cherrypick d531cf36 from litecoin-project/litecoin

configure.ac

@@ -221,6 +221,12 @@ AC_ARG_ENABLE([bip70],
   [enable_bip70=$enableval],
   [enable_bip70=auto])
 
+AC_ARG_ENABLE([sse2],
+    [AS_HELP_STRING([--enable-sse2],
+    [enable SSE2 instructions in the scrypt library. (default is disabled)])],
+    [use_sse2=$enableval],
+    [use_sse2=no])
+
 AC_ARG_WITH([protoc-bindir],[AS_HELP_STRING([--with-protoc-bindir=BIN_DIR],[specify protoc bin path])], [protoc_bin_path=$withval], [])
 
 AC_ARG_ENABLE(man,
@@ -1393,6 +1399,16 @@ else
   BUILD_TEST=""
 fi
 
+AC_MSG_CHECKING([whether to enable sse2 instructions])
+if test x$use_sse2 != xno; then
+  AC_MSG_RESULT(yes)
+  AC_DEFINE([USE_SSE2],[1],[Define if SSE2 support should be compiled in])
+  use_sse2=yes
+  CPPFLAGS="$CPPFLAGS -DUSE_SSE2=1"
+else
+  AC_MSG_RESULT(no)
+fi
+
 AC_MSG_CHECKING([whether to reduce exports])
 if test x$use_reduce_exports = xyes; then
   AC_MSG_RESULT([yes])
@@ -1415,6 +1431,7 @@ AM_CONDITIONAL([ENABLE_QT_TESTS],[test x$BUILD_TEST_QT = xyes])
 AM_CONDITIONAL([ENABLE_BIP70],[test x$enable_bip70 = xyes])
 AM_CONDITIONAL([ENABLE_BENCH],[test x$use_bench = xyes])
 AM_CONDITIONAL([USE_QRCODE], [test x$use_qr = xyes])
+AM_CONDITIONAL([USE_SSE2], [test x$use_sse2 = xyes])
 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])
@@ -1472,6 +1489,7 @@ AC_SUBST(SHANI_CXXFLAGS)
 AC_SUBST(LIBTOOL_APP_LDFLAGS)
 AC_SUBST(USE_UPNP)
 AC_SUBST(USE_QRCODE)
+AC_SUBST(USE_SSE2)
 AC_SUBST(BOOST_LIBS)
 AC_SUBST(TESTDEFS)
 AC_SUBST(LEVELDB_TARGET_FLAGS)