Start TargetRegisterClass indices at 0 instead of 1, so that

MachineRegisterInfo doesn't have to confusingly allocate an extra
entry.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@106296 91177308-0d34-0410-b5e6-96231b3b80d8

9 files changed, 56 insertions, 49 deletions

diff --git a/include/llvm/CodeGen/MachineRegisterInfo.h b/include/llvm/CodeGen/MachineRegisterInfo.h
index fa14fdc3f1..bea64de15f 100644
--- a/include/llvm/CodeGen/MachineRegisterInfo.h
+++ b/include/llvm/CodeGen/MachineRegisterInfo.h
@@ -35,7 +35,7 @@ class MachineRegisterInfo {
   /// RegClassVRegMap - This vector acts as a map from TargetRegisterClass to
   /// virtual registers. For each target register class, it keeps a list of
   /// virtual registers belonging to the class.
-  std::vector<std::vector<unsigned> > RegClass2VRegMap;
+  std::vector<unsigned> *RegClass2VRegMap;
 
   /// RegAllocHints - This vector records register allocation hints for virtual
   /// registers. For each virtual register, it keeps a register and hint type
diff --git a/include/llvm/Target/TargetInstrDesc.h b/include/llvm/Target/TargetInstrDesc.h
index a004f95ebc..8f0a6cb1a6 100644
--- a/include/llvm/Target/TargetInstrDesc.h
+++ b/include/llvm/Target/TargetInstrDesc.h
@@ -55,7 +55,7 @@ public:
   ///
   /// NOTE: This member should be considered to be private, all access should go
   /// through "getRegClass(TRI)" below.
-  unsigned short RegClass;
+  short RegClass;
   
   /// Flags - These are flags from the TOI::OperandFlags enum.
   unsigned short Flags;
diff --git a/include/llvm/Target/TargetRegisterInfo.h b/include/llvm/Target/TargetRegisterInfo.h
index c75a856bc5..16a2be9539 100644
--- a/include/llvm/Target/TargetRegisterInfo.h
+++ b/include/llvm/Target/TargetRegisterInfo.h
@@ -523,8 +523,8 @@ public:
   /// getRegClass - Returns the register class associated with the enumeration
   /// value.  See class TargetOperandInfo.
   const TargetRegisterClass *getRegClass(unsigned i) const {
-    assert(i <= getNumRegClasses() && "Register Class ID out of range");
-    return i ? RegClassBegin[i - 1] : NULL;
+    assert(i < getNumRegClasses() && "Register Class ID out of range");
+    return RegClassBegin[i];
   }
 
   /// getPointerRegClass - Returns a TargetRegisterClass used for pointer
diff --git a/lib/CodeGen/MachineRegisterInfo.cpp b/lib/CodeGen/MachineRegisterInfo.cpp
index e09e7432d4..3982499eab 100644
--- a/lib/CodeGen/MachineRegisterInfo.cpp
+++ b/lib/CodeGen/MachineRegisterInfo.cpp
@@ -20,7 +20,7 @@ using namespace llvm;
 MachineRegisterInfo::MachineRegisterInfo(const TargetRegisterInfo &TRI) {
   VRegInfo.reserve(256);
   RegAllocHints.reserve(256);
-  RegClass2VRegMap.resize(TRI.getNumRegClasses()+1); // RC ID starts at 1.
+  RegClass2VRegMap = new std::vector<unsigned>[TRI.getNumRegClasses()];
   UsedPhysRegs.resize(TRI.getNumRegs());
   
   // Create the physreg use/def lists.
@@ -52,7 +52,7 @@ MachineRegisterInfo::setRegClass(unsigned Reg, const TargetRegisterClass *RC) {
   // Remove from old register class's vregs list. This may be slow but
   // fortunately this operation is rarely needed.
   std::vector<unsigned> &VRegs = RegClass2VRegMap[OldRC->getID()];
-  std::vector<unsigned>::iterator I=std::find(VRegs.begin(), VRegs.end(), VR);
+  std::vector<unsigned>::iterator I = std::find(VRegs.begin(), VRegs.end(), VR);
   VRegs.erase(I);
 
