[lfs-dev] Two changes to consider for 8.0

Bruce Dubbs bruce.dubbs at gmail.com
Fri Dec 30 19:01:57 PST 2016


DJ Lucas wrote:
> These have been brought up before, but figured it's a good time to revisit
> them with a new major version on the horizon.
>
> One, we've bounced around gold a few times on this list, always with the
> caveat that bfd remains the default linker, but gold is available for
> packages that know about it and are wanting to use it (or where a user
> want's to use it directly with something like 'LD=/usr/bin/ld.gold
> ./configure ...'). Nothing new here. Binutils with gold adds Bison to
> Chapter 5 (this was done manually on first build because I completely
> forgot about it, so build time/size provided is from my Chapter 6 build).
> FYI, we never removed chapter05/bison.xml.
>
> New CH5 Bison:         0.3 SBU and 32 MB  to build with 3.9 MB installed
> Binutils without gold: 1.3 SBU and 487 MB to build with 48 MB  installed
> Binutils with gold:    2.6 SBU and 1.3 GB to build with 175 MB installed
>
> Diffs are dwp (~50MB), ld.gold (~80MB), and multiple copies of gold.mo
> (translations ~1MB). This on 2.27 as 2.28 will not be released until after
> January 8th (branch is cut though).
>
> Two, I'd like to review our included libs for GCC. I mentioned this about
> a year ago and never followed up with build time/size. Really only
> ISL/Graphite loop optimization. Honestly, these optimizations aren't used
> in the wild very frequently, but again, same as binutils...I see us
> shipping without it and feel that our GCC installation is slightly
> incomplete (when everyone else _is_ shipping ISL). The older message
> included notes about libssp and libmpx. libssp doesn't cause harm on x86
> and x86_64, but is removed by RH and Debian distros due to issues with arm
> IIRC. I don't see a need to change ATM, but brought it up as I had before,
> and I guess maybe it is getting less testing with most distros dropping
> it. libmpx is already included by default now (no change).
>
> GCC without ISL:      33.6 SBU and 3.5 GB to build with 570 MB installed
> GCC with ISL:         35.7 SBU and 3.6 GB to build with 595 MB installed
>
> Diffs are libisl.{so,a} (and obviously linking).
>
> With both of the changes above, +3.7 SBU. Also, I've dropped the ball on
> the write-up about libtool archives...maybe this weekend while waiting for
> stuff to compile.

I don't have a problem with adding gold as you propose, but I do wonder 
what the benefits are for using it.  As best I can tell, it would only be 
useful in speeding up the link phase for some large projects.  Is that right?

If so, what are some performance improvements we can expect to see?

As far as ISL goes, what apps would use it?  Is the performance 
improvement significant?  I suppose there is a reason gcc doesn't 
build/install it by default.

   -- Bruce




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