Initial checkin of the new "fast" instruction selection support. See

the comments in FastISelEmitter.cpp for details on what this is.
This is currently experimental and unusable.

llvm-svn: 54751

llvm/Makefile.rules

@@ -1296,9 +1296,14 @@ $(ObjDir)/%GenCodeEmitter.inc.tmp: %.td $(ObjDir)/.dir
 
 $(TARGET:%=$(ObjDir)/%GenDAGISel.inc.tmp): \
 $(ObjDir)/%GenDAGISel.inc.tmp : %.td $(ObjDir)/.dir
-	$(Echo) "Building $(<F) instruction selector implementation with tblgen"
+	$(Echo) "Building $(<F) DAG instruction selector implementation with tblgen"
 	$(Verb) $(TableGen) -gen-dag-isel -o $(call SYSPATH, $@) $<
 
+$(TARGET:%=$(ObjDir)/%GenFastISel.inc.tmp): \
+$(ObjDir)/%GenFastISel.inc.tmp : %.td $(ObjDir)/.dir
+	$(Echo) "Building $(<F) \"fast\" instruction selector implementation with tblgen"
+	$(Verb) $(TableGen) -gen-fast-isel -o $(call SYSPATH, $@) $<
+
 $(TARGET:%=$(ObjDir)/%GenSubtarget.inc.tmp): \
 $(ObjDir)/%GenSubtarget.inc.tmp : %.td $(ObjDir)/.dir
 	$(Echo) "Building $(<F) subtarget information with tblgen"

llvm/include/llvm/CodeGen/FastISel.h

@@ -0,0 +1,71 @@
+//===-- FastISel.h - Definition of the FastISel class ---------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the FastISel class.
+//  
+//===----------------------------------------------------------------------===//
+  
+#ifndef LLVM_CODEGEN_FASTISEL_H
+#define LLVM_CODEGEN_FASTISEL_H
+
+#include "llvm/BasicBlock.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/CodeGen/SelectionDAGNodes.h"
+
+namespace llvm {
+
+class MachineBasicBlock;
+class MachineFunction;
+class TargetInstrInfo;
+class TargetRegisterClass;
+
+/// This file defines the FastISel class. This is a fast-path instruction
+/// selection class that generates poor code and doesn't support illegal
+/// types or non-trivial lowering, but runs quickly.
+class FastISel {
+  MachineBasicBlock *MBB;
+  MachineFunction *MF;
+  const TargetInstrInfo *TII;
+
+public:
+  FastISel(MachineBasicBlock *mbb, MachineFunction *mf,
+           const TargetInstrInfo *tii)
+    : MBB(mbb), MF(mf), TII(tii) {}
+
+  /// SelectInstructions - Do "fast" instruction selection over the
+  /// LLVM IR instructions in the range [Begin, N) where N is either
+  /// End or the first unsupported instruction. Return N.
+  /// ValueMap is filled in with a mapping of LLVM IR Values to
+  /// register numbers.
+  BasicBlock::iterator
+  SelectInstructions(BasicBlock::iterator Begin, BasicBlock::iterator End,
+                     DenseMap<const Value*, unsigned> &ValueMap);
+
+protected:
+  virtual unsigned FastEmit_(MVT::SimpleValueType VT,
+                             ISD::NodeType Opcode);
+  virtual unsigned FastEmit_r(MVT::SimpleValueType VT,
+                              ISD::NodeType Opcode, unsigned Op0);
+  virtual unsigned FastEmit_rr(MVT::SimpleValueType VT,
+                               ISD::NodeType Opcode,
+                               unsigned Op0, unsigned Op1);
+
+  unsigned FastEmitInst_(unsigned MachineInstOpcode,
+                         const TargetRegisterClass *RC);
+  unsigned FastEmitInst_r(unsigned MachineInstOpcode,
+                          const TargetRegisterClass *RC,
+                          unsigned Op0);
+  unsigned FastEmitInst_rr(unsigned MachineInstOpcode,
+                           const TargetRegisterClass *RC,
+                           unsigned Op0, unsigned Op1);
+};
+
+}
+
+#endif

