PR c++/70507
	PR c/68120
	* builtins.def (BUILT_IN_ADD_OVERFLOW_P, BUILT_IN_SUB_OVERFLOW_P,
	BUILT_IN_MUL_OVERFLOW_P): New builtins.
	* builtins.c: Include gimple-fold.h.
	(fold_builtin_arith_overflow): Handle
	BUILT_IN_{ADD,SUB,MUL}_OVERFLOW_P.
	(fold_builtin_3): Likewise.
	* doc/extend.texi (Integer Overflow Builtins): Document
	__builtin_{add,sub,mul}_overflow_p.
gcc/c/
	* c-typeck.c (convert_arguments): Don't promote last argument
	of BUILT_IN_{ADD,SUB,MUL}_OVERFLOW_P.
gcc/cp/
	* constexpr.c: Include gimple-fold.h.
	(cxx_eval_internal_function): New function.
	(cxx_eval_call_expression): Call it.
	(potential_constant_expression_1): Handle integer arithmetic
	overflow built-ins.
	* tree.c (builtin_valid_in_constant_expr_p): Handle
	BUILT_IN_{ADD,SUB,MUL}_OVERFLOW_P.
gcc/c-family/
	* c-common.c (check_builtin_function_arguments): Handle
	BUILT_IN_{ADD,SUB,MUL}_OVERFLOW_P.
gcc/testsuite/
	* c-c++-common/builtin-arith-overflow-1.c: Add test cases.
	* c-c++-common/builtin-arith-overflow-2.c: New test.
	* g++.dg/ext/builtin-arith-overflow-1.C: New test.
	* g++.dg/cpp0x/constexpr-arith-overflow.C: New test.
	* g++.dg/cpp1y/constexpr-arith-overflow.C: New test.

Co-Authored-By: Jakub Jelinek <jakub@redhat.com>

From-SVN: r237238