This enhancement was reported by Yuta Sato ( @yuu1127 ) on GitHub PR.

When using Compiler Directive such as java -XX:+UnlockDiagnosticVMOptions -XX:CompilerDirectivesFile=<CompilerDirectives.json> <Java.class> ,
it shows totally the same message for c1 and c2 compiler and the user would be confused about
which compiler is affected by this message.
This should show messages with their compiler name so that the user knows which compiler shows this message.

My change result would be like the below.

OpenJDK 64-Bit Server VM warning: printing of assembly code is enabled; turning on DebugNonSafepoints to gain additional output
OpenJDK 64-Bit Server VM warning: printing of assembly code is enabled; turning on DebugNonSafepoints to gain additional output

->

OpenJDK 64-Bit Server VM warning: c1: printing of assembly code is enabled; turning on DebugNonSafepoints to gain additional output
OpenJDK 64-Bit Server VM warning: c2: printing of assembly code is enabled; turning on DebugNonSafepoints to gain additional output