build: configure scrypt-sse2 through autoconf

- Add --enable/disable-scrypt-sse2 configuration flag
- use bitcoin-config.h instead of CPPFLAGS, like all other
  features
- make the scrypt.h header guard to be similar to everything else

configure.ac

@@ -177,6 +177,12 @@ AC_ARG_ENABLE([zmq],
   [use_zmq=$enableval],
   [use_zmq=yes])
 
+AC_ARG_ENABLE([scrypt-sse2],
+  [AS_HELP_STRING([--enable-scrypt-sse2],
+  [Build with scrypt sse2 implementation (default is no)])],
+  [use_scrypt_sse2=$enableval],
+  [use_scrypt_sse2=no])
+
 AC_ARG_WITH([intel-avx2],
   [AS_HELP_STRING([--with-intel-avx2],
   [Build with intel avx2 (default is no)])],
@@ -725,6 +731,11 @@ BOOST_LIBS="$BOOST_LDFLAGS $BOOST_SYSTEM_LIB $BOOST_FILESYSTEM_LIB $BOOST_PROGRA
 
 fi
 
+# Configure Scrypt SSE2
+if test x$use_scrypt_sse2 = xyes; then
+  AC_DEFINE(USE_SSE2, 1, [Define this symbol if SSE2 works])
+fi
+
 if test x$intel_avx2 = xyes; then
   case $host in
      x86_64-*-linux*)
@@ -1028,6 +1039,7 @@ AM_CONDITIONAL([USE_LCOV],[test x$use_lcov = xyes])
 AM_CONDITIONAL([GLIBC_BACK_COMPAT],[test x$use_glibc_compat = xyes])
 AM_CONDITIONAL([HARDEN],[test x$use_hardening = xyes])
 AM_CONDITIONAL([WORDS_BIGENDIAN],[test x$ac_cv_c_bigendian = xyes])
+AM_CONDITIONAL([USE_SCRYPT_SSE2], [test x$use_scrypt_sse2 = xyes])
 
 AC_DEFINE(CLIENT_VERSION_MAJOR, _CLIENT_VERSION_MAJOR, [Major version])
 AC_DEFINE(CLIENT_VERSION_MINOR, _CLIENT_VERSION_MINOR, [Minor version])

src/Makefile.am

@@ -267,6 +267,11 @@ crypto_libdogecoin_crypto_a_SOURCES = \
   crypto/sha512.cpp \
   crypto/sha512.h
 
+# only include SSE2 scrypt sources if USE_SCRYPT_SSE2 is defined
+if USE_SCRYPT_SSE2
+crypto_libdogecoin_crypto_a_SOURCES += crypto/scrypt-sse2.cpp
+endif
+
 # consensus: shared between all executables that validate any consensus rules.
 libdogecoin_consensus_a_CPPFLAGS = $(AM_CPPFLAGS) $(BITCOIN_INCLUDES)
 libdogecoin_consensus_a_CXXFLAGS = $(AM_CXXFLAGS) $(PIE_FLAGS)

src/crypto/scrypt.h

@@ -1,8 +1,12 @@
-#ifndef SCRYPT_H
-#define SCRYPT_H
+#ifndef BITCOIN_CRYPTO_SCRYPT_H
+#define BITCOIN_CRYPTO_SCRYPT_H
 #include <stdlib.h>
 #include <stdint.h>
 
+#if defined(HAVE_CONFIG_H)
+#include "bitcoin-config.h" // for USE_SSE2
+#endif
+
 static const int SCRYPT_SCRATCHPAD_SIZE = 131072 + 63;
 
 void scrypt_1024_1_1_256(const char *input, char *output);
@@ -44,4 +48,4 @@ static inline void le32enc(void *pp, uint32_t x)
         p[3] = (x >> 24) & 0xff;
 }
 #endif
-#endif
+#endif // BITCOIN_CRYPTO_SCRYPT_H