RE: [PATCH,MIPS] Only pass floating-point options to the assembler then

[Matthew Fortune <Matthew dot Fortune at imgtec dot com>]

Moore, Catherine <Catherine_Moore@mentor.com> writes:
> > -----Original Message-----
> > From: Matthew Fortune [mailto:Matthew.Fortune@imgtec.com]
> > Sent: Monday, January 19, 2015 5:54 PM
> > To: Moore, Catherine
> > Cc: 'gcc-patches@gcc.gnu.org' (gcc-patches@gcc.gnu.org)
> > Subject: RE: [PATCH,MIPS] Only pass floating-point options to the
> > assembler then
> >
> > Hi Catherine,
> >
> > > The new behaviour of the GCC driver passing floating point options
> > > like -msoft-float to the assembler is essential for the new o32 ABI
> > > extensions but is a change in behaviour. In particular GCC 5 used
> > > with binutils 2.24 would require a user to fix any hand-crafted code
> > > that made use of floating-point instructions when building for soft-
> float.
> > > This patch limits the new behaviour to a combination of GCC and
> > > binutils that both have the new ABI support.
> > >
> > > This patch along with parts of several previous patches need
> > > backporting to GCC 4.9 (and GCC 4.8) to enable use of binutils 2.25
> > > with those compilers. The GCC 4.9 patch will be posted shortly.
> >
> > I'm not sure if you missed this patch last week or if you are unsure
> about it?
> > Since this is about restoring previous behaviour of MIPS GCC when
> > built alongside binutils <= 2.24 I believe this still fits with stage4
> criteria.
> >
> Hi Matthew,
> I didn't miss it, but I wanted to complete some testing with it.  Those
> tests have now completed and this patch is OK.
> Sorry for the delay.

No problem, just getting it resolved early so I can focus on bug hunting
and fixing. Thanks for doing some testing on it.

I'm going to try writing up the main MIPS changes for the GCC 5 changes
webpage. I'll send a list to you once I've been through the code changes.

Thanks,
Matthew

> Thanks,
> Catherine
> 
> > >
> > > gcc/
> > > 	* config/mips/mips.h (FP_ASM_SPEC): New define.
> > > 	(ASM_SPEC): Remove floating-point options and use FP_ASM_SPEC
> > > 	instead.
> > > ---
> > >  gcc/config/mips/mips.h | 21 ++++++++++++++++++---
> > >  1 file changed, 18 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/gcc/config/mips/mips.h b/gcc/config/mips/mips.h index
> > > 37d4cb4..ed241fa 100644
> > > --- a/gcc/config/mips/mips.h
> > > +++ b/gcc/config/mips/mips.h
> > > @@ -1243,6 +1243,22 @@ struct mips_cpu_info {  %{gcoff*:-mdebug}
> > > %{!gcoff*:-no-mdebug}"
> > >  #endif
> > >
> > > +/* FP_ASM_SPEC represents the floating-point options that must be
> > > passed
> > > +   to the assembler when FPXX support exists.  Prior to that point
> the
> > > +   assembler could accept the options but were not required for
> > > +   correctness.  We only add the options when absolutely necessary
> > > +   because passing -msoft-float to the assembler will cause it to
> > > reject
> > > +   all hard-float instructions which may require some user code to
> be
> > > +   updated.  */
> > > +
> > > +#ifdef HAVE_AS_DOT_MODULE
> > > +#define FP_ASM_SPEC "\
> > > +%{mhard-float} %{msoft-float} \
> > > +%{msingle-float} %{mdouble-float}"
> > > +#else
> > > +#define FP_ASM_SPEC
> > > +#endif
> > > +
> > >  /* SUBTARGET_ASM_SPEC is always passed to the assembler.  It may be
> > >     overridden by subtargets.  */
> > >
> > > @@ -1277,9 +1293,8 @@ struct mips_cpu_info {  %{modd-spreg} %{mno-
> > odd-
> > > spreg} \  %{mshared} %{mno-shared} \  %{msym32} %{mno-sym32} \ -
> > > %{mtune=*} \ -%{mhard-float} %{msoft-float} \ -%{msingle-float}
> > > %{mdouble-float} \
> > > +%{mtune=*}" \
> > > +FP_ASM_SPEC "\
> > >  %(subtarget_asm_spec)"
> > >
> > >  /* Extra switches sometimes passed to the linker.  */
> > > --
> > > 2.2.1