lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp

   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/TargetFrameInfo.h"
  33 #include "llvm/Target/TargetInstrInfo.h"
  34 #include "llvm/Target/TargetLowering.h"
  35 #include "llvm/Target/TargetOptions.h"
  36 #include "llvm/Support/Debug.h"
  37 #include "llvm/Support/ErrorHandling.h"
  38 #include "llvm/Support/MathExtras.h"
  39 #include <algorithm>
  40 using namespace llvm;
  41
  42 /// isUsedOutsideOfDefiningBlock - Return true if this instruction is used by
  43 /// PHI nodes or outside of the basic block that defines it, or used by a
  44 /// switch or atomic instruction, which may expand to multiple basic blocks.
  45 static bool isUsedOutsideOfDefiningBlock(const Instruction *I) {
  46   if (I->use_empty()) return false;
  47   if (isa<PHINode>(I)) return true;
  48   const BasicBlock *BB = I->getParent();
  49   for (Value::const_use_iterator UI = I->use_begin(), E = I->use_end();
  50         UI != E; ++UI) {
  51     const User *U = *UI;
  52     if (cast<Instruction>(U)->getParent() != BB || isa<PHINode>(U))
  53       return true;
  54   }
  55   return false;
  56 }
  57
  58 /// isOnlyUsedInEntryBlock - If the specified argument is only used in the
  59 /// entry block, return true.  This includes arguments used by switches, since
  60 /// the switch may expand into multiple basic blocks.
  61 static bool isOnlyUsedInEntryBlock(const Argument *A, bool EnableFastISel) {
  62   // With FastISel active, we may be splitting blocks, so force creation
  63   // of virtual registers for all non-dead arguments.
  64   if (EnableFastISel)
  65     return A->use_empty();
  66
  67   const BasicBlock *Entry = A->getParent()->begin();
  68   for (Value::const_use_iterator UI = A->use_begin(), E = A->use_end();
  69        UI != E; ++UI) {
  70     const User *U = *UI;
  71     if (cast<Instruction>(U)->getParent() != Entry || isa<SwitchInst>(U))
  72       return false;  // Use not in entry block.
  73   }
  74   return true;
  75 }
  76
  77 FunctionLoweringInfo::FunctionLoweringInfo(const TargetLowering &tli)
  78   : TLI(tli) {
  79 }
  80
  81 void FunctionLoweringInfo::set(const Function &fn, MachineFunction &mf) {
  82   Fn = &fn;
  83   MF = &mf;
  84   RegInfo = &MF->getRegInfo();
  85
  86   // Check whether the function can return without sret-demotion.
  87   SmallVector<ISD::OutputArg, 4> Outs;
  88   GetReturnInfo(Fn->getReturnType(),
  89                 Fn->getAttributes().getRetAttributes(), Outs, TLI);
  90   CanLowerReturn = TLI.CanLowerReturn(Fn->getCallingConv(), Fn->isVarArg(),
  91                                       Outs, Fn->getContext());
  92
  93   // Create a vreg for each argument register that is not dead and is used
  94   // outside of the entry block for the function.
  95   for (Function::const_arg_iterator AI = Fn->arg_begin(), E = Fn->arg_end();
  96        AI != E; ++AI)
  97     if (!isOnlyUsedInEntryBlock(AI, EnableFastISel))
  98       InitializeRegForValue(AI);
  99
 100   // Initialize the mapping of values to registers.  This is only set up for
 101   // instruction values that are used outside of the block that defines
 102   // them.
 103   Function::const_iterator BB = Fn->begin(), EB = Fn->end();
 104   for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I)
 105     if (const AllocaInst *AI = dyn_cast<AllocaInst>(I))
 106       if (const ConstantInt *CUI = dyn_cast<ConstantInt>(AI->getArraySize())) {
 107         const Type *Ty = AI->getAllocatedType();
 108         uint64_t TySize = TLI.getTargetData()->getTypeAllocSize(Ty);
 109         unsigned Align =
 110           std::max((unsigned)TLI.getTargetData()->getPrefTypeAlignment(Ty),
 111                    AI->getAlignment());
 112
 113         TySize *= CUI->getZExtValue();   // Get total allocated size.
 114         if (TySize == 0) TySize = 1; // Don't create zero-sized stack objects.
 115
 116         // The object may need to be placed onto the stack near the stack
 117         // protector if one exists. Determine here if this object is a suitable
 118         // candidate. I.e., it would trigger the creation of a stack protector.
 119         bool MayNeedSP =
 120           (AI->isArrayAllocation() ||
 121            (TySize > 8 && isa<ArrayType>(Ty) &&
 122             cast<ArrayType>(Ty)->getElementType()->isIntegerTy(8)));
 123         StaticAllocaMap[AI] =
 124           MF->getFrameInfo()->CreateStackObject(TySize, Align, false, MayNeedSP);
 125       }
 126
 127   for (; BB != EB; ++BB)
 128     for (BasicBlock::const_iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
 129       // Mark values used outside their block as exported, by allocating
 130       // a virtual register for them.
