gcc original rev. 1.89:
* combine.c (if_then_else_cond): If comparing against zero,
just return thing being compared.
gcc original rev. 1.132:
* combine.c (combine_simplify_rtx): Don't create an if_then_else
unless both args are general_operand.
(http://egcs.cygnus.com/ml/gcc/1999-10/msg00400.html).
Log message:
* combine.c (get_last_value): If the last set of a register
is after subst_low_cuid, then we can not use it to determine
the register's last value.
msaitoh