   // Add to new register class's vregs list.
diff --git a/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp b/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp
index 6d0f529263..a0742937f8 100644
--- a/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp
+++ b/lib/Target/ARM/Disassembler/ARMDisassemblerCore.cpp
@@ -765,7 +765,7 @@ static bool DisassembleBrFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
           || Opcode == ARM::SMC || Opcode == ARM::SVC) &&
          "Unexpected Opcode");
 
-  assert(NumOps >= 1 && OpInfo[0].RegClass == 0 && "Reg operand expected");
+  assert(NumOps >= 1 && OpInfo[0].RegClass < 0 && "Reg operand expected");
 
   int Imm32 = 0;
   if (Opcode == ARM::SMC) {
@@ -1106,7 +1106,7 @@ static bool DisassembleDPSoRegFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
 
   assert((OpInfo[OpIdx].RegClass == ARM::GPRRegClassID) &&
          (OpInfo[OpIdx+1].RegClass == ARM::GPRRegClassID) &&
-         (OpInfo[OpIdx+2].RegClass == 0) &&
+         (OpInfo[OpIdx+2].RegClass < 0) &&
          "Expect 3 reg operands");
 
   // Register-controlled shifts have Inst{7} = 0 and Inst{4} = 1.
@@ -1201,7 +1201,7 @@ static bool DisassembleLdStFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
     return false;
 
   assert((OpInfo[OpIdx].RegClass == ARM::GPRRegClassID) &&
-         (OpInfo[OpIdx+1].RegClass == 0) &&
+         (OpInfo[OpIdx+1].RegClass < 0) &&
          "Expect 1 reg operand followed by 1 imm operand");
 
   ARM_AM::AddrOpc AddrOpcode = getUBit(insn) ? ARM_AM::add : ARM_AM::sub;
@@ -1323,7 +1323,7 @@ static bool DisassembleLdStMiscFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
     return false;
 
   assert((OpInfo[OpIdx].RegClass == ARM::GPRRegClassID) &&
-         (OpInfo[OpIdx+1].RegClass == 0) &&
+         (OpInfo[OpIdx+1].RegClass < 0) &&
          "Expect 1 reg operand followed by 1 imm operand");
 
   ARM_AM::AddrOpc AddrOpcode = getUBit(insn) ? ARM_AM::add : ARM_AM::sub;
@@ -1494,7 +1494,7 @@ static bool DisassembleArithMiscFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
 
   // If there is still an operand info left which is an immediate operand, add
   // an additional imm5 LSL/ASR operand.
-  if (ThreeReg && OpInfo[OpIdx].RegClass == 0
+  if (ThreeReg && OpInfo[OpIdx].RegClass < 0
       && !OpInfo[OpIdx].isPredicate() && !OpInfo[OpIdx].isOptionalDef()) {
     // Extract the 5-bit immediate field Inst{11-7}.
     unsigned ShiftAmt = (insn >> ARMII::ShiftShift) & 0x1F;
@@ -1540,7 +1540,7 @@ static bool DisassembleExtFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
 
   // If there is still an operand info left which is an immediate operand, add
   // an additional rotate immediate operand.
-  if (OpIdx < NumOps && OpInfo[OpIdx].RegClass == 0
+  if (OpIdx < NumOps && OpInfo[OpIdx].RegClass < 0
       && !OpInfo[OpIdx].isPredicate() && !OpInfo[OpIdx].isOptionalDef()) {
     // Extract the 2-bit rotate field Inst{11-10}.
     unsigned rot = (insn >> ARMII::ExtRotImmShift) & 3;
@@ -1725,7 +1725,7 @@ static bool DisassembleVFPConv1Frm(MCInst &MI, unsigned Opcode, uint32_t insn,
            "Tied to operand expected");
     MI.addOperand(MI.getOperand(0));
 
