1 //===-- FastISel.cpp - Implementation of the FastISel class ---------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file contains the implementation of the FastISel class.
12 // "Fast" instruction selection is designed to emit very poor code quickly.
13 // Also, it is not designed to be able to do much lowering, so most illegal
14 // types (e.g. i64 on 32-bit targets) and operations are not supported. It is
15 // also not intended to be able to do much optimization, except in a few cases
16 // where doing optimizations reduces overall compile time. For example, folding
17 // constants into immediate fields is often done, because it's cheap and it
18 // reduces the number of instructions later phases have to examine.
20 // "Fast" instruction selection is able to fail gracefully and transfer
21 // control to the SelectionDAG selector for operations that it doesn't
22 // support. In many cases, this allows us to avoid duplicating a lot of
23 // the complicated lowering logic that SelectionDAG currently has.
25 // The intended use for "fast" instruction selection is "-O0" mode
26 // compilation, where the quality of the generated code is irrelevant when
27 // weighed against the speed at which the code can be generated. Also,
28 // at -O0, the LLVM optimizers are not running, and this makes the
29 // compile time of codegen a much higher portion of the overall compile
30 // time. Despite its limitations, "fast" instruction selection is able to
31 // handle enough code on its own to provide noticeable overall speedups
34 // Basic operations are supported in a target-independent way, by reading
35 // the same instruction descriptions that the SelectionDAG selector reads,
36 // and identifying simple arithmetic operations that can be directly selected
37 // from simple operators. More complicated operations currently require
38 // target-specific code.
40 //===----------------------------------------------------------------------===//
42 #include "llvm/Function.h"
43 #include "llvm/GlobalVariable.h"
44 #include "llvm/Instructions.h"
45 #include "llvm/IntrinsicInst.h"
46 #include "llvm/Operator.h"
47 #include "llvm/CodeGen/FastISel.h"
48 #include "llvm/CodeGen/FunctionLoweringInfo.h"
49 #include "llvm/CodeGen/MachineInstrBuilder.h"
50 #include "llvm/CodeGen/MachineModuleInfo.h"
51 #include "llvm/CodeGen/MachineRegisterInfo.h"
52 #include "llvm/Analysis/DebugInfo.h"
53 #include "llvm/Analysis/Loads.h"
54 #include "llvm/Target/TargetData.h"
55 #include "llvm/Target/TargetInstrInfo.h"
56 #include "llvm/Target/TargetLowering.h"
57 #include "llvm/Target/TargetMachine.h"
58 #include "llvm/Support/ErrorHandling.h"
59 #include "llvm/Support/Debug.h"
62 /// startNewBlock - Set the current block to which generated machine
63 /// instructions will be appended, and clear the local CSE map.
65 void FastISel::startNewBlock() {
66 LocalValueMap.clear();
68 // Start out as null, meaining no local-value instructions have
72 // Advance the last local value past any EH_LABEL instructions.
73 MachineBasicBlock::iterator
74 I = FuncInfo.MBB->begin(), E = FuncInfo.MBB->end();
75 while (I != E && I->getOpcode() == TargetOpcode::EH_LABEL) {
81 bool FastISel::hasTrivialKill(const Value *V) const {
82 // Don't consider constants or arguments to have trivial kills.
83 const Instruction *I = dyn_cast<Instruction>(V);
87 // No-op casts are trivially coalesced by fast-isel.
88 if (const CastInst *Cast = dyn_cast<CastInst>(I))
89 if (Cast->isNoopCast(TD.getIntPtrType(Cast->getContext())) &&
90 !hasTrivialKill(Cast->getOperand(0)))
93 // Only instructions with a single use in the same basic block are considered
94 // to have trivial kills.
95 return I->hasOneUse() &&
96 !(I->getOpcode() == Instruction::BitCast ||
97 I->getOpcode() == Instruction::PtrToInt ||
98 I->getOpcode() == Instruction::IntToPtr) &&
99 cast<Instruction>(*I->use_begin())->getParent() == I->getParent();
102 unsigned FastISel::getRegForValue(const Value *V) {
103 EVT RealVT = TLI.getValueType(V->getType(), /*AllowUnknown=*/true);
104 // Don't handle non-simple values in FastISel.
105 if (!RealVT.isSimple())
108 // Ignore illegal types. We must do this before looking up the value
109 // in ValueMap because Arguments are given virtual registers regardless
110 // of whether FastISel can handle them.
111 MVT VT = RealVT.getSimpleVT();
112 if (!TLI.isTypeLegal(VT)) {
113 // Promote MVT::i1 to a legal type though, because it's common and easy.
115 VT = TLI.getTypeToTransformTo(V->getContext(), VT).getSimpleVT();
120 // Look up the value to see if we already have a register for it. We
121 // cache values defined by Instructions across blocks, and other values
122 // only locally. This is because Instructions already have the SSA
123 // def-dominates-use requirement enforced.
124 DenseMap<const Value *, unsigned>::iterator I = FuncInfo.ValueMap.find(V);
125 if (I != FuncInfo.ValueMap.end())
128 unsigned Reg = LocalValueMap[V];
132 // In bottom-up mode, just create the virtual register which will be used
133 // to hold the value. It will be materialized later.
134 if (isa<Instruction>(V) &&
135 (!isa<AllocaInst>(V) ||
136 !FuncInfo.StaticAllocaMap.count(cast<AllocaInst>(V))))
137 return FuncInfo.InitializeRegForValue(V);
139 SavePoint SaveInsertPt = enterLocalValueArea();
141 // Materialize the value in a register. Emit any instructions in the
143 Reg = materializeRegForValue(V, VT);
145 leaveLocalValueArea(SaveInsertPt);
150 /// materializeRegForValue - Helper for getRegForValue. This function is
151 /// called when the value isn't already available in a register and must
152 /// be materialized with new instructions.
153 unsigned FastISel::materializeRegForValue(const Value *V, MVT VT) {
156 if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
157 if (CI->getValue().getActiveBits() <= 64)
158 Reg = FastEmit_i(VT, VT, ISD::Constant, CI->getZExtValue());
159 } else if (isa<AllocaInst>(V)) {
160 Reg = TargetMaterializeAlloca(cast<AllocaInst>(V));
161 } else if (isa<ConstantPointerNull>(V)) {
162 // Translate this as an integer zero so that it can be
163 // local-CSE'd with actual integer zeros.
