[Info-vax] Volatile, was: Re: yet another sys$qiow question

[Simon Clubley]

On 2015-08-24, George Cornelius <cornelius at eisner.decus.org> wrote:
> [VAXMAN wrote:]
>
>>> 	TSTL	IOSB
>>> 	BNEQ	10$
>>> 20$:	BRB	20$
>>> 10$:
>
> Actually, to test just the status in VMS you would use TSTW.  But
> when testing for nonzero TSTL works as well and does not require
> any extra word extraction code on the newer architectures.
>

BTW, on ARM you can conditionally execute the following instructions
(not just jumps) based on the last test you did so no messy jumping
such as the above is required if you are doing something a bit more
more complicated than the above.

However, I have a question about the above code. First off, it's been
a couple of decades since I last wrote some MACRO-32 code so go easy
if I've got this wrong. :-)

Brian wrote:
	TSTL	IOSB
	BNEQ	10$
20$:	BRB	20$
10$:

Couldn't you make that more efficient with:

	TSTL	IOSB
10$:
	BEQ	10$	; Or whatever branch if equal to zero is on VAX

It's not important; I'm just curious as that style is something which
works on ARM just fine. I was just wondering if there's something on
VAX I've forgotten about which stops the above from being usable.

BTW, I wish the x86 was as elegant as ARM...

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
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