-    assert(OpInfo[2].RegClass == 0 && !OpInfo[2].isPredicate() &&
+    assert(OpInfo[2].RegClass < 0 && !OpInfo[2].isPredicate() &&
            !OpInfo[2].isOptionalDef() && "Imm operand expected");
     MI.addOperand(MCOperand::CreateImm(fbits));
 
@@ -1984,7 +1984,7 @@ static bool DisassembleVFPMiscFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
   ++OpIdx;
 
   // Extract/decode the f64/f32 immediate.
-  if (OpIdx < NumOps && OpInfo[OpIdx].RegClass == 0
+  if (OpIdx < NumOps && OpInfo[OpIdx].RegClass < 0
         && !OpInfo[OpIdx].isPredicate() && !OpInfo[OpIdx].isOptionalDef()) {
     // The asm syntax specifies the before-expanded <imm>.
     // Not VFPExpandImm(slice(insn,19,16) << 4 | slice(insn, 3, 0),
@@ -2273,7 +2273,7 @@ static bool DisassembleNLdSt0(MCInst &MI, unsigned Opcode, uint32_t insn,
     }
 
     assert((OpIdx+1) < NumOps && OpInfo[OpIdx].RegClass == ARM::GPRRegClassID &&
-           OpInfo[OpIdx + 1].RegClass == 0 && "Addrmode #6 Operands expected");
+           OpInfo[OpIdx + 1].RegClass < 0 && "Addrmode #6 Operands expected");
     MI.addOperand(MCOperand::CreateReg(getRegisterEnum(B, ARM::GPRRegClassID,
                                                        Rn)));
     MI.addOperand(MCOperand::CreateImm(0)); // Alignment ignored?
@@ -2299,7 +2299,7 @@ static bool DisassembleNLdSt0(MCInst &MI, unsigned Opcode, uint32_t insn,
     }
 
     // Handle possible lane index.
-    if (OpIdx < NumOps && OpInfo[OpIdx].RegClass == 0
+    if (OpIdx < NumOps && OpInfo[OpIdx].RegClass < 0
         && !OpInfo[OpIdx].isPredicate() && !OpInfo[OpIdx].isOptionalDef()) {
       MI.addOperand(MCOperand::CreateImm(decodeLaneIndex(insn)));
       ++OpIdx;
@@ -2325,7 +2325,7 @@ static bool DisassembleNLdSt0(MCInst &MI, unsigned Opcode, uint32_t insn,
     }
 
     assert((OpIdx+1) < NumOps && OpInfo[OpIdx].RegClass == ARM::GPRRegClassID &&
-           OpInfo[OpIdx + 1].RegClass == 0 && "Addrmode #6 Operands expected");
+           OpInfo[OpIdx + 1].RegClass < 0 && "Addrmode #6 Operands expected");
     MI.addOperand(MCOperand::CreateReg(getRegisterEnum(B, ARM::GPRRegClassID,
                                                        Rn)));
     MI.addOperand(MCOperand::CreateImm(0)); // Alignment ignored?
@@ -2344,7 +2344,7 @@ static bool DisassembleNLdSt0(MCInst &MI, unsigned Opcode, uint32_t insn,
     }
 
     // Handle possible lane index.
-    if (OpIdx < NumOps && OpInfo[OpIdx].RegClass == 0
+    if (OpIdx < NumOps && OpInfo[OpIdx].RegClass < 0
         && !OpInfo[OpIdx].isPredicate() && !OpInfo[OpIdx].isOptionalDef()) {
       MI.addOperand(MCOperand::CreateImm(decodeLaneIndex(insn)));
       ++OpIdx;
@@ -2408,7 +2408,7 @@ static bool DisassembleN1RegModImmFrm(MCInst &MI, unsigned Opcode,
   assert(NumOps >= 2 &&
          (OpInfo[0].RegClass == ARM::DPRRegClassID ||
           OpInfo[0].RegClass == ARM::QPRRegClassID) &&
-         (OpInfo[1].RegClass == 0) &&
+         (OpInfo[1].RegClass < 0) &&
          "Expect 1 reg operand followed by 1 imm operand");
 
