commit 7bf4d4eee01df4debe56daa02912a479970c38f4
author Hans Wennborg <hans@hanshq.net> Mon Apr 27 23:52:19 2015 +0000
committer Hans Wennborg <hans@hanshq.net> Mon Apr 27 23:52:19 2015 +0000
tree 24093ddb0dffd22a9d448e97237adc60c32d1947
parent 948a4bbc92d48127136dd9436f7419d6ee6f4641

Switch lowering: use uint32_t for weights everywhere

I previously thought switch clusters would need to use uint64_t in case
the weights of multiple cases overflowed a 32-bit int. It turns
out that the weights on a terminator instruction are capped to allow for
being added together, so using a uint32_t should be safe.

llvm-svn: 235945

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 985a4df..71b221a 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2126,6 +2126,7 @@
       // the previous cluster.
       Clusters[DstIndex - 1].High = CaseVal;
       Clusters[DstIndex - 1].Weight += CC.Weight;
+      assert(Clusters[DstIndex - 1].Weight >= CC.Weight && "Weight overflow!");
     } else {
       std::memmove(&Clusters[DstIndex++], &Clusters[SrcIndex],
                    sizeof(Clusters[SrcIndex]));
@@ -7230,13 +7231,14 @@
                                          CaseCluster &JTCluster) {
   assert(First <= Last);
 
-  uint64_t Weight = 0;
+  uint32_t Weight = 0;
   unsigned NumCmps = 0;
   std::vector<MachineBasicBlock*> Table;
   DenseMap<MachineBasicBlock*, uint32_t> JTWeights;
   for (unsigned I = First; I <= Last; ++I) {
     assert(Clusters[I].Kind == CC_Range);
     Weight += Clusters[I].Weight;
+    assert(Weight >= Clusters[I].Weight && "Weight overflow!");
     APInt Low = Clusters[I].Low->getValue();
     APInt High = Clusters[I].High->getValue();
     NumCmps += (Low == High) ? 1 : 2;
@@ -7463,7 +7465,7 @@
   }
 
   CaseBitsVector CBV;
-  uint64_t TotalWeight = 0;
+  uint32_t TotalWeight = 0;
   for (unsigned i = First; i <= Last; ++i) {
     // Find the CaseBits for this destination.
     unsigned j;
@@ -7482,8 +7484,8 @@
       CB->Bits++;
     }
     CB->ExtraWeight += Clusters[i].Weight;
-    assert(CB->ExtraWeight >= Clusters[i].Weight && "Weight sum overflowed!");
     TotalWeight += Clusters[i].Weight;
+    assert(TotalWeight >= Clusters[i].Weight && "Weight overflow!");
   }
 
   BitTestInfo BTI;
@@ -7693,8 +7695,10 @@
 
   // Compute total weight.
   uint32_t UnhandledWeights = 0;
-  for (CaseClusterIt I = W.FirstCluster; I <= W.LastCluster; ++I)
+  for (CaseClusterIt I = W.FirstCluster; I <= W.LastCluster; ++I) {
     UnhandledWeights += I->Weight;
+    assert(UnhandledWeights >= I->Weight && "Weight overflow!");
+  }
 
   MachineBasicBlock *CurMBB = W.MBB;
   for (CaseClusterIt I = W.FirstCluster, E = W.LastCluster; I <= E; ++I) {
@@ -7859,8 +7863,10 @@
     MachineBasicBlock *Succ = FuncInfo.MBBMap[I.getCaseSuccessor()];
     const ConstantInt *CaseVal = I.getCaseValue();
     uint32_t Weight = 0; // FIXME: Use 1 instead?
-    if (BPI)
+    if (BPI) {
       Weight = BPI->getEdgeWeight(SI.getParent(), I.getSuccessorIndex());
+      assert(Weight <= UINT32_MAX / SI.getNumSuccessors());
+    }
     Clusters.push_back(CaseCluster::range(CaseVal, CaseVal, Succ, Weight));
   }
 

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h

diff --git a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
index 7c2cef6..ba6d974 100644
--- a/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
+++ b/llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.h
@@ -153,7 +153,7 @@
       unsigned JTCasesIndex;
       unsigned BTCasesIndex;
     };
-    uint64_t Weight;
+    uint32_t Weight;
 
     static CaseCluster range(const ConstantInt *Low, const ConstantInt *High,
                              MachineBasicBlock *MBB, uint32_t Weight) {