[avr-libc-dev] Re: [bug #24231] AVR Mistakes Value in Register

[Chris Troutner]

I am compiling with optimization turned off. I couldn't find where in the
assembly that r1 gets assigned the value of one. However, it appeared to me
that the compiler expected register r1 to be zero, but when I simulate, it
always contains the value of 1 when I get to the breakpoint, before the
instruction "STS 0x0100, R1" is executed.

Chris

On Tue, Sep 9, 2008 at 3:44 PM, Weddington, Eric
<address@hidden>wrote:

>
>
> > -----Original Message-----
> > From: Chris Troutner [mailto:address@hidden
> > Sent: Tuesday, September 09, 2008 3:27 PM
> > To: Eric Weddington
> > Cc: Weddington, Eric; address@hidden
> > Subject: Re: [bug #24231] AVR Mistakes Value in Register
> >
> > I'm using the latest, 1.6.2 of AVR Libc. As to the rest, I'm
> > using whatever comes with the latest 20080610 release of WinAVR.
> >
> > I've noticed some discrepancy in simulation behavior in AVR
> > Studio between the Simulator, Simulator 2, and use of JTAG
> > mkII for emulation.
> >
> > If you set a break point at the "service = 0" line, and then
> > go to dissassebly when the simulator reaches that point, you
> > should see it call the "STS 0x0100,R1" instruction. Are you
> > not seeing it on your machine?
> >
> > I was able to get around it by using the instruction "service
> > &= ~(1<<0)".
> >
>
> One thing at a time.
> At this point I'm only concerned about the compiler, not the AVR Studio
> Simulator 1/2, or JTAG debugging.
>
> I see the instruction in e.g., the .lss file:
>                                 //Clear service variable
>                                service = 0;
>  230:   10 92 00 01     sts     0x0100, r1
>
> What I do *not* see in the assembly is r1 getting set to some other value
> other than 0. So I'm still not sure about your claim that this a compiler
> error.
>
> Are you compiling with -Os and then debugging? If so, then turn of
> optimizations by specifying -O0, and then debug.
>
> Can you find in the assembly where r1 gets set to 1?
>
>