birthpoints in rtl.

[Steven Bosscher]

On Tue, Mar 4, 2008 at 9:46 PM, Richard Sandiford
<rsandifo@nildram.co.uk> wrote:
>  I don't see why hard registers are special as far as FUD chains go.
>  We have DU chains for hard regs, so why not FUDs too?

We have them, but does anyone use them?  Does anyone actually even
compute them?  (Apparently fwprop does.)

It all depends on what you want to do with this.  If you want to make
it easier to do the existing optimizations over a factored UD/DU web,
then ignoring hard registers would have made sense: Easier, less
expensive to compute; easier to maintain; easier to rewrite into SSA
(pseudos are not shared); etc.

But Kenny has already said he wants to have a full replacement for
reaching defs, so the point's become moot :-)

Gr.
Steven