FastISel.cpp revision 46aa2f5aab3d39e9cba840ecd8068a6531f8f8a9 
1///===-- FastISel.cpp - Implementation of the FastISel class --------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file contains the implementation of the FastISel class.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Instructions.h"
15#include "llvm/CodeGen/FastISel.h"
16#include "llvm/CodeGen/MachineInstrBuilder.h"
17#include "llvm/CodeGen/MachineRegisterInfo.h"
18#include "llvm/Target/TargetData.h"
19#include "llvm/Target/TargetInstrInfo.h"
20#include "llvm/Target/TargetLowering.h"
21#include "llvm/Target/TargetMachine.h"
22using namespace llvm;
23
24/// SelectBinaryOp - Select and emit code for a binary operator instruction,
25/// which has an opcode which directly corresponds to the given ISD opcode.
26///
27bool FastISel::SelectBinaryOp(Instruction *I, ISD::NodeType ISDOpcode,
28                              DenseMap<const Value*, unsigned> &ValueMap) {
29  MVT VT = MVT::getMVT(I->getType(), /*HandleUnknown=*/true);
30  if (VT == MVT::Other || !VT.isSimple())
31    // Unhandled type. Halt "fast" selection and bail.
32    return false;
33
34  unsigned Op0 = ValueMap[I->getOperand(0)];
35  if (Op0 == 0)
36    // Unhandled operand. Halt "fast" selection and bail.
37    return false;
38
39  // Check if the second operand is a constant and handle it appropriately.
40  if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
41    unsigned ResultReg = FastEmit_ri_(VT.getSimpleVT(), ISDOpcode, Op0,
42                                      CI->getZExtValue(), VT.getSimpleVT());
43    if (ResultReg == 0)
44      // Target-specific code wasn't able to find a machine opcode for
45      // the given ISD opcode and type. Halt "fast" selection and bail.
46      return false;
47
48    // We successfully emitted code for the given LLVM Instruction.
49    ValueMap[I] = ResultReg;
50    return true;
51  }
52
53  unsigned Op1 = ValueMap[I->getOperand(1)];
54  if (Op1 == 0)
55    // Unhandled operand. Halt "fast" selection and bail.
56    return false;
57
58  unsigned ResultReg = FastEmit_rr(VT.getSimpleVT(), VT.getSimpleVT(),
59                                   ISDOpcode, Op0, Op1);
60  if (ResultReg == 0)
61    // Target-specific code wasn't able to find a machine opcode for
62    // the given ISD opcode and type. Halt "fast" selection and bail.
63    return false;
64
65  // We successfully emitted code for the given LLVM Instruction.
66  ValueMap[I] = ResultReg;
67  return true;
68}
69
70bool FastISel::SelectGetElementPtr(Instruction *I,
71                                   DenseMap<const Value*, unsigned> &ValueMap) {
72  unsigned N = ValueMap[I->getOperand(0)];
73  if (N == 0)
74    // Unhandled operand. Halt "fast" selection and bail.
75    return false;
76
77  const Type *Ty = I->getOperand(0)->getType();
78  MVT::SimpleValueType VT = TLI.getPointerTy().getSimpleVT();
79  for (GetElementPtrInst::op_iterator OI = I->op_begin()+1, E = I->op_end();
80       OI != E; ++OI) {
81    Value *Idx = *OI;
82    if (const StructType *StTy = dyn_cast<StructType>(Ty)) {
83      unsigned Field = cast<ConstantInt>(Idx)->getZExtValue();
84      if (Field) {
85        // N = N + Offset
86        uint64_t Offs = TD.getStructLayout(StTy)->getElementOffset(Field);
87        // FIXME: This can be optimized by combining the add with a
88        // subsequent one.
89        N = FastEmit_ri_(VT, ISD::ADD, N, Offs, VT);
90        if (N == 0)
91          // Unhandled operand. Halt "fast" selection and bail.
