[PATCH] D81981: [PGO] Supplement PGO profile with Sample profile

[Wei Mi via Phabricator via llvm-commits]

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Comment at: llvm/tools/llvm-profdata/llvm-profdata.cpp:400
+  InstrProfRecord *ProfRecord = IFE.ProfRecord;
+  if (!InstrEntryCount) {
+    // If the function is never executed in instrumentation profile,
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davidxl wrote:
> handling this case (all zero case) in this way won't help much -- The branch Probablity pass will set all branch weights to 1 making all branch unbiased -- it is worse than using static heuristic based.
> 
> The right way I think is to remove their profile entries completely. I assume the compiler pass later will treat such functions as unknown and not put into .text.unlikely.
But I think for a large part of the functions missing in loadtest, they have all zero counter values, so it is better to have a way to handle them. 

Is it possible for PGO to handle the functions with only entry counter not being zero and with other counters all being zero in a special way -- for those functions, just set the entry count and skip the metadata setting inside of the function? So that those functions can use static profiling inside. 


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https://reviews.llvm.org/D81981