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

[Simon Clubley]

On 2015-08-20, VAXman-  @SendSpamHere.ORG <VAXman- at SendSpamHere.ORG> wrote:
> In article <mr4j0a$8ua$1 at dont-email.me>, Simon Clubley <clubley at remove_me.eisner.decus.org-Earth.UFP> writes:
>>On 2015-08-19, VAXman-  @SendSpamHere.ORG <VAXman- at SendSpamHere.ORG> wrote:
>>>
>>>     sp = (void *)asm("bis %r29,%r31,%r0;");	// get FP address                        
>>
>>It doesn't apply here because you are using the output from the asm()
>>insert, but if you use an asm() insert in gcc that doesn't have any
>>obvious side effects, then the gcc optimiser can remove the asm insert.
>
> Who said anything about 'gcc'?
>

As I said, I've no experience of what LLVM's optimiser will do with an
asm statement that doesn't have any obvious side effects. However, I do
know what gcc does, so I am commenting on the issues with gcc based on
the idea that similar issues may arise with LLVM's optimiser.

Simon.

-- 
Simon Clubley, clubley at remove_me.eisner.decus.org-Earth.UFP
Microsoft: Bringing you 1980s technology to a 21st century world