RFR(XS): 7198074: NPG: assert(((Metadata*)obj)->is_valid()) failed: obj is valid

[Vladimir Kozlov]

Good.

Vladimir

Roland Westrelin wrote:
> http://cr.openjdk.java.net/~roland/7198074/webrev.00/
> 
> The C1 register allocator allocates O7 to a piece of tiered compilation profiling code due to a missing test for T_METADATA in LinearScanWalker::pd_init_regs_for_alloc() following changes for 7195816. O7 should never be allocated by the register allocator. O7 is used to contain a Method pointer. A counter overflows, the profiling code calls the runtime, it moves O7 to another register in the shadow of the call and because O7 is used to keep the return address of the call, the Method pointer is overwritten with an address in the code. So when the runtime code tries to manipulate the Method pointer, something bad happens.
> 
> Roland.