[NFC] rename member of BitTestBlock and JumpTableHeader

Follow up to suggestions in D109103 via hans:
  I think UnreachableDefault (or UnreachableFallthrough) would be a
  better name now, since it doesn't just omit the range check, it also
  omits the last bit test.

Reviewed By: hans

Differential Revision: https://reviews.llvm.org/D109455

Author: nickdesaulniers

llvm/include/llvm/CodeGen/SwitchLoweringUtils.h

@@ -183,12 +183,12 @@ struct JumpTableHeader {
   const Value *SValue;
   MachineBasicBlock *HeaderBB;
   bool Emitted;
-  bool OmitRangeCheck;
+  bool FallthroughUnreachable;
 
   JumpTableHeader(APInt F, APInt L, const Value *SV, MachineBasicBlock *H,
                   bool E = false)
       : First(std::move(F)), Last(std::move(L)), SValue(SV), HeaderBB(H),
-        Emitted(E), OmitRangeCheck(false) {}
+        Emitted(E), FallthroughUnreachable(false) {}
 };
 using JumpTableBlock = std::pair<JumpTableHeader, JumpTable>;
 
@@ -218,14 +218,14 @@ struct BitTestBlock {
   BitTestInfo Cases;
   BranchProbability Prob;
   BranchProbability DefaultProb;
-  bool OmitRangeCheck;
+  bool FallthroughUnreachable;
 
   BitTestBlock(APInt F, APInt R, const Value *SV, unsigned Rg, MVT RgVT, bool E,
                bool CR, MachineBasicBlock *P, MachineBasicBlock *D,
                BitTestInfo C, BranchProbability Pr)
       : First(std::move(F)), Range(std::move(R)), SValue(SV), Reg(Rg),
         RegVT(RgVT), Emitted(E), ContiguousRange(CR), Parent(P), Default(D),
-        Cases(std::move(C)), Prob(Pr), OmitRangeCheck(false) {}
+        Cases(std::move(C)), Prob(Pr), FallthroughUnreachable(false) {}
 };
 
 /// Return the range of values within a range.

llvm/lib/CodeGen/GlobalISel/IRTranslator.cpp

@@ -785,7 +785,7 @@ bool IRTranslator::emitJumpTableHeader(SwitchCG::JumpTable &JT,
 
   JT.Reg = Sub.getReg(0);
 
-  if (JTH.OmitRangeCheck) {
+  if (JTH.FallthroughUnreachable) {
     if (JT.MBB != HeaderBB->getNextNode())
       MIB.buildBr(*JT.MBB);
     return true;
@@ -937,11 +937,10 @@ bool IRTranslator::lowerJumpTableWorkItem(SwitchCG::SwitchWorkListItem W,
     }
   }
 
-  // Skip the range check if the fallthrough block is unreachable.
   if (FallthroughUnreachable)
-    JTH->OmitRangeCheck = true;
+    JTH->FallthroughUnreachable = true;
 
-  if (!JTH->OmitRangeCheck)
+  if (!JTH->FallthroughUnreachable)
     addSuccessorWithProb(CurMBB, Fallthrough, FallthroughProb);
   addSuccessorWithProb(CurMBB, JumpMBB, JumpProb);
   CurMBB->normalizeSuccProbs();
@@ -1024,13 +1023,13 @@ void IRTranslator::emitBitTestHeader(SwitchCG::BitTestBlock &B,
 
   MachineBasicBlock *MBB = B.Cases[0].ThisBB;
 
-  if (!B.OmitRangeCheck)
+  if (!B.FallthroughUnreachable)
     addSuccessorWithProb(SwitchBB, B.Default, B.DefaultProb);
   addSuccessorWithProb(SwitchBB, MBB, B.Prob);
 
   SwitchBB->normalizeSuccProbs();
 
-  if (!B.OmitRangeCheck) {
+  if (!B.FallthroughUnreachable) {
     // Conditional branch to the default block.
     auto RangeCst = MIB.buildConstant(SwitchOpTy, B.Range);
     auto RangeCmp = MIB.buildICmp(CmpInst::Predicate::ICMP_UGT, LLT::scalar(1),
@@ -1130,10 +1129,8 @@ bool IRTranslator::lowerBitTestWorkItem(
     BTB->DefaultProb -= DefaultProb / 2;
   }
 
-  if (FallthroughUnreachable) {
-    // Skip the range check if the fallthrough block is unreachable.
-    BTB->OmitRangeCheck = true;
-  }
+  if (FallthroughUnreachable)
+    BTB->FallthroughUnreachable = true;
 
   // If we're in the right place, emit the bit test header right now.
   if (CurMBB == SwitchMBB) {
@@ -3019,7 +3016,7 @@ void IRTranslator::finalizeBasicBlock() {
       // test, and delete the last bit test.
 