165 getRegForValue(Constant::getNullValue(TD.getIntPtrType(V->getContext())));
166 } else if (const ConstantFP *CF = dyn_cast<ConstantFP>(V)) {
167 // Try to emit the constant directly.
168 Reg = FastEmit_f(VT, VT, ISD::ConstantFP, CF);
171 // Try to emit the constant by using an integer constant with a cast.
172 const APFloat &Flt = CF->getValueAPF();
173 EVT IntVT = TLI.getPointerTy();
176 uint32_t IntBitWidth = IntVT.getSizeInBits();
178 (void) Flt.convertToInteger(x, IntBitWidth, /*isSigned=*/true,
179 APFloat::rmTowardZero, &isExact);
181 APInt IntVal(IntBitWidth, 2, x);
183 unsigned IntegerReg =
184 getRegForValue(ConstantInt::get(V->getContext(), IntVal));
186 Reg = FastEmit_r(IntVT.getSimpleVT(), VT, ISD::SINT_TO_FP,
187 IntegerReg, /*Kill=*/false);
190 } else if (const Operator *Op = dyn_cast<Operator>(V)) {
191 if (!SelectOperator(Op, Op->getOpcode()))
192 if (!isa<Instruction>(Op) ||
193 !TargetSelectInstruction(cast<Instruction>(Op)))
195 Reg = lookUpRegForValue(Op);
196 } else if (isa<UndefValue>(V)) {
197 Reg = createResultReg(TLI.getRegClassFor(VT));
198 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL,
199 TII.get(TargetOpcode::IMPLICIT_DEF), Reg);
202 // If target-independent code couldn't handle the value, give target-specific
204 if (!Reg && isa<Constant>(V))
205 Reg = TargetMaterializeConstant(cast<Constant>(V));
207 // Don't cache constant materializations in the general ValueMap.
208 // To do so would require tracking what uses they dominate.
210 LocalValueMap[V] = Reg;
211 LastLocalValue = MRI.getVRegDef(Reg);
216 unsigned FastISel::lookUpRegForValue(const Value *V) {
217 // Look up the value to see if we already have a register for it. We
218 // cache values defined by Instructions across blocks, and other values
219 // only locally. This is because Instructions already have the SSA
220 // def-dominates-use requirement enforced.
221 DenseMap<const Value *, unsigned>::iterator I = FuncInfo.ValueMap.find(V);
222 if (I != FuncInfo.ValueMap.end())
224 return LocalValueMap[V];
227 /// UpdateValueMap - Update the value map to include the new mapping for this
228 /// instruction, or insert an extra copy to get the result in a previous
229 /// determined register.
230 /// NOTE: This is only necessary because we might select a block that uses
231 /// a value before we select the block that defines the value. It might be
232 /// possible to fix this by selecting blocks in reverse postorder.
233 unsigned FastISel::UpdateValueMap(const Value *I, unsigned Reg) {
234 if (!isa<Instruction>(I)) {
235 LocalValueMap[I] = Reg;
239 unsigned &AssignedReg = FuncInfo.ValueMap[I];
240 if (AssignedReg == 0)
241 // Use the new register.
243 else if (Reg != AssignedReg) {
244 // Arrange for uses of AssignedReg to be replaced by uses of Reg.
245 FuncInfo.RegFixups[AssignedReg] = Reg;
253 std::pair<unsigned, bool> FastISel::getRegForGEPIndex(const Value *Idx) {
254 unsigned IdxN = getRegForValue(Idx);
256 // Unhandled operand. Halt "fast" selection and bail.
257 return std::pair<unsigned, bool>(0, false);
259 bool IdxNIsKill = hasTrivialKill(Idx);
261 // If the index is smaller or larger than intptr_t, truncate or extend it.
262 MVT PtrVT = TLI.getPointerTy();
263 EVT IdxVT = EVT::getEVT(Idx->getType(), /*HandleUnknown=*/false);
264 if (IdxVT.bitsLT(PtrVT)) {
265 IdxN = FastEmit_r(IdxVT.getSimpleVT(), PtrVT, ISD::SIGN_EXTEND,
269 else if (IdxVT.bitsGT(PtrVT)) {
270 IdxN = FastEmit_r(IdxVT.getSimpleVT(), PtrVT, ISD::TRUNCATE,
274 return std::pair<unsigned, bool>(IdxN, IdxNIsKill);
277 void FastISel::recomputeInsertPt() {
278 if (getLastLocalValue()) {
279 FuncInfo.InsertPt = getLastLocalValue();
280 FuncInfo.MBB = FuncInfo.InsertPt->getParent();
283 FuncInfo.InsertPt = FuncInfo.MBB->getFirstNonPHI();
285 // Now skip past any EH_LABELs, which must remain at the beginning.
286 while (FuncInfo.InsertPt != FuncInfo.MBB->end() &&
287 FuncInfo.InsertPt->getOpcode() == TargetOpcode::EH_LABEL)
291 FastISel::SavePoint FastISel::enterLocalValueArea() {
292 MachineBasicBlock::iterator OldInsertPt = FuncInfo.InsertPt;
296 SavePoint SP = { OldInsertPt, OldDL };
300 void FastISel::leaveLocalValueArea(SavePoint OldInsertPt) {
301 if (FuncInfo.InsertPt != FuncInfo.MBB->begin())
302 LastLocalValue = llvm::prior(FuncInfo.InsertPt);
304 // Restore the previous insert position.
305 FuncInfo.InsertPt = OldInsertPt.InsertPt;
309 /// SelectBinaryOp - Select and emit code for a binary operator instruction,
310 /// which has an opcode which directly corresponds to the given ISD opcode.
312 bool FastISel::SelectBinaryOp(const User *I, unsigned ISDOpcode) {
313 EVT VT = EVT::getEVT(I->getType(), /*HandleUnknown=*/true);
314 if (VT == MVT::Other || !VT.isSimple())
315 // Unhandled type. Halt "fast" selection and bail.
