InstCombineCalls.cpp revision 795e70e4319bb38eb92701c2a463eeb7584a9b25 
1//===- InstCombineCalls.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 file implements the visitCall and visitInvoke functions.
11//
12//===----------------------------------------------------------------------===//
13
14#include "InstCombine.h"
15#include "llvm/IntrinsicInst.h"
16#include "llvm/Support/CallSite.h"
17#include "llvm/Target/TargetData.h"
18#include "llvm/Analysis/MemoryBuiltins.h"
19#include "llvm/Transforms/Utils/BuildLibCalls.h"
20using namespace llvm;
21
22/// getPromotedType - Return the specified type promoted as it would be to pass
23/// though a va_arg area.
24static const Type *getPromotedType(const Type *Ty) {
25  if (const IntegerType* ITy = dyn_cast<IntegerType>(Ty)) {
26    if (ITy->getBitWidth() < 32)
27      return Type::getInt32Ty(Ty->getContext());
28  }
29  return Ty;
30}
31
32/// EnforceKnownAlignment - If the specified pointer points to an object that
33/// we control, modify the object's alignment to PrefAlign. This isn't
34/// often possible though. If alignment is important, a more reliable approach
35/// is to simply align all global variables and allocation instructions to
36/// their preferred alignment from the beginning.
37///
38static unsigned EnforceKnownAlignment(Value *V,
39                                      unsigned Align, unsigned PrefAlign) {
40
41  User *U = dyn_cast<User>(V);
42  if (!U) return Align;
43
44  switch (Operator::getOpcode(U)) {
45  default: break;
46  case Instruction::BitCast:
47    return EnforceKnownAlignment(U->getOperand(0), Align, PrefAlign);
48  case Instruction::GetElementPtr: {
49    // If all indexes are zero, it is just the alignment of the base pointer.
50    bool AllZeroOperands = true;
51    for (User::op_iterator i = U->op_begin() + 1, e = U->op_end(); i != e; ++i)
52      if (!isa<Constant>(*i) ||
53          !cast<Constant>(*i)->isNullValue()) {
54        AllZeroOperands = false;
55        break;
56      }
57
58    if (AllZeroOperands) {
59      // Treat this like a bitcast.
60      return EnforceKnownAlignment(U->getOperand(0), Align, PrefAlign);
61    }
62    return Align;
63  }
64  case Instruction::Alloca: {
65    AllocaInst *AI = cast<AllocaInst>(V);
66    // If there is a requested alignment and if this is an alloca, round up.
67    if (AI->getAlignment() >= PrefAlign)
68      return AI->getAlignment();
69    AI->setAlignment(PrefAlign);
70    return PrefAlign;
71  }
72  }
73
74  if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
75    // If there is a large requested alignment and we can, bump up the alignment
76    // of the global.
77    if (GV->isDeclaration()) return Align;
78
79    if (GV->getAlignment() >= PrefAlign)
80      return GV->getAlignment();
81    // We can only increase the alignment of the global if it has no alignment
82    // specified or if it is not assigned a section.  If it is assigned a
83    // section, the global could be densely packed with other objects in the
84    // section, increasing the alignment could cause padding issues.
85    if (!GV->hasSection() || GV->getAlignment() == 0)
86      GV->setAlignment(PrefAlign);
87    return GV->getAlignment();
88  }
89
90  return Align;
91}
92
93/// GetOrEnforceKnownAlignment - If the specified pointer has an alignment that
94/// we can determine, return it, otherwise return 0.  If PrefAlign is specified,
95/// and it is more than the alignment of the ultimate object, see if we can
96/// increase the alignment of the ultimate object, making this check succeed.
97unsigned InstCombiner::GetOrEnforceKnownAlignment(Value *V,
98                                                  unsigned PrefAlign) {
99  assert(V->getType()->isPointerTy() &&
100         "GetOrEnforceKnownAlignment expects a pointer!");
101  unsigned BitWidth = TD ? TD->getPointerSizeInBits() : 64;
102  APInt Mask = APInt::getAllOnesValue(BitWidth);
103  APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
104  ComputeMaskedBits(V, Mask, KnownZero, KnownOne);
105  unsigned TrailZ = KnownZero.countTrailingOnes();
106
107  // Avoid trouble with rediculously large TrailZ values, such as
108  // those computed from a null pointer.
109  TrailZ = std::min(TrailZ, unsigned(sizeof(unsigned) * CHAR_BIT - 1));
110
111  unsigned Align = 1u << std::min(BitWidth - 1, TrailZ);
112
113  // LLVM doesn't support alignments larger than this currently.
