Re: -fssa kicks butt on alphaev6 ieee floating point code

[Richard Henderson <rth at cygnus dot com>]

On Thu, Mar 16, 2000 at 01:37:52PM -0500, Brad Lucier wrote:
> > It's an accident.  What it means is that our register allocator
> > really bites.
> 
> The register allocator cannot deal well with the constraint
> that a source operand cannot overlap a destination operand.

Yes.  Which exactly proves my point.

A better register allocator would take these constraints into
account much earlier.  A slightly smarter register allocator
that's not quite smart enough will happily undo any changes
that going toand from SSA form bought you.  Combine will often
work to thwart you was well.


r~