PR sanitizer/88291

	PR sanitizer/88291
	* asan.c (asan_clear_shadow): Move assert that len is multiple of 4
	to the start of the function.
	(asan_emit_stack_protection): When emitting clearing sequence for
	epilogue, align offset down to ASAN_RED_ZONE_SIZE granularity,
	add last_size_aligned which is last_size padded to multiples of
	ASAN_RED_ZONE_SIZE and emit asan_clear_shadow always on 4 byte
	boundaries.

	* c-c++-common/asan/pr88291.c: New test.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@266721 138bc75d-0d04-0410-961f-82ee72b054a4

(cherry picked b0d945ba743397d845ab6bc3c3834241f28bb91f)

Change-Id: I8a86e9d61617253e8439ca2c5659a2436604d30b