llvm/lib/CodeGen/SelectionDAG/FastISel.cpp

@@ -0,0 +1,104 @@
+///===-- FastISel.cpp - Implementation of the FastISel class --------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains the implementation of the FastISel class.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/CodeGen/FastISel.h"
+#include "llvm/CodeGen/MachineInstrBuilder.h"
+#include "llvm/CodeGen/MachineRegisterInfo.h"
+#include "llvm/Target/TargetInstrInfo.h"
+using namespace llvm;
+
+BasicBlock::iterator
+FastISel::SelectInstructions(BasicBlock::iterator Begin, BasicBlock::iterator End,
+                             DenseMap<const Value*, unsigned> &ValueMap) {
+  BasicBlock::iterator I = Begin;
+
+  for (; I != End; ++I) {
+    switch (I->getOpcode()) {
+    case Instruction::Add: {
+      unsigned Op0 = ValueMap[I->getOperand(0)];
+      unsigned Op1 = ValueMap[I->getOperand(1)];
+      MVT VT = MVT::getMVT(I->getType(), /*HandleUnknown=*/true);
+      if (VT == MVT::Other || !VT.isSimple()) {
+        // Unhandled type. Halt "fast" selection and bail.
+        return I;
+      }
+      unsigned ResultReg = FastEmit_rr(VT.getSimpleVT(), ISD::ADD, Op0, Op1);
+      ValueMap[I] = ResultReg;
+      break;
+    }
+    default:
+      // Unhandled instruction. Halt "fast" selection and bail.
+      return I;
+    }
+  }
+
+  return I;
+}
+
+unsigned FastISel::FastEmit_(MVT::SimpleValueType, ISD::NodeType) {
+  return 0;
+}
+
+unsigned FastISel::FastEmit_r(MVT::SimpleValueType, ISD::NodeType,
+                              unsigned /*Op0*/) {
+  return 0;
+}
+
+unsigned FastISel::FastEmit_rr(MVT::SimpleValueType, ISD::NodeType,
+                               unsigned /*Op0*/, unsigned /*Op0*/) {
+  return 0;
+}
+
+unsigned FastISel::FastEmitInst_(unsigned MachineInstOpcode,
+                                    const TargetRegisterClass* RC) {
+  MachineRegisterInfo &MRI = MF->getRegInfo();
+  const TargetInstrDesc &II = TII->get(MachineInstOpcode);
+  MachineInstr *MI = BuildMI(*MF, II);
+  unsigned ResultReg = MRI.createVirtualRegister(RC);
+
+  MI->addOperand(MachineOperand::CreateReg(ResultReg, true));
+
+  MBB->push_back(MI);
+  return ResultReg;
+}
+
+unsigned FastISel::FastEmitInst_r(unsigned MachineInstOpcode,
+                                  const TargetRegisterClass *RC,
+                                  unsigned Op0) {
+  MachineRegisterInfo &MRI = MF->getRegInfo();
+  const TargetInstrDesc &II = TII->get(MachineInstOpcode);
+  MachineInstr *MI = BuildMI(*MF, II);
+  unsigned ResultReg = MRI.createVirtualRegister(RC);
+
+  MI->addOperand(MachineOperand::CreateReg(ResultReg, true));
+  MI->addOperand(MachineOperand::CreateReg(Op0, false));
+
+  MBB->push_back(MI);
+  return ResultReg;
+}
+
+unsigned FastISel::FastEmitInst_rr(unsigned MachineInstOpcode,
+                                   const TargetRegisterClass *RC,
+                                   unsigned Op0, unsigned Op1) {
+  MachineRegisterInfo &MRI = MF->getRegInfo();
+  const TargetInstrDesc &II = TII->get(MachineInstOpcode);
+  MachineInstr *MI = BuildMI(*MF, II);
+  unsigned ResultReg = MRI.createVirtualRegister(RC);
+
+  MI->addOperand(MachineOperand::CreateReg(ResultReg, true));
+  MI->addOperand(MachineOperand::CreateReg(Op0, false));
+  MI->addOperand(MachineOperand::CreateReg(Op1, false));
+
+  MBB->push_back(MI);
+  return ResultReg;
+}

