Messages in this thread | | | Date | Wed, 21 May 2008 23:46:08 +0200 | From | Sam Ravnborg <> | Subject | Re: [PATCH] Fix Immediate Values x86_64 support old gcc |
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On Wed, May 21, 2008 at 05:28:09PM -0400, Mathieu Desnoyers wrote: > * 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. Same with USE_IMMEDIATE - as USE_IMMEDIATE is only used in a x86 Makefile. Or did I miss sothing?
Sam
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