[PATCH]: Fix PR tree-optimization/19038

[Jeffrey A Law]

On Fri, 2005-01-21 at 14:54 -0500, Daniel Berlin wrote:
> The reason the two names in this testcase can't coalesce (which blocks
> us from creating a single loop bb) is because we replace a loop
> invariant name with a loop variant one.
> 
> Andrew Pinski says:
> 
> <pinskia> DannyB: all the loops in thin6d.f looks so much better now,
> thanks
> 
> In general, replacing invariant things with variant ones is a bad idea,
> and can only increase register pressure, besides the affect it had on
> coalescing.
> 
> This patch stops DOM from performing this copy propagation.
> An earlier patch had stopped DOM from doing this during expression
> replacement, so hopefully this isn't controversial.
> 
> Bootstrapped and regtested on i686-pc-linux-gnu.
> Okay for mainline?
This is fine.

Jeff