I think one reason is that allowing zero_extracts of multi-word modes is
(like this subreg thing) a little hard to pin down. What happens when
WORDS_BIG_ENDIAN && !BYTES_BIG_ENDIAN
Unless I had my grep wrong, the only such machines to do this are PDP11
and ARM with special flags (-mbig-endian -mwords-little-endian) that
were "for backward compatibility with older versions of GCC" in 1999 [1].
So, is this special case worth keeping?
Paolo
[1]
http://www.ecos.sourceware.org/ecos/docs-1.2.1/ref/gnupro-ref/arm/index.html