114  Align = std::min(Align, +Value::MaximumAlignment);
115
116  if (PrefAlign > Align)
117    Align = EnforceKnownAlignment(V, Align, PrefAlign);
118
119    // We don't need to make any adjustment.
120  return Align;
121}
122
123Instruction *InstCombiner::SimplifyMemTransfer(MemIntrinsic *MI) {
124  unsigned DstAlign = GetOrEnforceKnownAlignment(MI->getArgOperand(0));
125  unsigned SrcAlign = GetOrEnforceKnownAlignment(MI->getArgOperand(1));
126  unsigned MinAlign = std::min(DstAlign, SrcAlign);
127  unsigned CopyAlign = MI->getAlignment();
128
129  if (CopyAlign < MinAlign) {
130    MI->setAlignment(ConstantInt::get(MI->getAlignmentType(),
131                                             MinAlign, false));
132    return MI;
133  }
134
135  // If MemCpyInst length is 1/2/4/8 bytes then replace memcpy with
136  // load/store.
137  ConstantInt *MemOpLength = dyn_cast<ConstantInt>(MI->getArgOperand(2));
138  if (MemOpLength == 0) return 0;
139
140  // Source and destination pointer types are always "i8*" for intrinsic.  See
141  // if the size is something we can handle with a single primitive load/store.
142  // A single load+store correctly handles overlapping memory in the memmove
143  // case.
144  unsigned Size = MemOpLength->getZExtValue();
145  if (Size == 0) return MI;  // Delete this mem transfer.
146
147  if (Size > 8 || (Size&(Size-1)))
148    return 0;  // If not 1/2/4/8 bytes, exit.
149
150  // Use an integer load+store unless we can find something better.
151  unsigned SrcAddrSp =
152    cast<PointerType>(MI->getArgOperand(1)->getType())->getAddressSpace();
153  unsigned DstAddrSp =
154    cast<PointerType>(MI->getArgOperand(0)->getType())->getAddressSpace();
155
156  const IntegerType* IntType = IntegerType::get(MI->getContext(), Size<<3);
157  Type *NewSrcPtrTy = PointerType::get(IntType, SrcAddrSp);
158  Type *NewDstPtrTy = PointerType::get(IntType, DstAddrSp);
159
160  // Memcpy forces the use of i8* for the source and destination.  That means
161  // that if you're using memcpy to move one double around, you'll get a cast
162  // from double* to i8*.  We'd much rather use a double load+store rather than
163  // an i64 load+store, here because this improves the odds that the source or
164  // dest address will be promotable.  See if we can find a better type than the
165  // integer datatype.
166  Value *StrippedDest = MI->getArgOperand(0)->stripPointerCasts();
167  if (StrippedDest != MI->getArgOperand(0)) {
168    const Type *SrcETy = cast<PointerType>(StrippedDest->getType())
169                                    ->getElementType();
170    if (TD && SrcETy->isSized() && TD->getTypeStoreSize(SrcETy) == Size) {
171      // The SrcETy might be something like {{{double}}} or [1 x double].  Rip
172      // down through these levels if so.
173      while (!SrcETy->isSingleValueType()) {
174        if (const StructType *STy = dyn_cast<StructType>(SrcETy)) {
175          if (STy->getNumElements() == 1)
176            SrcETy = STy->getElementType(0);
177          else
178            break;
179        } else if (const ArrayType *ATy = dyn_cast<ArrayType>(SrcETy)) {
180          if (ATy->getNumElements() == 1)
181            SrcETy = ATy->getElementType();
182          else
183            break;
184        } else
185          break;
186      }
187
188      if (SrcETy->isSingleValueType()) {
189        NewSrcPtrTy = PointerType::get(SrcETy, SrcAddrSp);
190        NewDstPtrTy = PointerType::get(SrcETy, DstAddrSp);
191      }
192    }
193  }
194
195
196  // If the memcpy/memmove provides better alignment info than we can
197  // infer, use it.
198  SrcAlign = std::max(SrcAlign, CopyAlign);
199  DstAlign = std::max(DstAlign, CopyAlign);
200
201  Value *Src = Builder->CreateBitCast(MI->getArgOperand(1), NewSrcPtrTy);
202  Value *Dest = Builder->CreateBitCast(MI->getArgOperand(0), NewDstPtrTy);
203  Instruction *L = new LoadInst(Src, "tmp", MI->isVolatile(), SrcAlign);
204  InsertNewInstBefore(L, *MI);
205  InsertNewInstBefore(new StoreInst(L, Dest, MI->isVolatile(), DstAlign),
206                      *MI);
207
208  // Set the size of the copy to 0, it will be deleted on the next iteration.
