RFR: 8278079: C2: expand_dtrace_alloc_probe doesn't take effect in macro.cpp

[Denghui Dong]

On Fri, 3 Dec 2021 08:00:29 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

> > I think that explains why ciEnv need to cache DTrace flags before compilation, and _dtrace_method_probes/_dtrace_alloc_probes is set enabled if ExtendedDTraceProbes is true, so I think ExtendedDTraceProbes may still be useful, right?
> 
> Yes, it makes perfect sense that the flag values are cached but what I'm saying is that with your change, `-XX:+ExtendedDTraceProbes` degrades to an alias for `-XX:+DTraceMethodProbes -XX:+DTraceAllocProbes`. Maybe that's intended or am I missing something?

Yes, after the change, `-XX:+ExtendedDTraceProbes` is just an alias for `-XX:+DTraceMethodProbes -XX:+DTraceAllocProbes`, I think `ExtendedDTraceProbes` was originally designed for this purpose.

Or do you mean we should remove ExtendedDTraceProbes?

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PR: https://git.openjdk.java.net/jdk/pull/6639