GC changes

[Mike Stump]

> From: Joern Rennecke <amylaar@cambridge.redhat.com>
> To: egcs@tantalophile.demon.co.uk (Jamie Lokier)
> Date: Sun, 14 Jan 2001 23:03:51 +0000 (GMT)

> That is not safe.  You can't predict what kind of address arithmetic
> the compiler will make.  For example, strength reduction could cause
> a pointer to be pointing into the middle of an array, or worse,
> somewhere beyond it (incorporating some constant adjustments).

We already need a switch to disable GC unfriendly optimizations.