Add genmatch support for internal functions

Add genmatch support for internal functions

This patch makes genmatch match calls based on combined_fn rather
than built_in_function and extends the matching to internal functions.
It also uses fold_const_call to fold the calls to a constant, rather
than going through fold_builtin_n.

In order to slightly simplify the code and remove potential
ambiguity, the patch enforces lower case for tree codes
(foo->FOO_EXPR), caps for functions (no built_in_hypot->BUILT_IN_HYPOT)
and requires an exact match for user-defined identifiers.  The first two
were already met in practice but there were a couple of cases where
operator lists were defined in one case and used in another.

Tested on x86_64-linux-gnu, aarch64-linux-gnu and arm-linux-gnueabi.

gcc/
	* match.pd: Use HYPOT and COS rather than hypot and cos.
	Use CASE_CFN_* macros.  Guard log/exp folds with
	SCALAR_FLOAT_TYPE_P.
	* genmatch.c (internal_fn): New enum.
	(fn_id::fn): Change to an unsigned int.
	(fn_id::fn_id): Accept internal_fn too.
	(add_builtin): Rename to...
	(add_function): ...this and turn into a template.
	(get_operator): Only try one variation if the original name fails.
	Only add _EXPR if the original name was all lower case.
	Try converting internal and built-in function names to their
	CFN equivalents.
	(expr::gen_transform): Use maybe_build_call_expr_loc for generic.
	(dt_simplify::gen_1): Likewise.
	(dt_node::gen_kids_1): Use gimple_call_combined_fn for gimple
	and get_call_combined_fn for generic.
	(dt_simplify::gen): Use combined_fn as the type of fn_ids.
	(decision_tree::gen): Likewise.
	(main): Use lower case in the strings for {VIEW_,}CONVERT[012].
	Use add_function rather than add_builtin.  Register internal
	functions too.
	* generic-match-head.c: Include case-cfn-macros.h.
	* gimple-fold.c (replace_stmt_with_simplification): Use
	gimple_call_combined_fn to test whether we can keep an
	existing call.
	* gimple-match.h (code_helper): Replace built_in_function
	with combined_fn.
	* gimple-match-head.c: Include fold-const-call.h, internal-fn.h
	and case-fn-macros.h.
	(gimple_resimplify1): Use fold_const_call.
	(gimple_resimplify2, gimple_resimplify3): Likewise.
	(build_call_internal, build_call): New functions.
	(maybe_push_res_to_seq): Use them.
	(gimple_simplify): Use fold_const_call.  Set *rcode to a combined_fn
	rather than a built-in function.
	* tree.h (build_call_expr_internal_loc): Declare.
	(maybe_build_call_expr_loc): Likewise.
	* tree.c (build_call_expr_internal_loc_array): New function.
	(maybe_build_call_expr_loc): Likewise.

From-SVN: r230484