[PATCH] Constant Hoisting Pass

Hal Finkel hfinkel at anl.gov
Thu Jan 23 16:06:04 PST 2014

----- Original Message -----
> From: "Juergen Ributzka" <juergen at apple.com>
> To: "Hal Finkel" <hfinkel at anl.gov>
> Cc: "LLVM Commits" <llvm-commits at cs.uiuc.edu>, "Owen Anderson" <owen at apple.com>
> Sent: Thursday, January 23, 2014 5:58:47 PM
> Subject: Re: [PATCH] Constant Hoisting Pass
> That would be great.
> Yes, the TCC_LOAD part was and is still a little bit flaky. I think
> the only place where this is actually used is in the SelectionDAG.
> A targets definition of how expensive a load is also not well defined
> in this context, so maybe it would be better if we have a
> separate target hook to model this better?

Makes sense to me.

Thanks again,

> -Juergen
> On Jan 23, 2014, at 3:44 PM, Hal Finkel < hfinkel at anl.gov > wrote:
> Hi Juergen,
> I think this looks useful, and I'd like to take advantage of this for
> PowerPC when it lands. One small request: I'd like to have some cost
> level in between "basic" and "load". There are constants on PPC that
> take a few add-cost instructions to materialize... hoisting these is
> likely useful, but loads of these constants should still be
> transformed into immediates (because the several integer
> instructions necessary are still cheaper than a load).
> Thanks,
> Hal

Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory

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