diff -r bbe0fcde6e13 -r 2de7fe0e9693 hotspot/src/cpu/sparc/vm/c1_Runtime1_sparc.cpp
--- a/hotspot/src/cpu/sparc/vm/c1_Runtime1_sparc.cpp	Wed Oct 09 16:32:21 2013 +0200
+++ b/hotspot/src/cpu/sparc/vm/c1_Runtime1_sparc.cpp	Fri Oct 11 10:14:02 2013 -0700
@@ -1067,6 +1067,25 @@
 
   __ verify_not_null_oop(Oexception);
 
+#ifdef ASSERT
+  // check that fields in JavaThread for exception oop and issuing pc are
+  // empty before writing to them
+  Label oop_empty;
+  Register scratch = I7;  // We can use I7 here because it's overwritten later anyway.
+  __ ld_ptr(Address(G2_thread, JavaThread::exception_oop_offset()), scratch);
+  __ br_null(scratch, false, Assembler::pt, oop_empty);
+  __ delayed()->nop();
+  __ stop("exception oop already set");
+  __ bind(oop_empty);
+
+  Label pc_empty;
+  __ ld_ptr(Address(G2_thread, JavaThread::exception_pc_offset()), scratch);
+  __ br_null(scratch, false, Assembler::pt, pc_empty);
+  __ delayed()->nop();
+  __ stop("exception pc already set");
+  __ bind(pc_empty);
+#endif
+
   // save the exception and issuing pc in the thread
   __ st_ptr(Oexception,  G2_thread, in_bytes(JavaThread::exception_oop_offset()));
   __ st_ptr(Oissuing_pc, G2_thread, in_bytes(JavaThread::exception_pc_offset()));