Control: tag -1 - patch + moreinfo
Control: retitle -1 dpkg-buildflags: Add support for an optimize area for 
things like LTO

On Tue, 2019-09-17 at 14:36:44 +0200, Matthias Klose wrote:
> Package: src:dpkg
> Version: 1.19.7
> Tags: patch

> Please add an optimization area (opt, optimization) for extra optimizations
> like lto (link time optimization) and pgo (profile guided optimization).

> lto can be directly translated into compiler flags, as seen in the attached
> patch, assuming that no lto across package boundaries is done (ensured by
> the debhelper patch in #939656).  The patch assumes that just nolto can be
> used to disable lto until an area is introduced in dpkg.
> Some upstream packages also provide build support for lto builds, so for
> these an option should be given to disable the addition to the compiler
> flags (like the nolto in the proposed patch).

I take you are requesting both adding this and also enabling LTO by

I'm fine with the former (even implementing that myself), but the latter
would need to go through [Q] first. And I see this can cause breakage [O]
according to the OpenSUSE people.


> pgo doesn't directly translate into compiler flags, but almost always
> requires upstream support in the build system.  pgo usually is enabled by
> some configure options which are specific to the upstream build.  pgo
> usually requires running a profiling task, so this optimization probably
> should be disabled for cross builds, otoh, the cross build then is different
> to the native build (although it should create a functional identical
> package).

I don't see how dpkg can support PGO, so I'm excluding that from this
request, as it seems this would be pretty much unactionable.


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