+#ifndef _RISCV_MULHI_H
+#define _RISCV_MULHI_H
+
+#include <cstdint>
+
+inline uint64_t mulhu(uint64_t a, uint64_t b)
+{
+ uint64_t t;
+ uint32_t y1, y2, y3;
+ uint64_t a0 = (uint32_t)a, a1 = a >> 32;
+ uint64_t b0 = (uint32_t)b, b1 = b >> 32;
+
+ t = a1*b0 + ((a0*b0) >> 32);
+ y1 = t;
+ y2 = t >> 32;
+
+ t = a0*b1 + y1;
+ y1 = t;
+
+ t = a1*b1 + y2 + (t >> 32);
+ y2 = t;
+ y3 = t >> 32;
+
+ return ((uint64_t)y3 << 32) | y2;
+}
+
+inline int64_t mulh(int64_t a, int64_t b)
+{
+ int negate = (a < 0) != (b < 0);
+ uint64_t res = mulhu(a < 0 ? -a : a, b < 0 ? -b : b);
+ return negate ? ~res + (a * b == 0) : res;
+}
+
+inline int64_t mulhsu(int64_t a, uint64_t b)
+{
+ int negate = a < 0;
+ uint64_t res = mulhu(a < 0 ? -a : a, b);
+ return negate ? ~res + (a * b == 0) : res;
+}
+
+#endif