Extract precompile_inlinable_child_iseq to separate alloca for each iseq

[nobu]

No description provided.

[k0kubun]

separate alloca for each iseq

Could you elaborate more on this? Are you saying calling the same alloca multiple times in a single function call may cause problems? I'm not against carving out the function, but for future refactoring, I'd like to confirm whether it's mandatory or not.

[k0kubun]

Ah, I guess alloca continues to allocate another buffer instead of re-using the same buffer used by the previous alloca call, and the only way to release a buffer allocated by alloca is leaving a function that called it? Then this PR makes sense.

[nobu]

Yes, that's right.