FunctionLoweringInfo.cpp revision a46cd97818ac6fa336b093adecf2006fb041ca1c 
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/Analysis/DebugInfo.h"
24#include "llvm/CodeGen/Analysis.h"
25#include "llvm/CodeGen/MachineFunction.h"
26#include "llvm/CodeGen/MachineFrameInfo.h"
27#include "llvm/CodeGen/MachineInstrBuilder.h"
28#include "llvm/CodeGen/MachineModuleInfo.h"
29#include "llvm/CodeGen/MachineRegisterInfo.h"
30#include "llvm/Target/TargetRegisterInfo.h"
31#include "llvm/Target/TargetData.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  // Check whether the function can return without sret-demotion.
86  SmallVector<ISD::OutputArg, 4> Outs;
87  GetReturnInfo(Fn->getReturnType(),
88                Fn->getAttributes().getRetAttributes(), Outs, TLI);
89  CanLowerReturn = TLI.CanLowerReturn(Fn->getCallingConv(), Fn->isVarArg(),
90                                      Outs, Fn->getContext());
91
92  // Create a vreg for each argument register that is not dead and is used
93  // outside of the entry block for the function.
94  for (Function::const_arg_iterator AI = Fn->arg_begin(), E = Fn->arg_end();
95       AI != E; ++AI)
96    if (!isOnlyUsedInEntryBlock(AI, EnableFastISel))
97      InitializeRegForValue(AI);
98
99  // Initialize the mapping of values to registers.  This is only set up for
100  // instruction values that are used outside of the block that defines
101  // them.
102  Function::const_iterator BB = Fn->begin(), EB = Fn->end();
103  for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I)
104    if (const AllocaInst *AI = dyn_cast<AllocaInst>(I))
105      if (const ConstantInt *CUI = dyn_cast<ConstantInt>(AI->getArraySize())) {
106        const Type *Ty = AI->getAllocatedType();
107        uint64_t TySize = TLI.getTargetData()->getTypeAllocSize(Ty);
108        unsigned Align =
109          std::max((unsigned)TLI.getTargetData()->getPrefTypeAlignment(Ty),
110                   AI->getAlignment());
111
112        TySize *= CUI->getZExtValue();   // Get total allocated size.
113        if (TySize == 0) TySize = 1; // Don't create zero-sized stack objects.
114
115        // The object may need to be placed onto the stack near the stack
116        // protector if one exists. Determine here if this object is a suitable
117        // candidate. I.e., it would trigger the creation of a stack protector.
118        bool MayNeedSP =
119          (AI->isArrayAllocation() ||
120           (TySize > 8 && isa<ArrayType>(Ty) &&
121            cast<ArrayType>(Ty)->getElementType()->isIntegerTy(8)));
122        StaticAllocaMap[AI] =
123          MF->getFrameInfo()->CreateStackObject(TySize, Align, false, MayNeedSP);
124      }
125
126  for (; BB != EB; ++BB)
127    for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
128      // Mark values used outside their block as exported, by allocating
129      // a virtual register for them.
130      if (isUsedOutsideOfDefiningBlock(I))
131        if (!isa<AllocaInst>(I) ||
132            !StaticAllocaMap.count(cast<AllocaInst>(I)))
133          InitializeRegForValue(I);
134
135      // Collect llvm.dbg.declare information. This is done now instead of
136      // during the initial isel pass through the IR so that it is done
137      // in a predictable order.
138      if (const DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(I)) {
139        MachineModuleInfo &MMI = MF->getMMI();
140        if (MMI.hasDebugInfo() &&
141            DIVariable(DI->getVariable()).Verify() &&
142            !DI->getDebugLoc().isUnknown()) {
143          // Don't handle byval struct arguments or VLAs, for example.
144          // Non-byval arguments are handled here (they refer to the stack
145          // temporary alloca at this point).
146          const Value *Address = DI->getAddress();
147          if (Address) {
148            if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Address))
149              Address = BCI->getOperand(0);
150            if (const AllocaInst *AI = dyn_cast<AllocaInst>(Address)) {
151              DenseMap<const AllocaInst *, int>::iterator SI =
152                StaticAllocaMap.find(AI);
153              if (SI != StaticAllocaMap.end()) { // Check for VLAs.
