paired register loads and stores

[David Edelsohn]

>>>>> Erich Plondke writes:

Erich> I guess in a way this is "autovectorization of random code snippets" so maybe
Erich> it's too complex but it seems within the realm of what combine could do...

	Yes, this is more appropriately addressed by straight-line code
vectorizations, i.e., SLP.  The peephole and GCC register allocator are
not trying to provide that functionality.

David