chapoly: Add an SSSE3 based driver

We always build the driver on x86/x64, but enable it only if SSSE3 support
is detected during runtime.

Poly1305 uses parallel 32-bit multiplication operands yielding a 64-bit result,
for which two can be done in parallel in SSE. This is minimally faster than
multiplication with 64-bit operands, and also works on 32-bit builds not having
a __int128 result type.

On a 32-bit architecture, this is more than twice as fast as the portable
driver, and on 64-bit it is ~30% faster.

src/libstrongswan/plugins/chapoly/Makefile.am

@@ -4,8 +4,9 @@ AM_CPPFLAGS = \
 AM_CFLAGS = \
 	$(PLUGIN_CFLAGS)
 
+noinst_LTLIBRARIES =
 if MONOLITHIC
-noinst_LTLIBRARIES = libstrongswan-chapoly.la
+noinst_LTLIBRARIES += libstrongswan-chapoly.la
 else
 plugin_LTLIBRARIES = libstrongswan-chapoly.la
 endif
@@ -16,4 +17,13 @@ libstrongswan_chapoly_la_SOURCES = \
 	chapoly_drv_portable.h chapoly_drv_portable.c \
 	chapoly_aead.h chapoly_aead.c
 
+noinst_LTLIBRARIES += libchapoly-drv-ssse3.la
+libchapoly_drv_ssse3_la_SOURCES = chapoly_drv_ssse3.h chapoly_drv_ssse3.c
+if USE_X86X64
+  libchapoly_drv_ssse3_la_CFLAGS = $(PLUGIN_CFLAGS) -mssse3
+endif
+
+libstrongswan_chapoly_la_LIBADD = \
+	libchapoly-drv-ssse3.la
+
 libstrongswan_chapoly_la_LDFLAGS = -module -avoid-version