(reg_nonzero_bits): Should be unsigned.
(reg_last_set_{mode,nonzero_bits,sign_bit_copies}): New variables.
(combine_instructions): Allocate and initialized them.
(nonzero_bits, num_sign_bit_copies, case REG): Use new variables to get
information on regs we've seen before.
(record_value_for_reg): Set new variables for register being modified.
(record_dead_and_set_regs): Invalidate regs clobbered by CALL_INSN.

From-SVN: r4051