1 files changed, 93 insertions, 0 deletions
diff --git a/gcc/testsuite/gcc.dg/simulate-thread/subfields.c b/gcc/testsuite/gcc.dg/simulate-thread/subfields.c
new file mode 100644
index 00000000000..2d931176e7d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/simulate-thread/subfields.c
@@ -0,0 +1,93 @@
+/* { dg-do link } */
+/* { dg-options "--param allow-packed-store-data-races=0" } */
+/* { dg-final { simulate-thread } } */
+
+#include <stdio.h>
+#include "simulate-thread.h"
+
+/* This test verifies that data races aren't introduced by structure subfield 
+   stores. */
+
+struct test_struct {
+  char a;
+  char b;
+  char c;
+  char d;
+} var = {0,0,0,0};
+
+
+/* This routine sets field a to 'x'.  If executed properly, it will
+   not affect any of the other fields in the structure.  An improper
+   implementation may load an entire word, change the 8 bits for field
+   'a' and write the entire word back out. */
+__attribute__((noinline))
+void set_a(char x)
+{
+  var.a = x;
+}
+
+static int global = 0;
+
+/* The other thread increments the value of each of the other fields
+   in the structure every cycle.  If the store to the 'a' field does
+   an incorrect full or partial word load, mask and store, it will
+   write back an incorrect value to one or more of the other
+   fields.  */
+void simulate_thread_other_threads() 
+{
+  global++;
+  var.b = global;
+  var.c = global;
+  var.d = global;
+}
+
+
+/* Make sure that none of the other fields have been changed.  */
+int simulate_thread_step_verify()
+{
+  int ret = 0;
+  if (var.b != global)
+    {
+      printf("FAIL: Unexpected value. var.b is %d, should be %d\n",
+	     var.b, global);
+      ret = 1;
+    }
+  if (var.c != global)
+    {
+      printf("FAIL: Unexpected value. var.c is %d, should be %d\n",
+	     var.c, global);
+      ret = 1;
+    }
+  if (var.d != global)
+    {
+      printf("FAIL: Unexpected value. var.d is %d, should be %d\n",
+	     var.d, global);
+      ret = 1;
+    }
+  return ret;
+}
+
+/* Verify that every variable has the correct value.  */
+int simulate_thread_final_verify()
+{
+  int ret = simulate_thread_step_verify();
+  if (var.a != 1)
+    {
+      printf("FAIL: Unexpected value. var.a is %d, should be %d\n", var.a, 1);
+      ret = 1;
+    }
+  return ret;
+}
+
+__attribute__((noinline))
+void simulate_thread_main()
+{
+  set_a(1);
+}
+
+int main ()
+{
+  simulate_thread_main();
+  simulate_thread_done();
+  return 0;
+}