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Re: [avr-gcc-list] AVR GCC Version 3.3 20030421 - taget mega128

From: Bruce D. Lightner (La Jolla Shores)
Subject: Re: [avr-gcc-list] AVR GCC Version 3.3 20030421 - taget mega128
Date: Thu, 07 Aug 2003 23:06:56 -0700


> > -----Original Message-----
> > From: address@hidden
> > [mailto:address@hidden Behalf Of Bruce D. Lightner
> > Sent: Friday, August 08, 2003 12:19 AM
> > To: Denis Chertykov; address@hidden
> > Cc: E. Weddington
> > Subject: Re: [avr-gcc-list] AVR GCC Version 3.3 20030421 - taget mega128
> ...
> > This likely explains differing behavior we saw for a large application
> > moved from and AT90S8515/ATmega8515 (under avr-gcc 2.95) to the
> > ATmega162L.  Lowering the gcc 3.3 optimization level causes the code to
> ...
> But this bug esits on the AT90S8515 as well.
> For clearness - fact that you move from the AT90S8515/ATmega8515 to the
> ATmega162L doesn't matter for that case. The key point is that you change
> compiler version.

True.  We moved from avr-gcc 2.95 to avr-gcc 3.3 because we had no
choice if we wanted to target the newer ATmega162.  This has always been
my complaint with "gcc"...high levels of optimization are sometimes
dangerous!  Of course, with a microcontroller, you typically need high
levels of optimization to get your application to fit.  I liked avr-gcc
2.95 because it was stable...it just took 95 tries to get "gcc version
2" right! :-)

BTW: The code size of our ~8 Kbyte application was reduced by about 15%
in switching from avr-gcc 2.95 to avr-gcc 3.3, using "-Os" in both
cases.  Unfortunately, the 15% smaller code with avr-gcc 3.3 is clearly
not quite correct!

Best regards,


  Bruce D. Lightner
  Lightner Engineering
  La Jolla, California
  Voice: +1-858-551-4011
  FAX: +1-858-551-0777
  Email: address@hidden
  URLs: http://www.lightner.net/lightner/bruce/

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