Address Eli's comments

Author: Shimin Cui

llvm/include/llvm/CodeGen/TargetLowering.h

@@ -1441,10 +1441,9 @@ class LLVM_ABI TargetLoweringBase {
   /// \p High as its lowest and highest case values, and expects \p NumCmps
   /// case value comparisons. Check if the number of destinations, comparison
   /// metric, and range are all suitable.
-  bool
-  isSuitableForBitTests(DenseMap<const BasicBlock *, unsigned int> DestCmps,
-                        const APInt &Low, const APInt &High,
-                        const DataLayout &DL) const {
+  bool isSuitableForBitTests(
+      const DenseMap<const BasicBlock *, unsigned int> DestCmps,
+      const APInt &Low, const APInt &High, const DataLayout &DL) const {
     // FIXME: I don't think NumCmps is the correct metric: a single case and a
     // range of cases both require only one branch to lower. Just looking at the
     // number of clusters and destinations should be enough to decide whether to
@@ -3726,6 +3725,9 @@ class LLVM_ABI TargetLoweringBase {
   /// backend supports.
   unsigned MinCmpXchgSizeInBits;
 
+  /// The minimum of largest number of comparisons to use bit test for switch.
+  unsigned MinimumBitTestCmps;
+
   /// This indicates if the target supports unaligned atomic operations.
   bool SupportsUnalignedAtomics;
 

llvm/lib/CodeGen/SwitchLoweringUtils.cpp

@@ -379,7 +379,7 @@ bool SwitchCG::SwitchLowering::buildBitTests(CaseClusterVector &Clusters,
     assert(Clusters[I].Kind == CC_Range);
     unsigned NumCmp = (Clusters[I].Low == Clusters[I].High) ? 1 : 2;
     const BasicBlock *BB = Clusters[I].MBB->getBasicBlock();
-    DestMap[BB] = DestMap.count(BB) ? (DestMap[BB] + NumCmp) : NumCmp;
+    DestMap[BB] += NumCmp;
   }
 
   APInt Low = Clusters[First].Low->getValue();

llvm/lib/CodeGen/TargetLoweringBase.cpp

@@ -91,10 +91,10 @@ static cl::opt<unsigned> OptsizeJumpTableDensity(
     cl::desc("Minimum density for building a jump table in "
              "an optsize function"));
 
-static cl::opt<unsigned>
-    MinimumBitTestCmps("min-bit-test-cmps", cl::init(2), cl::Hidden,
-                       cl::desc("Set minimum of largest number of comparisons "
-                                "to use bit test for switch."));
+static cl::opt<unsigned> MinimumBitTestCmpsOverride(
+    "min-bit-test-cmps", cl::init(2), cl::Hidden,
+    cl::desc("Set minimum of largest number of comparisons "
+             "to use bit test for switch."));
 
 // FIXME: This option is only to test if the strict fp operation processed
 // correctly by preventing mutating strict fp operation to normal fp operation
@@ -725,6 +725,8 @@ TargetLoweringBase::TargetLoweringBase(const TargetMachine &tm)
 
   MinCmpXchgSizeInBits = 0;
   SupportsUnalignedAtomics = false;
+
+  MinimumBitTestCmps = MinimumBitTestCmpsOverride;
 }
 
 // Define the virtual destructor out-of-line to act as a key method to anchor