RFR: 8143730 [JVMCI] infopoint recording is too restrictive

[Doug Simon]

JVMCI compilers can optionally record extra debug info for compiled code in addition to the debug info required for safepoints, calls and exceptions. This is the kind of extra information recorded for  -XX:+DebugNonSafepoints. Currently, CompilationResult only allows one piece of debug info to be recorded per machine code position. This means the compiler has to insert extra no-ops if it does not want to discard any of the extra debug info. 

The proposed change here is to relax the constraint in the VM independent JVMCI code. If the VM only supports one piece of debug info per machine code position, it should have local logic to decide which of multiple debug infos to record when installing code.

https://bugs.openjdk.java.net/browse/JDK-8143730
http://cr.openjdk.java.net/~dnsimon/8143730/