       MachineBasicBlock *NextMBB;
-      if ((BTB.ContiguousRange || BTB.OmitRangeCheck) && j + 2 == ej) {
+      if ((BTB.ContiguousRange || BTB.FallthroughUnreachable) && j + 2 == ej) {
         // Second-to-last bit-test with contiguous range: fall through to the
         // target of the final bit test.
         NextMBB = BTB.Cases[j + 1].TargetBB;
@@ -3033,7 +3030,7 @@ void IRTranslator::finalizeBasicBlock() {
 
       emitBitTestCase(BTB, NextMBB, UnhandledProb, BTB.Reg, BTB.Cases[j], MBB);
 
-      if ((BTB.ContiguousRange || BTB.OmitRangeCheck) && j + 2 == ej) {
+      if ((BTB.ContiguousRange || BTB.FallthroughUnreachable) && j + 2 == ej) {
         // We need to record the replacement phi edge here that normally
         // happens in emitBitTestCase before we delete the case, otherwise the
         // phi edge will be lost.

llvm/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp

@@ -2572,7 +2572,7 @@ void SelectionDAGBuilder::visitJumpTableHeader(SwitchCG::JumpTable &JT,
                                     JumpTableReg, SwitchOp);
   JT.Reg = JumpTableReg;
 
-  if (!JTH.OmitRangeCheck) {
+  if (!JTH.FallthroughUnreachable) {
     // Emit the range check for the jump table, and branch to the default block
     // for the switch statement if the value being switched on exceeds the
     // largest case in the switch.
@@ -2784,13 +2784,13 @@ void SelectionDAGBuilder::visitBitTestHeader(BitTestBlock &B,
 
   MachineBasicBlock* MBB = B.Cases[0].ThisBB;
 
-  if (!B.OmitRangeCheck)
+  if (!B.FallthroughUnreachable)
     addSuccessorWithProb(SwitchBB, B.Default, B.DefaultProb);
   addSuccessorWithProb(SwitchBB, MBB, B.Prob);
   SwitchBB->normalizeSuccProbs();
 
   SDValue Root = CopyTo;
-  if (!B.OmitRangeCheck) {
+  if (!B.FallthroughUnreachable) {
     // Conditional branch to the default block.
     SDValue RangeCmp = DAG.getSetCC(dl,
         TLI.getSetCCResultType(DAG.getDataLayout(), *DAG.getContext(),
@@ -10826,12 +10826,10 @@ void SelectionDAGBuilder::lowerWorkItem(SwitchWorkListItem W, Value *Cond,
           }
         }
 
-        if (FallthroughUnreachable) {
-          // Skip the range check if the fallthrough block is unreachable.
-          JTH->OmitRangeCheck = true;
-        }
+        if (FallthroughUnreachable)
+          JTH->FallthroughUnreachable = true;
 
-        if (!JTH->OmitRangeCheck)
+        if (!JTH->FallthroughUnreachable)
           addSuccessorWithProb(CurMBB, Fallthrough, FallthroughProb);
         addSuccessorWithProb(CurMBB, JumpMBB, JumpProb);
         CurMBB->normalizeSuccProbs();
@@ -10869,9 +10867,8 @@ void SelectionDAGBuilder::lowerWorkItem(SwitchWorkListItem W, Value *Cond,
           BTB->DefaultProb -= DefaultProb / 2;
         }
 
-        // Skip the range check if the fallthrough block is unreachable.
         if (FallthroughUnreachable)
-          BTB->OmitRangeCheck = true;
+          BTB->FallthroughUnreachable = true;
 
         // If we're in the right place, emit the bit test header right now.
         if (CurMBB == SwitchMBB) {

llvm/lib/CodeGen/SelectionDAG/SelectionDAGISel.cpp

@@ -1864,7 +1864,7 @@ SelectionDAGISel::FinishBasicBlock() {
       // test, and delete the last bit test.
 
       MachineBasicBlock *NextMBB;
-      if ((BTB.ContiguousRange || BTB.OmitRangeCheck) && j + 2 == ej) {
+      if ((BTB.ContiguousRange || BTB.FallthroughUnreachable) && j + 2 == ej) {
         // Second-to-last bit-test with contiguous range or omitted range
         // check: fall through to the target of the final bit test.
         NextMBB = BTB.Cases[j + 1].TargetBB;
@@ -1883,7 +1883,7 @@ SelectionDAGISel::FinishBasicBlock() {
       SDB->clear();
       CodeGenAndEmitDAG();
 
-      if ((BTB.ContiguousRange || BTB.OmitRangeCheck) && j + 2 == ej) {
+      if ((BTB.ContiguousRange || BTB.FallthroughUnreachable) && j + 2 == ej) {
         // Since we're not going to use the final bit test, remove it.
         BTB.Cases.pop_back();
         break;