Switch lowering: Take branch weight into account when ordering for fall-through

[oota-llvm.git] / lib / CodeGen / SelectionDAG / SelectionDAGBuilder.cpp

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index d7edd2c19665550ff27ab09cf2caa3c575f7512e..985a4dfd49d76adc0412b6df6ebf07538e4ebfcf 100644 (file)
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -7678,11 +7678,12 @@ void SelectionDAGBuilder::lowerWorkItem(SwitchWorkListItem W, Value *Cond,
       return a.Weight > b.Weight;
     });
 
-    // Rearrange the case blocks so that the last one falls through if possible.
-    // Start at the bottom as that's the case with the lowest weight.
-    // FIXME: Take branch probability into account.
+    // Rearrange the case blocks so that the last one falls through if possible
+    // without without changing the order of weights.
     for (CaseClusterIt I = W.LastCluster; I > W.FirstCluster; ) {
       --I;
+      if (I->Weight > W.LastCluster->Weight)
+        break;
       if (I->Kind == CC_Range && I->MBB == NextMBB) {
         std::swap(*I, *W.LastCluster);
         break;