This bug is introduced by my commit r236181 where the inner rtx of
SUBREG haven't been checked while it should as "in_class_p" only
works with REG, and SUBREG_REG is actually not always REG.  If REG_P
check failed,  then we should fall back to normal code patch. The
following simple testcase for x86 can reproduce this bug.

long
foo (long a)
{
   return (unsigned) foo;
}

OK for trunk?

x86-64 bootstrap OK and no regression on check-gcc/g++.

2016-05-17  Jiong Wang  <jiong.wang@arm.com>

gcc/
   PR rtl-optimization/71150
   * lra-constraint (process_addr_reg): Guard "in_class_p" with REG_P check.