--- a/src/cpu/x86/vm/interp_masm_x86_64.cpp	Mon Aug 20 15:21:31 2012 +0200
+++ b/src/cpu/x86/vm/interp_masm_x86_64.cpp	Tue Aug 21 10:39:19 2012 +0200
@@ -256,8 +256,12 @@
   // little-endian machines allow us that.
   movl(bytecode, Address(cache, index, Address::times_ptr, constantPoolCacheOopDesc::base_offset() + ConstantPoolCacheEntry::indices_offset()));
   const int shift_count = (1 + byte_no) * BitsPerByte;
+  assert((byte_no == TemplateTable::f1_byte && shift_count == ConstantPoolCacheEntry::bytecode_1_shift) ||
+         (byte_no == TemplateTable::f2_byte && shift_count == ConstantPoolCacheEntry::bytecode_2_shift),
+         "correct shift count");
   shrl(bytecode, shift_count);
-  andl(bytecode, 0xFF);
+  assert(ConstantPoolCacheEntry::bytecode_1_mask == ConstantPoolCacheEntry::bytecode_2_mask, "common mask");
+  andl(bytecode, ConstantPoolCacheEntry::bytecode_1_mask);
 }