From: Paolo Bonzini <bonzini@gnu.org>
To: Michael Matz <matz@suse.de>
Cc: gcc-patches@gcc.gnu.org
Subject: Re: RFC patch: invariant addresses too cheap
Date: Mon, 19 Oct 2009 16:45:00 -0000 [thread overview]
Message-ID: <f865508f0910190942h1440349aqf88abbb135586d3c@mail.gmail.com> (raw)
In-Reply-To: <Pine.LNX.4.64.0910191743440.15566@wotan.suse.de>
> We could also change the i386 target hook to return something >
> COSTS_N_INSN(1) when two regs are mentioned and something smaller
> (0,1,2,3) when not. I.e. "half" insn costs. That doesn't sound too
> appealing either, OTOH that may be the reason why COSTS_N_INSN is scaled
> at all.
I have no qualms with your patch at all, but I think that fractional costs
do make sense if you want address_cost to have the same unit as
rtx_costs (which the default implementation suggests).
I would just write < 3 in your patch as "<= COSTS_N_INSN (1) / 2".
Which shows even more how it is taken from thin air :-) but at least
shows that it is supposed to be in the same unit as rtx_costs.
Paolo
next prev parent reply other threads:[~2009-10-19 16:43 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-10-19 16:17 Michael Matz
2009-10-19 16:45 ` Paolo Bonzini [this message]
2009-10-20 9:04 ` Richard Guenther
2009-10-20 12:07 ` Paolo Bonzini
2009-10-20 16:00 ` Michael Matz
2009-10-20 16:06 ` Richard Guenther
2009-10-31 10:05 ` Richard Sandiford
2009-10-31 11:14 ` Paolo Bonzini
2009-10-31 11:16 ` Richard Guenther
2009-10-31 12:56 ` Paolo Bonzini
2009-10-31 13:53 ` Richard Sandiford
2009-10-31 14:31 ` Paolo Bonzini
2009-11-01 10:24 ` Richard Sandiford
2009-11-01 10:25 ` Paolo Bonzini
2009-11-14 11:19 ` Richard Sandiford
2009-11-15 16:50 ` Paolo Bonzini
2009-11-15 21:36 ` Richard Sandiford
2009-11-28 10:53 ` Richard Sandiford
2009-12-01 13:05 ` Michael Matz
2009-12-02 22:24 ` Richard Sandiford
2009-12-03 12:57 ` Michael Matz
2009-11-17 18:02 ` Mark Mitchell
2009-10-31 19:23 ` Michael Matz
2009-11-01 10:13 ` Richard Sandiford
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