318 // We only handle legal types. For example, on x86-32 the instruction
319 // selector contains all of the 64-bit instructions from x86-64,
320 // under the assumption that i64 won't be used if the target doesn't
322 if (!TLI.isTypeLegal(VT)) {
323 // MVT::i1 is special. Allow AND, OR, or XOR because they
324 // don't require additional zeroing, which makes them easy.
326 (ISDOpcode == ISD::AND || ISDOpcode == ISD::OR ||
327 ISDOpcode == ISD::XOR))
328 VT = TLI.getTypeToTransformTo(I->getContext(), VT);
333 // Check if the first operand is a constant, and handle it as "ri". At -O0,
334 // we don't have anything that canonicalizes operand order.
335 if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(0)))
336 if (isa<Instruction>(I) && cast<Instruction>(I)->isCommutative()) {
337 unsigned Op1 = getRegForValue(I->getOperand(1));
338 if (Op1 == 0) return false;
340 bool Op1IsKill = hasTrivialKill(I->getOperand(1));
342 unsigned ResultReg = FastEmit_ri_(VT.getSimpleVT(), ISDOpcode, Op1,
343 Op1IsKill, CI->getZExtValue(),
345 if (ResultReg == 0) return false;
347 // We successfully emitted code for the given LLVM Instruction.
348 UpdateValueMap(I, ResultReg);
353 unsigned Op0 = getRegForValue(I->getOperand(0));
354 if (Op0 == 0) // Unhandled operand. Halt "fast" selection and bail.
357 bool Op0IsKill = hasTrivialKill(I->getOperand(0));
359 // Check if the second operand is a constant and handle it appropriately.
360 if (ConstantInt *CI = dyn_cast<ConstantInt>(I->getOperand(1))) {
361 uint64_t Imm = CI->getZExtValue();
363 unsigned ResultReg = FastEmit_ri_(VT.getSimpleVT(), ISDOpcode, Op0,
364 Op0IsKill, Imm, VT.getSimpleVT());
365 if (ResultReg == 0) return false;
367 // We successfully emitted code for the given LLVM Instruction.
368 UpdateValueMap(I, ResultReg);
372 // Check if the second operand is a constant float.
373 if (ConstantFP *CF = dyn_cast<ConstantFP>(I->getOperand(1))) {
374 unsigned ResultReg = FastEmit_rf(VT.getSimpleVT(), VT.getSimpleVT(),
375 ISDOpcode, Op0, Op0IsKill, CF);
376 if (ResultReg != 0) {
377 // We successfully emitted code for the given LLVM Instruction.
378 UpdateValueMap(I, ResultReg);
383 unsigned Op1 = getRegForValue(I->getOperand(1));
385 // Unhandled operand. Halt "fast" selection and bail.
388 bool Op1IsKill = hasTrivialKill(I->getOperand(1));
390 // Now we have both operands in registers. Emit the instruction.
391 unsigned ResultReg = FastEmit_rr(VT.getSimpleVT(), VT.getSimpleVT(),
396 // Target-specific code wasn't able to find a machine opcode for
397 // the given ISD opcode and type. Halt "fast" selection and bail.
400 // We successfully emitted code for the given LLVM Instruction.
401 UpdateValueMap(I, ResultReg);
405 bool FastISel::SelectGetElementPtr(const User *I) {
406 unsigned N = getRegForValue(I->getOperand(0));
408 // Unhandled operand. Halt "fast" selection and bail.
411 bool NIsKill = hasTrivialKill(I->getOperand(0));
413 const Type *Ty = I->getOperand(0)->getType();
414 MVT VT = TLI.getPointerTy();
415 for (GetElementPtrInst::const_op_iterator OI = I->op_begin()+1,
416 E = I->op_end(); OI != E; ++OI) {
417 const Value *Idx = *OI;
418 if (const StructType *StTy = dyn_cast<StructType>(Ty)) {
419 unsigned Field = cast<ConstantInt>(Idx)->getZExtValue();
422 uint64_t Offs = TD.getStructLayout(StTy)->getElementOffset(Field);
423 // FIXME: This can be optimized by combining the add with a
425 N = FastEmit_ri_(VT, ISD::ADD, N, NIsKill, Offs, VT);
427 // Unhandled operand. Halt "fast" selection and bail.
431 Ty = StTy->getElementType(Field);
433 Ty = cast<SequentialType>(Ty)->getElementType();
435 // If this is a constant subscript, handle it quickly.
436 if (const ConstantInt *CI = dyn_cast<ConstantInt>(Idx)) {
437 if (CI->isZero()) continue;
439 TD.getTypeAllocSize(Ty)*cast<ConstantInt>(CI)->getSExtValue();
440 N = FastEmit_ri_(VT, ISD::ADD, N, NIsKill, Offs, VT);
442 // Unhandled operand. Halt "fast" selection and bail.
448 // N = N + Idx * ElementSize;
449 uint64_t ElementSize = TD.getTypeAllocSize(Ty);
450 std::pair<unsigned, bool> Pair = getRegForGEPIndex(Idx);
451 unsigned IdxN = Pair.first;
452 bool IdxNIsKill = Pair.second;
454 // Unhandled operand. Halt "fast" selection and bail.
457 if (ElementSize != 1) {
458 IdxN = FastEmit_ri_(VT, ISD::MUL, IdxN, IdxNIsKill, ElementSize, VT);
460 // Unhandled operand. Halt "fast" selection and bail.
464 N = FastEmit_rr(VT, VT, ISD::ADD, N, NIsKill, IdxN, IdxNIsKill);
466 // Unhandled operand. Halt "fast" selection and bail.
471 // We successfully emitted code for the given LLVM Instruction.
472 UpdateValueMap(I, N);
476 bool FastISel::SelectCall(const User *I) {
477 const Function *F = cast<CallInst>(I)->getCalledFunction();
478 if (!F) return false;
480 // Handle selected intrinsic function calls.
481 unsigned IID = F->getIntrinsicID();
484 case Intrinsic::dbg_declare: {
485 const DbgDeclareInst *DI = cast<DbgDeclareInst>(I);
486 if (!DIVariable(DI->getVariable()).Verify() ||
487 !FuncInfo.MF->getMMI().hasDebugInfo())
490 const Value *Address = DI->getAddress();
491 if (!Address || isa<UndefValue>(Address) || isa<AllocaInst>(Address))
496 if (const Argument *Arg = dyn_cast<Argument>(Address)) {
497 if (Arg->hasByValAttr()) {
498 // Byval arguments' frame index is recorded during argument lowering.
