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by boomanaiden154 78 days ago
Post link optimization (PLO) tools have been around for quite a while. In particular, Meta’s BOLT (fully upstream in LLVM) and Google’s Propeller (somewhat upstream in LLVM, but fully open source) have been around for 5+ years at this point.

It doesn’t seem like Intel’s BOT delivers more performance gains, and it is closed source.
2 comments
tyushk 78 days ago
Intel BOT seems to be patches for specific binaries (hence why they didn't see a difference for Geekbench 6.7), unlike BOLT/Propeller which are for arbitrary programs. The second image from their help page [1] showcases this.

[1] https://www.intel.com/content/www/us/en/support/articles/000...

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userbinator 78 days ago
Applying targeted binary patches shouldn't take 40 seconds... unless that's also a fake "so it looks like it's working really hard" delay.
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boomanaiden154 78 days ago
I might be thinking of a different project then...

I swore Intel had their own PLO tool, but I can only find https://github.com/clearlinux/distribution/issues/2996.

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boomanaiden154 78 days ago
Found it. It was https://www.phoronix.com/news/Intel-Thin-Layout-Optimizer.

It was open source, but has since been deprecated.

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trynumber9 78 days ago
Question: do those vectorize code as in the example here? I was of the understanding they performed a more limited subset of optimizations.
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boomanaiden154 78 days ago
Propeller can’t really do many instruction level modifications due to how it works (constructs a layout file that then gets passed to the linker).

BOLT could do this, but does not as far as I’m aware.

Most of vectorization like this is also probably better done in a compiler middle end. At least in LLVM, the loop vectorizer and especially the SLP Vectorizer do a decent job of picking up most of the gains.

You might be able to pick up some gains by doing it post-link at the MC level, but writing an IR level SLP Vectorizer is already quite difficult.

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