Add ifunc demo

src/ifunc.c

+#include <stdio.h>
+#include <stdlib.h>
+
+static void
+func (void) __attribute__((ifunc ("resolve_func")));
+
+static void
+func_base (void)
+{
+    puts ("Base");
+}
+
+static void
+func_avx2 (void)
+{
+    puts ("AVX2");
+}
+
+// declare resolve_func as static function (void) returning pointer to function (void) returning void
+static void
+(*resolve_func (void)) (void)
+{
+    __builtin_cpu_init ();
+
+    if (__builtin_cpu_supports ("avx2"))
+        return func_avx2;
+    else
+        return func_base;
+}
+
+int
+main (void)
+{
+    func ();
+
+    return 0;
+}

src/meson.build

@@ -33,6 +33,10 @@ if has_endian_h
   executable('bytedouble', 'bytedouble.c')
 endif
 
+if host_machine.cpu_family() == 'x86_64' and cc.has_function_attribute('ifunc')
+  executable('ifunc', 'ifunc.c')
+endif
+
 if openmp_dep.found()
     subdir('openmp')
 endif