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Re: [PATCH] Use flag_general_regs_only with -mgeneral-regs-only
- From: Uros Bizjak <ubizjak at gmail dot com>
- To: "H.J. Lu" <hjl dot tools at gmail dot com>
- Cc: Rainer Orth <ro at cebitec dot uni-bielefeld dot de>, "Koval, Julia" <julia dot koval at intel dot com>, "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, "Lu, Hongjiu" <hongjiu dot lu at intel dot com>, "vaalfreja at gmail dot com" <vaalfreja at gmail dot com>, "law at redhat dot com" <law at redhat dot com>, "Zamyatin, Igor" <igor dot zamyatin at intel dot com>, Kirill Yukhin <kirill dot yukhin at gmail dot com>
- Date: Tue, 24 May 2016 17:52:18 +0200
- Subject: Re: [PATCH] Use flag_general_regs_only with -mgeneral-regs-only
- Authentication-results: sourceware.org; auth=none
- References: <CAMe9rOpjomeEMO+=8=XDyW+Q4SRVE1jPHL7xsvm5Ckqk3ySQcg at mail dot gmail dot com> <CAFULd4aksAjy1ejRu37U2abC5wxWSVUy4VsqzhNrtu7+gJ=VMw at mail dot gmail dot com> <CAMe9rOri+hx1E5RrPh30LNppNF77Y2r-C++cpGyKp7gk5ydTAQ at mail dot gmail dot com>
On Tue, May 24, 2016 at 5:40 PM, H.J. Lu <hjl.tools@gmail.com> wrote:
>> No, this is a flag, not a variable. Let's figure out how to extend
>> target flags to more than 63 flags first.
>
> Extending target flags to more than 63 bits requires replacing
> HOST_WIDE_INT with a bit vector. Since target flags is used in
> TARGET_SUBTARGET_DEFAULT, change it to a bit vector is a
> non-trivial change. On the other hand, -mgeneral-regs-only is a
> command-line option which doesn't require support for
> TARGET_SUBTARGET_DEFAULT, similar to other -m options like
> -mmitigate-rop. Using flag_general_regs_only is an option.
I have been informed that Intel people are looking into how to extend
target flags to accommodate additional ISA flags. There is no point to
hurry with an unoptimal solution. Perhaps you can coordinate your
patch with their efforts?
Uros.