[PATCH] D136698: [SampleFDO] Persist profile staleness metrics into binary

[Lei Wang via Phabricator via llvm-commits]

wlei added a comment.

In D136698#3883720 <https://reviews.llvm.org/D136698#3883720>, @davidxl wrote:

> The use case of the feature is still  a little fuzzy to me. Why is the mismatch issue not caught and handled at build time?

Sorry it was not clear. It is caught and handled at build time for one object file, the previous patch is supposed to run in an early compile-time not any linker time, one set of metrics for one obj file, but we'd like to report one aggregated metrics for the whole binary, so this patch is mostly to merge/aggregate them.

Also we' like to catch and monitor it in real time not during the off-line investigation time, one issue we hit is the incremental build, the object files are built(sometimes remotely) and cached in the database(can be shared with other users), so if we want to aggregate the metrics from old cached object file, we need also to cache the compile-time warning/stdouts, that requires a bit work on the build infra side.  Hence, we chose to use the way in this patch for the merge.


Repository:
  rG LLVM Github Monorepo

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https://reviews.llvm.org/D136698