Enable x25519 64-bit code path for Microsoft compilers

1 files changed, 14 insertions, 5 deletions

diff --git a/donna.h b/donna.h
index 2c0f3ea8..e80b2666 100644
--- a/donna.h
+++ b/donna.h
@@ -39,14 +39,23 @@ int curve25519(byte sharedKey[32], const byte secretKey[32], const byte othersKe
 

 //****************************** Internal ******************************//

 

-#if (UINTPTR_MAX == 0xffffffff) || !defined(CRYPTOPP_WORD128_AVAILABLE)

-# define CRYPTOPP_CURVE25519_32BIT 1

-#else

+// CRYPTOPP_WORD128_AVAILABLE mostly depends upon GCC support for

+// __SIZEOF_INT128__. If __SIZEOF_INT128__ is not available then Moon

+// provides routines for MSC and GCC. It should cover most platforms,

+// but there are gaps like MS ARM64 and XLC. We tried to enable the

+// 64-bit path for SunCC from 12.5 but we got the dreaded compile

+// error "The operand ___LCM cannot be assigned to".

+

+#if defined(CRYPTOPP_WORD128_AVAILABLE) || \

+   (defined(_MSC_VER) && defined(_M_X64)) || \

+   (defined(__GNUC__) && (defined(__amd64__) || defined(__x86_64__)))

 # define CRYPTOPP_CURVE25519_64BIT 1

+#else

+# define CRYPTOPP_CURVE25519_32BIT 1

 #endif

 

-// Benchmarking on a modern Core i5-6400 shows SSE2 on Linux is

-// not profitable. Here are the numbers in milliseconds/operation:

+// Benchmarking on a modern 64-bit Core i5-6400 shows SSE2 on Linux

+// is not profitable. Here are the numbers in milliseconds/operation:

 //

 //   * Langley, C++, 0.050

 //   * Moon, C++: 0.040