From: Jim Dehnert <dehnert@gmail.com>
To: Cary Coutant <ccoutant@gmail.com>
Cc: "H.J. Lu" <hjl.tools@gmail.com>, Michael Matz <matz@suse.de>,
x86-64-abi <x86-64-abi@googlegroups.com>,
Binutils <binutils@sourceware.org>
Subject: Re: OR_AND semantics (was: GNU property saga)
Date: Fri, 08 Mar 2019 06:25:00 -0000 [thread overview]
Message-ID: <CAPWn4jeJZABEyKUBy5a7yRjDCWuyphKT4u891S0WYijSt8rA7A@mail.gmail.com> (raw)
In-Reply-To: <CAJimCsHME4+0nW1w+Xnpb-WmxUS1bkCprpc_63GXk6=L28VK3A@mail.gmail.com>
On Thu, Mar 7, 2019 at 10:06 PM Cary Coutant <ccoutant@gmail.com> wrote:
> > > Now the above language would include FEATURE_X in the output, but bit 4
> > > would be reliable (set a.bit4 && b.bit4) while bit 5 would be
> unreliable
> > > (it is zero, even if it is one in a.o and _would_ be one in b.o had we
> > > used a newer producer).
> >
> > We can't add a bit to FEATURE_X in such a way that FEATURE_X generated
> > by older producers become invalid. We must add the bit to FEATURE_Y
> which is
> > unsupported to all prior producers. Am I missing something obvious?
>
> Yes, I think so. This is the point Michael (and I) were making. By
> using KNOWN bits, you can add new feature bits without having to start
> a whole new word of bits.
>
You also don't need to assume that a producer that has implemented support
for the tenth feature bit is also generating valid values for the
previously-defined nine, just because the words containing them are present.
Jim
>
> -cary
>
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--
--
Jim Dehnert
dehnert@gmail.com
next prev parent reply other threads:[~2019-03-08 6:25 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-04 17:25 GNU property saga Michael Matz
2019-03-04 17:40 ` OR_AND semantics (was: GNU property saga) Michael Matz
2019-03-05 0:48 ` Cary Coutant
2019-03-06 13:57 ` Michael Matz
2019-03-07 6:56 ` Cary Coutant
2019-03-08 3:44 ` H.J. Lu
2019-03-08 6:06 ` Cary Coutant
2019-03-08 6:25 ` Jim Dehnert [this message]
2019-03-11 7:34 ` H.J. Lu
2019-03-20 14:51 ` GNU property saga Mark Wielaard
[not found] ` <25adbffa-fc4c-1b01-7949-fbe0dc212f70@arm.com>
2019-05-10 18:37 ` Mark Wielaard
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