499 // Use this info directly.
500 Offset = FuncInfo.getByValArgumentFrameIndex(Arg);
502 Reg = TRI.getFrameRegister(*FuncInfo.MF);
506 Reg = getRegForValue(Address);
509 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL,
510 TII.get(TargetOpcode::DBG_VALUE))
511 .addReg(Reg, RegState::Debug).addImm(Offset)
512 .addMetadata(DI->getVariable());
515 case Intrinsic::dbg_value: {
516 // This form of DBG_VALUE is target-independent.
517 const DbgValueInst *DI = cast<DbgValueInst>(I);
518 const TargetInstrDesc &II = TII.get(TargetOpcode::DBG_VALUE);
519 const Value *V = DI->getValue();
521 // Currently the optimizer can produce this; insert an undef to
522 // help debugging. Probably the optimizer should not do this.
523 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II)
524 .addReg(0U).addImm(DI->getOffset())
525 .addMetadata(DI->getVariable());
526 } else if (const ConstantInt *CI = dyn_cast<ConstantInt>(V)) {
527 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II)
528 .addImm(CI->getZExtValue()).addImm(DI->getOffset())
529 .addMetadata(DI->getVariable());
530 } else if (const ConstantFP *CF = dyn_cast<ConstantFP>(V)) {
531 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II)
532 .addFPImm(CF).addImm(DI->getOffset())
533 .addMetadata(DI->getVariable());
534 } else if (unsigned Reg = lookUpRegForValue(V)) {
535 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II)
536 .addReg(Reg, RegState::Debug).addImm(DI->getOffset())
537 .addMetadata(DI->getVariable());
539 // We can't yet handle anything else here because it would require
540 // generating code, thus altering codegen because of debug info.
541 DEBUG(dbgs() << "Dropping debug info for " << DI);
545 case Intrinsic::eh_exception: {
546 EVT VT = TLI.getValueType(I->getType());
547 switch (TLI.getOperationAction(ISD::EXCEPTIONADDR, VT)) {
549 case TargetLowering::Expand: {
550 assert(FuncInfo.MBB->isLandingPad() &&
551 "Call to eh.exception not in landing pad!");
552 unsigned Reg = TLI.getExceptionAddressRegister();
553 const TargetRegisterClass *RC = TLI.getRegClassFor(VT);
554 unsigned ResultReg = createResultReg(RC);
555 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TargetOpcode::COPY),
556 ResultReg).addReg(Reg);
557 UpdateValueMap(I, ResultReg);
563 case Intrinsic::eh_selector: {
564 EVT VT = TLI.getValueType(I->getType());
565 switch (TLI.getOperationAction(ISD::EHSELECTION, VT)) {
567 case TargetLowering::Expand: {
568 if (FuncInfo.MBB->isLandingPad())
569 AddCatchInfo(*cast<CallInst>(I), &FuncInfo.MF->getMMI(), FuncInfo.MBB);
572 FuncInfo.CatchInfoLost.insert(cast<CallInst>(I));
574 // FIXME: Mark exception selector register as live in. Hack for PR1508.
575 unsigned Reg = TLI.getExceptionSelectorRegister();
576 if (Reg) FuncInfo.MBB->addLiveIn(Reg);
579 unsigned Reg = TLI.getExceptionSelectorRegister();
580 EVT SrcVT = TLI.getPointerTy();
581 const TargetRegisterClass *RC = TLI.getRegClassFor(SrcVT);
582 unsigned ResultReg = createResultReg(RC);
583 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TargetOpcode::COPY),
584 ResultReg).addReg(Reg);
586 bool ResultRegIsKill = hasTrivialKill(I);
588 // Cast the register to the type of the selector.
589 if (SrcVT.bitsGT(MVT::i32))
590 ResultReg = FastEmit_r(SrcVT.getSimpleVT(), MVT::i32, ISD::TRUNCATE,
591 ResultReg, ResultRegIsKill);
592 else if (SrcVT.bitsLT(MVT::i32))
593 ResultReg = FastEmit_r(SrcVT.getSimpleVT(), MVT::i32,
594 ISD::SIGN_EXTEND, ResultReg, ResultRegIsKill);
596 // Unhandled operand. Halt "fast" selection and bail.
599 UpdateValueMap(I, ResultReg);
608 // An arbitrary call. Bail.
612 bool FastISel::SelectCast(const User *I, unsigned Opcode) {
613 EVT SrcVT = TLI.getValueType(I->getOperand(0)->getType());
614 EVT DstVT = TLI.getValueType(I->getType());
616 if (SrcVT == MVT::Other || !SrcVT.isSimple() ||
617 DstVT == MVT::Other || !DstVT.isSimple())
618 // Unhandled type. Halt "fast" selection and bail.
621 // Check if the destination type is legal. Or as a special case,
622 // it may be i1 if we're doing a truncate because that's
623 // easy and somewhat common.
624 if (!TLI.isTypeLegal(DstVT))
625 if (DstVT != MVT::i1 || Opcode != ISD::TRUNCATE)
626 // Unhandled type. Halt "fast" selection and bail.
629 // Check if the source operand is legal. Or as a special case,
630 // it may be i1 if we're doing zero-extension because that's
631 // easy and somewhat common.
632 if (!TLI.isTypeLegal(SrcVT))
633 if (SrcVT != MVT::i1 || Opcode != ISD::ZERO_EXTEND)
634 // Unhandled type. Halt "fast" selection and bail.
637 unsigned InputReg = getRegForValue(I->getOperand(0));
639 // Unhandled operand. Halt "fast" selection and bail.
642 bool InputRegIsKill = hasTrivialKill(I->getOperand(0));
644 // If the operand is i1, arrange for the high bits in the register to be zero.
645 if (SrcVT == MVT::i1) {
646 SrcVT = TLI.getTypeToTransformTo(I->getContext(), SrcVT);
647 InputReg = FastEmitZExtFromI1(SrcVT.getSimpleVT(), InputReg, InputRegIsKill);
650 InputRegIsKill = true;
652 // If the result is i1, truncate to the target's type for i1 first.
