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Message-ID: <20080516124811.GC4226@Krystal> Date: Fri, 16 May 2008 08:48:11 -0400 From: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> To: Jeremy Fitzhardinge <jeremy@...p.org> Cc: Ingo Molnar <mingo@...e.hu>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "H. Peter Anvin" <hpa@...or.com> Subject: [PATCH] Fix immediate asm constraint for gcc 3 x86_64 * Jeremy Fitzhardinge (jeremy@...p.org) wrote: > I'm getting this when I build for x86-64 with > > jeremy@...worth:~/hg/xen/paravirt/linux-x86_64$ gcc -v > Reading specs from /usr/lib/gcc/x86_64-linux/3.4.4/specs > Configured with: ../src/configure -v > --enable-languages=c,c++,java,f77,pascal,objc,ada,treelang --prefix=/usr > --libexecdir=/usr/lib --with-gxx-include-dir=/usr/include/c++/3.4 > --enable-shared --with-system-zlib --enable-nls --without-included-gettext > --program-suffix=-3.4 --enable-__cxa_atexit --enable-libstdcxx-allocator=mt > --enable-clocale=gnu --enable-libstdcxx-debug --enable-java-gc=boehm > --enable-java-awt=gtk --disable-werror x86_64-linux > Thread model: posix > gcc version 3.4.4 20050314 (prerelease) (Debian 3.4.3-13) > > > CC kernel/sched.o > /home/jeremy/hg/xen/paravirt/linux/kernel/sched_trace.h: In function > `wait_task_inactive': > /home/jeremy/hg/xen/paravirt/linux/kernel/sched_trace.h:5: warning: asm > operand 1 probably doesn't match constraints > /home/jeremy/hg/xen/paravirt/linux/kernel/sched_trace.h:5: error: > impossible constraint in `asm' > /home/jeremy/hg/xen/paravirt/linux/kernel/sched_trace.h:5: warning: 'value' > might be used uninitialized in this function > /home/jeremy/hg/xen/paravirt/linux/kernel/sched.c: At top level: > /home/jeremy/hg/xen/paravirt/linux/kernel/sched_fair.c:1167: warning: > 'wakeup_preempt_entity' defined but not used > make[3]: *** [kernel/sched.o] Error 1 > > It seems that include/asm-x86/immediate.h in sched-devel.git causes this. gcc-3.4 does not seem to like the "i" (&name##__imv) constraint. I have seen no such problem with gcc-4.1. This is weird. It seems that relaxing the constraint helps fixing this, but it's not clear whether fixing the code or gcc-3.4 is the correct solution... here is the fix : Fix immediate asm constraint for gcc 3 x86_64 make CC=gcc-3.4 HOSTCC=gcc-3.4 causes this problem with immediate values on x86_64 : kernel/sched_trace.h: In function `wait_task_inactive': kernel/sched_trace.h:5: warning: asm operand 1 probably doesn't match constraints kernel/sched_trace.h:5: error: impossible constraint in `asm' kernel/sched_trace.h:5: warning: 'value' might be used uninitialized in this function make[1]: *** [kernel/sched.o] Error 1 make: *** [kernel/] Error 2 gcc-4.1 does not have this problem. Fix this by changing the "i" (&name##__imv) for a "g" (&name##__imv) constraint. Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca> CC: Jeremy Fitzhardinge <jeremy@...p.org> CC: Ingo Molnar <mingo@...e.hu> CC: "H. Peter Anvin" <hpa@...or.com> --- include/asm-x86/immediate.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) Index: linux-2.6-sched-devel/include/asm-x86/immediate.h =================================================================== --- linux-2.6-sched-devel.orig/include/asm-x86/immediate.h 2008-05-16 05:07:55.000000000 -0400 +++ linux-2.6-sched-devel/include/asm-x86/immediate.h 2008-05-16 05:08:29.000000000 -0400 @@ -63,7 +63,7 @@ "mov $0,%0\n\t" \ "3:\n\t" \ : "=q" (value) \ - : "i" (&name##__imv), \ + : "g" (&name##__imv), \ "i" (sizeof(value))); \ break; \ case 2: \ @@ -81,7 +81,7 @@ "mov $0,%0\n\t" \ "3:\n\t" \ : "=r" (value) \ - : "i" (&name##__imv), \ + : "g" (&name##__imv), \ "i" (sizeof(value))); \ break; \ case 8: \ @@ -102,7 +102,7 @@ "mov $0xFEFEFEFE01010101,%0\n\t" \ "3:\n\t" \ : "=r" (value) \ - : "i" (&name##__imv), \ + : "g" (&name##__imv), \ "i" (sizeof(value))); \ break; \ }; \ @@ -143,7 +143,7 @@ "mov $0,%0\n\t" \ "3:\n\t" \ : "=a" (value) \ - : "i" (&name##__imv), \ + : "g" (&name##__imv), \ "i" (sizeof(value)), \ "i" (sizeof(__typeof__(name##__imv)))); \ value; \ > Turning CONFIG_MARKER off avoids the problem. > > J -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 -- 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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