llvm/utils/TableGen/FastISelEmitter.cpp

@@ -0,0 +1,362 @@
+//===- FastISelEmitter.cpp - Generate an instruction selector -------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This tablegen backend emits a "fast" instruction selector.
+//
+// This instruction selection method is designed to emit very poor code
+// quickly. Also, it is not designed to do much lowering, so most illegal
+// types (e.g. i64 on 32-bit targets) and operations (e.g. calls) are not
+// supported and cannot easily be added. Blocks containing operations
+// that are not supported need to be handled by a more capable selector,
+// such as the SelectionDAG selector.
+//
+// The intended use for "fast" instruction selection is "-O0" mode
+// compilation, where the quality of the generated code is irrelevant when
+// weighed against the speed at which the code can be generated.
+//
+// If compile time is so important, you might wonder why we don't just
+// skip codegen all-together, emit LLVM bytecode files, and execute them
+// with an interpreter. The answer is that it would complicate linking and
+// debugging, and also because that isn't how a compiler is expected to
+// work in some circles.
+//
+// If you need better generated code or more lowering than what this
+// instruction selector provides, use the SelectionDAG (DAGISel) instruction
+// selector instead. If you're looking here because SelectionDAG isn't fast
+// enough, consider looking into improving the SelectionDAG infastructure
+// instead. At the time of this writing there remain several major
+// opportunities for improvement.
+// 
+//===----------------------------------------------------------------------===//
+
+#include "FastISelEmitter.h"
+#include "Record.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/Streams.h"
+#include "llvm/ADT/VectorExtras.h"
+using namespace llvm;
+
+namespace {
+
+struct OperandsSignature {
+  std::vector<std::string> Operands;
+
+  bool operator<(const OperandsSignature &O) const {
+    return Operands < O.Operands;
+  }
+
+  bool empty() const { return Operands.empty(); }
+
+  void PrintParameters(std::ostream &OS) const {
+    for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
+      if (Operands[i] == "r") {
+        OS << "unsigned Op" << i;
+      } else {
+        assert("Unknown operand kind!");
+        abort();
+      }
+      if (i + 1 != e)
+        OS << ", ";
+    }
+  }
+
+  void PrintArguments(std::ostream &OS) const {
+    for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
+      if (Operands[i] == "r") {
+        OS << "Op" << i;
+      } else {
+        assert("Unknown operand kind!");
+        abort();
+      }
+      if (i + 1 != e)
+        OS << ", ";
+    }
+  }
+
+  void PrintManglingSuffix(std::ostream &OS) const {
+    for (unsigned i = 0, e = Operands.size(); i != e; ++i) {
+      OS << Operands[i];
+    }
+  }
+};
+
+struct InstructionMemo {
+  std::string Name;
+  const CodeGenRegisterClass *RC;
+};
+
+}
+
+static std::string getOpcodeName(Record *Op, CodeGenDAGPatterns &CGP) {
+  return CGP.getSDNodeInfo(Op).getEnumName();
+}
+
+static std::string getLegalCName(std::string OpName) {
+  std::string::size_type pos = OpName.find("::");
+  if (pos != std::string::npos)
+    OpName.replace(pos, 2, "_");
+  return OpName;
+}
+
+void FastISelEmitter::run(std::ostream &OS) {
+  EmitSourceFileHeader("\"Fast\" Instruction Selector for the " +
+                       CGP.getTargetInfo().getName() + " target", OS);
+  
+  const CodeGenTarget &Target = CGP.getTargetInfo();
+  
+  // Get the namespace to insert instructions into.  Make sure not to pick up
+  // "TargetInstrInfo" by accidentally getting the namespace off the PHI
+  // instruction or something.
+  std::string InstNS;
+  for (CodeGenTarget::inst_iterator i = Target.inst_begin(),
+       e = Target.inst_end(); i != e; ++i) {
+    InstNS = i->second.Namespace;
+    if (InstNS != "TargetInstrInfo")
+      break;
+  }
+
+  OS << "namespace llvm {\n";
+  OS << "namespace " << InstNS << " {\n";
+  OS << "class FastISel;\n";
+  OS << "}\n";
+  OS << "}\n";
+  OS << "\n";
