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Message-ID: <20080521203743.GA12982@uranus.ravnborg.org> Date: Wed, 21 May 2008 22:37:43 +0200 From: Sam Ravnborg <sam@...nborg.org> To: Mathieu Desnoyers <compudj@...stal.dyndns.org> Cc: "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org, Jeremy Fitzhardinge <jeremy@...p.org>, Ingo Molnar <mingo@...e.hu> Subject: Re: [PATCH] Fix Immediate Values x86_64 support old gcc 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@...ymtl.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! Consider something like this (note: no negative logic involved): export USE_IMMEDIATE := $(call cc-ifversion, -ge, 0400, $(CONFIG_IMMEDIATE)) Then the MAkefile fragment can be simplified as: > -obj-$(CONFIG_IMMEDIATE) += immediate.o > +obj-$(USE_IMMEDIATE) += immediate.o (Or find a better name than "USE_IMMEDIATE". > endif > > # Stackpointer is addressed different for 32 bit and 64 bit x86 > Index: linux-2.6-sched-devel/include/asm-x86/immediate.h > =================================================================== > --- linux-2.6-sched-devel.orig/include/asm-x86/immediate.h 2008-05-21 09:10:59.000000000 -0400 > +++ linux-2.6-sched-devel/include/asm-x86/immediate.h 2008-05-21 09:15:43.000000000 -0400 > @@ -12,6 +12,10 @@ > > #include <asm/asm.h> > > +#if (defined(CONFIG_X86_64) && __GNUC__ < 4) /* Detect broken x86_64 gcc */ > +#undef CONFIG_IMMEDIATE > +#else And now in the source we use a direct check of the GNUC version. So this is a duplicate of GCC_BROKEN_IMMEDIATE and not sensible comments. "I ask myself in what way is gcc broken?" And you DO NOT fiddle with the CONFIG_* variables - this is just plain wrong. > --- linux-2.6-sched-devel.orig/include/linux/immediate.h 2008-05-21 09:12:22.000000000 -0400 > +++ linux-2.6-sched-devel/include/linux/immediate.h 2008-05-21 09:12:59.000000000 -0400 > @@ -11,8 +11,10 @@ > */ > > #ifdef CONFIG_IMMEDIATE > +#include <asm/immediate.h> /* May undef CONFIG_IMMEDIATE */ > +#endif So you need to find a better way for this. > > -#include <asm/immediate.h> > +#ifdef CONFIG_IMMEDIATE > > /** > * imv_set - set immediate variable (with locking) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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