[PR107130] range-ops: Separate out ffs and popcount optimizations.
__builtin_popcount and __builtin_ffs were sharing the same range-ops
entry, but the nonzero mask optimization is not valid for ffs.
Separate them out into two entries.
PR tree-optimization/107130
gcc/ChangeLog:
* gimple-range-op.cc (class cfn_popcount): Call op_cfn_ffs.
(class cfn_ffs): New.
(gimple_range_op_handler::maybe_builtin_call): Separate out
CASE_CFN_FFS into its own case.