Add SSE4 based SHA256

Author: sipa

Diff for: src/Makefile.am

@@ -263,6 +263,7 @@ crypto_libbitcoin_crypto_a_SOURCES = \
   crypto/sha1.cpp \
   crypto/sha1.h \
   crypto/sha256.cpp \
+  crypto/sha256_sse4.cpp \
   crypto/sha256.h \
   crypto/sha512.cpp \
   crypto/sha512.h

Diff for: src/crypto/sha256.cpp

@@ -3,13 +3,19 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include "crypto/sha256.h"
-
 #include "crypto/common.h"
 
 #include <string.h>
-
 #include <atomic>
 
+#if defined(__x86_64__) || defined(__amd64__)
+#include <cpuid.h>
+namespace sha256_sse4
+{
+void Transform(uint32_t* s, const unsigned char* chunk, size_t blocks);
+}
+#endif
+
 // Internal implementation code.
 namespace
 {
@@ -140,6 +146,14 @@ void (*Transform)(uint32_t*, const unsigned char*, size_t) = sha256::Transform;
 
 std::string SHA256AutoDetect()
 {
+#if defined(__x86_64__) || defined(__amd64__)
+    uint32_t eax, ebx, ecx, edx;
+    if (__get_cpuid(1, &eax, &ebx, &ecx, &edx) && (ecx >> 19) & 1) {
+        Transform = sha256_sse4::Transform;
+        return "sse4";
+    }
+#endif
+
     return "standard";
 }