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[avr-gcc-list] Re: optimizer removes volatile pin access code. why?

From: Joerg Desch
Subject: [avr-gcc-list] Re: optimizer removes volatile pin access code. why?
Date: Wed, 28 Oct 2009 07:22:19 +0100

On Tue, 27 Oct 2009 20:17:46 +0100 (MET)
address@hidden (Joerg Wunsch) wrote:

> How did you verify it?

First I can't see the pulse on the oscilloscope ;-)

Than I had a look in the list file.

> I don't believe the compiler removed the code.  (If you really think
> it does, please supply a compilable code example.)

Give me some time. I try to put it in a simple snippet. Is it OK to
attach it as tgz to this mailing list?

> However, the
> optimized code will just toggle the pin for a single CPU cycles only,
> while the pin will stay a little longer at high in the non-optimized
> example.  So if your oscilloscope is too slow, you might not notice
> the pin actually becoming high for one clock period.

Tektroniks TDS784 with 4GS/s ;-)

Email: Joerg Desch <jd DOT vvd AT web DOT de>

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