209  MI->setArgOperand(2, Constant::getNullValue(MemOpLength->getType()));
210  return MI;
211}
212
213Instruction *InstCombiner::SimplifyMemSet(MemSetInst *MI) {
214  unsigned Alignment = GetOrEnforceKnownAlignment(MI->getDest());
215  if (MI->getAlignment() < Alignment) {
216    MI->setAlignment(ConstantInt::get(MI->getAlignmentType(),
217                                             Alignment, false));
218    return MI;
219  }
220
221  // Extract the length and alignment and fill if they are constant.
222  ConstantInt *LenC = dyn_cast<ConstantInt>(MI->getLength());
223  ConstantInt *FillC = dyn_cast<ConstantInt>(MI->getValue());
224  if (!LenC || !FillC || !FillC->getType()->isIntegerTy(8))
225    return 0;
226  uint64_t Len = LenC->getZExtValue();
227  Alignment = MI->getAlignment();
228
229  // If the length is zero, this is a no-op
230  if (Len == 0) return MI; // memset(d,c,0,a) -> noop
231
232  // memset(s,c,n) -> store s, c (for n=1,2,4,8)
233  if (Len <= 8 && isPowerOf2_32((uint32_t)Len)) {
234    const Type *ITy = IntegerType::get(MI->getContext(), Len*8);  // n=1 -> i8.
235
236    Value *Dest = MI->getDest();
237    Dest = Builder->CreateBitCast(Dest, PointerType::getUnqual(ITy));
238
239    // Alignment 0 is identity for alignment 1 for memset, but not store.
240    if (Alignment == 0) Alignment = 1;
241
242    // Extract the fill value and store.
243    uint64_t Fill = FillC->getZExtValue()*0x0101010101010101ULL;
244    InsertNewInstBefore(new StoreInst(ConstantInt::get(ITy, Fill),
245                                      Dest, false, Alignment), *MI);
246
247    // Set the size of the copy to 0, it will be deleted on the next iteration.
248    MI->setLength(Constant::getNullValue(LenC->getType()));
249    return MI;
250  }
251
252  return 0;
253}
254
255/// visitCallInst - CallInst simplification.  This mostly only handles folding
256/// of intrinsic instructions.  For normal calls, it allows visitCallSite to do
257/// the heavy lifting.
258///
259Instruction *InstCombiner::visitCallInst(CallInst &CI) {
260  if (isFreeCall(&CI))
261    return visitFree(CI);
262  if (isMalloc(&CI))
263    return visitMalloc(CI);
264
265  // If the caller function is nounwind, mark the call as nounwind, even if the
266  // callee isn't.
267  if (CI.getParent()->getParent()->doesNotThrow() &&
268      !CI.doesNotThrow()) {
269    CI.setDoesNotThrow();
270    return &CI;
271  }
272
273  IntrinsicInst *II = dyn_cast<IntrinsicInst>(&CI);
274  if (!II) return visitCallSite(&CI);
275
276  // Intrinsics cannot occur in an invoke, so handle them here instead of in
277  // visitCallSite.
278  if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(II)) {
279    bool Changed = false;
280
281    // memmove/cpy/set of zero bytes is a noop.
282    if (Constant *NumBytes = dyn_cast<Constant>(MI->getLength())) {
283      if (NumBytes->isNullValue()) return EraseInstFromFunction(CI);
284
285      if (ConstantInt *CI = dyn_cast<ConstantInt>(NumBytes))
286        if (CI->getZExtValue() == 1) {
287          // Replace the instruction with just byte operations.  We would
288          // transform other cases to loads/stores, but we don't know if
289          // alignment is sufficient.
290        }
291    }
292
293    // If we have a memmove and the source operation is a constant global,
294    // then the source and dest pointers can't alias, so we can change this
295    // into a call to memcpy.
296    if (MemMoveInst *MMI = dyn_cast<MemMoveInst>(MI)) {
297      if (GlobalVariable *GVSrc = dyn_cast<GlobalVariable>(MMI->getSource()))
298        if (GVSrc->isConstant()) {
299          Module *M = CI.getParent()->getParent()->getParent();
300          Intrinsic::ID MemCpyID = Intrinsic::memcpy;
301          const Type *Tys[3] = { CI.getArgOperand(0)->getType(),
302                                 CI.getArgOperand(1)->getType(),
303                                 CI.getArgOperand(2)->getType() };
304          CI.setCalledFunction(Intrinsic::getDeclaration(M, MemCpyID, Tys, 3));
305          Changed = true;
306        }
307    }
308
309    if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(MI)) {
310      // memmove(x,x,size) -> noop.
311      if (MTI->getSource() == MTI->getDest())
312        return EraseInstFromFunction(CI);
313    }
314
315    // If we can determine a pointer alignment that is bigger than currently
316    // set, update the alignment.
