Re: [tree-ssa-branch] Optimizing non-SIMPLE trees

[Diego Novillo <dnovillo at redhat dot com>]

On Sat, 2002-08-10 at 17:31, Richard Henderson wrote:

> > You have to tell the optimizers that they cannot look *into* those
> > trees.  MD builtins have this problem as well, we can't really
> > simplify those trees as we don't know what the backend might expect.
> 
> You won't be incorrect if you treat them like a regular
> function call.
> 
That's exactly what we're doing now.  Trees that cannot be simplified
are flagged TF_NOT_SIMPLE.  This causes the reference finder to create
definitions for all the symbols referenced by the expression.  Safe and
easy.

> > Builtin functions are always expanded after constant propagation.
> > Aren't builtins expanded as part of the tree->RTL expansion?
> 
> Not all of them.  See fold_builtin.
> 
Thanks.

> > Will fold() deal with __builtin_strncmp if all its arguments are
> > constants?
> 
> Apparently not, though it ought to.
> 
OK.  Will look into this.


Diego.