When does Stored Procedure execution plan get determined?

[Robert Rothkopf]

In SQL Server, Stored Procedure (SP) execution plans are saved at compile time and used whenever the SP is invoked, even if SP parameters in subsequent calls would make a different execution plan more efficient. Using WITH RECOMPILE forces new plans to be considered with each call.

Per MySQL docs, there is no equivalent "with recompile".

So my question is: "does MySQL reevaluate the execution plans within an SP each time it is called, or are they saved when the SP is first loaded (or first called) and always used regardless of new and changing parameters?"

I've searched the docs, Web and forum and can't find info on this.