[PATCH] D57805: [HotColdSplit] Move splitting after instrumented PGO use

[Vedant Kumar via Phabricator via llvm-commits]

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In D57805#1393516 <https://reviews.llvm.org/D57805#1393516>, @tejohnson wrote:

> ... I will try moving the splitting to after the ThinLTO backend (post-thinlink) inlining and see what effect there is. Theoretically we should be getting more accurate importing/inlining, it would be good to understand where this is going wrong if not!


I have not yet tried the experiment you've described here. We've noticed that scheduling splitting early causes a regression for certain benchmarks in SPEC even without PGO data applied, however. As the heuristics for splitting are very conservative without PGO, this suggests that splitting before inlining may inadvertently hide important context from the optimizer.


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