When built with the April 2005 Platform SDK on AMD64 with /O2, Hotspot fails a number of NSK tests (the complete list is attached). The failures are due to the PSDK optimizing compiler generating bad code for CompressedLineNumberWriteStream::write_pair. As a result when line number tables are read from class files, every line number is mapped to a bci of 0, causing problems when the JDI tests try to set breakpoints.