> * Sam Ravnborg (
sam@ravnborg.org) wrote:
> > Hi Mathieu
> > > Does this fix make more sense ?
> > >
> > > GCC < 4, on x86_64, does not accept symbol+offset operands for "i" constraints
> > > asm statements. Fallback on generic immediate values if this compiler is
> > > detected.
> > >
> > > Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
> > > ---
> > > arch/x86/Makefile | 3 +++
> > > arch/x86/kernel/Makefile | 4 +++-
> > > include/asm-x86/immediate.h | 5 +++++
> > > include/linux/immediate.h | 4 +++-
> > > kernel/Makefile | 4 +++-
> > > 5 files changed, 17 insertions(+), 3 deletions(-)
> > >
> > > Index: linux-2.6-sched-devel/arch/x86/Makefile
> > > ===================================================================
> > > --- linux-2.6-sched-devel.orig/arch/x86/Makefile 2008-05-21 09:04:52.000000000 -0400
> > > +++ linux-2.6-sched-devel/arch/x86/Makefile 2008-05-21 09:22:05.000000000 -0400
> > > @@ -78,6 +78,9 @@
> > > "$(CC)" -fstack-protector-all )
> > >
> > > KBUILD_CFLAGS += $(stackp-y)
> > > +
> > > + export GCC_BROKEN_IMMEDIATE
> > > + GCC_BROKEN_IMMEDIATE := $(shell if [ $(call cc-version) -lt 0400 ] ; then echo "y"; fi)
> >
> > So here we introduce a global environment variable that tells
> > us that gcc has "BROKEN_IMMEDIATE".
> > I have absolutely no clue what "BROKEN_IMMEDIATE" is so I guess others
> > are in the same boat. Comment please!
> >
>
> Yes, I guess this worth being commented, you are right. I'll write
> something along the lines written in the patch header.
>
> > Consider something like this (note: no negative logic involved):
> > export USE_IMMEDIATE := $(call cc-ifversion, -ge, 0400, $(CONFIG_IMMEDIATE))
> >
>
> Hrm, if I do that, I would have to add USE_IMMEDIATE to each
> architecture's makefiles for which immediate values are supported, e.g.:
>
> export USE_IMMEDIATE := $(CONFIG_IMMEDIATE)
>
> The "BROKEN_IMMEDIATE" (negative) approach only needs to be defined on
> x86_64 where gcc 3.x does not support symbol+offset correctly.