317    if (isa<MemTransferInst>(MI)) {
318      if (Instruction *I = SimplifyMemTransfer(MI))
319        return I;
320    } else if (MemSetInst *MSI = dyn_cast<MemSetInst>(MI)) {
321      if (Instruction *I = SimplifyMemSet(MSI))
322        return I;
323    }
324
325    if (Changed) return II;
326  }
327
328  switch (II->getIntrinsicID()) {
329  default: break;
330  case Intrinsic::objectsize: {
331    // We need target data for just about everything so depend on it.
332    if (!TD) break;
333
334    const Type *ReturnTy = CI.getType();
335    bool Min = (cast<ConstantInt>(II->getArgOperand(1))->getZExtValue() == 1);
336
337    // Get to the real allocated thing and offset as fast as possible.
338    Value *Op1 = II->getArgOperand(0)->stripPointerCasts();
339
340    // If we've stripped down to a single global variable that we
341    // can know the size of then just return that.
342    if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op1)) {
343      if (GV->hasDefinitiveInitializer()) {
344        Constant *C = GV->getInitializer();
345        uint64_t GlobalSize = TD->getTypeAllocSize(C->getType());
346        return ReplaceInstUsesWith(CI, ConstantInt::get(ReturnTy, GlobalSize));
347      } else {
348        // Can't determine size of the GV.
349        Constant *RetVal = ConstantInt::get(ReturnTy, Min ? 0 : -1ULL);
350        return ReplaceInstUsesWith(CI, RetVal);
351      }
352    } else if (AllocaInst *AI = dyn_cast<AllocaInst>(Op1)) {
353      // Get alloca size.
354      if (AI->getAllocatedType()->isSized()) {
355        uint64_t AllocaSize = TD->getTypeAllocSize(AI->getAllocatedType());
356        if (AI->isArrayAllocation()) {
357          const ConstantInt *C = dyn_cast<ConstantInt>(AI->getArraySize());
358          if (!C) break;
359          AllocaSize *= C->getZExtValue();
360        }
361        return ReplaceInstUsesWith(CI, ConstantInt::get(ReturnTy, AllocaSize));
362      }
363    } else if (CallInst *MI = extractMallocCall(Op1)) {
364      const Type* MallocType = getMallocAllocatedType(MI);
365      // Get alloca size.
366      if (MallocType && MallocType->isSized()) {
367        if (Value *NElems = getMallocArraySize(MI, TD, true)) {
368          if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems))
369        return ReplaceInstUsesWith(CI, ConstantInt::get(ReturnTy,
370               (NElements->getZExtValue() * TD->getTypeAllocSize(MallocType))));
371        }
372      }
373    } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op1)) {
374      // Only handle constant GEPs here.
375      if (CE->getOpcode() != Instruction::GetElementPtr) break;
376      GEPOperator *GEP = cast<GEPOperator>(CE);
377
378      // Make sure we're not a constant offset from an external
379      // global.
380      Value *Operand = GEP->getPointerOperand();
381      Operand = Operand->stripPointerCasts();
382      if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Operand))
383        if (!GV->hasDefinitiveInitializer()) break;
384
385      // Get what we're pointing to and its size.
386      const PointerType *BaseType =
387        cast<PointerType>(Operand->getType());
388      uint64_t Size = TD->getTypeAllocSize(BaseType->getElementType());
389
390      // Get the current byte offset into the thing. Use the original
391      // operand in case we're looking through a bitcast.
392      SmallVector<Value*, 8> Ops(CE->op_begin()+1, CE->op_end());
393      const PointerType *OffsetType =
394        cast<PointerType>(GEP->getPointerOperand()->getType());
395      uint64_t Offset = TD->getIndexedOffset(OffsetType, &Ops[0], Ops.size());
396
397      if (Size < Offset) {
398        // Out of bound reference? Negative index normalized to large
399        // index? Just return "I don't know".
400        Constant *RetVal = ConstantInt::get(ReturnTy, Min ? 0 : -1ULL);
401        return ReplaceInstUsesWith(CI, RetVal);
402      }
403
404      Constant *RetVal = ConstantInt::get(ReturnTy, Size-Offset);
405      return ReplaceInstUsesWith(CI, RetVal);
406    }
407
408    // Do not return "I don't know" here. Later optimization passes could
409    // make it possible to evaluate objectsize to a constant.