92          return false;
93      }
94      Ty = StTy->getElementType(Field);
95    } else {
96      Ty = cast<SequentialType>(Ty)->getElementType();
97
98      // If this is a constant subscript, handle it quickly.
99      if (ConstantInt *CI = dyn_cast<ConstantInt>(Idx)) {
100        if (CI->getZExtValue() == 0) continue;
101        uint64_t Offs =
102          TD.getABITypeSize(Ty)*cast<ConstantInt>(CI)->getSExtValue();
103        N = FastEmit_ri_(VT, ISD::ADD, N, Offs, VT);
104        if (N == 0)
105          // Unhandled operand. Halt "fast" selection and bail.
106          return false;
107        continue;
108      }
109
110      // N = N + Idx * ElementSize;
111      uint64_t ElementSize = TD.getABITypeSize(Ty);
112      unsigned IdxN = ValueMap[Idx];
113      if (IdxN == 0)
114        // Unhandled operand. Halt "fast" selection and bail.
115        return false;
116
117      // If the index is smaller or larger than intptr_t, truncate or extend
118      // it.
119      MVT IdxVT = MVT::getMVT(Idx->getType(), /*HandleUnknown=*/false);
120      if (IdxVT.bitsLT(VT))
121        IdxN = FastEmit_r(VT, VT, ISD::SIGN_EXTEND, IdxN);
122      else if (IdxVT.bitsGT(VT))
123        IdxN = FastEmit_r(VT, VT, ISD::TRUNCATE, IdxN);
124      if (IdxN == 0)
125        // Unhandled operand. Halt "fast" selection and bail.
126        return false;
127
128      if (ElementSize != 1)
129        IdxN = FastEmit_ri_(VT, ISD::MUL, IdxN, ElementSize, VT);
130      if (IdxN == 0)
131        // Unhandled operand. Halt "fast" selection and bail.
132        return false;
133      N = FastEmit_rr(VT, VT, ISD::ADD, N, IdxN);
134      if (N == 0)
135        // Unhandled operand. Halt "fast" selection and bail.
136        return false;
137    }
138  }
139
140  // We successfully emitted code for the given LLVM Instruction.
141  ValueMap[I] = N;
142  return true;
143}
144
145BasicBlock::iterator
146FastISel::SelectInstructions(BasicBlock::iterator Begin,
147                             BasicBlock::iterator End,
148                             DenseMap<const Value*, unsigned> &ValueMap,
149                             DenseMap<const BasicBlock*,
150                                      MachineBasicBlock *> &MBBMap,
151                             MachineBasicBlock *mbb) {
152  MBB = mbb;
153  BasicBlock::iterator I = Begin;
154
155  for (; I != End; ++I) {
156    switch (I->getOpcode()) {
157    case Instruction::Add: {
158      ISD::NodeType Opc = I->getType()->isFPOrFPVector() ? ISD::FADD : ISD::ADD;
159      if (!SelectBinaryOp(I, Opc, ValueMap))  return I; break;
160    }
161    case Instruction::Sub: {
162      ISD::NodeType Opc = I->getType()->isFPOrFPVector() ? ISD::FSUB : ISD::SUB;
163      if (!SelectBinaryOp(I, Opc, ValueMap))  return I; break;
164    }
165    case Instruction::Mul: {
166      ISD::NodeType Opc = I->getType()->isFPOrFPVector() ? ISD::FMUL : ISD::MUL;
167      if (!SelectBinaryOp(I, Opc, ValueMap))  return I; break;
168    }
169    case Instruction::SDiv:
170      if (!SelectBinaryOp(I, ISD::SDIV, ValueMap)) return I; break;
171    case Instruction::UDiv:
172      if (!SelectBinaryOp(I, ISD::UDIV, ValueMap)) return I; break;
173    case Instruction::FDiv:
174      if (!SelectBinaryOp(I, ISD::FDIV, ValueMap)) return I; break;
175    case Instruction::SRem:
176      if (!SelectBinaryOp(I, ISD::SREM, ValueMap)) return I; break;
