Add wi_fold_in_parts.
range-ops uses wi_fold to individually fold subranges one at a time and
then combined them. This patch first calls wi_fold_in_parts which checks if
one of the subranges is small, and if so, further splits that subrange
into constants.
gcc/
PR tree-optimization/96542
* range-op.cc (range_operator::wi_fold_in_parts): New.
(range_operator::fold_range): Call wi_fold_in_parts.
(operator_lshift::wi_fold): Fix broken lshift by [0,0].
* range-op.h (wi_fold_in_parts): Add prototype.
gcc/testsuite
* gcc.dg/pr96542.c: New.