410    break;
411  }
412  case Intrinsic::bswap:
413    // bswap(bswap(x)) -> x
414    if (IntrinsicInst *Operand = dyn_cast<IntrinsicInst>(II->getArgOperand(0)))
415      if (Operand->getIntrinsicID() == Intrinsic::bswap)
416        return ReplaceInstUsesWith(CI, Operand->getArgOperand(0));
417
418    // bswap(trunc(bswap(x))) -> trunc(lshr(x, c))
419    if (TruncInst *TI = dyn_cast<TruncInst>(II->getArgOperand(0))) {
420      if (IntrinsicInst *Operand = dyn_cast<IntrinsicInst>(TI->getOperand(0)))
421        if (Operand->getIntrinsicID() == Intrinsic::bswap) {
422          unsigned C = Operand->getType()->getPrimitiveSizeInBits() -
423                       TI->getType()->getPrimitiveSizeInBits();
424          Value *CV = ConstantInt::get(Operand->getType(), C);
425          Value *V = Builder->CreateLShr(Operand->getArgOperand(0), CV);
426          return new TruncInst(V, TI->getType());
427        }
428    }
429
430    break;
431  case Intrinsic::powi:
432    if (ConstantInt *Power = dyn_cast<ConstantInt>(II->getArgOperand(1))) {
433      // powi(x, 0) -> 1.0
434      if (Power->isZero())
435        return ReplaceInstUsesWith(CI, ConstantFP::get(CI.getType(), 1.0));
436      // powi(x, 1) -> x
437      if (Power->isOne())
438        return ReplaceInstUsesWith(CI, II->getArgOperand(0));
439      // powi(x, -1) -> 1/x
440      if (Power->isAllOnesValue())
441        return BinaryOperator::CreateFDiv(ConstantFP::get(CI.getType(), 1.0),
442                                          II->getArgOperand(0));
443    }
444    break;
445  case Intrinsic::cttz: {
446    // If all bits below the first known one are known zero,
447    // this value is constant.
448    const IntegerType *IT = cast<IntegerType>(II->getArgOperand(0)->getType());
449    uint32_t BitWidth = IT->getBitWidth();
450    APInt KnownZero(BitWidth, 0);
451    APInt KnownOne(BitWidth, 0);
452    ComputeMaskedBits(II->getArgOperand(0), APInt::getAllOnesValue(BitWidth),
453                      KnownZero, KnownOne);
454    unsigned TrailingZeros = KnownOne.countTrailingZeros();
455    APInt Mask(APInt::getLowBitsSet(BitWidth, TrailingZeros));
456    if ((Mask & KnownZero) == Mask)
457      return ReplaceInstUsesWith(CI, ConstantInt::get(IT,
458                                 APInt(BitWidth, TrailingZeros)));
459
460    }
461    break;
462  case Intrinsic::ctlz: {
463    // If all bits above the first known one are known zero,
464    // this value is constant.
465    const IntegerType *IT = cast<IntegerType>(II->getArgOperand(0)->getType());
466    uint32_t BitWidth = IT->getBitWidth();
467    APInt KnownZero(BitWidth, 0);
468    APInt KnownOne(BitWidth, 0);
469    ComputeMaskedBits(II->getArgOperand(0), APInt::getAllOnesValue(BitWidth),
470                      KnownZero, KnownOne);
471    unsigned LeadingZeros = KnownOne.countLeadingZeros();
472    APInt Mask(APInt::getHighBitsSet(BitWidth, LeadingZeros));
473    if ((Mask & KnownZero) == Mask)
474      return ReplaceInstUsesWith(CI, ConstantInt::get(IT,
475                                 APInt(BitWidth, LeadingZeros)));
476
477    }
478    break;
479  case Intrinsic::uadd_with_overflow: {
480    Value *LHS = II->getArgOperand(0), *RHS = II->getArgOperand(1);
481    const IntegerType *IT = cast<IntegerType>(II->getArgOperand(0)->getType());
482    uint32_t BitWidth = IT->getBitWidth();
483    APInt Mask = APInt::getSignBit(BitWidth);
484    APInt LHSKnownZero(BitWidth, 0);
485    APInt LHSKnownOne(BitWidth, 0);
486    ComputeMaskedBits(LHS, Mask, LHSKnownZero, LHSKnownOne);
487    bool LHSKnownNegative = LHSKnownOne[BitWidth - 1];
488    bool LHSKnownPositive = LHSKnownZero[BitWidth - 1];
489
490    if (LHSKnownNegative || LHSKnownPositive) {
491      APInt RHSKnownZero(BitWidth, 0);
492      APInt RHSKnownOne(BitWidth, 0);
493      ComputeMaskedBits(RHS, Mask, RHSKnownZero, RHSKnownOne);
494      bool RHSKnownNegative = RHSKnownOne[BitWidth - 1];
495      bool RHSKnownPositive = RHSKnownZero[BitWidth - 1];
496      if (LHSKnownNegative && RHSKnownNegative) {
497        // The sign bit is set in both cases: this MUST overflow.