154                int FI = SI->second;
155                MMI.setVariableDbgInfo(DI->getVariable(),
156                                       FI, DI->getDebugLoc());
157              }
158            }
159          }
160        }
161      }
162    }
163
164  // Create an initial MachineBasicBlock for each LLVM BasicBlock in F.  This
165  // also creates the initial PHI MachineInstrs, though none of the input
166  // operands are populated.
167  for (BB = Fn->begin(); BB != EB; ++BB) {
168    MachineBasicBlock *MBB = mf.CreateMachineBasicBlock(BB);
169    MBBMap[BB] = MBB;
170    MF->push_back(MBB);
171
172    // Transfer the address-taken flag. This is necessary because there could
173    // be multiple MachineBasicBlocks corresponding to one BasicBlock, and only
174    // the first one should be marked.
175    if (BB->hasAddressTaken())
176      MBB->setHasAddressTaken();
177
178    // Create Machine PHI nodes for LLVM PHI nodes, lowering them as
179    // appropriate.
180    for (BasicBlock::const_iterator I = BB->begin();
181         const PHINode *PN = dyn_cast<PHINode>(I); ++I) {
182      if (PN->use_empty()) continue;
183
184      DebugLoc DL = PN->getDebugLoc();
185      unsigned PHIReg = ValueMap[PN];
186      assert(PHIReg && "PHI node does not have an assigned virtual register!");
187
188      SmallVector<EVT, 4> ValueVTs;
189      ComputeValueVTs(TLI, PN->getType(), ValueVTs);
190      for (unsigned vti = 0, vte = ValueVTs.size(); vti != vte; ++vti) {
191        EVT VT = ValueVTs[vti];
192        unsigned NumRegisters = TLI.getNumRegisters(Fn->getContext(), VT);
193        const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
194        for (unsigned i = 0; i != NumRegisters; ++i)
195          BuildMI(MBB, DL, TII->get(TargetOpcode::PHI), PHIReg + i);
196        PHIReg += NumRegisters;
197      }
198    }
199  }
200
201  // Mark landing pad blocks.
202  for (BB = Fn->begin(); BB != EB; ++BB)
203    if (const InvokeInst *Invoke = dyn_cast<InvokeInst>(BB->getTerminator()))
204      MBBMap[Invoke->getSuccessor(1)]->setIsLandingPad();
205}
206
207/// clear - Clear out all the function-specific state. This returns this
208/// FunctionLoweringInfo to an empty state, ready to be used for a
209/// different function.
210void FunctionLoweringInfo::clear() {
211  assert(CatchInfoFound.size() == CatchInfoLost.size() &&
212         "Not all catch info was assigned to a landing pad!");
213
214  MBBMap.clear();
215  ValueMap.clear();
216  StaticAllocaMap.clear();
217#ifndef NDEBUG
218  CatchInfoLost.clear();
219  CatchInfoFound.clear();
220#endif
221  LiveOutRegInfo.clear();
222  VisitedBBs.clear();
223  ArgDbgValues.clear();
224  ByValArgFrameIndexMap.clear();
225  RegFixups.clear();
226}
227
228/// CreateReg - Allocate a single virtual register for the given type.
229unsigned FunctionLoweringInfo::CreateReg(EVT VT) {
230  return RegInfo->createVirtualRegister(TLI.getRegClassFor(VT));
231}
232
233/// CreateRegs - Allocate the appropriate number of virtual registers of
234/// the correctly promoted or expanded types.  Assign these registers
235/// consecutive vreg numbers and return the first assigned number.
236///
237/// In the case that the given value has struct or array type, this function
238/// will assign registers for each member or element.
239///
240unsigned FunctionLoweringInfo::CreateRegs(const Type *Ty) {
241  SmallVector<EVT, 4> ValueVTs;
242  ComputeValueVTs(TLI, Ty, ValueVTs);
243
244  unsigned FirstReg = 0;
245  for (unsigned Value = 0, e = ValueVTs.size(); Value != e; ++Value) {
246    EVT ValueVT = ValueVTs[Value];
247    EVT RegisterVT = TLI.getRegisterType(Ty->getContext(), ValueVT);
248
249    unsigned NumRegs = TLI.getNumRegisters(Ty->getContext(), ValueVT);
250    for (unsigned i = 0; i != NumRegs; ++i) {
251      unsigned R = CreateReg(RegisterVT);
252      if (!FirstReg) FirstReg = R;
253    }
254  }
255  return FirstReg;
256}
257
258/// setByValArgumentFrameIndex - Record frame index for the byval
259/// argument. This overrides previous frame index entry for this argument,
260/// if any.
