As work towards fixing PR tree-optimization/87025, this patch
eliminates global state from optinfo-emit-json.cc in favor
of adding an optional m_json_writer field to dump_context,
replacing the m_forcibly_enable_optinfo flag.

This allows for writing selftests for the interaction of the
JSON-building code with the dumpfile.c code.
In particular, the existing selftest that created optinfo
instances now exercise the JSON-building code (although no
JSON is actually written out).

The patch also simplifies the layering by replacing optinfo::emit ()
with dump_context::emit_optinfo, so that dump_context has
responsibility for keeping track of dump destinations.

gcc/ChangeLog:
	PR tree-optimization/87025
	* dump-context.h: Include "optinfo.h".
	(class optrecord_json_writer): New forward decl.
	(dump_context::forcibly_enable_optinfo_p): Delete.
	(dump_context::optinfo_enabled_p): New member function.
	(dump_context::optimization_records_enabled_p): New member
	function.
	(dump_context::set_json_writer): New member function.
	(dump_context::emit_optinfo): New member function.
	(dump_context::m_forcibly_enable_optinfo): Delete.
	(dump_context::m_json_writer): New member data.
	* dumpfile.c (dump_context::set_json_writer): New member function.
	(dump_context::finish_any_json_writer): New member function.
	(dump_context::end_scope): Replace call to
	optimization_records_maybe_pop_dump_scope with call to
	m_json_writer->pop_scope.
	(dump_context::optinfo_enabled_p): New member function.
	(dump_context::end_any_optinfo): Replace call to optinfo::emit with call
	to dump_context::emit_optinfo.
	(dump_context::emit_optinfo): New member function.
	(temp_dump_context::temp_dump_context): Replace
	m_forcibly_enable_optinfo with call to set_json_writer.
	(temp_dump_context::~temp_dump_context): Clean up any json writer.
	* optinfo-emit-json.cc (class optrecord_json_writer): Move to
	optinfo-emit-json.h
	(the_json_writer): Delete.
	(optimization_records_start): Delete.
	(optimization_records_finish): Delete.
	(optimization_records_enabled_p): Delete, in favor of
	dump_context::optimization_records_enabled_p.
	(optimization_records_maybe_record_optinfo): Delete.
	(optimization_records_maybe_pop_dump_scope): Delete.
	* optinfo-emit-json.h: Include "json.h".  Delete forward
	decl of opt_pass.
	(optimization_records_start): Delete.
	(optimization_records_finish): Delete.
	(optimization_records_enabled_p): Delete.
	(optimization_records_maybe_record_optinfo): Delete.
	(optimization_records_maybe_pop_dump_scope): Delete.
	(class optrecord_json_writer): Move here from
	optinfo-emit-json.cc.
	* optinfo.cc (optinfo::emit_for_opt_problem): Replace call
	to optinfo::emit with call to dump_context::emit_optinfo.
	(optinfo::emit): Delete, in favor of dump_context::emit_optinfo.
	(optinfo_enabled_p): Delete, in favor of
	dump_context::optinfo_enabled_p.
	(optinfo_wants_inlining_info_p): Update for conversion o
	optimization_records_enabled_p to a member function of
	dump_context.
	* optinfo.h (optinfo_enabled_p): Delete, in favor of
	dump_context::optinfo_enabled_p.
	(optinfo::emit): Delete, in favor of dump_context::emit_optinfo.
	* toplev.c: Include "dump-context.h".
	(compile_file): Replace call to optimization_records_finish with
	dump_context::finish_any_json_writer.
	(do_compile): Replace call to optimization_records_start with
	conditionally creating a optrecord_json_writer for the
	dump_context.

From-SVN: r266279