498        // Create a simple add instruction, and insert it into the struct.
499        Instruction *Add = BinaryOperator::CreateAdd(LHS, RHS, "", &CI);
500        Worklist.Add(Add);
501        Constant *V[] = {
502          UndefValue::get(LHS->getType()),ConstantInt::getTrue(II->getContext())
503        };
504        Constant *Struct = ConstantStruct::get(II->getContext(), V, 2, false);
505        return InsertValueInst::Create(Struct, Add, 0);
506      }
507
508      if (LHSKnownPositive && RHSKnownPositive) {
509        // The sign bit is clear in both cases: this CANNOT overflow.
510        // Create a simple add instruction, and insert it into the struct.
511        Instruction *Add = BinaryOperator::CreateNUWAdd(LHS, RHS, "", &CI);
512        Worklist.Add(Add);
513        Constant *V[] = {
514          UndefValue::get(LHS->getType()),
515          ConstantInt::getFalse(II->getContext())
516        };
517        Constant *Struct = ConstantStruct::get(II->getContext(), V, 2, false);
518        return InsertValueInst::Create(Struct, Add, 0);
519      }
520    }
521  }
522  // FALL THROUGH uadd into sadd
523  case Intrinsic::sadd_with_overflow:
524    // Canonicalize constants into the RHS.
525    if (isa<Constant>(II->getArgOperand(0)) &&
526        !isa<Constant>(II->getArgOperand(1))) {
527      Value *LHS = II->getArgOperand(0);
528      II->setArgOperand(0, II->getArgOperand(1));
529      II->setArgOperand(1, LHS);
530      return II;
531    }
532
533    // X + undef -> undef
534    if (isa<UndefValue>(II->getArgOperand(1)))
535      return ReplaceInstUsesWith(CI, UndefValue::get(II->getType()));
536
537    if (ConstantInt *RHS = dyn_cast<ConstantInt>(II->getArgOperand(1))) {
538      // X + 0 -> {X, false}
539      if (RHS->isZero()) {
540        Constant *V[] = {
541          UndefValue::get(II->getCalledValue()->getType()),
542          ConstantInt::getFalse(II->getContext())
543        };
544        Constant *Struct = ConstantStruct::get(II->getContext(), V, 2, false);
545        return InsertValueInst::Create(Struct, II->getArgOperand(0), 0);
546      }
547    }
548    break;
549  case Intrinsic::usub_with_overflow:
550  case Intrinsic::ssub_with_overflow:
551    // undef - X -> undef
552    // X - undef -> undef
553    if (isa<UndefValue>(II->getArgOperand(0)) ||
554        isa<UndefValue>(II->getArgOperand(1)))
555      return ReplaceInstUsesWith(CI, UndefValue::get(II->getType()));
556
557    if (ConstantInt *RHS = dyn_cast<ConstantInt>(II->getArgOperand(1))) {
558      // X - 0 -> {X, false}
559      if (RHS->isZero()) {
560        Constant *V[] = {
561          UndefValue::get(II->getArgOperand(0)->getType()),
562          ConstantInt::getFalse(II->getContext())
563        };
564        Constant *Struct = ConstantStruct::get(II->getContext(), V, 2, false);
565        return InsertValueInst::Create(Struct, II->getArgOperand(0), 0);
566      }
567    }
568    break;
569  case Intrinsic::umul_with_overflow:
570  case Intrinsic::smul_with_overflow:
571    // Canonicalize constants into the RHS.
572    if (isa<Constant>(II->getArgOperand(0)) &&
573        !isa<Constant>(II->getArgOperand(1))) {
574      Value *LHS = II->getArgOperand(0);
575      II->setArgOperand(0, II->getArgOperand(1));
576      II->setArgOperand(1, LHS);
577      return II;
578    }
579
580    // X * undef -> undef
581    if (isa<UndefValue>(II->getArgOperand(1)))
582      return ReplaceInstUsesWith(CI, UndefValue::get(II->getType()));
583
584    if (ConstantInt *RHSI = dyn_cast<ConstantInt>(II->getArgOperand(1))) {
585      // X*0 -> {0, false}
586      if (RHSI->isZero())
587        return ReplaceInstUsesWith(CI, Constant::getNullValue(II->getType()));
588
589      // X * 1 -> {X, false}
590      if (RHSI->equalsInt(1)) {
591        Constant *V[] = {
592          UndefValue::get(II->getArgOperand(0)->getType()),
593          ConstantInt::getFalse(II->getContext())
594        };
595        Constant *Struct = ConstantStruct::get(II->getContext(), V, 2, false);
596        return InsertValueInst::Create(Struct, II->getArgOperand(0), 0);
597      }
598    }
599    break;
600  case Intrinsic::ppc_altivec_lvx:
601  case Intrinsic::ppc_altivec_lvxl:
602  case Intrinsic::x86_sse_loadu_ps:
603  case Intrinsic::x86_sse2_loadu_pd:
604  case Intrinsic::x86_sse2_loadu_dq:
605    // Turn PPC lvx     -> load if the pointer is known aligned.
