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Re: [Patch] rtx_cost of SUBREG
- From: Eric Botcazou <ebotcazou at libertysurf dot fr>
- To: Roger Sayle <roger at eyesopen dot com>
- Cc: gcc-patches at gcc dot gnu dot org,Mark Dettinger <mdetting at yahoo dot com>
- Date: Sat, 22 Jan 2005 18:20:20 +0100
- Subject: Re: [Patch] rtx_cost of SUBREG
- References: <Pine.LNX.4.44.0501220815300.14386-100000@www.eyesopen.com>
> Could you outline the gory details? The clock is ticking on the 48 hour
> rule, but in stage3 its clearly better to address the "real problem"
> that was exposed by this change rather than leave it latent to potentially
> cause problems elsewhere before a release.
Sure, see my answer to Ulrich. But every generic change like this is very
likely to uncover latent problems. That's why I think they should not be done
at the end of stage3.
> There's also the compromise suggested in my review of Mark's patch that
> allows the backends to override the code of REG and SUBREG themselves.
> This would allow the sparc (in 64-bit mode) to specify a cost for a
> SUBREG and avoid the problem. But you'll appreciate this is also just
> a (target-specific) workaround as the cost of the SUBREGs in the RTL
> you give really should be the same as the cost of a REG.
For any SUBREGs?
> I'm building a tree to sparc64-sun-solaris2.8 to investigate the issue.
> Whatever the outcome, this should be resolved by Monday morning.
> Sorry for the inconvenience,
A cross is enough, I'll send you a testcase privately.
--
Eric Botcazou