1 files changed, 58 insertions, 0 deletions
diff --git a/lib/builtins/multi3.c b/lib/builtins/multi3.c
new file mode 100644
index 000000000000..e0d52d430b66
--- /dev/null
+++ b/lib/builtins/multi3.c
@@ -0,0 +1,58 @@
+/* ===-- multi3.c - Implement __multi3 -------------------------------------===
+ *
+ *                     The LLVM Compiler Infrastructure
+ *
+ * This file is dual licensed under the MIT and the University of Illinois Open
+ * Source Licenses. See LICENSE.TXT for details.
+ *
+ * ===----------------------------------------------------------------------===
+
+ * This file implements __multi3 for the compiler_rt library.
+ *
+ * ===----------------------------------------------------------------------===
+ */
+
+#include "int_lib.h"
+
+#ifdef CRT_HAS_128BIT
+
+/* 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 */
+
+COMPILER_RT_ABI 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;
+}
+
+#endif /* CRT_HAS_128BIT */