Make SSE2 configurable via CRYPTOPP_SSE2_INTRIN_AVAILABLE

Benchmarking shows things run a little slower with SSE2 on modern Core i5's. Also update comments and links

1 files changed, 14 insertions, 7 deletions

diff --git a/donna_sse.cpp b/donna_sse.cpp
index 65dab78a..c6e926d8 100644
--- a/donna_sse.cpp
+++ b/donna_sse.cpp
@@ -1,13 +1,14 @@
 // donna_sse.cpp - written and placed in public domain by Jeffrey Walton

-//                 This is an integration of Andrew Moon's public domain code.

-//                 Also see curve25519-donna-sse2.h.

+//                 This is a integration of Andrew Moon's public domain code.

+//                 Also see https://github.com/floodyberry/curve25519-donna.

 

 // This is a integration of Andrew Moon's public domain code. The port was

 // clean, but it has one potential problem. The original code is C and relies

 // upon unions. Accessing the inactive union member is undefined behavior in

 // C++. That means copying the array into packedelem8.u is OK; but then using

-// packedelem8.v in a calcualtion is undefined behavior. We will have to

-// keep an eye on things or rewrite significant portions of this code.

+// packedelem8.v in a calcualtion is UB. Fortunately most (all?) compilers

+// take pity on C++ developers and compile the code. We will have to keep an

+// eye on things or rewrite significant portions of this code.

 

 // If needed, see Moon's commit "Go back to ignoring 256th bit [sic]",

 // https://github.com/floodyberry/curve25519-donna/commit/57a683d18721a658

@@ -19,14 +20,20 @@
 #include "secblock.h"

 #include "misc.h"

 

-#if (CRYPTOPP_SSE2_INTRIN_AVAILABLE)

+#if (CRYPTOPP_CURVE25519_SSE2)

 # include <emmintrin.h>

 #endif

 

+// The data is aligned, but Clang issues warning based on type

+// and not the actual alignment of the variable and data.

+#if CRYPTOPP_GCC_DIAGNOSTIC_AVAILABLE

+# pragma GCC diagnostic ignored "-Wcast-align"

+#endif

+

 // Squash MS LNK4221 and libtool warnings

 extern const char DONNA_SSE_FNAME[] = __FILE__;

 

-#if (CRYPTOPP_SSE2_INTRIN_AVAILABLE)

+#if (CRYPTOPP_CURVE25519_SSE2)

 

 typedef __m128i xmmi;

 #define ALIGN(n) CRYPTOPP_ALIGN_DATA(n)

@@ -1164,4 +1171,4 @@ int curve25519_SSE2(byte sharedKey[32], const byte secretKey[32], const byte oth
 NAMESPACE_END  // Donna

 NAMESPACE_END  // CryptoPP

 

-#endif  // CRYPTOPP_SSE2_INTRIN_AVAILABLE

+#endif  // CRYPTOPP_CURVE25519_SSE2