177    case Instruction::URem:
178      if (!SelectBinaryOp(I, ISD::UREM, ValueMap)) return I; break;
179    case Instruction::FRem:
180      if (!SelectBinaryOp(I, ISD::FREM, ValueMap)) return I; break;
181    case Instruction::Shl:
182      if (!SelectBinaryOp(I, ISD::SHL, ValueMap)) return I; break;
183    case Instruction::LShr:
184      if (!SelectBinaryOp(I, ISD::SRL, ValueMap)) return I; break;
185    case Instruction::AShr:
186      if (!SelectBinaryOp(I, ISD::SRA, ValueMap)) return I; break;
187    case Instruction::And:
188      if (!SelectBinaryOp(I, ISD::AND, ValueMap)) return I; break;
189    case Instruction::Or:
190      if (!SelectBinaryOp(I, ISD::OR, ValueMap)) return I; break;
191    case Instruction::Xor:
192      if (!SelectBinaryOp(I, ISD::XOR, ValueMap)) return I; break;
193
194    case Instruction::GetElementPtr:
195      if (!SelectGetElementPtr(I, ValueMap)) return I;
196      break;
197
198    case Instruction::Br: {
199      BranchInst *BI = cast<BranchInst>(I);
200
201      if (BI->isUnconditional()) {
202        MachineFunction::iterator NextMBB =
203           next(MachineFunction::iterator(MBB));
204        BasicBlock *LLVMSucc = BI->getSuccessor(0);
205        MachineBasicBlock *MSucc = MBBMap[LLVMSucc];
206
207        if (NextMBB != MF.end() && MSucc == NextMBB) {
208          // The unconditional fall-through case, which needs no instructions.
209        } else {
210          // The unconditional branch case.
211          TII.InsertBranch(*MBB, MSucc, NULL, SmallVector<MachineOperand, 0>());
212        }
213        MBB->addSuccessor(MSucc);
214        break;
215      }
216
217      // Conditional branches are not handed yet.
218      // Halt "fast" selection and bail.
219      return I;
220    }
221
222    case Instruction::PHI:
223      // PHI nodes are already emitted.
224      break;
225
226    case Instruction::BitCast:
227      // BitCast consists of either an immediate to register move
228      // or a register to register move.
229      if (ConstantInt* CI = dyn_cast<ConstantInt>(I->getOperand(0))) {
230        if (I->getType()->isInteger()) {
231          MVT VT = MVT::getMVT(I->getType(), /*HandleUnknown=*/false);
232          unsigned result = FastEmit_i(VT.getSimpleVT(), VT.getSimpleVT(),
233                                       ISD::Constant,
234                                       CI->getZExtValue());
235          if (!result)
236            return I;
237
238          ValueMap[I] = result;
239          break;
240        } else
241          // TODO: Support vector and fp constants.
242          return I;
243      } else if (!isa<Constant>(I->getOperand(0))) {
244        // Bitcasts of non-constant values become reg-reg copies.
245        MVT SrcVT = MVT::getMVT(I->getOperand(0)->getType());
246        MVT DstVT = MVT::getMVT(I->getType());
247
248        if (SrcVT == MVT::Other || !SrcVT.isSimple() ||
249            DstVT == MVT::Other || !DstVT.isSimple() ||
250            !TLI.isTypeLegal(SrcVT) || !TLI.isTypeLegal(DstVT))
251          // Unhandled type. Halt "fast" selection and bail.
252          return I;
253        if (!TLI.isConvertLegal(SrcVT, DstVT))
254          // Illegal conversion.  Halt "fast" selection and bail.
255          return I;
256
257        // Otherwise, insert a register-to-register copy.
