[Python-Dev] first post introduction and question regarding lto (original) (raw)

Nick Coghlan ncoghlan at gmail.com
Wed Aug 9 09:06:41 EDT 2017


On 9 August 2017 at 17:52, Antoine Pitrou <solipsis at pitrou.net> wrote:

On Wed, 9 Aug 2017 13:36:28 +1000 Nick Coghlan <ncoghlan at gmail.com> wrote:

On 8 August 2017 at 10:12, Gregory P. Smith <greg at krypto.org> wrote: > I don't know whether it is beneficial or not - but having the capability to > build LTO without PGO seems reasonable. I can review any pull requests > altering configure.ac and Makefile.pre.in to make such a change.

Being able to separate them seems useful even if it's just from the performance research perspective of comparing "PGO only", "LTO only" and "PGO+LTO". That does not mean "LTO only" deserves a configure option, though. PGO is difficult to set up manually so it's fair that we provide dedicated build support for it. LTO should just be a matter of tweaking CFLAGS and LDFLAGS.

I wouldn't be confident in my own ability to get those right for gcc, let alone getting them right for clang as well. Whereas if the "--with-lto" configure option just works, then I'd never need to worry about it :)

It also means that if folks do investigate this, it eliminates a class of configuration bugs (i.e. "you didn't actually enable LTO correctly in your testing").

Cheers, Nick.

-- Nick Coghlan | ncoghlan at gmail.com | Brisbane, Australia



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