Re: [PATCH] Don't assume MEM_SIZE is always set in rs6000 adjacent_mem_locations (PR target/34225)

[David Edelsohn <dje at watson dot ibm dot com>]

	I assumed because the testcase involved stack_tie that all of the
failures involved stack_tie and the common parts of the compiler uniformly
established MEM attrs.  I don't disagree with current patch to protect the
test, but I think the patch may be incomplete.

	Because stack_tie is not a real instructon, I thought that the
size could be the mode size.  Also, because stack_tie it is not a real
instruction, I expected that is_store_insn() should ignore it -- like all
of the other byproducts of the GCC IR that unfortunately are treated as
real instructions.

Thanks, David