Add mt-helloworld example

tests/mt-hello.c

@@ -0,0 +1,48 @@
+#include "encoding.h"
+#include <stdio.h>
+#include "marchid.h"
+
+// EDIT THIS
+static size_t n_cores = 4;
+
+static void __attribute__((noinline)) barrier()
+{
+  static volatile int sense;
+  static volatile int count;
+  static __thread int threadsense;
+
+  __sync_synchronize();
+
+  threadsense = !threadsense;
+  if (__sync_fetch_and_add(&count, 1) == n_cores-1)
+  {
+    count = 0;
+    sense = threadsense;
+  }
+  else while(sense != threadsense)
+    ;
+
+  __sync_synchronize();
+}
+
+void __main(void) {
+  size_t mhartid = read_csr(mhartid);
+
+  if (mhartid >= n_cores) while (1);
+
+  const char* march = get_march(read_csr(marchid));
+  for (size_t i = 0; i < n_cores; i++) {
+    if (mhartid == i) {
+      printf("Hello world from core %lu, a %s\n", mhartid, march);
+    }
+    barrier();
+  }
+
+  // Spin if not core 0
+  if (mhartid > 0) while (1);
+}
+
+int main(void) {
+  __main();
+  return 0;
+}