Re: [PATCH v2 6/6] sim/common: Fix issue with wrong byte order on BE targets

[Andrew Burgess <andrew dot burgess at embecosm dot com>]

* Stafford Horne <shorne@gmail.com> [2019-04-13 05:21:45 +0900]:

> Hi Andrew,
> 
> On Thu, Apr 11, 2019 at 11:27:49PM +0100, Andrew Burgess wrote:
> > * Stafford Horne <shorne@gmail.com> [2019-04-10 06:39:25 +0900]:
> > 
> > > Currently only the OpenRISC sim uses this JOINSIDF() function to compose a
> > > double float from 2 registers.  The old code doesn't seem to work as the
> > > work order gets swapped when running on a x86_64 host.  This change
> > > fixes that, but I am not sure if its the best thing to do.
> > > 
> > > On mips they do similar reg pair floating point operations composing
> > > doubles from 2 32-bit registers in sim/mips/cp1.c value_fpr().
> > > 
> > > sim/common/ChangeLog:
> > > 
> > > 	* cgen-ops.h (JOINSIDF): Fix big endian check.
> > > ---
> > >  sim/common/cgen-ops.h | 8 ++------
> > >  1 file changed, 2 insertions(+), 6 deletions(-)
> > > 
> > > diff --git a/sim/common/cgen-ops.h b/sim/common/cgen-ops.h
> > > index 841552066f..d718394723 100644
> > > --- a/sim/common/cgen-ops.h
> > > +++ b/sim/common/cgen-ops.h
> > > @@ -431,12 +431,8 @@ JOINSIDI (SI x0, SI x1)
> > >  SEMOPS_INLINE DF
> > >  JOINSIDF (SI x0, SI x1)
> > >  {
> > > -  union { SI in[2]; DF out; } x;
> > > -  if (CURRENT_TARGET_BYTE_ORDER == BFD_ENDIAN_BIG)
> > 
> > I think this is the problem with the existing code, we're using memory
> > on the HOST to perform packing / unpacking, and so its the byte
> > ordering of the HOST that we care about here, not the target.
> > 
> > If I change the above line to instead be:
> > 
> >      if (HOST_BYTE_ORDER == BFD_ENDIAN_BIG)
> > 
> > then everything works fine.
> > 
> > On inspection I believe all of the uses of CURRENT_TARGET_BYTE_ORDER
> > in this file should be similarly replaced.
> > 
> > I've attached a patch for this change.  If you agree I'll go ahead and
> > push it.
> 
> I tested this with the or1k testsuite and it does seem to work fine, thank you.
> Please go ahead.
> 
> I thought I had tried this fix as well, I guess not.

Thanks for testing this.

I've pushed this patch now.

Andrew