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Re: [PATCH] powerpc: New feature - HWCAP/HWCAP2 bits in the TCB
- From: Rich Felker <dalias at libc dot org>
- To: Florian Weimer <fweimer at redhat dot com>
- Cc: munroesj at linux dot vnet dot ibm dot com, OndÅej BÃlka <neleai at seznam dot cz>, Szabolcs Nagy <szabolcs dot nagy at arm dot com>, Carlos Eduardo Seo <cseo at linux dot vnet dot ibm dot com>, GLIBC Devel <libc-alpha at sourceware dot org>, Steve Munroe <sjmunroe at us dot ibm dot com>
- Date: Tue, 9 Jun 2015 14:26:36 -0400
- Subject: Re: [PATCH] powerpc: New feature - HWCAP/HWCAP2 bits in the TCB
- Authentication-results: sourceware.org; auth=none
- References: <55760314 dot 6070601 at linux dot vnet dot ibm dot com> <5576FC80 dot 1090806 at arm dot com> <1433862393 dot 21101 dot 9 dot camel at sjmunroe-ThinkPad-W500> <20150609154223 dot GA20028 at domone> <1433865684 dot 21101 dot 20 dot camel at sjmunroe-ThinkPad-W500> <55772EB2 dot 5080103 at redhat dot com>
On Tue, Jun 09, 2015 at 08:21:38PM +0200, Florian Weimer wrote:
> On 06/09/2015 06:01 PM, Steven Munroe wrote:
>
> > A Static variable would require a an indirect load via the TOC/GOT
> > (which can be megabytes for a large program/library). I really really
> > want the avoid that.
>
> Could you encode the information in the address itself? Then the
> indirection goes away.
You mean using (unsigned long)&__hwcap_hack or similar as the hwcap
bits? I don't see how you could make that work for static linking,
where the linker is going to put the GOT in the read-only text
segment. Otherwise it's a neat idea.
Rich