7005241: C1: SEGV in java.util.concurrent.LinkedTransferQueue.xfer() with compressed oops Summary: Implementation of the CAS primitive for x64 compressed oops was incorrect. It kills rscratch2 register (r11), which is allocatable in C1. Also, we don't need to restore cmpval as it's never used after that, so we need only one temporary register, which can be scratch1. Reviewed-by: kvn, never