+  
+  if (!InstNS.empty()) InstNS += "::";
+
+  typedef std::map<MVT::SimpleValueType, InstructionMemo> TypeMap;
+  typedef std::map<std::string, TypeMap> OpcodeTypeMap;
+  typedef std::map<OperandsSignature, OpcodeTypeMap> OperandsOpcodeTypeMap;
+  OperandsOpcodeTypeMap SimplePatterns;
+
+  // Create the supported type signatures.
+  OperandsSignature KnownOperands;
+  SimplePatterns[KnownOperands] = OpcodeTypeMap();
+  KnownOperands.Operands.push_back("r");
+  SimplePatterns[KnownOperands] = OpcodeTypeMap();
+  KnownOperands.Operands.push_back("r");
+  SimplePatterns[KnownOperands] = OpcodeTypeMap();
+
+  for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(),
+       E = CGP.ptm_end(); I != E; ++I) {
+    const PatternToMatch &Pattern = *I;
+
+    // For now, just look at Instructions, so that we don't have to worry
+    // about emitting multiple instructions for a pattern.
+    TreePatternNode *Dst = Pattern.getDstPattern();
+    if (Dst->isLeaf()) continue;
+    Record *Op = Dst->getOperator();
+    if (!Op->isSubClassOf("Instruction"))
+      continue;
+    CodeGenInstruction &II = CGP.getTargetInfo().getInstruction(Op->getName());
+    if (II.OperandList.empty())
+      continue;
+    Record *Op0Rec = II.OperandList[0].Rec;
+    if (!Op0Rec->isSubClassOf("RegisterClass"))
+      continue;
+    const CodeGenRegisterClass *DstRC = &Target.getRegisterClass(Op0Rec);
+    if (!DstRC)
+      continue;
+
+    // Inspect the pattern.
+    TreePatternNode *InstPatNode = Pattern.getSrcPattern();
+    if (!InstPatNode) continue;
+    if (InstPatNode->isLeaf()) continue;
+
+    Record *InstPatOp = InstPatNode->getOperator();
+    std::string OpcodeName = getOpcodeName(InstPatOp, CGP);
+    MVT::SimpleValueType VT = InstPatNode->getTypeNum(0);
+
+    // For now, filter out instructions which just set a register to
+    // an Operand, like MOV32ri.
+    if (InstPatOp->isSubClassOf("Operand"))
+      continue;
+
+    // Check all the operands. For now only accept register operands.
+    OperandsSignature Operands;
+    for (unsigned i = 0, e = InstPatNode->getNumChildren(); i != e; ++i) {
+      TreePatternNode *Op = InstPatNode->getChild(i);
+      if (!Op->isLeaf())
+        goto continue_label;
+      DefInit *OpDI = dynamic_cast<DefInit*>(Op->getLeafValue());
+      if (!OpDI)
+        goto continue_label;
+      Record *OpLeafRec = OpDI->getDef();
+      if (!OpLeafRec->isSubClassOf("RegisterClass"))
+        goto continue_label;
+      const CodeGenRegisterClass *RC = &Target.getRegisterClass(OpLeafRec);
+      if (!RC)
+        goto continue_label;
+      if (Op->getTypeNum(0) != VT)
+        goto continue_label;
+      Operands.Operands.push_back("r");
+    }
+
+    // If it's not a known signature, ignore it.
+    if (!SimplePatterns.count(Operands))
+      continue;
+
+    // Ok, we found a pattern that we can handle. Remember it.
+    {
+      InstructionMemo Memo = { Pattern.getDstPattern()->getOperator()->getName(),
+                               DstRC };
+      SimplePatterns[Operands][OpcodeName][VT] = Memo;
+    }
+
+  continue_label:;
+  }
+
+  OS << "#include \"llvm/CodeGen/FastISel.h\"\n";
+  OS << "\n";
+  OS << "namespace llvm {\n";
+  OS << "\n";
+
+  // Declare the target FastISel class.
+  OS << "class " << InstNS << "FastISel : public llvm::FastISel {\n";
+  for (OperandsOpcodeTypeMap::const_iterator OI = SimplePatterns.begin(),
+       OE = SimplePatterns.end(); OI != OE; ++OI) {
+    const OperandsSignature &Operands = OI->first;
+    const OpcodeTypeMap &OTM = OI->second;
+
+    for (OpcodeTypeMap::const_iterator I = OTM.begin(), E = OTM.end();
+         I != E; ++I) {
+      const std::string &Opcode = I->first;
+      const TypeMap &TM = I->second;
+
+      for (TypeMap::const_iterator TI = TM.begin(), TE = TM.end();
+           TI != TE; ++TI) {
+        MVT::SimpleValueType VT = TI->first;
+
+        OS << "  unsigned FastEmit_" << getLegalCName(Opcode)
+           << "_" << getLegalCName(getName(VT)) << "(";
+        Operands.PrintParameters(OS);
+        OS << ");\n";
+      }
+
