1 files changed, 63 insertions, 0 deletions
diff --git a/usr/src/common/util/multi3.c b/usr/src/common/util/multi3.c
new file mode 100644
index 0000000000..b098eb37ac
--- /dev/null
+++ b/usr/src/common/util/multi3.c
@@ -0,0 +1,63 @@
+/*
+ * Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+ * See https://llvm.org/LICENSE.txt for license information.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#include <sys/byteorder.h>
+
+#define	CHAR_BIT 8
+
+typedef int		di_int __attribute__((mode(DI)));
+typedef unsigned int	du_int __attribute__((mode(DI)));
+typedef int		ti_int __attribute__((mode(TI)));
+
+typedef union {
+	ti_int all;
+	struct {
+#if _LITTLE_ENDIAN
+		du_int low;
+		di_int high;
+#else
+		di_int high;
+		du_int low;
+#endif /* _LITTLE_ENDIAN */
+	} s;
+} twords;
+
+/* Returns: a * b */
+static
+ti_int
+__mulddi3(du_int a, du_int b)
+{
+	twords r;
+	const int bits_in_dword_2 = (int)(sizeof (di_int) * CHAR_BIT) / 2;
+	const du_int lower_mask = (du_int)~0 >> bits_in_dword_2;
+	r.s.low = (a & lower_mask) * (b & lower_mask);
+	du_int t = r.s.low >> bits_in_dword_2;
+	r.s.low &= lower_mask;
+	t += (a >> bits_in_dword_2) * (b & lower_mask);
+	r.s.low += (t & lower_mask) << bits_in_dword_2;
+	r.s.high = t >> bits_in_dword_2;
+	t = r.s.low >> bits_in_dword_2;
+	r.s.low &= lower_mask;
+	t += (b >> bits_in_dword_2) * (a & lower_mask);
+	r.s.low += (t & lower_mask) << bits_in_dword_2;
+	r.s.high += t >> bits_in_dword_2;
+	r.s.high += (a >> bits_in_dword_2) * (b >> bits_in_dword_2);
+	return (r.all);
+}
+
+/* Returns: a * b */
+ti_int
+__multi3(ti_int a, ti_int b)
+{
+	twords x;
+	x.all = a;
+	twords y;
+	y.all = b;
+	twords r;
+	r.all = __mulddi3(x.s.low, y.s.low);
+	r.s.high += x.s.high * y.s.low + x.s.low * y.s.high;
+	return (r.all);
+}