261void FunctionLoweringInfo::setByValArgumentFrameIndex(const Argument *A,
262                                                      int FI) {
263  assert (A->hasByValAttr() && "Argument does not have byval attribute!");
264  ByValArgFrameIndexMap[A] = FI;
265}
266
267/// getByValArgumentFrameIndex - Get frame index for the byval argument.
268/// If the argument does not have any assigned frame index then 0 is
269/// returned.
270int FunctionLoweringInfo::getByValArgumentFrameIndex(const Argument *A) {
271  assert (A->hasByValAttr() && "Argument does not have byval attribute!");
272  DenseMap<const Argument *, int>::iterator I =
273    ByValArgFrameIndexMap.find(A);
274  if (I != ByValArgFrameIndexMap.end())
275    return I->second;
276  DEBUG(dbgs() << "Argument does not have assigned frame index!");
277  return 0;
278}
279
280/// AddCatchInfo - Extract the personality and type infos from an eh.selector
281/// call, and add them to the specified machine basic block.
282void llvm::AddCatchInfo(const CallInst &I, MachineModuleInfo *MMI,
283                        MachineBasicBlock *MBB) {
284  // Inform the MachineModuleInfo of the personality for this landing pad.
285  const ConstantExpr *CE = cast<ConstantExpr>(I.getArgOperand(1));
286  assert(CE->getOpcode() == Instruction::BitCast &&
287         isa<Function>(CE->getOperand(0)) &&
288         "Personality should be a function");
289  MMI->addPersonality(MBB, cast<Function>(CE->getOperand(0)));
290
291  // Gather all the type infos for this landing pad and pass them along to
292  // MachineModuleInfo.
293  std::vector<const GlobalVariable *> TyInfo;
294  unsigned N = I.getNumArgOperands();
295
296  for (unsigned i = N - 1; i > 1; --i) {
297    if (const ConstantInt *CI = dyn_cast<ConstantInt>(I.getArgOperand(i))) {
298      unsigned FilterLength = CI->getZExtValue();
299      unsigned FirstCatch = i + FilterLength + !FilterLength;
300      assert(FirstCatch <= N && "Invalid filter length");
301
302      if (FirstCatch < N) {
303        TyInfo.reserve(N - FirstCatch);
304        for (unsigned j = FirstCatch; j < N; ++j)
305          TyInfo.push_back(ExtractTypeInfo(I.getArgOperand(j)));
306        MMI->addCatchTypeInfo(MBB, TyInfo);
307        TyInfo.clear();
308      }
309
310      if (!FilterLength) {
311        // Cleanup.
312        MMI->addCleanup(MBB);
313      } else {
314        // Filter.
315        TyInfo.reserve(FilterLength - 1);
316        for (unsigned j = i + 1; j < FirstCatch; ++j)
317          TyInfo.push_back(ExtractTypeInfo(I.getArgOperand(j)));
318        MMI->addFilterTypeInfo(MBB, TyInfo);
319        TyInfo.clear();
320      }
321
322      N = i;
323    }
324  }
325
326  if (N > 2) {
327    TyInfo.reserve(N - 2);
328    for (unsigned j = 2; j < N; ++j)
329      TyInfo.push_back(ExtractTypeInfo(I.getArgOperand(j)));
330    MMI->addCatchTypeInfo(MBB, TyInfo);
331  }
332}
333
334void llvm::CopyCatchInfo(const BasicBlock *SrcBB, const BasicBlock *DestBB,
335                         MachineModuleInfo *MMI, FunctionLoweringInfo &FLI) {
336  for (BasicBlock::const_iterator I = SrcBB->begin(), E = --SrcBB->end();
337       I != E; ++I)
338    if (const EHSelectorInst *EHSel = dyn_cast<EHSelectorInst>(I)) {
339      // Apply the catch info to DestBB.
340      AddCatchInfo(*EHSel, MMI, FLI.MBBMap[DestBB]);
341#ifndef NDEBUG
342      if (!FLI.MBBMap[SrcBB]->isLandingPad())
343        FLI.CatchInfoFound.insert(EHSel);
344#endif
345    }
346}
347