5 (Berkeley) 3/18/91
+ */
+
+#include <machine/asm.h>
+#if defined(LIBC_SCCS)
+	RCSID("$NetBSD: modf.S,v 1.5 1997/07/16 14:37:18 christos Exp $")
+#endif
+__FBSDID("$FreeBSD$");
+
+/*
+ * modf(value, iptr): return fractional part of value, and stores the
+ * integral part into iptr (a pointer to double).
+ *
+ * Written by Sean Eric Fagan (sef@kithrup.COM)
+ * Sun Mar 11 20:27:30 PST 1990
+ */
+
+/* With CHOP mode on, frndint behaves as TRUNC does.  Useful. */
+ENTRY(modf)
+	pushq	%rbp
+	movq	%rsp,%rbp
+	subq	$24,%rsp
+
+	/*
+	 * Set chop mode.
+	 */
+	fnstcw	-12(%rbp)
+	movw	-12(%rbp),%dx
+	orw	$3072,%dx
+	movw	%dx,-16(%rbp)
+	fldcw	-16(%rbp)
+
+	/*
+	 * Get integral part.
+	 */
+	movsd	%xmm0,-24(%rbp)
+	fldl	-24(%rbp)
+	frndint
+	fstpl	-8(%rbp)
+
+	/*
+	 * Restore control word.
+	 */
+	fldcw	-12(%rbp)
+
+	/*
+	 * Store integral part.
+	 */
+	movsd	-8(%rbp),%xmm0
+	movsd	%xmm0,(%rdi)
+
+	/*
+	 * Get fractional part and return it.
+	 */
+	fldl	-24(%rbp)
+	fsubl	-8(%rbp)
+	movsd   -8(%rbp),%xmm0
+
+	leave
+	ret