RFC: variant and ODR based type merging during LTO streaming

[Richard Biener]

On Mon, 1 Oct 2018, Jan Hubicka wrote:

> > > I see.  So one possible canonicalization is to make _all_
> > > pointer-typed FIELD_DECLs point to incomplete variants since the memory
> > > accesses should already have the "proper" access types.  Can you
> > > get statistics on that?  Not sure how to get an "incomplete" type
> > > though (iff we can simply copy the type and NULL TYPE_FIELDs and
> > > TYPE_SIZE and friends) - again I'd do that at FLD time.
> > 
> > So sth like
> > 
> >  tp = build_distinct_type_copy (t);
> >  TYPE_FIELDS (tp) = NULL_TREE;
> >  TYPE_SIZE (tp) = NULL_TREE;
> >  TYPE_SIZE_UNIT (tp) = NULL_TREE;
> >  tp = type_hash_canon (tp);
> > 
> > of course we "leak" the original type in used COMPONENT_REFs
> > (may also cause some verifier ICEs here if the types mismatch that
> > of the FIELD_DECLs) and in aggregate copies, etc.  But I wonder
> > how much "unused" unnecessary types we have.  That is, I'd paper
> > over the ICEs this causes and not fixup the IL stream at first for
> > example.
> 
> I had patch to play with this as well, let me see if I can revive it.
> One problem here is that we will lose info about ODR violations that happens
> through pointers.

How so, if we keep the mangled name of the pointed-to types?

Richard.

> Honza
> 
> 

-- 
Richard Biener <rguenther@suse.de>
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