606    // Turn X86 loadups -> load if the pointer is known aligned.
607    if (GetOrEnforceKnownAlignment(II->getArgOperand(0), 16) >= 16) {
608      Value *Ptr = Builder->CreateBitCast(II->getArgOperand(0),
609                                         PointerType::getUnqual(II->getType()));
610      return new LoadInst(Ptr);
611    }
612    break;
613  case Intrinsic::ppc_altivec_stvx:
614  case Intrinsic::ppc_altivec_stvxl:
615    // Turn stvx -> store if the pointer is known aligned.
616    if (GetOrEnforceKnownAlignment(II->getArgOperand(1), 16) >= 16) {
617      const Type *OpPtrTy =
618        PointerType::getUnqual(II->getArgOperand(0)->getType());
619      Value *Ptr = Builder->CreateBitCast(II->getArgOperand(1), OpPtrTy);
620      return new StoreInst(II->getArgOperand(0), Ptr);
621    }
622    break;
623  case Intrinsic::x86_sse_storeu_ps:
624  case Intrinsic::x86_sse2_storeu_pd:
625  case Intrinsic::x86_sse2_storeu_dq:
626    // Turn X86 storeu -> store if the pointer is known aligned.
627    if (GetOrEnforceKnownAlignment(II->getArgOperand(0), 16) >= 16) {
628      const Type *OpPtrTy =
629        PointerType::getUnqual(II->getArgOperand(1)->getType());
630      Value *Ptr = Builder->CreateBitCast(II->getArgOperand(0), OpPtrTy);
631      return new StoreInst(II->getArgOperand(1), Ptr);
632    }
633    break;
634
635  case Intrinsic::x86_sse_cvttss2si: {
636    // These intrinsics only demands the 0th element of its input vector.  If
637    // we can simplify the input based on that, do so now.
638    unsigned VWidth =
639      cast<VectorType>(II->getArgOperand(0)->getType())->getNumElements();
640    APInt DemandedElts(VWidth, 1);
641    APInt UndefElts(VWidth, 0);
642    if (Value *V = SimplifyDemandedVectorElts(II->getArgOperand(0),
643                                              DemandedElts, UndefElts)) {
644      II->setArgOperand(0, V);
645      return II;
646    }
647    break;
648  }
649
650  case Intrinsic::ppc_altivec_vperm:
651    // Turn vperm(V1,V2,mask) -> shuffle(V1,V2,mask) if mask is a constant.
652    if (ConstantVector *Mask = dyn_cast<ConstantVector>(II->getArgOperand(2))) {
653      assert(Mask->getNumOperands() == 16 && "Bad type for intrinsic!");
654
655      // Check that all of the elements are integer constants or undefs.
656      bool AllEltsOk = true;
657      for (unsigned i = 0; i != 16; ++i) {
658        if (!isa<ConstantInt>(Mask->getOperand(i)) &&
659            !isa<UndefValue>(Mask->getOperand(i))) {
660          AllEltsOk = false;
661          break;
662        }
663      }
664
665      if (AllEltsOk) {
666        // Cast the input vectors to byte vectors.
667        Value *Op0 = Builder->CreateBitCast(II->getArgOperand(0),
668                                            Mask->getType());
669        Value *Op1 = Builder->CreateBitCast(II->getArgOperand(1),
670                                            Mask->getType());
671        Value *Result = UndefValue::get(Op0->getType());
672
673        // Only extract each element once.
674        Value *ExtractedElts[32];
675        memset(ExtractedElts, 0, sizeof(ExtractedElts));
676
677        for (unsigned i = 0; i != 16; ++i) {
678          if (isa<UndefValue>(Mask->getOperand(i)))
679            continue;
680          unsigned Idx=cast<ConstantInt>(Mask->getOperand(i))->getZExtValue();
681          Idx &= 31;  // Match the hardware behavior.
682
683          if (ExtractedElts[Idx] == 0) {
684            ExtractedElts[Idx] =
685              Builder->CreateExtractElement(Idx < 16 ? Op0 : Op1,
686                  ConstantInt::get(Type::getInt32Ty(II->getContext()),
687                                   Idx&15, false), "tmp");
688          }
689
690          // Insert this value into the result vector.