+      OS << "  unsigned FastEmit_" << getLegalCName(Opcode)
+         << "(MVT::SimpleValueType VT";
+      if (!Operands.empty())
+        OS << ", ";
+      Operands.PrintParameters(OS);
+      OS << ");\n";
+    }
+
+    OS << "unsigned FastEmit_";
+    Operands.PrintManglingSuffix(OS);
+    OS << "(MVT::SimpleValueType VT, ISD::NodeType Opcode";
+    if (!Operands.empty())
+      OS << ", ";
+    Operands.PrintParameters(OS);
+    OS << ");\n";
+  }
+  OS << "public:\n";
+  OS << "  FastISel(MachineBasicBlock *mbb, MachineFunction *mf, ";
+  OS << "const TargetInstrInfo *tii) : llvm::FastISel(mbb, mf, tii) {}\n";
+  OS << "};\n";
+  OS << "\n";
+
+  // Define the target FastISel creation function.
+  OS << "llvm::FastISel *" << InstNS
+     << "createFastISel(MachineBasicBlock *mbb, MachineFunction *mf, ";
+  OS << "const TargetInstrInfo *tii) {\n";
+  OS << "  return new " << InstNS << "FastISel(mbb, mf, tii);\n";
+  OS << "}\n";
+  OS << "\n";
+
+  // Now emit code for all the patterns that we collected.
+  for (OperandsOpcodeTypeMap::const_iterator OI = SimplePatterns.begin(),
+       OE = SimplePatterns.end(); OI != OE; ++OI) {
+    const OperandsSignature &Operands = OI->first;
+    const OpcodeTypeMap &OTM = OI->second;
+
+    for (OpcodeTypeMap::const_iterator I = OTM.begin(), E = OTM.end();
+         I != E; ++I) {
+      const std::string &Opcode = I->first;
+      const TypeMap &TM = I->second;
+
+      OS << "// FastEmit functions for " << Opcode << ".\n";
+      OS << "\n";
+
+      // Emit one function for each opcode,type pair.
+      for (TypeMap::const_iterator TI = TM.begin(), TE = TM.end();
+           TI != TE; ++TI) {
+        MVT::SimpleValueType VT = TI->first;
+        const InstructionMemo &Memo = TI->second;
+  
+        OS << "unsigned " << InstNS << "FastISel::FastEmit_"
+           << getLegalCName(Opcode)
+           << "_" << getLegalCName(getName(VT)) << "(";
+        Operands.PrintParameters(OS);
+        OS << ") {\n";
+        OS << "  return FastEmitInst_";
+        Operands.PrintManglingSuffix(OS);
+        OS << "(" << InstNS << Memo.Name << ", ";
+        OS << InstNS << Memo.RC->getName() << "RegisterClass";
+        if (!Operands.empty())
+          OS << ", ";
+        Operands.PrintArguments(OS);
+        OS << ");\n";
+        OS << "}\n";
+        OS << "\n";
+      }
+
+      // Emit one function for the opcode that demultiplexes based on the type.
+      OS << "unsigned " << InstNS << "FastISel::FastEmit_"
+         << getLegalCName(Opcode) << "(MVT::SimpleValueType VT";
+      if (!Operands.empty())
+        OS << ", ";
+      Operands.PrintParameters(OS);
+      OS << ") {\n";
+      OS << "  switch (VT) {\n";
+      for (TypeMap::const_iterator TI = TM.begin(), TE = TM.end();
+           TI != TE; ++TI) {
+        MVT::SimpleValueType VT = TI->first;
+        std::string TypeName = getName(VT);
+        OS << "  case " << TypeName << ": return FastEmit_"
+           << getLegalCName(Opcode) << "_" << getLegalCName(TypeName) << "(";
+        Operands.PrintArguments(OS);
+        OS << ");\n";
+      }
+      OS << "  default: return 0;\n";
+      OS << "  }\n";
+      OS << "}\n";
+      OS << "\n";
+    }
+
+    // Emit one function for the operand signature that demultiplexes based
+    // on opcode and type.
+    OS << "unsigned " << InstNS << "FastISel::FastEmit_";
+    Operands.PrintManglingSuffix(OS);
+    OS << "(MVT::SimpleValueType VT, ISD::NodeType Opcode";
+    if (!Operands.empty())
+      OS << ", ";
+    Operands.PrintParameters(OS);
+    OS << ") {\n";
+    OS << "  switch (Opcode) {\n";
+    for (OpcodeTypeMap::const_iterator I = OTM.begin(), E = OTM.end();
+         I != E; ++I) {
+      const std::string &Opcode = I->first;
+
+      OS << "  case " << Opcode << ": return FastEmit_"
+         << getLegalCName(Opcode) << "(VT";
+      if (!Operands.empty())
+        OS << ", ";
+      Operands.PrintArguments(OS);
+      OS << ");\n";
+    }
+    OS << "  default: return 0;\n";
+    OS << "  }\n";
+    OS << "}\n";
+    OS << "\n";
+  }
+
+  OS << "}\n";
+}
+
+// todo: really filter out Constants

