More on c-gimplify.c:gimplify_decl_stmt

[Richard Kenner]

Remember that one of these days we need to also support arrays whose
sizes aren't multiple of a byte.  This is currently done by the Ada part
of the Ada front end by converting these references into explicit indexing
and shift operations.  But when you do that, you lose all loop optimizations.

There wasn't much a point in doing this support until now because once it's
in RTL, you also lose the knowlege that it was a loop.

But with tree-ssa, all the high-level loop operations can be done even on
single-bit arrays since only RTL generation needs to know the detailed
representation.

However, this depends on keeping the tree level representation and not going
down to address arithmetic until RTL.