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

[Richard Earnshaw <rearnsha at gcc dot gnu dot org>]

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, 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.

R.

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