On 1/4/21 12:22 PM, Tom Stellard wrote:
> On 12/30/20 11:52 AM, Ben Cotton wrote:
>> https://fedoraproject.org/wiki/Changes/LTOBuildImprovements
>>
>>
>> == Summary ==
>> Currently all packages that are not opted out of LTO include
>> -ffat-lto-objects in their build flags.  This proposal would remove
>> -ffat-lto-objects from the default LTO flags and only use it for
>> packages that actually need it.
>>
>> == Owner ==
>> * Name: [[User:law | Jeff Law]]
>> * Email: l...@redhat.com
>>
>>
>> == Detailed Description ==
>> -ffat-lto-objects was added to the default LTO flags to ensure that
>> any installed .o/.a files included actual compiled code rather than
>> just LTO bytecodes (which are stripped after the install phase).
>> However, that is wasteful from a compile-time standpoint as few
>> packages actually install any .o/.a files.
>>
>> This proposal would remove -ffat-lto-objects from the default LTO
>> flags and packages that actually need the option would have to opt-in
>> via an RPM macro in their .spec file.  This should significantly
>> improve build times for most packages in Fedora.
>>
>
> What is this macro going to be called?  I would like to get an early
> start on updating my packages.
No idea.  I'm open to suggestions.

IIRC we had kicked around the idea of having the clang/llvm path
instantiate the LTO bytecodes in .o/.a files, which would avoid these
issues for packages using clang/llvm.  Is that something we still want
to pursue?  I vaguely recall discussing this with David B. and he came
up with a reason why that needed to happen before brp-strip-lto, but I
can't remember any of the details at this point.

Jeff
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