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

[Denghui Dong]

On Thu, 2 Dec 2021 12:41:15 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

> But isn't the intention of this code to always go to the slow path when `DTraceAllocProbes` is true (hence the `expand_fast_path = false;`) and apply dtrace probes in the runtime?

C->env()->dtrace_alloc_probes() return true if ExtendedDTraceProbes is enabled(see ciEnv::cache_dtrace_flags()), which means PhaseMacroExpand::expand_dtrace_alloc_probe always doesn't take effect now.

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