clean up portable 128-bit multiply

src/common/int-util.h

@@ -68,6 +68,17 @@ static inline uint64_t lo_dword(uint64_t val) {
   return val & 0xFFFFFFFF;
 }
 
+#if defined(__GNUC__) && defined(__x86_64__)
+
+static inline uint64_t mul128(uint64_t a, uint64_t b, uint64_t *high) {
+  typedef unsigned __int128 uint128_t;
+  uint128_t res = (uint128_t) a * (uint128_t) b;
+  *high = (uint64_t) (res >> 64);
+  return (uint64_t) res;
+}
+
+#else
+
 static inline uint64_t mul128(uint64_t multiplier, uint64_t multiplicand, uint64_t* product_hi) {
   // multiplier   = ab = a * 2^32 + b
   // multiplicand = cd = c * 2^32 + d
@@ -93,6 +104,7 @@ static inline uint64_t mul128(uint64_t multiplier, uint64_t multiplicand, uint64
 
   return product_lo;
 }
+#endif
 
 static inline uint64_t div_with_reminder(uint64_t dividend, uint32_t divisor, uint32_t* remainder) {
   dividend |= ((uint64_t)*remainder) << 32;

src/cryptonote_core/difficulty.cpp

@@ -45,25 +45,10 @@ namespace cryptonote {
   using std::uint64_t;
   using std::vector;
 
-#if defined(_MSC_VER)
-#include <windows.h>
-#include <winnt.h>
-
   static inline void mul(uint64_t a, uint64_t b, uint64_t &low, uint64_t &high) {
     low = mul128(a, b, &high);
   }
 
-#else
-
-  static inline void mul(uint64_t a, uint64_t b, uint64_t &low, uint64_t &high) {
-    typedef unsigned __int128 uint128_t;
-    uint128_t res = (uint128_t) a * (uint128_t) b;
-    low = (uint64_t) res;
-    high = (uint64_t) (res >> 64);
-  }
-
-#endif
-
   static inline bool cadd(uint64_t a, uint64_t b) {
     return a + b < a;
   }