re PR sanitizer/88291 (asan ICE in asan_clear_shadow)

re PR sanitizer/88291 (asan ICE in asan_clear_shadow)

	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.

From-SVN: r266721