[lld] r249752 - Revert: r249728 - Roll back r249726 and r249723 because they broke buildbots.

[Hal Finkel via llvm-commits]

----- Original Message -----
> From: "Rafael Espíndola" <rafael.espindola at gmail.com>
> To: "Hal Finkel" <hfinkel at anl.gov>
> Cc: "llvm-commits" <llvm-commits at lists.llvm.org>, "Shankar Easwaran" <shankare at codeaurora.org>
> Sent: Wednesday, October 14, 2015 8:28:08 AM
> Subject: Re: [lld] r249752 - Revert: r249728 - Roll back r249726 and r249723 because they broke buildbots.
> 
> > Alan Modra @ IBM was kind enough to do some research on my behalf,
> > and binutils has set TEXT_START_ADDR=0x10000000 in elf64ppc.sh
> > since 1999. This was done to implement this suggestion in the
> > PPC64 ELF ABI
> > (http://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi.html):
> 
> Awesome!
> 
> >   It is normally desirable to put segments with different
> >   characteristics in separate 256 Mbyte portions of the address
> >   space, to give the operating system full paging flexibility in
> >   the 64-bit address space.
> >
> > And the lowest non-zero 256M boundary is 0x10000000.
> 
> Interesting. Do you know what "characteristics" they are referring
> to?

I don't know exactly.

> It cannot be permissions, otherwise we would need to align segments
> to
> 256MB.
> 
> In any case. That is sufficient IMHO to have the target specific VA
> support. I would only ask that we use the TargetInfo constructor to
> set the current value and only the ppc64 one changes the value and
> references the above spec.

Sounds good. r250378.

Thanks again,
Hal

> 
> Thanks,
> Rafael
> 

-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory