[llvm-dev] Supporting Regular and Thin LTO with a Single LTO Bitcode Format

[Petr Hosek via llvm-dev]

We're using regular LTO for our Clang toolchain build because we don't mind
spending more resources to squeeze out as much performance as possible.
However, when looking into our build performance, I've noticed that we only
spent about 1/3 of the total build time in building distribution
components, the rest is spent on building unit tests and tools that are
only used by lit tests. For the latter, we don't care about the
performance, so it'd be nice to avoid doing regular LTO to speed up the
build.

The idea I had would be to use a single LTO bitcode format for all
translation units, and then decide only at link time whether to use regular
LTO for distribution components or ThinLTO for everything else.

After doing some research, I found the "Supporting Regular and Thin LTO
with a Single LTO Bitcode Format
<https://www.snsystems.com/technology/tech-blog/supporting-regular-and-thin-lto-with-a-single-lto-bitcode-format>"
talk presented by Matthew Voss at LLVM Developers’ Meeting 2019 which does
exactly what I described, but it seems like this was only implemented
downstream.

Has there been any progress on upstreaming the implementation? Is there any
way to do what I described using the in-tree LTO implementation?
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20210413/3a39018d/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 3996 bytes
Desc: S/MIME Cryptographic Signature
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20210413/3a39018d/attachment.bin>