FunctionLoweringInfo.cpp revision ec25c929e718999b22b3fcee506104f995b3b457 
1//===-- FunctionLoweringInfo.cpp ------------------------------------------===//
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 implements routines for translating functions from LLVM IR into
11// Machine IR.
12//
13//===----------------------------------------------------------------------===//
14
15#define DEBUG_TYPE "function-lowering-info"
16#include "llvm/CodeGen/FunctionLoweringInfo.h"
17#include "llvm/DerivedTypes.h"
18#include "llvm/Function.h"
19#include "llvm/Instructions.h"
20#include "llvm/IntrinsicInst.h"
21#include "llvm/LLVMContext.h"
22#include "llvm/Module.h"
23#include "llvm/CodeGen/Analysis.h"
24#include "llvm/CodeGen/MachineFunction.h"
25#include "llvm/CodeGen/MachineFrameInfo.h"
26#include "llvm/CodeGen/MachineInstrBuilder.h"
27#include "llvm/CodeGen/MachineModuleInfo.h"
28#include "llvm/CodeGen/MachineRegisterInfo.h"
29#include "llvm/Target/TargetRegisterInfo.h"
30#include "llvm/Target/TargetData.h"
31#include "llvm/Target/TargetFrameInfo.h"
32#include "llvm/Target/TargetInstrInfo.h"
33#include "llvm/Target/TargetLowering.h"
34#include "llvm/Target/TargetOptions.h"
35#include "llvm/Support/Debug.h"
36#include "llvm/Support/ErrorHandling.h"
37#include "llvm/Support/MathExtras.h"
38#include <algorithm>
39using namespace llvm;
40
41/// isUsedOutsideOfDefiningBlock - Return true if this instruction is used by
42/// PHI nodes or outside of the basic block that defines it, or used by a
43/// switch or atomic instruction, which may expand to multiple basic blocks.
44static bool isUsedOutsideOfDefiningBlock(const Instruction *I) {
45  if (I->use_empty()) return false;
46  if (isa<PHINode>(I)) return true;
47  const BasicBlock *BB = I->getParent();
48  for (Value::const_use_iterator UI = I->use_begin(), E = I->use_end();
49        UI != E; ++UI) {
50    const User *U = *UI;
51    if (cast<Instruction>(U)->getParent() != BB || isa<PHINode>(U))
52      return true;
53  }
54  return false;
55}
56
57/// isOnlyUsedInEntryBlock - If the specified argument is only used in the
58/// entry block, return true.  This includes arguments used by switches, since
59/// the switch may expand into multiple basic blocks.
60static bool isOnlyUsedInEntryBlock(const Argument *A, bool EnableFastISel) {
61  // With FastISel active, we may be splitting blocks, so force creation
62  // of virtual registers for all non-dead arguments.
63  if (EnableFastISel)
64    return A->use_empty();
65
66  const BasicBlock *Entry = A->getParent()->begin();
67  for (Value::const_use_iterator UI = A->use_begin(), E = A->use_end();
68       UI != E; ++UI) {
69    const User *U = *UI;
70    if (cast<Instruction>(U)->getParent() != Entry || isa<SwitchInst>(U))
71      return false;  // Use not in entry block.
72  }
73  return true;
74}
75
76FunctionLoweringInfo::FunctionLoweringInfo(const TargetLowering &tli)
77  : TLI(tli) {
78}
79
80void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf) {
81  Fn = &fn;
82  MF = &mf;
83  RegInfo = &MF->getRegInfo();
84
85  // Create a vreg for each argument register that is not dead and is used
86  // outside of the entry block for the function.
87  for (Function::const_arg_iterator AI = Fn->arg_begin(), E = Fn->arg_end();
88       AI != E; ++AI)
89    if (!isOnlyUsedInEntryBlock(AI, EnableFastISel))
90      InitializeRegForValue(AI);
91
92  // Initialize the mapping of values to registers.  This is only set up for
93  // instruction values that are used outside of the block that defines
94  // them.
