diff -r 53028d751155 -r e961c11b85fe src/cpu/x86/vm/stubGenerator_x86_32.cpp
--- a/src/cpu/x86/vm/stubGenerator_x86_32.cpp	Tue Apr 02 09:30:07 2013 +0200
+++ b/src/cpu/x86/vm/stubGenerator_x86_32.cpp	Wed Apr 03 11:12:57 2013 -0700
@@ -835,6 +835,11 @@
   __ BIND(L_copy_64_bytes);
     __ subl(qword_count, 8);
     __ jcc(Assembler::greaterEqual, L_copy_64_bytes_loop);
+
+    if (UseUnalignedLoadStores && (UseAVX >= 2)) {
+      // clean upper bits of YMM registers
+      __ vzeroupper();
+    }
     __ addl(qword_count, 8);
     __ jccb(Assembler::zero, L_exit);
     //