vendor/llvm/llvm-release_70-r348011

1 files changed, 14 insertions, 0 deletions

diff --git a/include/llvm/Support/GenericDomTreeConstruction.h b/include/llvm/Support/GenericDomTreeConstruction.h
index 103ff8ca476a9..977f209f92b39 100644
--- a/include/llvm/Support/GenericDomTreeConstruction.h
+++ b/include/llvm/Support/GenericDomTreeConstruction.h
@@ -1186,6 +1186,20 @@ struct SemiNCAInfo {
                << '\t' << U << "\n");
     LLVM_DEBUG(dbgs() << "\n");
 
+    // Recalculate the DominatorTree when the number of updates
+    // exceeds a threshold, which usually makes direct updating slower than
+    // recalculation. We select this threshold proportional to the
+    // size of the DominatorTree. The constant is selected
+    // by choosing the one with an acceptable performance on some real-world
+    // inputs.
+
+    // Make unittests of the incremental algorithm work
+    if (DT.DomTreeNodes.size() <= 100) {
+      if (NumLegalized > DT.DomTreeNodes.size())
+        CalculateFromScratch(DT, &BUI);
+    } else if (NumLegalized > DT.DomTreeNodes.size() / 40)
+      CalculateFromScratch(DT, &BUI);
+
     // If the DominatorTree was recalculated at some point, stop the batch
     // updates. Full recalculations ignore batch updates and look at the actual
     // CFG.