1 files changed, 56 insertions, 0 deletions
diff --git a/lib/builtins/mulvsi3.c b/lib/builtins/mulvsi3.c
new file mode 100644
index 000000000..d372b2017
--- /dev/null
+++ b/lib/builtins/mulvsi3.c
@@ -0,0 +1,56 @@
+/* ===-- mulvsi3.c - Implement __mulvsi3 -----------------------------------===
+ *
+ *                     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 __mulvsi3 for the compiler_rt library.
+ *
+ * ===----------------------------------------------------------------------===
+ */
+
+#include "int_lib.h"
+
+/* Returns: a * b */
+
+/* Effects: aborts if a * b overflows */
+
+si_int
+__mulvsi3(si_int a, si_int b)
+{
+    const int N = (int)(sizeof(si_int) * CHAR_BIT);
+    const si_int MIN = (si_int)1 << (N-1);
+    const si_int MAX = ~MIN;
+    if (a == MIN)
+    {
+        if (b == 0 || b == 1)
+            return a * b;
+        compilerrt_abort();
+    }
+    if (b == MIN)
+    {
+        if (a == 0 || a == 1)
+            return a * b;
+        compilerrt_abort();
+    }
+    si_int sa = a >> (N - 1);
+    si_int abs_a = (a ^ sa) - sa;
+    si_int sb = b >> (N - 1);
+    si_int abs_b = (b ^ sb) - sb;
+    if (abs_a < 2 || abs_b < 2)
+        return a * b;
+    if (sa == sb)
+    {
+        if (abs_a > MAX / abs_b)
+            compilerrt_abort();
+    }
+    else
+    {
+        if (abs_a > MIN / -abs_b)
+            compilerrt_abort();
+    }
+    return a * b;
+}