   // Qd/Dd = Inst{22:15-12} => NEON Rd
@@ -2522,7 +2522,7 @@ static bool DisassembleNVdVmOptImm(MCInst &MI, unsigned Opc, uint32_t insn,
   }
 
   // Add the imm operand, if required.
-  if (OpIdx < NumOps && OpInfo[OpIdx].RegClass == 0
+  if (OpIdx < NumOps && OpInfo[OpIdx].RegClass < 0
       && !OpInfo[OpIdx].isPredicate() && !OpInfo[OpIdx].isOptionalDef()) {
 
     unsigned imm = 0xFFFFFFFF;
@@ -2602,7 +2602,7 @@ static bool DisassembleNVectorShift(MCInst &MI, unsigned Opcode, uint32_t insn,
                                                      decodeNEONRm(insn))));
   ++OpIdx;
 
-  assert(OpInfo[OpIdx].RegClass == 0 && "Imm operand expected");
+  assert(OpInfo[OpIdx].RegClass < 0 && "Imm operand expected");
 
   // Add the imm operand.
   
@@ -2732,7 +2732,7 @@ static bool DisassembleNVdVnVmOptImm(MCInst &MI, unsigned Opcode, uint32_t insn,
                   getRegisterEnum(B, OpInfo[OpIdx].RegClass, m)));
   ++OpIdx;
 
-  if (OpIdx < NumOps && OpInfo[OpIdx].RegClass == 0
+  if (OpIdx < NumOps && OpInfo[OpIdx].RegClass < 0
       && !OpInfo[OpIdx].isPredicate() && !OpInfo[OpIdx].isOptionalDef()) {
     // Add the imm operand.
     unsigned Imm = 0;
@@ -2857,7 +2857,7 @@ static bool DisassembleNEONGetLnFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
   assert(TID.getNumDefs() == 1 && NumOps >= 3 &&
          OpInfo[0].RegClass == ARM::GPRRegClassID &&
          OpInfo[1].RegClass == ARM::DPRRegClassID &&
-         OpInfo[2].RegClass == 0 &&
+         OpInfo[2].RegClass < 0 &&
          "Expect >= 3 operands with one dst operand");
 
   ElemSize esize =
@@ -2893,7 +2893,7 @@ static bool DisassembleNEONSetLnFrm(MCInst &MI, unsigned Opcode, uint32_t insn,
          OpInfo[1].RegClass == ARM::DPRRegClassID &&
          TID.getOperandConstraint(1, TOI::TIED_TO) != -1 &&
          OpInfo[2].RegClass == ARM::GPRRegClassID &&
-         OpInfo[3].RegClass == 0 &&
+         OpInfo[3].RegClass < 0 &&
          "Expect >= 3 operands with one dst operand");
 
