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Re: [avr-libc-dev] Inline assembler and compiler optimization


From: Joerg Wunsch
Subject: Re: [avr-libc-dev] Inline assembler and compiler optimization
Date: Mon, 23 Mar 2009 23:27:17 +0100
User-agent: Mutt/1.5.11

As Weddington, Eric wrote:

> > Likewise, the same goes for using nop(), as tempting as it is.
> > Again, _NOP() would be fine, as will __nop().

> Hmm. I think that might be included as part of the new builtins for
> the AVR port.

I don't think there's a reason to have that as a builtin, when it can
be so conveniently had as an inline asm statement.  That's much
different from __delay_cycles.

(JTD bit)

> We definitely need to create an API for this, and all other timed
> sequences. There are a number of timed sequences in the xmega chips
> that need to be added.

> I know you don't care too much about xmega, because of inability to
> program it with avrdude. But a visual inspection of the resulting
> code from an inline assembly macro would be good enough for me.

OK.

> > If we decide for a new header file, how to name it?  <avr/asm.h>?
> > <avr/misc.h>?

> I don't like misc as it is too vague.

Then why not <avr/asm.h> or <avr/asmbits.h>?  Linux and FreeBSD ship
that kind of inline asm stuff in similarly named headers.

> For the JTD timed sequence, why not a new <avr/jtag.h> file? It
> doesn't matter to me that it may only have one macro in it. At least
> it would be easy to remember.

Well, it would rather be <avr/nojtag.h> :).  Rather something like
<avr/mcufeatures.h> or such.  After all, it's about MCUCR/MCUCSR.

-- 
cheers, J"org               .-.-.   --... ...--   -.. .  DL8DTL

http://www.sax.de/~joerg/                        NIC: JW11-RIPE
Never trust an operating system you don't have sources for. ;-)




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