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Re: [avr-gcc-list] Optimizer bug, again?

From: David Brown
Subject: Re: [avr-gcc-list] Optimizer bug, again?
Date: Tue, 08 Apr 2008 13:32:00 +0200
User-agent: Thunderbird (Windows/20080213)

Erik Zane wrote:
I'm working on Ubuntu, and I've downloaded GCC 4.3.0 and applied all the patches delivered with WinAVR, and it appears that there is what could be a reappearance of an optimization bug. Is the distribution missing a patch, or do I have to start trying to figure out where my code is broken.

My problem seems to occur when I try to send a message to my application requesting a USART bitrate change. If I had to hazard a guess, it seems that the target has a hard time dealing with the 32-bit data and generates a bad value for UBRR register. Once that happens, it's time to reset. Unfortunately, one of my applications is essentially a 4-way soft UART, which gets the problem doubled.

For the record, it seems fine if I compile with -O0 on 4.3.0, and I still have one of my PCs with a 4.2.2 avr-gcc in which I compiled doing the same as I did above for 4.3.0, and anything of mine compiled with that continues to work. as expected.

Can you isolate the problem and post minimal sample code illustrating the effect? There is almost no way anyone can help without such details.

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