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+/* $NetBSD: mul.S,v 1.3 1997/07/16 14:37:42 christos Exp $ */
+
+/*
+ * Copyright (c) 1992, 1993
+ * The Regents of the University of California. All rights reserved.
+ *
+ * This software was developed by the Computer Systems Engineering group
+ * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
+ * contributed to Berkeley.
+ *
+ * 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: Header: mul.s,v 1.5 92/06/25 13:24:03 torek Exp
+ */
+
+#include <machine/asm.h>
+#if defined(LIBC_SCCS) && !defined(lint)
+#if 0
+ .asciz "@(#)mul.s 8.1 (Berkeley) 6/4/93"
+#else
+ RCSID("$NetBSD: mul.S,v 1.3 1997/07/16 14:37:42 christos Exp $")
+#endif
+#endif /* LIBC_SCCS and not lint */
+
+/*
+ * Signed multiply, from Appendix E of the Sparc Version 8
+ * Architecture Manual.
+ *
+ * Returns %o0 * %o1 in %o1%o0 (i.e., %o1 holds the upper 32 bits of
+ * the 64-bit product).
+ *
+ * This code optimizes short (less than 13-bit) multiplies.
+ */
+
+FUNC(.mul)
+ mov %o0, %y ! multiplier -> Y
+ andncc %o0, 0xfff, %g0 ! test bits 12..31
+ be Lmul_shortway ! if zero, can do it the short way
+ andcc %g0, %g0, %o4 ! zero the partial product and clear N and V
+
+ /*
+ * Long multiply. 32 steps, followed by a final shift step.
+ */
+ mulscc %o4, %o1, %o4 ! 1
+ mulscc %o4, %o1, %o4 ! 2
+ mulscc %o4, %o1, %o4 ! 3
+ mulscc %o4, %o1, %o4 ! 4
+ mulscc %o4, %o1, %o4 ! 5
+ mulscc %o4, %o1, %o4 ! 6
+ mulscc %o4, %o1, %o4 ! 7
+ mulscc %o4, %o1, %o4 ! 8
+ mulscc %o4, %o1, %o4 ! 9
+ mulscc %o4, %o1, %o4 ! 10
+ mulscc %o4, %o1, %o4 ! 11
+ mulscc %o4, %o1, %o4 ! 12
+ mulscc %o4, %o1, %o4 ! 13
+ mulscc %o4, %o1, %o4 ! 14
+ mulscc %o4, %o1, %o4 ! 15
+ mulscc %o4, %o1, %o4 ! 16
+ mulscc %o4, %o1, %o4 ! 17
+ mulscc %o4, %o1, %o4 ! 18
+ mulscc %o4, %o1, %o4 ! 19
+ mulscc %o4, %o1, %o4 ! 20
+ mulscc %o4, %o1, %o4 ! 21
+ mulscc %o4, %o1, %o4 ! 22
+ mulscc %o4, %o1, %o4 ! 23
+ mulscc %o4, %o1, %o4 ! 24
+ mulscc %o4, %o1, %o4 ! 25
+ mulscc %o4, %o1, %o4 ! 26
+ mulscc %o4, %o1, %o4 ! 27
+ mulscc %o4, %o1, %o4 ! 28
+ mulscc %o4, %o1, %o4 ! 29
+ mulscc %o4, %o1, %o4 ! 30
+ mulscc %o4, %o1, %o4 ! 31
+ mulscc %o4, %o1, %o4 ! 32
+ mulscc %o4, %g0, %o4 ! final shift
+
+ ! If %o0 was negative, the result is
+ ! (%o0 * %o1) + (%o1 << 32))
+ ! We fix that here.
+
+ tst %o0
+ bge 1f
+ rd %y, %o0
+
+ ! %o0 was indeed negative; fix upper 32 bits of result by subtracting
+ ! %o1 (i.e., return %o4 - %o1 in %o1).
+ retl
+ sub %o4, %o1, %o1
+
+1:
+ retl
+ mov %o4, %o1
+
+Lmul_shortway:
+ /*
+ * Short multiply. 12 steps, followed by a final shift step.
+ * The resulting bits are off by 12 and (32-12) = 20 bit positions,
+ * but there is no problem with %o0 being negative (unlike above).
+ */
+ mulscc %o4, %o1, %o4 ! 1
+ mulscc %o4, %o1, %o4 ! 2
+ mulscc %o4, %o1, %o4 ! 3
+ mulscc %o4, %o1, %o4 ! 4
+ mulscc %o4, %o1, %o4 ! 5
+ mulscc %o4, %o1, %o4 ! 6
+ mulscc %o4, %o1, %o4 ! 7
+ mulscc %o4, %o1, %o4 ! 8
+ mulscc %o4, %o1, %o4 ! 9
+ mulscc %o4, %o1, %o4 ! 10
+ mulscc %o4, %o1, %o4 ! 11
+ mulscc %o4, %o1, %o4 ! 12
+ mulscc %o4, %g0, %o4 ! final shift
+
+ /*
+ * %o4 has 20 of the bits that should be in the low part of the
+ * result; %y has the bottom 12 (as %y's top 12). That is:
+ *
+ * %o4 %y
+ * +----------------+----------------+
+ * | -12- | -20- | -12- | -20- |
+ * +------(---------+------)---------+
+ * --hi-- ----low-part----
+ *
+ * The upper 12 bits of %o4 should be sign-extended to form the
+ * high part of the product (i.e., highpart = %o4 >> 20).
+ */
+
+ rd %y, %o5
+ sll %o4, 12, %o0 ! shift middle bits left 12
+ srl %o5, 20, %o5 ! shift low bits right 20, zero fill at left
+ or %o5, %o0, %o0 ! construct low part of result
+ retl
+ sra %o4, 20, %o1 ! ... and extract high part of result