   ElemSize esize =
@@ -3203,7 +3203,8 @@ bool ARMBasicMCBuilder::DoPredicateOperands(MCInst& MI, unsigned Opcode,
   // a pair of TargetOperandInfos with isPredicate() property.
   if (NumOpsRemaining >= 2 &&
       OpInfo[Idx].isPredicate() && OpInfo[Idx+1].isPredicate() &&
-      OpInfo[Idx].RegClass == 0 && OpInfo[Idx+1].RegClass == ARM::CCRRegClassID)
+      OpInfo[Idx].RegClass < 0 &&
+      OpInfo[Idx+1].RegClass == ARM::CCRRegClassID)
   {
     // If we are inside an IT block, get the IT condition bits maintained via
     // ARMBasicMCBuilder::ITState[7:0], through ARMBasicMCBuilder::GetITCond().
@@ -3235,7 +3236,8 @@ bool ARMBasicMCBuilder::TryPredicateAndSBitModifier(MCInst& MI, unsigned Opcode,
   // a pair of TargetOperandInfos with isPredicate() property.
   if (NumOpsRemaining >= 2 &&
       OpInfo[Idx].isPredicate() && OpInfo[Idx+1].isPredicate() &&
-      OpInfo[Idx].RegClass == 0 && OpInfo[Idx+1].RegClass == ARM::CCRRegClassID)
+      OpInfo[Idx].RegClass < 0 &&
+      OpInfo[Idx+1].RegClass == ARM::CCRRegClassID)
   {
     // If we are inside an IT block, get the IT condition bits maintained via
     // ARMBasicMCBuilder::ITState[7:0], through ARMBasicMCBuilder::GetITCond().
diff --git a/lib/Target/ARM/Disassembler/ThumbDisassemblerCore.h b/lib/Target/ARM/Disassembler/ThumbDisassemblerCore.h
index 4b2e308248..4b7a0bf6fd 100644
--- a/lib/Target/ARM/Disassembler/ThumbDisassemblerCore.h
+++ b/lib/Target/ARM/Disassembler/ThumbDisassemblerCore.h
@@ -395,7 +395,7 @@ static bool DisassembleThumb1General(MCInst &MI, unsigned Opcode, uint32_t insn,
     MI.addOperand(MCOperand::CreateReg(getRegisterEnum(B, ARM::tGPRRegClassID,
                                                        getT1tRm(insn))));
   } else {
-    assert(OpInfo[OpIdx].RegClass == 0 &&
+    assert(OpInfo[OpIdx].RegClass < 0 &&
            !OpInfo[OpIdx].isPredicate() && !OpInfo[OpIdx].isOptionalDef()
            && "Pure imm operand expected");
     MI.addOperand(MCOperand::CreateImm(UseRt ? getT1Imm8(insn)
@@ -531,7 +531,7 @@ static bool DisassembleThumb1LdPC(MCInst &MI, unsigned Opcode, uint32_t insn,
   if (!OpInfo) return false;
 
   assert(NumOps >= 2 && OpInfo[0].RegClass == ARM::tGPRRegClassID &&
-         (OpInfo[1].RegClass == 0 &&
+         (OpInfo[1].RegClass < 0 &&
           !OpInfo[1].isPredicate() &&
           !OpInfo[1].isOptionalDef())
          && "Invalid arguments");
@@ -598,7 +598,7 @@ static bool DisassembleThumb1LdSt(unsigned opA, MCInst &MI, unsigned Opcode,
 
   assert(OpIdx < NumOps && "More operands expected");
 
-  if (OpInfo[OpIdx].RegClass == 0 && !OpInfo[OpIdx].isPredicate() &&
+  if (OpInfo[OpIdx].RegClass < 0 && !OpInfo[OpIdx].isPredicate() &&
       !OpInfo[OpIdx].isOptionalDef()) {
 
     MI.addOperand(MCOperand::CreateImm(Imm5 ? getT1Imm5(insn) : 0));
@@ -632,7 +632,7 @@ static bool DisassembleThumb1LdStSP(MCInst &MI, unsigned Opcode, uint32_t insn,
   assert(NumOps >= 3 &&
          OpInfo[0].RegClass == ARM::tGPRRegClassID &&
          OpInfo[1].RegClass == ARM::GPRRegClassID &&
-         (OpInfo[2].RegClass == 0 &&
+         (OpInfo[2].RegClass < 0 &&
           !OpInfo[2].isPredicate() &&
           !OpInfo[2].isOptionalDef())
          && "Invalid arguments");
@@ -658,7 +658,7 @@ static bool DisassembleThumb1AddPCi(MCInst &MI, unsigned Opcode, uint32_t insn,
   if (!OpInfo) return false;
 
