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

From: David Brown
Subject: [avr-gcc-list] Re: optimizer removes volatile pin access code. why?
Date: Wed, 28 Oct 2009 16:51:23 +0100
User-agent: Thunderbird (Windows/20090812)

Erik Christiansen wrote:
On Wed, Oct 28, 2009 at 02:08:05PM +0100, Joerg Desch wrote:
I've played with "inline" and with "__attribute__((gnu_inline,
always_inline))" to avoid this overhead, but it doesn't work as expected.

#if defined(__GNUC__)
#  define ALLWAYS_INLINE inline __attribute__((gnu_inline, always_inline))
ALLWAYS_INLINE int foo (void)
  // ...

I've tried it with -Os and foo() is still called.

Was this from a mail from Joerg Desch that did not make it to the mailing list? It is hard for others to comment - perhaps you or Joerg could re-post the problem code.

Ah, yes, optimisation needs to be used for inline to work. If the above
fails on a small test case, "avr-gcc -v" and the command-line don't show
a lurking "-fno-inline", and "-Wall -Wextra" doesn't provide any clues
either, I'd pretty soon be tempted to report it as a bug, unless a magic
method is revealed on the list. You've probably tried other
optimisations? (Just in case the size optimisation is absolute in its

I believe you need the -Winline to get a warning about functions declared "inline" that could not be inlined.

And an __attribute_((always_inline)) function will be inlined, regardless of the optimisation levels.

As you can see it receives in the list. But with 1/2 hour delay.

Oh goody, it works again! :-)


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