configure.ac: Fail the ARM/iwMMXt test if not compiling with -march=iwmmxt

If not compiling with -march=iwmmxt, the configure test will still pass,
thinking that the __builtin_arm_* intrinsic is a function instead of
generating a single instruction. Since no linking is done, the configure
test doesn't catch this, and we get linking errors in the build.

diff --git a/configure.ac b/configure.ac
index 5ff78eb..027a168 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -619,6 +619,9 @@ AC_COMPILE_IFELSE([AC_LANG_SOURCE([[
 #ifndef __arm__
 #error "IWMMXT is only available on ARM"
 #endif
+#ifndef __IWMMXT__
+#error "IWMMXT not enabled (with -march=iwmmxt)"
+#endif
 #if defined(__GNUC__) && (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 5))
 #error "Need GCC >= 4.5 for IWMMXT intrinsics"
 #endif