   assert(NumOps >= 2 && OpInfo[0].RegClass == ARM::tGPRRegClassID &&
-         (OpInfo[1].RegClass == 0 &&
+         (OpInfo[1].RegClass < 0 &&
           !OpInfo[1].isPredicate() &&
           !OpInfo[1].isOptionalDef())
          && "Invalid arguments");
@@ -685,7 +685,7 @@ static bool DisassembleThumb1AddSPi(MCInst &MI, unsigned Opcode, uint32_t insn,
   assert(NumOps >= 3 &&
          OpInfo[0].RegClass == ARM::tGPRRegClassID &&
          OpInfo[1].RegClass == ARM::GPRRegClassID &&
-         (OpInfo[2].RegClass == 0 &&
+         (OpInfo[2].RegClass < 0 &&
           !OpInfo[2].isPredicate() &&
           !OpInfo[2].isOptionalDef())
          && "Invalid arguments");
@@ -761,7 +761,7 @@ static bool DisassembleThumb1Misc(MCInst &MI, unsigned Opcode, uint32_t insn,
   // Predicate operands are handled elsewhere.
   if (NumOps == 2 &&
       OpInfo[0].isPredicate() && OpInfo[1].isPredicate() &&
-      OpInfo[0].RegClass == 0 && OpInfo[1].RegClass == ARM::CCRRegClassID) {
+      OpInfo[0].RegClass < 0 && OpInfo[1].RegClass == ARM::CCRRegClassID) {
     return true;
   }
 
@@ -808,7 +808,7 @@ static bool DisassembleThumb1Misc(MCInst &MI, unsigned Opcode, uint32_t insn,
   }
 
   assert(NumOps >= 2 && OpInfo[0].RegClass == ARM::tGPRRegClassID &&
-         (OpInfo[1].RegClass==0 || OpInfo[1].RegClass==ARM::tGPRRegClassID)
+         (OpInfo[1].RegClass < 0 || OpInfo[1].RegClass==ARM::tGPRRegClassID)
          && "Expect >=2 operands");
 
   // Add the destination operand.
@@ -913,7 +913,7 @@ static bool DisassembleThumb1CondBr(MCInst &MI, unsigned Opcode, uint32_t insn,
   const TargetOperandInfo *OpInfo = ARMInsts[Opcode].OpInfo;
   if (!OpInfo) return false;
 
-  assert(NumOps == 3 && OpInfo[0].RegClass == 0 &&
+  assert(NumOps == 3 && OpInfo[0].RegClass < 0 &&
          OpInfo[1].isPredicate() && OpInfo[2].RegClass == ARM::CCRRegClassID
          && "Exactly 3 operands expected");
 
@@ -939,7 +939,7 @@ static bool DisassembleThumb1Br(MCInst &MI, unsigned Opcode, uint32_t insn,
   const TargetOperandInfo *OpInfo = ARMInsts[Opcode].OpInfo;
   if (!OpInfo) return false;
 
-  assert(NumOps == 1 && OpInfo[0].RegClass == 0 && "1 imm operand expected");
+  assert(NumOps == 1 && OpInfo[0].RegClass < 0 && "1 imm operand expected");
 
   unsigned Imm11 = getT1Imm11(insn);
 
@@ -1239,7 +1239,7 @@ static bool DisassembleThumb2LdStDual(MCInst &MI, unsigned Opcode,
          && OpInfo[0].RegClass == ARM::GPRRegClassID
          && OpInfo[1].RegClass == ARM::GPRRegClassID
          && OpInfo[2].RegClass == ARM::GPRRegClassID
-         && OpInfo[3].RegClass == 0
+         && OpInfo[3].RegClass < 0
          && "Expect >= 4 operands and first 3 as reg operands");
 
