I'd say that black box means that the compiler can *not* tell.

--
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3

________________________________________
From: IBM Mainframe Assembler List [[email protected]] on behalf 
of Peter Relson [[email protected]]
Sent: Wednesday, November 24, 2021 8:39 AM
To: [email protected]
Subject: Re: Curious compiler optimization

<snip>
> In general the rule is if the compiler can see that
> there is no dependency on any code,
> the compiler is allowed to prune it.

Which is a different rule from "if the compiler can not see that there is
a dependency on any code , the compiler is allowed to prune it." The
second applies to the code, but not the first.
</snip>

True. But one might say that the treating of the __asm text as a black box
does mean that the compiler can "tell" -- basing its "knowledge" on the
user input.

Peter Relson
z/OS Core Technology Design

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