Introduce -fsanitize-address-use-after-scope

	* c-warn.c (warn_for_unused_label): Save all labels used
	in goto or in &label.
	* asan.c (enum asan_check_flags): Move the enum to header file.
	(asan_init_shadow_ptr_types): Make type creation more generic.
	(shadow_mem_size): New function.
	(asan_emit_stack_protection): Use newly added ASAN_SHADOW_GRANULARITY.
	Rewritten stack unpoisoning code.
	(build_shadow_mem_access): Add new argument return_address.
	(instrument_derefs): Instrument local variables if use after scope
	sanitization is enabled.
	(asan_store_shadow_bytes): New function.
	(asan_expand_mark_ifn): Likewise.
	(asan_sanitize_stack_p): Moved from asan_sanitize_stack_p.
	* asan.h (enum asan_mark_flags): Moved here from asan.c
	(asan_protect_stack_decl): Protect all declaration that need
	to live in memory.
	(asan_sanitize_use_after_scope): New function.
	(asan_no_sanitize_address_p): Likewise.
	* cfgexpand.c (partition_stack_vars): Consider
	asan_sanitize_use_after_scope in condition.
	(expand_stack_vars): Likewise.
	* common.opt (-fsanitize-address-use-after-scope): New option.
	* doc/invoke.texi (use-after-scope-direct-emission-threshold):
	Explain the parameter.
	* flag-types.h (enum sanitize_code): Define SANITIZE_USE_AFTER_SCOPE.
	* gimplify.c (build_asan_poison_call_expr): New function.
	(asan_poison_variable): Likewise.
	(gimplify_bind_expr): Generate poisoning/unpoisoning for local
	variables that have address taken.
	(gimplify_decl_expr): Likewise.
	(gimplify_target_expr): Likewise for C++ temporaries.
	(sort_by_decl_uid): New function.
	(gimplify_expr): Unpoison all variables for a label we can jump
	from outside of a scope.
	(gimplify_switch_expr): Unpoison variables defined in the switch
	context.
	(gimplify_function_tree): Clear asan_poisoned_variables.
	(asan_poison_variables): New function.
	(warn_switch_unreachable_r): Handle IFN_ASAN_MARK.
	* internal-fn.c (expand_ASAN_MARK): New function.
	* internal-fn.def (ASAN_MARK): Declare.
	* opts.c (finish_options): Handle -fstack-reuse if
	-fsanitize-address-use-after-scope is enabled.
	(common_handle_option): Enable address sanitization if
	-fsanitize-address-use-after-scope is enabled.
	* params.def (PARAM_USE_AFTER_SCOPE_DIRECT_EMISSION_THRESHOLD):
	New parameter.
	* params.h: Likewise.
	* sancov.c (pass_sanopt::execute): Handle IFN_ASAN_MARK.
	* sanitizer.def: Define __asan_poison_stack_memory and
	__asan_unpoison_stack_memory functions.
	* asan.c (asan_mark_poison_p): New function.
	(transform_statements): Handle asan_mark_poison_p calls.
	* gimple.c (nonfreeing_call_p): Handle IFN_ASAN_MARK.

From-SVN: r241896