653 if (DstVT == MVT::i1)
654 DstVT = TLI.getTypeToTransformTo(I->getContext(), DstVT);
656 unsigned ResultReg = FastEmit_r(SrcVT.getSimpleVT(),
659 InputReg, InputRegIsKill);
663 UpdateValueMap(I, ResultReg);
667 bool FastISel::SelectBitCast(const User *I) {
668 // If the bitcast doesn't change the type, just use the operand value.
669 if (I->getType() == I->getOperand(0)->getType()) {
670 unsigned Reg = getRegForValue(I->getOperand(0));
673 UpdateValueMap(I, Reg);
677 // Bitcasts of other values become reg-reg copies or BITCAST operators.
678 EVT SrcVT = TLI.getValueType(I->getOperand(0)->getType());
679 EVT DstVT = TLI.getValueType(I->getType());
681 if (SrcVT == MVT::Other || !SrcVT.isSimple() ||
682 DstVT == MVT::Other || !DstVT.isSimple() ||
683 !TLI.isTypeLegal(SrcVT) || !TLI.isTypeLegal(DstVT))
684 // Unhandled type. Halt "fast" selection and bail.
687 unsigned Op0 = getRegForValue(I->getOperand(0));
689 // Unhandled operand. Halt "fast" selection and bail.
692 bool Op0IsKill = hasTrivialKill(I->getOperand(0));
694 // First, try to perform the bitcast by inserting a reg-reg copy.
695 unsigned ResultReg = 0;
696 if (SrcVT.getSimpleVT() == DstVT.getSimpleVT()) {
697 TargetRegisterClass* SrcClass = TLI.getRegClassFor(SrcVT);
698 TargetRegisterClass* DstClass = TLI.getRegClassFor(DstVT);
699 // Don't attempt a cross-class copy. It will likely fail.
700 if (SrcClass == DstClass) {
701 ResultReg = createResultReg(DstClass);
702 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TargetOpcode::COPY),
703 ResultReg).addReg(Op0);
707 // If the reg-reg copy failed, select a BITCAST opcode.
709 ResultReg = FastEmit_r(SrcVT.getSimpleVT(), DstVT.getSimpleVT(),
710 ISD::BITCAST, Op0, Op0IsKill);
715 UpdateValueMap(I, ResultReg);
720 FastISel::SelectInstruction(const Instruction *I) {
721 // Just before the terminator instruction, insert instructions to
722 // feed PHI nodes in successor blocks.
723 if (isa<TerminatorInst>(I))
724 if (!HandlePHINodesInSuccessorBlocks(I->getParent()))
727 DL = I->getDebugLoc();
729 // First, try doing target-independent selection.
730 if (SelectOperator(I, I->getOpcode())) {
735 // Next, try calling the target to attempt to handle the instruction.
736 if (TargetSelectInstruction(I)) {
745 /// FastEmitBranch - Emit an unconditional branch to the given block,
746 /// unless it is the immediate (fall-through) successor, and update
749 FastISel::FastEmitBranch(MachineBasicBlock *MSucc, DebugLoc DL) {
750 if (FuncInfo.MBB->isLayoutSuccessor(MSucc)) {
751 // The unconditional fall-through case, which needs no instructions.
753 // The unconditional branch case.
754 TII.InsertBranch(*FuncInfo.MBB, MSucc, NULL,
755 SmallVector<MachineOperand, 0>(), DL);
757 FuncInfo.MBB->addSuccessor(MSucc);
760 /// SelectFNeg - Emit an FNeg operation.
763 FastISel::SelectFNeg(const User *I) {
764 unsigned OpReg = getRegForValue(BinaryOperator::getFNegArgument(I));
765 if (OpReg == 0) return false;
767 bool OpRegIsKill = hasTrivialKill(I);
769 // If the target has ISD::FNEG, use it.
770 EVT VT = TLI.getValueType(I->getType());
771 unsigned ResultReg = FastEmit_r(VT.getSimpleVT(), VT.getSimpleVT(),
772 ISD::FNEG, OpReg, OpRegIsKill);
773 if (ResultReg != 0) {
774 UpdateValueMap(I, ResultReg);
778 // Bitcast the value to integer, twiddle the sign bit with xor,
779 // and then bitcast it back to floating-point.
780 if (VT.getSizeInBits() > 64) return false;
781 EVT IntVT = EVT::getIntegerVT(I->getContext(), VT.getSizeInBits());
782 if (!TLI.isTypeLegal(IntVT))
785 unsigned IntReg = FastEmit_r(VT.getSimpleVT(), IntVT.getSimpleVT(),
786 ISD::BITCAST, OpReg, OpRegIsKill);
790 unsigned IntResultReg = FastEmit_ri_(IntVT.getSimpleVT(), ISD::XOR,
791 IntReg, /*Kill=*/true,
792 UINT64_C(1) << (VT.getSizeInBits()-1),
793 IntVT.getSimpleVT());
794 if (IntResultReg == 0)
797 ResultReg = FastEmit_r(IntVT.getSimpleVT(), VT.getSimpleVT(),
798 ISD::BITCAST, IntResultReg, /*Kill=*/true);
802 UpdateValueMap(I, ResultReg);
807 FastISel::SelectOperator(const User *I, unsigned Opcode) {
809 case Instruction::Add:
810 return SelectBinaryOp(I, ISD::ADD);
811 case Instruction::FAdd:
812 return SelectBinaryOp(I, ISD::FADD);
813 case Instruction::Sub:
814 return SelectBinaryOp(I, ISD::SUB);
815 case Instruction::FSub:
816 // FNeg is currently represented in LLVM IR as a special case of FSub.