   // Add the <Rt> <Rt2> operands.
@@ -1322,8 +1322,8 @@ static bool DisassembleThumb2DPSoReg(MCInst &MI, unsigned Opcode, uint32_t insn,
     assert(NumOps == 4
            && OpInfo[0].RegClass == ARM::GPRRegClassID
            && OpInfo[1].RegClass == ARM::GPRRegClassID
-           && OpInfo[2].RegClass == 0
-           && OpInfo[3].RegClass == 0
+           && OpInfo[2].RegClass < 0
+           && OpInfo[3].RegClass < 0
            && "Exactlt 4 operands expect and first two as reg operands");
     // Only need to populate the src reg operand.
     MI.addOperand(MCOperand::CreateReg(getRegisterEnum(B, ARM::GPRRegClassID,
@@ -1375,7 +1375,7 @@ static bool DisassembleThumb2DPSoReg(MCInst &MI, unsigned Opcode, uint32_t insn,
   if (NumOps == OpIdx)
     return true;
 
-  if (OpInfo[OpIdx].RegClass == 0 && !OpInfo[OpIdx].isPredicate()
+  if (OpInfo[OpIdx].RegClass < 0 && !OpInfo[OpIdx].isPredicate()
       && !OpInfo[OpIdx].isOptionalDef()) {
 
     if (Thumb2ShiftOpcode(Opcode))
@@ -1440,7 +1440,7 @@ static bool DisassembleThumb2DPModImm(MCInst &MI, unsigned Opcode,
   }
 
   // The modified immediate operand should come next.
-  assert(OpIdx < NumOps && OpInfo[OpIdx].RegClass == 0 &&
+  assert(OpIdx < NumOps && OpInfo[OpIdx].RegClass < 0 &&
          !OpInfo[OpIdx].isPredicate() && !OpInfo[OpIdx].isOptionalDef()
          && "Pure imm operand expected");
 
@@ -1555,7 +1555,7 @@ static bool DisassembleThumb2DPBinImm(MCInst &MI, unsigned Opcode,
     ++OpIdx;
   }
 
-  assert(OpInfo[OpIdx].RegClass == 0 && !OpInfo[OpIdx].isPredicate()
+  assert(OpInfo[OpIdx].RegClass < 0 && !OpInfo[OpIdx].isPredicate()
          && !OpInfo[OpIdx].isOptionalDef()
          && "Pure imm operand expected");
 
@@ -1772,7 +1772,7 @@ static bool DisassembleThumb2PreLoad(MCInst &MI, unsigned Opcode, uint32_t insn,
     MI.addOperand(MCOperand::CreateReg(getRegisterEnum(B, ARM::GPRRegClassID,
                                                        decodeRm(insn))));
   } else {
-    assert(OpInfo[OpIdx].RegClass == 0 && !OpInfo[OpIdx].isPredicate()
+    assert(OpInfo[OpIdx].RegClass < 0 && !OpInfo[OpIdx].isPredicate()
            && !OpInfo[OpIdx].isOptionalDef()
            && "Pure imm operand expected");
     int Offset = 0;
@@ -1792,7 +1792,7 @@ static bool DisassembleThumb2PreLoad(MCInst &MI, unsigned Opcode, uint32_t insn,
   }
   ++OpIdx;
 
-  if (OpIdx < NumOps && OpInfo[OpIdx].RegClass == 0 &&
+  if (OpIdx < NumOps && OpInfo[OpIdx].RegClass < 0 &&
       !OpInfo[OpIdx].isPredicate() && !OpInfo[OpIdx].isOptionalDef()) {
     // Fills in the shift amount for t2PLDs, t2PLDWs, t2PLIs.
     MI.addOperand(MCOperand::CreateImm(slice(insn, 5, 4)));
@@ -1818,7 +1818,7 @@ static bool DisassembleThumb2Ldpci(MCInst &MI, unsigned Opcode,
 
   assert(NumOps >= 2 &&
          OpInfo[0].RegClass == ARM::GPRRegClassID &&
-         OpInfo[1].RegClass == 0 &&
+         OpInfo[1].RegClass < 0 &&
          "Expect >= 2 operands, first as reg, and second as imm operand");
 
