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Re: [whopr] Design/implementation alternatives for the driver and WPA
On Wed, Jun 4, 2008 at 12:50, Kenneth Zadeck <zadeck@naturalbridge.com> wrote:
> While i agree that some form of lto needs to support monster apps, that
> should not inhibit us from supporting transformations or models of
> compilation that are only practical with 100k line programs.
Of course not. That was never the intent. Supporting small/medium
sized applications is inherent in the WHOPR design. If we can't
handle that efficiently, then we have a design/implementation bug.
While we (Google) are mostly interested in summary-based IPA for very
large applications, we do not want the design to negate other uses of
LTO. WHOPR is designed to support the whole spectrum, from
small/medium sized applications where the whole program fits in
memory, to extremely large applications where memory/computing
requirements are prohibitive for a single machine.
In practice, the full distributed model that WHOPR offers will not
need to be triggered for small applications, only very large ones.
Ideally, we should be able to hide all that behind 'gcc -flto' and let
the compiler decide how to operate.
The natural restriction is that passes of type SMALL_IPA will not be
able to run when the full distributed version is being used. Again,
this is something I expect the compiler to be able to figure out for
itself.
Diego.