817 if (BinaryOperator::isFNeg(I))
818 return SelectFNeg(I);
819 return SelectBinaryOp(I, ISD::FSUB);
820 case Instruction::Mul:
821 return SelectBinaryOp(I, ISD::MUL);
822 case Instruction::FMul:
823 return SelectBinaryOp(I, ISD::FMUL);
824 case Instruction::SDiv:
825 return SelectBinaryOp(I, ISD::SDIV);
826 case Instruction::UDiv:
827 return SelectBinaryOp(I, ISD::UDIV);
828 case Instruction::FDiv:
829 return SelectBinaryOp(I, ISD::FDIV);
830 case Instruction::SRem:
831 return SelectBinaryOp(I, ISD::SREM);
832 case Instruction::URem:
833 return SelectBinaryOp(I, ISD::UREM);
834 case Instruction::FRem:
835 return SelectBinaryOp(I, ISD::FREM);
836 case Instruction::Shl:
837 return SelectBinaryOp(I, ISD::SHL);
838 case Instruction::LShr:
839 return SelectBinaryOp(I, ISD::SRL);
840 case Instruction::AShr:
841 return SelectBinaryOp(I, ISD::SRA);
842 case Instruction::And:
843 return SelectBinaryOp(I, ISD::AND);
844 case Instruction::Or:
845 return SelectBinaryOp(I, ISD::OR);
846 case Instruction::Xor:
847 return SelectBinaryOp(I, ISD::XOR);
849 case Instruction::GetElementPtr:
850 return SelectGetElementPtr(I);
852 case Instruction::Br: {
853 const BranchInst *BI = cast<BranchInst>(I);
855 if (BI->isUnconditional()) {
856 const BasicBlock *LLVMSucc = BI->getSuccessor(0);
857 MachineBasicBlock *MSucc = FuncInfo.MBBMap[LLVMSucc];
858 FastEmitBranch(MSucc, BI->getDebugLoc());
862 // Conditional branches are not handed yet.
863 // Halt "fast" selection and bail.
867 case Instruction::Unreachable:
871 case Instruction::Alloca:
872 // FunctionLowering has the static-sized case covered.
873 if (FuncInfo.StaticAllocaMap.count(cast<AllocaInst>(I)))
876 // Dynamic-sized alloca is not handled yet.
879 case Instruction::Call:
880 return SelectCall(I);
882 case Instruction::BitCast:
883 return SelectBitCast(I);
885 case Instruction::FPToSI:
886 return SelectCast(I, ISD::FP_TO_SINT);
887 case Instruction::ZExt:
888 return SelectCast(I, ISD::ZERO_EXTEND);
889 case Instruction::SExt:
890 return SelectCast(I, ISD::SIGN_EXTEND);
891 case Instruction::Trunc:
892 return SelectCast(I, ISD::TRUNCATE);
893 case Instruction::SIToFP:
894 return SelectCast(I, ISD::SINT_TO_FP);
896 case Instruction::IntToPtr: // Deliberate fall-through.
897 case Instruction::PtrToInt: {
898 EVT SrcVT = TLI.getValueType(I->getOperand(0)->getType());
899 EVT DstVT = TLI.getValueType(I->getType());
900 if (DstVT.bitsGT(SrcVT))
901 return SelectCast(I, ISD::ZERO_EXTEND);
902 if (DstVT.bitsLT(SrcVT))
903 return SelectCast(I, ISD::TRUNCATE);
904 unsigned Reg = getRegForValue(I->getOperand(0));
905 if (Reg == 0) return false;
906 UpdateValueMap(I, Reg);
910 case Instruction::PHI:
911 llvm_unreachable("FastISel shouldn't visit PHI nodes!");
914 // Unhandled instruction. Halt "fast" selection and bail.
919 FastISel::FastISel(FunctionLoweringInfo &funcInfo)
920 : FuncInfo(funcInfo),
921 MRI(FuncInfo.MF->getRegInfo()),
922 MFI(*FuncInfo.MF->getFrameInfo()),
923 MCP(*FuncInfo.MF->getConstantPool()),
924 TM(FuncInfo.MF->getTarget()),
925 TD(*TM.getTargetData()),
926 TII(*TM.getInstrInfo()),
927 TLI(*TM.getTargetLowering()),
928 TRI(*TM.getRegisterInfo()) {
931 FastISel::~FastISel() {}
933 unsigned FastISel::FastEmit_(MVT, MVT,
938 unsigned FastISel::FastEmit_r(MVT, MVT,
940 unsigned /*Op0*/, bool /*Op0IsKill*/) {
944 unsigned FastISel::FastEmit_rr(MVT, MVT,
946 unsigned /*Op0*/, bool /*Op0IsKill*/,
947 unsigned /*Op1*/, bool /*Op1IsKill*/) {
951 unsigned FastISel::FastEmit_i(MVT, MVT, unsigned, uint64_t /*Imm*/) {
955 unsigned FastISel::FastEmit_f(MVT, MVT,
956 unsigned, const ConstantFP * /*FPImm*/) {
960 unsigned FastISel::FastEmit_ri(MVT, MVT,
962 unsigned /*Op0*/, bool /*Op0IsKill*/,
967 unsigned FastISel::FastEmit_rf(MVT, MVT,
969 unsigned /*Op0*/, bool /*Op0IsKill*/,
970 const ConstantFP * /*FPImm*/) {
974 unsigned FastISel::FastEmit_rri(MVT, MVT,
976 unsigned /*Op0*/, bool /*Op0IsKill*/,
977 unsigned /*Op1*/, bool /*Op1IsKill*/,
982 /// FastEmit_ri_ - This method is a wrapper of FastEmit_ri. It first tries
983 /// to emit an instruction with an immediate operand using FastEmit_ri.
984 /// If that fails, it materializes the immediate into a register and try
985 /// FastEmit_rr instead.
986 unsigned FastISel::FastEmit_ri_(MVT VT, unsigned Opcode,
987 unsigned Op0, bool Op0IsKill,
988 uint64_t Imm, MVT ImmType) {
989 // If this is a multiply by a power of two, emit this as a shift left.
990 if (Opcode == ISD::MUL && isPowerOf2_64(Imm)) {
995 // Horrible hack (to be removed), check to make sure shift amounts are
997 if ((Opcode == ISD::SHL || Opcode == ISD::SRA || Opcode == ISD::SRL) &&
998 Imm >= VT.getSizeInBits())
1001 // First check if immediate type is legal. If not, we can't use the ri form.
