[Bug c/60819] dse1 removing not-dead insn (aliasing issue?)

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60819

--- Comment #12 from Marc Glisse <glisse at gcc dot gnu.org> ---
Created attachment 32586
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=32586&action=edit
Richard's small patch

I regtested it (patch from comment #9 plus a testcase) on x86_64-linux-gnu and
it passed. I think we should go with this in the short term. Would you care to
handle it? Or should I post it for review by Joseph/Jason?

The array-based expansion (for later) would require the same may_alias
treatment. may_alias morally belongs to TYPE_QUALS (like const/volatile, it is
safe to add, not to remove) and it is logical to propagate it in the same
place.