llvm/utils/TableGen/FastISelEmitter.h

@@ -0,0 +1,38 @@
+//===- FastISelEmitter.h - Generate an instruction selector -----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This tablegen backend emits a "fast" instruction selector.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef FASTISEL_EMITTER_H
+#define FASTISEL_EMITTER_H
+
+#include "TableGenBackend.h"
+#include "CodeGenDAGPatterns.h"
+#include <set>
+
+namespace llvm {
+
+/// FastISelEmitter - The top-level class which coordinates construction
+/// and emission of the instruction selector.
+///
+class FastISelEmitter : public TableGenBackend {
+  RecordKeeper &Records;
+  CodeGenDAGPatterns CGP;
+public:
+  explicit FastISelEmitter(RecordKeeper &R) : Records(R), CGP(R) {}
+
+  // run - Output the isel, returning true on failure.
+  void run(std::ostream &OS);
+};
+
+} // End llvm namespace
+
+#endif

llvm/utils/TableGen/TableGen.cpp

@@ -29,6 +29,7 @@
 #include "InstrEnumEmitter.h"
 #include "AsmWriterEmitter.h"
 #include "DAGISelEmitter.h"
+#include "FastISelEmitter.h"
 #include "SubtargetEmitter.h"
 #include "IntrinsicEmitter.h"
 #include "LLVMCConfigurationEmitter.h"
@@ -45,6 +46,7 @@ enum ActionType {
   GenInstrEnums, GenInstrs, GenAsmWriter,
   GenCallingConv,
   GenDAGISel,
+  GenFastISel,
   GenSubtarget,
   GenIntrinsic,
   GenLLVMCConf,
@@ -74,6 +76,8 @@ namespace {
                                "Generate assembly writer"),
                     clEnumValN(GenDAGISel, "gen-dag-isel",
                                "Generate a DAG instruction selector"),
+                    clEnumValN(GenFastISel, "gen-fast-isel",
+                               "Generate a \"fast\" instruction selector"),
                     clEnumValN(GenSubtarget, "gen-subtarget",
                                "Generate subtarget enumerations"),
                     clEnumValN(GenIntrinsic, "gen-intrinsic",
@@ -177,6 +181,9 @@ int main(int argc, char **argv) {
     case GenDAGISel:
       DAGISelEmitter(Records).run(*Out);
       break;
+    case GenFastISel:
+      FastISelEmitter(Records).run(*Out);
+      break;
     case GenSubtarget:
       SubtargetEmitter(Records).run(*Out);
       break;