1002 unsigned ResultReg = FastEmit_ri(VT, VT, Opcode, Op0, Op0IsKill, Imm);
1005 unsigned MaterialReg = FastEmit_i(ImmType, ImmType, ISD::Constant, Imm);
1006 if (MaterialReg == 0)
1008 return FastEmit_rr(VT, VT, Opcode,
1010 MaterialReg, /*Kill=*/true);
1013 /// FastEmit_rf_ - This method is a wrapper of FastEmit_ri. It first tries
1014 /// to emit an instruction with a floating-point immediate operand using
1015 /// FastEmit_rf. If that fails, it materializes the immediate into a register
1016 /// and try FastEmit_rr instead.
1017 unsigned FastISel::FastEmit_rf_(MVT VT, unsigned Opcode,
1018 unsigned Op0, bool Op0IsKill,
1019 const ConstantFP *FPImm, MVT ImmType) {
1020 // First check if immediate type is legal. If not, we can't use the rf form.
1021 unsigned ResultReg = FastEmit_rf(VT, VT, Opcode, Op0, Op0IsKill, FPImm);
1025 // Materialize the constant in a register.
1026 unsigned MaterialReg = FastEmit_f(ImmType, ImmType, ISD::ConstantFP, FPImm);
1027 if (MaterialReg == 0) {
1028 // If the target doesn't have a way to directly enter a floating-point
1029 // value into a register, use an alternate approach.
1030 // TODO: The current approach only supports floating-point constants
1031 // that can be constructed by conversion from integer values. This should
1032 // be replaced by code that creates a load from a constant-pool entry,
1033 // which will require some target-specific work.
1034 const APFloat &Flt = FPImm->getValueAPF();
1035 EVT IntVT = TLI.getPointerTy();
1038 uint32_t IntBitWidth = IntVT.getSizeInBits();
1040 (void) Flt.convertToInteger(x, IntBitWidth, /*isSigned=*/true,
1041 APFloat::rmTowardZero, &isExact);
1044 APInt IntVal(IntBitWidth, 2, x);
1046 unsigned IntegerReg = FastEmit_i(IntVT.getSimpleVT(), IntVT.getSimpleVT(),
1047 ISD::Constant, IntVal.getZExtValue());
1048 if (IntegerReg == 0)
1050 MaterialReg = FastEmit_r(IntVT.getSimpleVT(), VT,
1051 ISD::SINT_TO_FP, IntegerReg, /*Kill=*/true);
1052 if (MaterialReg == 0)
1055 return FastEmit_rr(VT, VT, Opcode,
1057 MaterialReg, /*Kill=*/true);
1060 unsigned FastISel::createResultReg(const TargetRegisterClass* RC) {
1061 return MRI.createVirtualRegister(RC);
1064 unsigned FastISel::FastEmitInst_(unsigned MachineInstOpcode,
1065 const TargetRegisterClass* RC) {
1066 unsigned ResultReg = createResultReg(RC);
1067 const TargetInstrDesc &II = TII.get(MachineInstOpcode);
1069 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II, ResultReg);
1073 unsigned FastISel::FastEmitInst_r(unsigned MachineInstOpcode,
1074 const TargetRegisterClass *RC,
1075 unsigned Op0, bool Op0IsKill) {
1076 unsigned ResultReg = createResultReg(RC);
1077 const TargetInstrDesc &II = TII.get(MachineInstOpcode);
1079 if (II.getNumDefs() >= 1)
1080 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II, ResultReg)
1081 .addReg(Op0, Op0IsKill * RegState::Kill);
1083 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II)
1084 .addReg(Op0, Op0IsKill * RegState::Kill);
1085 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TargetOpcode::COPY),
1086 ResultReg).addReg(II.ImplicitDefs[0]);
1092 unsigned FastISel::FastEmitInst_rr(unsigned MachineInstOpcode,
1093 const TargetRegisterClass *RC,
1094 unsigned Op0, bool Op0IsKill,
1095 unsigned Op1, bool Op1IsKill) {
1096 unsigned ResultReg = createResultReg(RC);
1097 const TargetInstrDesc &II = TII.get(MachineInstOpcode);
1099 if (II.getNumDefs() >= 1)
1100 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II, ResultReg)
1101 .addReg(Op0, Op0IsKill * RegState::Kill)
1102 .addReg(Op1, Op1IsKill * RegState::Kill);
1104 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II)
1105 .addReg(Op0, Op0IsKill * RegState::Kill)
1106 .addReg(Op1, Op1IsKill * RegState::Kill);
1107 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TargetOpcode::COPY),
1108 ResultReg).addReg(II.ImplicitDefs[0]);
1113 unsigned FastISel::FastEmitInst_ri(unsigned MachineInstOpcode,
1114 const TargetRegisterClass *RC,
1115 unsigned Op0, bool Op0IsKill,
1117 unsigned ResultReg = createResultReg(RC);
1118 const TargetInstrDesc &II = TII.get(MachineInstOpcode);
1120 if (II.getNumDefs() >= 1)
1121 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II, ResultReg)
1122 .addReg(Op0, Op0IsKill * RegState::Kill)
1125 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II)
1126 .addReg(Op0, Op0IsKill * RegState::Kill)
1128 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TargetOpcode::COPY),
1129 ResultReg).addReg(II.ImplicitDefs[0]);
1134 unsigned FastISel::FastEmitInst_rii(unsigned MachineInstOpcode,
1135 const TargetRegisterClass *RC,
1136 unsigned Op0, bool Op0IsKill,
1137 uint64_t Imm1, uint64_t Imm2) {
1138 unsigned ResultReg = createResultReg(RC);
1139 const TargetInstrDesc &II = TII.get(MachineInstOpcode);
1141 if (II.getNumDefs() >= 1)
1142 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II, ResultReg)
1143 .addReg(Op0, Op0IsKill * RegState::Kill)
1147 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II)
1148 .addReg(Op0, Op0IsKill * RegState::Kill)
1151 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TargetOpcode::COPY),
1152 ResultReg).addReg(II.ImplicitDefs[0]);
1157 unsigned FastISel::FastEmitInst_rf(unsigned MachineInstOpcode,
1158 const TargetRegisterClass *RC,
1159 unsigned Op0, bool Op0IsKill,
1160 const ConstantFP *FPImm) {
