PR c/64249
	* c-common.c (warn_duplicated_cond_add_or_warn): New function.
	* c-common.h (warn_duplicated_cond_add_or_warn): Declare.
	* c.opt (Wduplicated-cond): New option.

	* c-parser.c (c_parser_statement_after_labels): Add CHAIN parameter
	and pass it down to c_parser_if_statement.
	(c_parser_else_body): Add CHAIN parameter and pass it down to
	c_parser_statement_after_labels.
	(c_parser_if_statement): Add CHAIN parameter.  Add code to warn about
	duplicated if-else-if conditions.

	* parser.c (cp_parser_statement): Add CHAIN parameter and pass it
	down to cp_parser_selection_statement.
	(cp_parser_selection_statement): Add CHAIN parameter.  Add code to
	warn about duplicated if-else-if conditions.
	(cp_parser_implicitly_scoped_statement): Add CHAIN parameter and pass
	it down to cp_parser_statement.

	* doc/invoke.texi: Document -Wduplicated-cond.
	* Makefile.in (insn-latencytab.o): Use -Wno-duplicated-cond.
	(insn-dfatab.o): Likewise.
	* genemit.c (gen_exp): Rewrite condition to avoid -Wduplicated-cond
	warning.

	* c-c++-common/Wduplicated-cond-1.c: New test.
	* c-c++-common/Wduplicated-cond-2.c: New test.
	* c-c++-common/Wduplicated-cond-3.c: New test.
	* c-c++-common/Wduplicated-cond-4.c: New test.
	* c-c++-common/Wmisleading-indentation.c (fn_37): Avoid
	-Wduplicated-cond warning.

From-SVN: r228388