gcc/
	* asan.h (asan_sanitize_allocas_p): Declare.
	* asan.c (asan_sanitize_allocas_p): New function.
	(handle_builtin_stack_restore): Bail out if !asan_sanitize_allocas_p.
	(handle_builtin_alloca): Likewise.
	* cfgexpand.c (expand_used_vars): Do not add allocas unpoisoning stuff
	if !asan_sanitize_allocas_p.
	* params.def (asan-instrument-allocas): Add new option.
	* params.h (ASAN_PROTECT_ALLOCAS): Define.
	* opts.c (common_handle_option): Disable allocas sanitization for
	KASan by default.

gcc/testsuite/
	* c-c++-common/asan/kasan-alloca-1.c: New test.
	* c-c++-common/asan/kasan-alloca-2.c: Likewise.

From-SVN: r250032