diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp index fe96f33d7729..f0a4c867f8cf 100644 --- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp +++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp @@ -7927,17 +7927,15 @@ void SelectionDAGBuilder::splitWorkItem(SwitchWorkList &WorkList, // Move LastLeft and FirstRight towards each other from opposite directions to // find a partitioning of the clusters which balances the weight on both - // sides. + // sides. If LeftWeight and RightWeight are equal, alternate which side is + // taken to ensure 0-weight nodes are distributed evenly. + unsigned I = 0; while (LastLeft + 1 < FirstRight) { - // Zero-weight nodes would cause skewed trees since they don't affect - // LeftWeight or RightWeight. - assert(LastLeft->Weight != 0); - assert(FirstRight->Weight != 0); - - if (LeftWeight < RightWeight) + if (LeftWeight < RightWeight || (LeftWeight == RightWeight && (I & 1))) LeftWeight += (++LastLeft)->Weight; else RightWeight += (--FirstRight)->Weight; + I++; } assert(LastLeft + 1 == FirstRight); assert(LastLeft >= W.FirstCluster); @@ -8007,15 +8005,8 @@ void SelectionDAGBuilder::visitSwitch(const SwitchInst &SI) { for (auto I : SI.cases()) { MachineBasicBlock *Succ = FuncInfo.MBBMap[I.getCaseSuccessor()]; const ConstantInt *CaseVal = I.getCaseValue(); - uint32_t Weight = 1; - if (BPI) { - // TODO - BPI used to guarantee non-zero weights, but this produces - // information loss (see PR 22718). Since we can't handle zero weights - // here, use the same flooring mechanism previously used by BPI. - Weight = std::max( - 1u, BPI->getEdgeWeight(SI.getParent(), I.getSuccessorIndex())); - assert(Weight <= UINT32_MAX / SI.getNumSuccessors()); - } + uint32_t Weight = + BPI ? BPI->getEdgeWeight(SI.getParent(), I.getSuccessorIndex()) : 0; Clusters.push_back(CaseCluster::range(CaseVal, CaseVal, Succ, Weight)); }