 131       if (isUsedOutsideOfDefiningBlock(I))
 132         if (!isa<AllocaInst>(I) ||
 133             !StaticAllocaMap.count(cast<AllocaInst>(I)))
 134           InitializeRegForValue(I);
 135
 136       // Collect llvm.dbg.declare information. This is done now instead of
 137       // during the initial isel pass through the IR so that it is done
 138       // in a predictable order.
 139       if (const DbgDeclareInst *DI = dyn_cast<DbgDeclareInst>(I)) {
 140         MachineModuleInfo &MMI = MF->getMMI();
 141         if (MMI.hasDebugInfo() &&
 142             DIVariable(DI->getVariable()).Verify() &&
 143             !DI->getDebugLoc().isUnknown()) {
 144           // Don't handle byval struct arguments or VLAs, for example.
 145           // Non-byval arguments are handled here (they refer to the stack
 146           // temporary alloca at this point).
 147           const Value *Address = DI->getAddress();
 148           if (Address) {
 149             if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Address))
 150               Address = BCI->getOperand(0);
 151             if (const AllocaInst *AI = dyn_cast<AllocaInst>(Address)) {
 152               DenseMap<const AllocaInst *, int>::iterator SI =
 153                 StaticAllocaMap.find(AI);
 154               if (SI != StaticAllocaMap.end()) { // Check for VLAs.
 155                 int FI = SI->second;
 156                 MMI.setVariableDbgInfo(DI->getVariable(),
 157                                        FI, DI->getDebugLoc());
 158               }
 159             }
 160           }
 161         }
 162       }
 163     }
 164
 165   // Create an initial MachineBasicBlock for each LLVM BasicBlock in F.  This
 166   // also creates the initial PHI MachineInstrs, though none of the input
 167   // operands are populated.
 168   for (BB = Fn->begin(); BB != EB; ++BB) {
 169     MachineBasicBlock *MBB = mf.CreateMachineBasicBlock(BB);
 170     MBBMap[BB] = MBB;
 171     MF->push_back(MBB);
 172
 173     // Transfer the address-taken flag. This is necessary because there could
 174     // be multiple MachineBasicBlocks corresponding to one BasicBlock, and only
 175     // the first one should be marked.
 176     if (BB->hasAddressTaken())
 177       MBB->setHasAddressTaken();
 178
 179     // Create Machine PHI nodes for LLVM PHI nodes, lowering them as
 180     // appropriate.
 181     for (BasicBlock::const_iterator I = BB->begin();
 182          const PHINode *PN = dyn_cast<PHINode>(I); ++I) {
 183       if (PN->use_empty()) continue;
 184
 185       DebugLoc DL = PN->getDebugLoc();
 186       unsigned PHIReg = ValueMap[PN];
 187       assert(PHIReg && "PHI node does not have an assigned virtual register!");
 188
 189       SmallVector<EVT, 4> ValueVTs;
 190       ComputeValueVTs(TLI, PN->getType(), ValueVTs);
 191       for (unsigned vti = 0, vte = ValueVTs.size(); vti != vte; ++vti) {
 192         EVT VT = ValueVTs[vti];
 193         unsigned NumRegisters = TLI.getNumRegisters(Fn->getContext(), VT);
 194         const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
 195         for (unsigned i = 0; i != NumRegisters; ++i)
 196           BuildMI(MBB, DL, TII->get(TargetOpcode::PHI), PHIReg + i);
 197         PHIReg += NumRegisters;
 198       }
 199     }
 200   }
 201
 202   // Mark landing pad blocks.
 203   for (BB = Fn->begin(); BB != EB; ++BB)
 204     if (const InvokeInst *Invoke = dyn_cast<InvokeInst>(BB->getTerminator()))
 205       MBBMap[Invoke->getSuccessor(1)]->setIsLandingPad();
 206 }
 207
 208 /// clear - Clear out all the function-specific state. This returns this
 209 /// FunctionLoweringInfo to an empty state, ready to be used for a
 210 /// different function.
 211 void FunctionLoweringInfo::clear() {
 212   assert(CatchInfoFound.size() == CatchInfoLost.size() &&
 213          "Not all catch info was assigned to a landing pad!");
 214
 215   MBBMap.clear();
 216   ValueMap.clear();
 217   StaticAllocaMap.clear();
 218 #ifndef NDEBUG
 219   CatchInfoLost.clear();
 220   CatchInfoFound.clear();
 221 #endif
 222   LiveOutRegInfo.clear();
 223   ArgDbgValues.clear();
 224   ByValArgFrameIndexMap.clear();
 225   RegFixups.clear();
 226 }
 227
 228 /// CreateReg - Allocate a single virtual register for the given type.
 229 unsigned 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 ///
 240 unsigned 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.
 261 void 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.
 270 int 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.
 282 void 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
 334 void 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 }