1161 unsigned ResultReg = createResultReg(RC);
1162 const TargetInstrDesc &II = TII.get(MachineInstOpcode);
1164 if (II.getNumDefs() >= 1)
1165 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II, ResultReg)
1166 .addReg(Op0, Op0IsKill * RegState::Kill)
1169 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II)
1170 .addReg(Op0, Op0IsKill * RegState::Kill)
1172 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TargetOpcode::COPY),
1173 ResultReg).addReg(II.ImplicitDefs[0]);
1178 unsigned FastISel::FastEmitInst_rri(unsigned MachineInstOpcode,
1179 const TargetRegisterClass *RC,
1180 unsigned Op0, bool Op0IsKill,
1181 unsigned Op1, bool Op1IsKill,
1183 unsigned ResultReg = createResultReg(RC);
1184 const TargetInstrDesc &II = TII.get(MachineInstOpcode);
1186 if (II.getNumDefs() >= 1)
1187 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II, ResultReg)
1188 .addReg(Op0, Op0IsKill * RegState::Kill)
1189 .addReg(Op1, Op1IsKill * RegState::Kill)
1192 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II)
1193 .addReg(Op0, Op0IsKill * RegState::Kill)
1194 .addReg(Op1, Op1IsKill * RegState::Kill)
1196 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TargetOpcode::COPY),
1197 ResultReg).addReg(II.ImplicitDefs[0]);
1202 unsigned FastISel::FastEmitInst_i(unsigned MachineInstOpcode,
1203 const TargetRegisterClass *RC,
1205 unsigned ResultReg = createResultReg(RC);
1206 const TargetInstrDesc &II = TII.get(MachineInstOpcode);
1208 if (II.getNumDefs() >= 1)
1209 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II, ResultReg).addImm(Imm);
1211 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, II).addImm(Imm);
1212 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt, DL, TII.get(TargetOpcode::COPY),
1213 ResultReg).addReg(II.ImplicitDefs[0]);
1218 unsigned FastISel::FastEmitInst_extractsubreg(MVT RetVT,
1219 unsigned Op0, bool Op0IsKill,
1221 unsigned ResultReg = createResultReg(TLI.getRegClassFor(RetVT));
1222 assert(TargetRegisterInfo::isVirtualRegister(Op0) &&
1223 "Cannot yet extract from physregs");
1224 BuildMI(*FuncInfo.MBB, FuncInfo.InsertPt,
1225 DL, TII.get(TargetOpcode::COPY), ResultReg)
1226 .addReg(Op0, getKillRegState(Op0IsKill), Idx);
1230 /// FastEmitZExtFromI1 - Emit MachineInstrs to compute the value of Op
1231 /// with all but the least significant bit set to zero.
1232 unsigned FastISel::FastEmitZExtFromI1(MVT VT, unsigned Op0, bool Op0IsKill) {
1233 return FastEmit_ri(VT, VT, ISD::AND, Op0, Op0IsKill, 1);
1236 /// HandlePHINodesInSuccessorBlocks - Handle PHI nodes in successor blocks.
1237 /// Emit code to ensure constants are copied into registers when needed.
1238 /// Remember the virtual registers that need to be added to the Machine PHI
1239 /// nodes as input. We cannot just directly add them, because expansion
1240 /// might result in multiple MBB's for one BB. As such, the start of the
1241 /// BB might correspond to a different MBB than the end.
1242 bool FastISel::HandlePHINodesInSuccessorBlocks(const BasicBlock *LLVMBB) {
1243 const TerminatorInst *TI = LLVMBB->getTerminator();
1245 SmallPtrSet<MachineBasicBlock *, 4> SuccsHandled;
1246 unsigned OrigNumPHINodesToUpdate = FuncInfo.PHINodesToUpdate.size();
1248 // Check successor nodes' PHI nodes that expect a constant to be available
1250 for (unsigned succ = 0, e = TI->getNumSuccessors(); succ != e; ++succ) {
1251 const BasicBlock *SuccBB = TI->getSuccessor(succ);
1252 if (!isa<PHINode>(SuccBB->begin())) continue;
1253 MachineBasicBlock *SuccMBB = FuncInfo.MBBMap[SuccBB];
1255 // If this terminator has multiple identical successors (common for
1256 // switches), only handle each succ once.
1257 if (!SuccsHandled.insert(SuccMBB)) continue;
1259 MachineBasicBlock::iterator MBBI = SuccMBB->begin();
1261 // At this point we know that there is a 1-1 correspondence between LLVM PHI
1262 // nodes and Machine PHI nodes, but the incoming operands have not been
1264 for (BasicBlock::const_iterator I = SuccBB->begin();
1265 const PHINode *PN = dyn_cast<PHINode>(I); ++I) {
1267 // Ignore dead phi's.
1268 if (PN->use_empty()) continue;
1270 // Only handle legal types. Two interesting things to note here. First,
1271 // by bailing out early, we may leave behind some dead instructions,
1272 // since SelectionDAG's HandlePHINodesInSuccessorBlocks will insert its
1273 // own moves. Second, this check is necessary because FastISel doesn't
1274 // use CreateRegs to create registers, so it always creates
1275 // exactly one register for each non-void instruction.
1276 EVT VT = TLI.getValueType(PN->getType(), /*AllowUnknown=*/true);
1277 if (VT == MVT::Other || !TLI.isTypeLegal(VT)) {
1280 VT = TLI.getTypeToTransformTo(LLVMBB->getContext(), VT);
1282 FuncInfo.PHINodesToUpdate.resize(OrigNumPHINodesToUpdate);
1287 const Value *PHIOp = PN->getIncomingValueForBlock(LLVMBB);
1289 // Set the DebugLoc for the copy. Prefer the location of the operand
1290 // if there is one; use the location of the PHI otherwise.
1291 DL = PN->getDebugLoc();
1292 if (const Instruction *Inst = dyn_cast<Instruction>(PHIOp))
1293 DL = Inst->getDebugLoc();
1295 unsigned Reg = getRegForValue(PHIOp);
1297 FuncInfo.PHINodesToUpdate.resize(OrigNumPHINodesToUpdate);
1300 FuncInfo.PHINodesToUpdate.push_back(std::make_pair(MBBI++, Reg));