forked from OSchip/llvm-project
365b225d46
1. PGOMemOPSizeOpt grabs only the first, up to five (by default) entries from the value profile metadata and preserves the remaining entries for the fallback memop call site. If there are more than five entries, the rest of the entries would get dropped. This is fine for PGOMemOPSizeOpt itself as it only promotes up to 3 (by default) values, but potentially not for other downstream passes that may use the value profile metadata. 2. PGOMemOPSizeOpt originally assumed that only values 0 through 8 are kept track of. When the range buckets were introduced, it was changed to skip the range buckets, but since it does not grab all entries (only five), if some range buckets exist in the first five entries, it could potentially cause fewer promotion opportunities (eg. if 4 out of 5 were range buckets, it may be able to promote up to one non-range bucket, as opposed to 3.) Also, combined with 1, it means that wrong entries may be preserved, as it didn't correctly keep track of which were entries were skipped. To fix this, PGOMemOPSizeOpt now grabs all the entries (up to the maximum number of value profile buckets), keeps track of which entries were skipped, and preserves all the remaining entries. Differential Revision: https://reviews.llvm.org/D97592 |
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| InstrProfData.inc | ||