Re: ARM: Forcing halfword operation for (short *)?

[Toralf Lund <toralf at procaptura dot com>]

Richard Earnshaw wrote:

> On Tue, 2004-11-09 at 15:22, Toralf Lund wrote:
>  
>
> > Sigh... Another problem with my ARM setup, after trying to access some 
> > additional hardware... Seems like I still have a lot to learn about the 
> > fine level of control over I/O-operations...
> >
> > Anyhow, the problem this time is the access size of a specific write 
> > operation. Consider the following function, which is a simplified 
> > version of one actually appearing in my application:
> >
> > int eraseTest()
> > {
> >  volatile unsigned short *sector=(unsigned short *)0x10000000;
> >
> >  *sector=(unsigned short )0x0030;
> > }
> >
> > The code generated for this is (from 'objdump -d' output):
> >    
>
>  
>
> > [sample code indicating use or strb]
> >    
>
> You need to tell the compiler that you are running the code on a core
> that has half-word memory instructions.  Early ARM processors did not
> have these instructions,
Yes. I didn't know that, although like I just said in another 
followup-message, I actually noticed the manual page mentioning this 
when I re-read it after posting the original question.

> and the default for some gcc configurations
> assume this restriction.
>
> If you know the CPU you will be running the code on you can use
> -mcpu=<name> when compiling.  See the manual for the list of known CPUs
> (it's a long list these days).  If you don't see an exact match, there's
> usually one that will be close enough for your purposes.
>  
Yup. "-mcpu=arm9" helps!

> R.
>
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>  



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