Introduce and use unknown_optab
Prep for a later patch where this becomes an enum value.
* optabs.h (unknown_optab): New.
* builtins.c (interclass_mathfn_icode): Use it.
* dojump.c (do_compare_rtx_and_jump): Likewise.
* optabs.c (optab_for_tree_code, expand_binop): Likewise.
* tree-vect-generic.c (add_rshift, expand_vector_divmod): Likewise.
(expand_vector_operations_1): Likewise.
* tree-vect-patterns.c (vect_recog_divmod_pattern): Likewise.
* tree-vect-stmts.c (supportable_narrowing_operation): Likewise.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@189816
138bc75d-0d04-0410-961f-
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