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RE: [avr-gcc-list] Problem with delay loop

From: Eric Weddington
Subject: RE: [avr-gcc-list] Problem with delay loop
Date: Tue, 02 Oct 2007 07:01:20 -0600

> -----Original Message-----
> From:
> address@hidden
> [mailto:address@hidden
> org] On Behalf Of David Brown
> Sent: Tuesday, October 02, 2007 2:48 AM
> Subject: Re: [avr-gcc-list] Problem with delay loop
> Graham Davies wrote:
> > Eric Weddington wrote:
> >> ... We were discussing the possibility of the compiler being
> >> smarter about 'volatile' and local automatic variables. I would
> >> definitely say that if the local variable's address is taken, then
> >> all bets are off.
> >
> > Second point first.  If the address of a variable is taken then the
> > compiler cannot put it in a register.  If it is declared automatic,
> > it goes on the stack, if there is one, or somewhere else in
> memory if
> > there
> Actually, you're slightly wrong on both accounts here.  On
> the AVR, the
> registers are available in the memory map, so it is possible to take
> their addresses (it's not commonly done, except perhaps on the old
> RAM-less Tiny's, but it's possible).

True. However in practice, I don't think the AVR port in GCC is aware of
these aliases and I don't think that it will use them.

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