Messages in this thread Patch in this message | | | Date | Fri, 16 May 2008 08:48:11 -0400 | From | Mathieu Desnoyers <> | Subject | [PATCH] Fix immediate asm constraint for gcc 3 x86_64 |
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* Jeremy Fitzhardinge (jeremy@goop.org) wrote: > I'm getting this when I build for x86-64 with > > jeremy@cosworth:~/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@polymtl.ca> CC: Jeremy Fitzhardinge <jeremy@goop.org> CC: Ingo Molnar <mingo@elte.hu> CC: "H. Peter Anvin" <hpa@zytor.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
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