[PATCH] D24638: [thinlto] Basic thinlto fdo heuristic

[Mehdi AMINI via llvm-commits]

mehdi_amini added a comment.

Great to see this!

Can you add a test with three functions, hot/cold/unknown, and show the impact of the importing with a fixed `-import-instr-limit` and varying `-import-hot-multiplier`?


================
Comment at: lib/Analysis/ModuleSummaryAnalysis.cpp:113
@@ -101,1 +112,3 @@
+            ScaledCount ? getHotness(ScaledCount.getValue(), PSI)
+                        : CalleeInfo::HotnessType::Unknown);
       } else {
----------------
Can you split the statement:

```
auto Hotness = ScaledCount ? getHotness(ScaledCount.getValue(), PSI)
                        : CalleeInfo::HotnessType::Unknown;
CallGraphEdges[CalleeId].updateHotness(Hotness);
```

Same number of lines, but the flow is easier to read.

================
Comment at: lib/LTO/ThinLTOCodeGenerator.cpp:382
@@ -381,1 +381,3 @@
+      ProfileSummaryInfo PSI(TheModule);
+      auto Index = buildModuleSummaryIndex(TheModule, nullptr, PSI);
       WriteBitcodeToFile(&TheModule, OS, true, &Index);
----------------
At this point, not having PSI (i.e. making it optional is fine).


https://reviews.llvm.org/D24638