Bug#393858: assembler error with -O0

[Matthias Klose]

Package: openser

seen while investigating #390694, see http://gcc.gnu.org/PR29329,
please forward it upstream.

compilation with -O0:

Andrew Pinski writes:
> $ gcc -c -fPIC -g -O0 -g tree234.i
> /tmp/cco6vA7j.s: Assembler messages:
> /tmp/cco6vA7j.s:172: Error: Rn must not overlap other operands -- `swpb r3,r2,[r3]'

That is a bug in the source:
 asm volatile(
   "# here \n\t"
   "swpb %0, %1, [%2] \n\t"
   : "=r" (val)
   : "r"(1), "r" (lock) : "memory"
 );

I don't know how to fix that in the inline-asm.  Maybe an early
clobber can fix that.  I doubt this is related to the ICE anyways.