[perl #59628] Calling 'Parrot_runops_fromc_args*' from within 'Parrot_pcc_invoke*' corrupts return signature

[Andrew Whitworth via RT]

I've seen a very similar issue when calling Parrot_run_method_fromc_args
and variants from inside a call to Parrot_PCCINVOKE or
Parrot_pcc_invoke_method_from_c_args. As part of the ongoing calling
conventions refactors, all calls to Parrot_run_sub_*,
Parrot_run_method_*, and probably calls to Parrot_runops_* will all be
replaced by calls to Parrot_pcc_invoke_method_from_c_args,
Parrot_pcc_invoke_sub_from_c_args, and
Parrot_pcc_invoke_from_sig_object, which I've found (see TT #321) to
resolve the issues.

We do run into an issue when making these translations, however, when we
talk about passing key arguments. Keys can contain, instead of direct
values, a reference to a register in the current context. Syntax like this:

 p[$S0, $I0]

in PIR actually takes a reference to $S0 and $I0 instead of resolving
those registers to their values immediately. In Parrot_run_method_* and
related functions, the values are attempting to be passed before a new
context is created for the callee. In Parrot_pcc_invoke_* functions, the
parameters are passed after the new context is created, causing he
register references to point to the wrong registers. I'm currently
working to resolve that issue, and will probably file a separate ticket
for it at trac.

Will post updates here as they come.