RFR: 8287393: AArch64: Remove trampoline_call1 [v2]

[Andrew Haley]

On Wed, 27 Jul 2022 10:54:26 GMT, Evgeny Astigeevich <duke at openjdk.org> wrote:

>> The addition is
>> `PhaseOutput* phase_output = Compile::current()->output();`
>> then
>> `phase_output != NULL && phase_output->in_scratch_emit_size()`
>> 
>> so AFAICS `Compile::current()->output()` is now checked for null, where it was not before.
>
> Now I get it. Thank you.
> 
> I agree this looks suspicious. I could not recall why I added it.
> Debugging helped me to find out.
> During the parsing phase of C2 compilation `ciTypeFlow::StateVector::do_invoke` causes `LinkResolver::resolve_static_call` which now has the following code:
> 
>   if (resolved_method->is_continuation_enter_intrinsic()
>       && resolved_method->from_interpreted_entry() == NULL) { // does a load_acquire
>     methodHandle mh(THREAD, resolved_method);
>     // Generate a compiled form of the enterSpecial intrinsic.
>     AdapterHandlerLibrary::create_native_wrapper(mh);
>   }
> 
> We generate a wrapper which is `nmethod` with trampoline calls.
> As we are in the parsing phase the output is not created.
> I can move `Compile::current()->output() != NULL` into the preceding IF and update the comment to the following:
> 
> Make sure this is code generation of a C2 compilation when Compile::current()->output() is not NULL.
> C2 can generate native wrappers for the continuation enter intrinsic before code generation.
> C1 allocates space only for trampoline stubs generated by Call LIR ops.

This is all rather complicated and obscure. It seems to me that passing a bool `check_emit_size` is exactly what we should do: it's more explicit and helps the reader.

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PR: https://git.openjdk.org/jdk/pull/9592