   // Build the register operand, followed by the (+/-)imm12 immediate.
@@ -1930,7 +1930,7 @@ static bool DisassembleThumb2LdSt(bool Load, MCInst &MI, unsigned Opcode,
     ++OpIdx;
   }
 
-  assert(OpInfo[OpIdx].RegClass == 0 && !OpInfo[OpIdx].isPredicate()
+  assert(OpInfo[OpIdx].RegClass < 0 && !OpInfo[OpIdx].isPredicate()
          && !OpInfo[OpIdx].isOptionalDef()
          && "Pure imm operand expected");
 
@@ -1981,7 +1981,7 @@ static bool DisassembleThumb2DPReg(MCInst &MI, unsigned Opcode, uint32_t insn,
                                                      decodeRm(insn))));
   ++OpIdx;
 
-  if (OpIdx < NumOps && OpInfo[OpIdx].RegClass == 0
+  if (OpIdx < NumOps && OpInfo[OpIdx].RegClass < 0
       && !OpInfo[OpIdx].isPredicate() && !OpInfo[OpIdx].isOptionalDef()) {
     // Add the rotation amount immediate.
     MI.addOperand(MCOperand::CreateImm(decodeRotate(insn)));
diff --git a/lib/Target/TargetInstrInfo.cpp b/lib/Target/TargetInstrInfo.cpp
index 094a57edb4..c099a7eaef 100644
--- a/lib/Target/TargetInstrInfo.cpp
+++ b/lib/Target/TargetInstrInfo.cpp
@@ -28,6 +28,10 @@ const TargetRegisterClass *
 TargetOperandInfo::getRegClass(const TargetRegisterInfo *TRI) const {
   if (isLookupPtrRegClass())
     return TRI->getPointerRegClass(RegClass);
+  // Instructions like INSERT_SUBREG do not have fixed register classes.
+  if (RegClass < 0)
+    return 0;
+  // Otherwise just look it up normally.
   return TRI->getRegClass(RegClass);
 }
 
diff --git a/utils/TableGen/InstrInfoEmitter.cpp b/utils/TableGen/InstrInfoEmitter.cpp
index e66192a221..f28af1589d 100644
--- a/utils/TableGen/InstrInfoEmitter.cpp
+++ b/utils/TableGen/InstrInfoEmitter.cpp
@@ -92,7 +92,8 @@ InstrInfoEmitter::GetOperandInfo(const CodeGenInstruction &Inst) {
       else if (OpR->isSubClassOf("PointerLikeRegClass"))
         Res += utostr(OpR->getValueAsInt("RegClassKind")) + ", ";
       else
-        Res += "0, ";
+        // -1 means the operand does not have a fixed register class.
+        Res += "-1, ";
       
       // Fill in applicable flags.
       Res += "0";
diff --git a/utils/TableGen/RegisterInfoEmitter.cpp b/utils/TableGen/RegisterInfoEmitter.cpp
index 26957472c0..a3ca0bc552 100644
--- a/utils/TableGen/RegisterInfoEmitter.cpp
+++ b/utils/TableGen/RegisterInfoEmitter.cpp
@@ -96,7 +96,7 @@ void RegisterInfoEmitter::runHeader(raw_ostream &OS) {
     for (unsigned i = 0, e = RegisterClasses.size(); i != e; ++i) {
       if (i) OS << ",\n";
       OS << "    " << RegisterClasses[i].getName() << "RegClassID";
-      OS << " = " << (i+1);
+      OS << " = " << i;
     }
     OS << "\n  };\n\n";