95  Function::const_iterator BB = Fn->begin(), EB = Fn->end();
96  for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I)
97    if (const AllocaInst *AI = dyn_cast<AllocaInst>(I))
98      if (const ConstantInt *CUI = dyn_cast<ConstantInt>(AI->getArraySize())) {
99        const Type *Ty = AI->getAllocatedType();
100        uint64_t TySize = TLI.getTargetData()->getTypeAllocSize(Ty);
101        unsigned Align =
102          std::max((unsigned)TLI.getTargetData()->getPrefTypeAlignment(Ty),
103                   AI->getAlignment());
104
105        TySize *= CUI->getZExtValue();   // Get total allocated size.
106        if (TySize == 0) TySize = 1; // Don't create zero-sized stack objects.
107        StaticAllocaMap[AI] =
108          MF->getFrameInfo()->CreateStackObject(TySize, Align, false);
109      }
110
111  for (; BB != EB; ++BB)
112    for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I)
113      if (isUsedOutsideOfDefiningBlock(I))
114        if (!isa<AllocaInst>(I) ||
115            !StaticAllocaMap.count(cast<AllocaInst>(I)))
116          InitializeRegForValue(I);
117
118  // Create an initial MachineBasicBlock for each LLVM BasicBlock in F.  This
119  // also creates the initial PHI MachineInstrs, though none of the input
120  // operands are populated.
121  for (BB = Fn->begin(); BB != EB; ++BB) {
122    MachineBasicBlock *MBB = mf.CreateMachineBasicBlock(BB);
123    MBBMap[BB] = MBB;
124    MF->push_back(MBB);
125
126    // Transfer the address-taken flag. This is necessary because there could
127    // be multiple MachineBasicBlocks corresponding to one BasicBlock, and only
128    // the first one should be marked.
129    if (BB->hasAddressTaken())
130      MBB->setHasAddressTaken();
131
132    // Create Machine PHI nodes for LLVM PHI nodes, lowering them as
133    // appropriate.
134    for (BasicBlock::const_iterator I = BB->begin();
135         const PHINode *PN = dyn_cast<PHINode>(I); ++I) {
136      if (PN->use_empty()) continue;
137
138      DebugLoc DL = PN->getDebugLoc();
139      unsigned PHIReg = ValueMap[PN];
140      assert(PHIReg && "PHI node does not have an assigned virtual register!");
141
142      SmallVector<EVT, 4> ValueVTs;
143      ComputeValueVTs(TLI, PN->getType(), ValueVTs);
144      for (unsigned vti = 0, vte = ValueVTs.size(); vti != vte; ++vti) {
145        EVT VT = ValueVTs[vti];
146        unsigned NumRegisters = TLI.getNumRegisters(Fn->getContext(), VT);
147        const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
148        for (unsigned i = 0; i != NumRegisters; ++i)
149          BuildMI(MBB, DL, TII->get(TargetOpcode::PHI), PHIReg + i);
150        PHIReg += NumRegisters;
151      }
152    }
153  }
154
155  // Mark landing pad blocks.
156  for (BB = Fn->begin(); BB != EB; ++BB)
157    if (const InvokeInst *Invoke = dyn_cast<InvokeInst>(BB->getTerminator()))
158      MBBMap[Invoke->getSuccessor(1)]->setIsLandingPad();
159}
160
161/// clear - Clear out all the function-specific state. This returns this
162/// FunctionLoweringInfo to an empty state, ready to be used for a
163/// different function.
164void FunctionLoweringInfo::clear() {
165  assert(CatchInfoFound.size() == CatchInfoLost.size() &&
166         "Not all catch info was assigned to a landing pad!");
167
168  MBBMap.clear();
169  ValueMap.clear();
170  StaticAllocaMap.clear();
171#ifndef NDEBUG
172  CatchInfoLost.clear();
173  CatchInfoFound.clear();
174#endif
175  LiveOutRegInfo.clear();
176  ArgDbgValues.clear();
177}
178
179/// CreateReg - Allocate a single virtual register for the given type.
180unsigned FunctionLoweringInfo::CreateReg(EVT VT) {
181  return RegInfo->createVirtualRegister(TLI.getRegClassFor(VT));
182}
183
184/// CreateRegs - Allocate the appropriate number of virtual registers of
185/// the correctly promoted or expanded types.  Assign these registers
186/// consecutive vreg numbers and return the first assigned number.
