ldrb vs ldrh in gcc-3.4.4 (ARM)
Richard Earnshaw
rearnsha@gcc.gnu.org
Thu Aug 18 08:32:00 GMT 2005
On Thu, 2005-08-18 at 09:07, Steven Scholz wrote:
> Steven Scholz wrote:
>
> > Richard,
> >
> >>> Thanks a million. Maybe you could explain the difference of arm920t
> >>> and arm9tdmi as well, please?
> >>
> >>
> >>
> >> The arm9tdmi is the main 'core' of the CPU. The arm920t is the core
> >> plus the associated cache, mmu, and system registers. Different models
> >> all have substantially the same 'core' but may have different (or
> >> missing) additional parts...
> >
> >
> > Thanks. So when I am using Freescale i.MX and Atmel AT91RM9200 which are
> > both arm920t I rather use
> >
> > GCC_EXTRA_CONFIG="--with-float=soft --with-cpu=arm920t \
> > --enable-cxx-flags=-mcpu=arm920t"
> >
> > instead of
> >
> > GCC_EXTRA_CONFIG="--with-float=soft --with-cpu=arm9tdmi \
> > --enable-cxx-flags=-mcpu=arm9tdmi"
> >
> > when building the toolchain. Right?
>
> ARGH! There's no "--with-cpu=arm920t" !
>
This has been fixed in gcc-4.0 and it's also been fixed in the
CodeSourcery version of 3.4
(http://www.codesourcery.com/gnu_toolchains/arm/).
> gcc/config/arm/arm.h only knows
>
> #define TARGET_CPU_arm9 0x0080
> #define TARGET_CPU_arm9tdmi 0x0080
>
> So when arm9tdmi is only thre core without caches will "--with-cpu=arm9tdmi" use
> the caches in a sane way ?
It probably makes no difference in 3.4 and earlier. It might have a
small effect in later versions, but gcc doesn't really understand caches
and their layout yet.
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