258        TargetRegisterClass* SrcClass = TLI.getRegClassFor(SrcVT);
259        TargetRegisterClass* DstClass = TLI.getRegClassFor(DstVT);
260        unsigned Op0 = ValueMap[I->getOperand(0)];
261        unsigned ResultReg = createResultReg(DstClass);
262
263        if (Op0 == 0)
264          // Unhandled operand. Halt "fast" selection and bail.
265          return false;
266
267        TII.copyRegToReg(*MBB, MBB->end(), ResultReg, Op0, DstClass, SrcClass);
268        ValueMap[I] = ResultReg;
269
270        break;
271      } else
272        // TODO: Casting a non-integral constant?
273        return I;
274
275    case Instruction::FPToSI:
276      if (!isa<ConstantFP>(I->getOperand(0))) {
277        MVT SrcVT = MVT::getMVT(I->getOperand(0)->getType());
278        MVT DstVT = MVT::getMVT(I->getType());
279
280        if (SrcVT == MVT::Other || !SrcVT.isSimple() ||
281            DstVT == MVT::Other || !DstVT.isSimple() ||
282            !TLI.isTypeLegal(SrcVT) || !TLI.isTypeLegal(DstVT))
283          // Unhandled type. Halt "fast" selection and bail.
284          return I;
285        if (TLI.getOperationAction(ISD::FP_TO_SINT, SrcVT) !=
286            TargetLowering::Legal)
287          // Unhandled opcode on this type.  Halt "fast" seleciton and bail.
288          return I;
289
290        unsigned InputReg = ValueMap[I->getOperand(0)];
291        if (!InputReg)
292          // Unhandled operand.  Halt "fast" selection and bail.
293          return I;
294
295        unsigned ResultReg = FastEmit_r(SrcVT.getSimpleVT(),
296                                        DstVT.getSimpleVT(),
297                                        ISD::FP_TO_SINT,
298                                        InputReg);
299        if (!ResultReg)
300          return I;
301
302        ValueMap[I] = ResultReg;
303        break;
304      } else
305        // TODO: Materialize the FP constant and then convert,
306        // or attempt constant folding.
307        return I;
308
309    default:
310      // Unhandled instruction. Halt "fast" selection and bail.
311      return I;
312    }
313  }
314
315  return I;
316}
317
318FastISel::FastISel(MachineFunction &mf)
319  : MF(mf),
320    MRI(mf.getRegInfo()),
321    TM(mf.getTarget()),
322    TD(*TM.getTargetData()),
323    TII(*TM.getInstrInfo()),
324    TLI(*TM.getTargetLowering()) {
325}
326
327FastISel::~FastISel() {}
328
329unsigned FastISel::FastEmit_(MVT::SimpleValueType, MVT::SimpleValueType, ISD::NodeType) {
330  return 0;
331}
332
333unsigned FastISel::FastEmit_r(MVT::SimpleValueType, MVT::SimpleValueType,
334                              ISD::NodeType, unsigned /*Op0*/) {
335  return 0;
336}
337
338unsigned FastISel::FastEmit_rr(MVT::SimpleValueType, MVT::SimpleValueType,
339                               ISD::NodeType, unsigned /*Op0*/,
340                               unsigned /*Op0*/) {
341  return 0;
342}
343
344unsigned FastISel::FastEmit_i(MVT::SimpleValueType, MVT::SimpleValueType,
345                              ISD::NodeType, uint64_t /*Imm*/) {
346  return 0;
347}
348
349unsigned FastISel::FastEmit_ri(MVT::SimpleValueType, MVT::SimpleValueType,
350                               ISD::NodeType, unsigned /*Op0*/,
351                               uint64_t /*Imm*/) {
352  return 0;
353}
354
355unsigned FastISel::FastEmit_rri(MVT::SimpleValueType, MVT::SimpleValueType,
356                                ISD::NodeType,
357                                unsigned /*Op0*/, unsigned /*Op1*/,
358                                uint64_t /*Imm*/) {
359  return 0;
360}
361
362/// FastEmit_ri_ - This method is a wrapper of FastEmit_ri. It first tries
363/// to emit an instruction with an immediate operand using FastEmit_ri.