187///
188/// In the case that the given value has struct or array type, this function
189/// will assign registers for each member or element.
190///
191unsigned FunctionLoweringInfo::CreateRegs(const Type *Ty) {
192  SmallVector<EVT, 4> ValueVTs;
193  ComputeValueVTs(TLI, Ty, ValueVTs);
194
195  unsigned FirstReg = 0;
196  for (unsigned Value = 0, e = ValueVTs.size(); Value != e; ++Value) {
197    EVT ValueVT = ValueVTs[Value];
198    EVT RegisterVT = TLI.getRegisterType(Ty->getContext(), ValueVT);
199
200    unsigned NumRegs = TLI.getNumRegisters(Ty->getContext(), ValueVT);
201    for (unsigned i = 0; i != NumRegs; ++i) {
202      unsigned R = CreateReg(RegisterVT);
203      if (!FirstReg) FirstReg = R;
204    }
205  }
206  return FirstReg;
207}
208
209/// AddCatchInfo - Extract the personality and type infos from an eh.selector
210/// call, and add them to the specified machine basic block.
211void llvm::AddCatchInfo(const CallInst &I, MachineModuleInfo *MMI,
212                        MachineBasicBlock *MBB) {
213  // Inform the MachineModuleInfo of the personality for this landing pad.
214  const ConstantExpr *CE = cast<ConstantExpr>(I.getArgOperand(1));
215  assert(CE->getOpcode() == Instruction::BitCast &&
216         isa<Function>(CE->getOperand(0)) &&
217         "Personality should be a function");
218  MMI->addPersonality(MBB, cast<Function>(CE->getOperand(0)));
219
220  // Gather all the type infos for this landing pad and pass them along to
221  // MachineModuleInfo.
222  std::vector<const GlobalVariable *> TyInfo;
223  unsigned N = I.getNumArgOperands();
224
225  for (unsigned i = N - 1; i > 1; --i) {
226    if (const ConstantInt *CI = dyn_cast<ConstantInt>(I.getArgOperand(i))) {
227      unsigned FilterLength = CI->getZExtValue();
228      unsigned FirstCatch = i + FilterLength + !FilterLength;
229      assert(FirstCatch <= N && "Invalid filter length");
230
231      if (FirstCatch < N) {
232        TyInfo.reserve(N - FirstCatch);
233        for (unsigned j = FirstCatch; j < N; ++j)
234          TyInfo.push_back(ExtractTypeInfo(I.getArgOperand(j)));
235        MMI->addCatchTypeInfo(MBB, TyInfo);
236        TyInfo.clear();
237      }
238
239      if (!FilterLength) {
240        // Cleanup.
241        MMI->addCleanup(MBB);
242      } else {
243        // Filter.
244        TyInfo.reserve(FilterLength - 1);
245        for (unsigned j = i + 1; j < FirstCatch; ++j)
246          TyInfo.push_back(ExtractTypeInfo(I.getArgOperand(j)));
247        MMI->addFilterTypeInfo(MBB, TyInfo);
248        TyInfo.clear();
249      }
250
251      N = i;
252    }
253  }
254
255  if (N > 2) {
256    TyInfo.reserve(N - 2);
257    for (unsigned j = 2; j < N; ++j)
258      TyInfo.push_back(ExtractTypeInfo(I.getArgOperand(j)));
259    MMI->addCatchTypeInfo(MBB, TyInfo);
260  }
261}
262
263void llvm::CopyCatchInfo(const BasicBlock *SrcBB, const BasicBlock *DestBB,
264                         MachineModuleInfo *MMI, FunctionLoweringInfo &FLI) {
265  for (BasicBlock::const_iterator I = SrcBB->begin(), E = --SrcBB->end();
266       I != E; ++I)
267    if (const EHSelectorInst *EHSel = dyn_cast<EHSelectorInst>(I)) {
268      // Apply the catch info to DestBB.
269      AddCatchInfo(*EHSel, MMI, FLI.MBBMap[DestBB]);
270#ifndef NDEBUG
271      if (!FLI.MBBMap[SrcBB]->isLandingPad())
272        FLI.CatchInfoFound.insert(EHSel);
273#endif
274    }
275}
276