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Re: [PATCH] Fix warnings building pdp11 port
- From: Richard Biener <richard dot guenther at gmail dot com>
- To: Jeff Law <law at redhat dot com>
- Cc: "gcc-patches at gcc dot gnu dot org >> gcc-patches" <gcc-patches at gcc dot gnu dot org>
- Date: Wed, 30 Sep 2015 09:48:19 +0200
- Subject: Re: [PATCH] Fix warnings building pdp11 port
- Authentication-results: sourceware.org; auth=none
- References: <560AC292 dot 3010608 at redhat dot com>
On Tue, Sep 29, 2015 at 6:55 PM, Jeff Law <law@redhat.com> wrote:
> The pdp11 port fails to build with the trunk because of a warning.
> Essentially VRP determines that the result of using BRANCH_COST is a
> constant with the range [0..1]. That's always less than 4, 3 and the
> various other magic constants used with BRANCH_COST and VRP issues a warning
> about that comparison.
It does? Huh. Is it about undefined overflow which is the only thing
VRP should end up
warning about? If so I wonder how that happens, at least I can't
reproduce it for
--target=pdp11 --enable-werror build of cc1.
> I expect we're going to be overhauling BRANCH_COST shortly. In the mean
> time, this just revectors BRANCH_COST for the pdp11 into a function to
> prevent VRP from collapsing the test and issuing the warning.
>
> Yes, this means more code in the pdp11 cross compiler. I'm not terribly
> concerned about that and I couldn't stand the idea of scattering diagnostic
> push/pop stuff all over the place to make just the pdp11 port happy.
>
>
> Tested by building the pdp11 targets from config-all.mk.
>
> Installed on the trunk.
>
> Jeff