Subject: Re: Possible bug in arm32 strongarm optimisations.
To: David Brownlee <abs@netbsd.org>
From: Richard Earnshaw <rearnsha@arm.com>
List: tech-toolchain
Date: 11/02/2000 09:48:08
> On Tue, 31 Oct 2000, Richard Earnshaw wrote:
>
> > > > The solution is to use -mcpu=arm7m -mtune=strongarm.
> > > >
> > >
> > > Just to confirm - that is more appropriate than mcpu=armv4?
> > >
> >
> > Yes; -mcpu=armv4 will produce code that can run incorrectly on Acorn
> > machines since the bus cannot handle half-word operations. (This includes
> > machines fitted with Kinetic cards -- since even these need to access the
> > system bus at times).
>
> Sorry - typo, I meant to ask if that is more appropriate than
> armv3m.
>
Ah! Makes more sense now (and I also note I made a small mistake in my
reply, since -mcpu doesn't accept an architecture name). It's better to
use the name of the CPU architecture with the -march flag than the -mcpu
flag. Think of
-mcpu=foo
as being short-hand for
-march=archof<foo> -mtune=foo
So what you have above is, in effect, two -mtune options.
So in this case you want
-march=armv3m -mtune=strongarm
Hope this is all clearer now,
Richard.