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Re: vtable optimization (was Re: TREE_UNCHANGING?)
- From: Daniel Berlin <dberlin at dberlin dot org>
- To: Jason Merrill <jason at redhat dot com>
- Cc: gcc at gcc dot gnu dot org
- Date: Thu, 9 May 2002 22:53:04 -0400 (EDT)
- Subject: Re: vtable optimization (was Re: TREE_UNCHANGING?)
On Fri, 10 May 2002, Jason Merrill wrote:
> Another tangent: if we know the static type of the object, we can do even
> better: we can skip the vtable lookup entirely and call the function
> directly. There is some simple code in the C++ frontend to handle this,
> mostly in fixed_type_or_null; a more C++-aware optimizer could track the
> static type information as well as the alias set, so that we could perform
> this optimization for code like
> A a;
> A *ap = &a;
> as well as the simpler
> A a;
> This stuff is probably better suited for an AST-level optimization pass.
These are generally language specific in some degree, but i've been
looking at doing it for C++.
On my list of things, however, devirtualization is pretty far down.