./:	* common.opt: Add fstrict-overflow.
	* opts.c (decode_options): Set flag_strict_overflow if -O2.
	* flags.h (TYPE_OVERFLOW_WRAPS): Define.
	(TYPE_OVERFLOW_UNDEFINED): Define.
	(TYPE_OVERFLOW_TRAPS): Define.  This replaces TYPE_TRAP_SIGNED.
	Replace all uses.
	* tree.h (TYPE_TRAP_SIGNED): Don't define.
	* fold-const.c (negate_expr_p): Use TYPE_OVERFLOW_UNDEFINED.
	(fold_negate_expr): Likewise.
	(make_range): Likewise.
	(extract_muldiv_1): Likewise.
	(maybe_canonicalize_comparison): Likewise.
	(fold_comparison): Likewise.
	(fold_binary): Likewise.
	(tree_expr_nonnegative_p): Likewise.
	(tree_expr_nonzero_p): Likewise.
	* tree-vrp.c (compare_values): Likewise.
	(extract_range_from_binary_expr): Likewise.
	(extract_range_from_unary_expr): Likewise.
	* tree-ssa-loop-niter.c (infer_loop_bounds_from_signedness):
	Likewise.
	(nowrap_type_p): Likewise.
	* tree-scalar-evolution.c (simple_iv): Likewise.
	* fold-const.c (negate_expr_p): Use TYPE_OVERFLOW_WRAPS.
	(build_range_check): Likewise.
	(extract_muldiv_1): Likewise.
	(fold_comparison): Likewise.
	* tree-vrp.c (vrp_int_const_binop): Likewise.
	(extract_range_from_unary_expr): Likewise.
	* convert.c (convert_to_integer): Likewise.
	* fold-const.c (fold_negate_expr): Use TYPE_OVERFLOW_TRAPS.
	(fold_comparison): Likewise.
	(fold_binary): Likewise.
	* optabs.c (optab_for_tree_code): Likewise.
	* tree-vectorizer.c (vect_is_simple_reduction): Likewise.
	* simplify-rtx.c (simplify_const_relational_operation): Check
	flag_strict_overflow and flag_trapv.
	(simplify_const_relational_operation): Likewise.
	* doc/invoke.texi (Option Summary): Mention -fstrict-overflow.
	(Optimize Options): Add -fstrict-overflow to -O2 list.  Document
	-fstrict-overflow.
testsuite/:
	* gcc.dg/strict-overflow-1.c: New test.
	* gcc.dg/no-strict-overflow-1.c: New test.
	* gcc.dg/strict-overflow-2.c: New test.
	* gcc.dg/no-strict-overflow-2.c: New test.
	* gcc.dg/strict-overflow-3.c: New test.
	* gcc.dg/no-strict-overflow-3.c: New test.
	* gcc.dg/strict-overflow-4.c: New test.
	* gcc.dg/no-strict-overflow-4.c: New test.
	* gcc.dg/fold-mod-1.c: Add -fstrict-overflow option.
	* gcc.dg/pr15784-1.c: Likewise.
	* gcc.dg/pr20922-1.c: Likewise.
	* gcc.dg/pr20922-3.c: Likewise.
	* gcc.dg/pr20922-4.c: Likewise.
	* gcc.dg/pr20922-6.c: Likewise.
	* gcc.dg/compare-4.c: Likewise.
	* gcc.dg/torture/pr26898-1.c: Likewise.
	* gcc.dg/tree-ssa/divide-1.c: Likewise.
	* gcc.dg/tree-ssa/divide-2.c: Likewise.
	* gcc.dg/tree-ssa/divide-3.c: Likewise.
	* gcc.dg/tree-ssa/divide-4.c: Likewise.
	* gcc.dg/tree-ssa/pr14490-1.c: Likewise.
	* gcc.dg/tree-ssa/pr14490-3.c: Likewise.
	* gcc.dg/tree-ssa/pr21082.c: Likewise.
	* gcc.dg/tree-ssa/pr26899.c: Likewise.
	* g++.dg/tree-ssa/pr21082.C: Likewise.

From-SVN: r121254