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Re: [avr-libc-dev] [bugs #12040] sbi in FAQ

From: Erik Walthinsen
Subject: Re: [avr-libc-dev] [bugs #12040] sbi in FAQ
Date: Tue, 01 Mar 2005 00:17:09 -0800
User-agent: Debian Thunderbird 1.0 (X11/20050116)

David Brown wrote:
> The first case here asks the compiler to set two bits
high at the same time, and it does that - something that cannot be expressed
with sbi/cbi.  The second case asks the compiler to set the bits one after
the other, and again it provides optimal correct code.  I can't see how the
compiler could produce anything better.

Yes, you're right. Sorry, I was trying to make a point in frustration and latched onto a bad example.

I'm currently drafting avr/bits.h mostly as per E. Weddington's initial spec, and an RFC explaining it. I'm putting a significant amount of information in the documentation regarding the use of various bit-twiddling method and their various side effects, such as those mentioned above. I hope to get it posted tonight, but it's already past midnight, we'll see.

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