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[avr-gcc-list] Re: char to int promotion in bitwise operators

From: David Brown
Subject: [avr-gcc-list] Re: char to int promotion in bitwise operators
Date: Mon, 24 Aug 2009 15:04:27 +0200
User-agent: Thunderbird (Windows/20090605)

Weddington, Eric wrote:

-----Original Message----- From: address@hidden [mailto:address@hidden org]
On Behalf Of address@hidden Sent: Friday, August 21, 2009
4:39 PM To: address@hidden; address@hidden Subject:
Re: [avr-gcc-list] char to int promotion in bitwise operators

Gcc does not permit backends to control optimization pass order.

I don't see any reason why we cannot apply an AVR-specific patch,
post-release to all distributions, that changes the pass order as we
see fit. As long as it works properly for our needs.

Has anyone versed in avr-gcc development looked at the new plugin architecture in gcc 4.5 ? To my limited understanding, it is (or will be) possible for a plugin to change the pass order:


The hope with the plugins is that it will make it easier and faster to develop gcc, and it would allow such changes to be done as a plugin rather than needing open-heart surgery on the gcc pass manager internals. Surely that would also make it easier to maintain these changes between gcc versions.

I would hope it is also possible to use plugins to allow extra peephole optimisations to be written and tested externally to gcc, allowing much easier and faster testing than rebuilding gcc for each change. Well-proven peepholes could then be moved back into the main gcc code for efficiency.



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