Check for __builtin_cpu_supports("ssse3") in make-only builds

Prevents failures on older compilers that don't have this
builtin, or don't support using it to test for ssse3.

Author: daviesrob

Makefile

@@ -334,10 +334,12 @@ config.h:
 	echo '#if defined __x86_64__ || defined __arm__ || defined __aarch64__' >> $@
 	echo '#define HAVE_ATTRIBUTE_CONSTRUCTOR 1' >> $@
 	echo '#endif' >> $@
-	echo '#if (defined(__x86_64__) || defined(_M_X64))' >> $@
-	echo '#define HAVE_ATTRIBUTE_TARGET_SSSE3 1' >> $@
-	echo '#define HAVE_BUILTIN_CPU_SUPPORT_SSSE3 1' >> $@
-	echo '#endif' >> $@
+	if [ "x$(HTS_HAVE_SSSE3_BUILTINS)" != "x" ]; then \
+	    echo '#if (defined(__x86_64__) || defined(_M_X64))' >> $@ ; \
+	    echo '#define HAVE_ATTRIBUTE_TARGET_SSSE3 1' >> $@ ; \
+	    echo '#define HAVE_BUILTIN_CPU_SUPPORT_SSSE3 1' >> $@ ; \
+	    echo '#endif' >> $@ ; \
+	fi
 	echo '#if defined __linux__' >> $@
 	echo '#define HAVE_GETAUXVAL' >> $@
 	echo '#elif defined __FreeBSD__' >> $@

hts_probe_cc.sh

@@ -60,9 +60,11 @@ run_test ()
     rm -f conftest conftest.err conftest.c
     cat - > conftest.c
     if run_compiler ; then
-        echo "$2 ="
+        if test "x$2" != x ; then
+            echo "$2 ="
+        fi
         echo "$3 = 1"
-    elif run_compiler "$1" ; then
+    elif test "x$1" != x && run_compiler "$1" ; then
         echo "$2 = $1"
         echo "$3 = 1"
     else
@@ -140,4 +142,29 @@ int main(int argc, char **argv) { return 0; }
 #endif
 EOF
 
+# Check for __builtin_cpu_supports("ssse3") and __attribute__((target("ssse3")))
+
+run_test '' '' HTS_HAVE_SSSE3_BUILTINS <<'EOF'
+#ifdef __x86_64__
+#include "x86intrin.h"
+__attribute__((target("ssse3")))
+static void shuffle(char *aptr, char *bptr) {
+    if (__builtin_cpu_supports("ssse3")) {
+        __m128i a = _mm_lddqu_si128((__m128i *)aptr);
+        __m128i b = _mm_shuffle_epi8(a, a);
+        _mm_storeu_si128((__m128i *)bptr, b);
+    }
+}
+
+int main(int argc, char **argv) {
+    char in[sizeof(__m128i)] = { 0 }, out[sizeof(__m128i)] = { 0 };
+    in[0] = argv[0][0];
+    shuffle(in, out);
+    return out[0];
+}
+#else
+int main(int argc, char **argv) { return 0; }
+#endif
+EOF
+
 rm -f conftest.c