364/// If that fails, it materializes the immediate into a register and try
365/// FastEmit_rr instead.
366unsigned FastISel::FastEmit_ri_(MVT::SimpleValueType VT, ISD::NodeType Opcode,
367                                unsigned Op0, uint64_t Imm,
368                                MVT::SimpleValueType ImmType) {
369  unsigned ResultReg = 0;
370  // First check if immediate type is legal. If not, we can't use the ri form.
371  if (TLI.getOperationAction(ISD::Constant, ImmType) == TargetLowering::Legal)
372    ResultReg = FastEmit_ri(VT, VT, Opcode, Op0, Imm);
373  if (ResultReg != 0)
374    return ResultReg;
375  unsigned MaterialReg = FastEmit_i(ImmType, ImmType, ISD::Constant, Imm);
376  if (MaterialReg == 0)
377    return 0;
378  return FastEmit_rr(VT, VT, Opcode, Op0, MaterialReg);
379}
380
381unsigned FastISel::createResultReg(const TargetRegisterClass* RC) {
382  return MRI.createVirtualRegister(RC);
383}
384
385unsigned FastISel::FastEmitInst_(unsigned MachineInstOpcode,
386                                 const TargetRegisterClass* RC) {
387  unsigned ResultReg = createResultReg(RC);
388  const TargetInstrDesc &II = TII.get(MachineInstOpcode);
389
390  BuildMI(MBB, II, ResultReg);
391  return ResultReg;
392}
393
394unsigned FastISel::FastEmitInst_r(unsigned MachineInstOpcode,
395                                  const TargetRegisterClass *RC,
396                                  unsigned Op0) {
397  unsigned ResultReg = createResultReg(RC);
398  const TargetInstrDesc &II = TII.get(MachineInstOpcode);
399
400  BuildMI(MBB, II, ResultReg).addReg(Op0);
401  return ResultReg;
402}
403
404unsigned FastISel::FastEmitInst_rr(unsigned MachineInstOpcode,
405                                   const TargetRegisterClass *RC,
406                                   unsigned Op0, unsigned Op1) {
407  unsigned ResultReg = createResultReg(RC);
408  const TargetInstrDesc &II = TII.get(MachineInstOpcode);
409
410  BuildMI(MBB, II, ResultReg).addReg(Op0).addReg(Op1);
411  return ResultReg;
412}
413
414unsigned FastISel::FastEmitInst_ri(unsigned MachineInstOpcode,
415                                   const TargetRegisterClass *RC,
416                                   unsigned Op0, uint64_t Imm) {
417  unsigned ResultReg = createResultReg(RC);
418  const TargetInstrDesc &II = TII.get(MachineInstOpcode);
419
420  BuildMI(MBB, II, ResultReg).addReg(Op0).addImm(Imm);
421  return ResultReg;
422}
423
424unsigned FastISel::FastEmitInst_rri(unsigned MachineInstOpcode,
425                                    const TargetRegisterClass *RC,
426                                    unsigned Op0, unsigned Op1, uint64_t Imm) {
427  unsigned ResultReg = createResultReg(RC);
428  const TargetInstrDesc &II = TII.get(MachineInstOpcode);
429
430  BuildMI(MBB, II, ResultReg).addReg(Op0).addReg(Op1).addImm(Imm);
431  return ResultReg;
432}
433
434unsigned FastISel::FastEmitInst_i(unsigned MachineInstOpcode,
435                                  const TargetRegisterClass *RC,
436                                  uint64_t Imm) {
437  unsigned ResultReg = createResultReg(RC);
438  const TargetInstrDesc &II = TII.get(MachineInstOpcode);
439
440  BuildMI(MBB, II, ResultReg).addImm(Imm);
441  return ResultReg;
442}
443