691          Result = Builder->CreateInsertElement(Result, ExtractedElts[Idx],
692                         ConstantInt::get(Type::getInt32Ty(II->getContext()),
693                                          i, false), "tmp");
694        }
695        return CastInst::Create(Instruction::BitCast, Result, CI.getType());
696      }
697    }
698    break;
699
700  case Intrinsic::stackrestore: {
701    // If the save is right next to the restore, remove the restore.  This can
702    // happen when variable allocas are DCE'd.
703    if (IntrinsicInst *SS = dyn_cast<IntrinsicInst>(II->getArgOperand(0))) {
704      if (SS->getIntrinsicID() == Intrinsic::stacksave) {
705        BasicBlock::iterator BI = SS;
706        if (&*++BI == II)
707          return EraseInstFromFunction(CI);
708      }
709    }
710
711    // Scan down this block to see if there is another stack restore in the
712    // same block without an intervening call/alloca.
713    BasicBlock::iterator BI = II;
714    TerminatorInst *TI = II->getParent()->getTerminator();
715    bool CannotRemove = false;
716    for (++BI; &*BI != TI; ++BI) {
717      if (isa<AllocaInst>(BI) || isMalloc(BI)) {
718        CannotRemove = true;
719        break;
720      }
721      if (CallInst *BCI = dyn_cast<CallInst>(BI)) {
722        if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(BCI)) {
723          // If there is a stackrestore below this one, remove this one.
724          if (II->getIntrinsicID() == Intrinsic::stackrestore)
725            return EraseInstFromFunction(CI);
726          // Otherwise, ignore the intrinsic.
727        } else {
728          // If we found a non-intrinsic call, we can't remove the stack
729          // restore.
730          CannotRemove = true;
731          break;
732        }
733      }
734    }
735
736    // If the stack restore is in a return/unwind block and if there are no
737    // allocas or calls between the restore and the return, nuke the restore.
738    if (!CannotRemove && (isa<ReturnInst>(TI) || isa<UnwindInst>(TI)))
739      return EraseInstFromFunction(CI);
740    break;
741  }
742  }
743
744  return visitCallSite(II);
745}
746
747// InvokeInst simplification
748//
749Instruction *InstCombiner::visitInvokeInst(InvokeInst &II) {
750  return visitCallSite(&II);
751}
752
753/// isSafeToEliminateVarargsCast - If this cast does not affect the value
754/// passed through the varargs area, we can eliminate the use of the cast.
755static bool isSafeToEliminateVarargsCast(const CallSite CS,
756                                         const CastInst * const CI,
757                                         const TargetData * const TD,
758                                         const int ix) {
759  if (!CI->isLosslessCast())
760    return false;
761
762  // The size of ByVal arguments is derived from the type, so we
763  // can't change to a type with a different size.  If the size were
764  // passed explicitly we could avoid this check.
765  if (!CS.paramHasAttr(ix, Attribute::ByVal))
766    return true;
767
768  const Type* SrcTy =
769            cast<PointerType>(CI->getOperand(0)->getType())->getElementType();
770  const Type* DstTy = cast<PointerType>(CI->getType())->getElementType();
771  if (!SrcTy->isSized() || !DstTy->isSized())
772    return false;
773  if (!TD || TD->getTypeAllocSize(SrcTy) != TD->getTypeAllocSize(DstTy))
774    return false;
775  return true;
776}
777
778namespace {
779class InstCombineFortifiedLibCalls : public SimplifyFortifiedLibCalls {
780  InstCombiner *IC;
781protected:
782  void replaceCall(Value *With) {
783    NewInstruction = IC->ReplaceInstUsesWith(*CI, With);
784  }
785  bool isFoldable(unsigned SizeCIOp, unsigned SizeArgOp, bool isString) const {
786    if (ConstantInt *SizeCI =
787                           dyn_cast<ConstantInt>(CI->getArgOperand(SizeCIOp))) {
788      if (SizeCI->isAllOnesValue())
789        return true;
790      if (isString)
791        return SizeCI->getZExtValue() >=
792               GetStringLength(CI->getArgOperand(SizeArgOp));
793      if (ConstantInt *Arg = dyn_cast<ConstantInt>(
794                                                  CI->getArgOperand(SizeArgOp)))
795        return SizeCI->getZExtValue() >= Arg->getZExtValue();
796    }
797    return false;
798  }
799public:
800  InstCombineFortifiedLibCalls(InstCombiner *IC) : IC(IC), NewInstruction(0) { }
801  Instruction *NewInstruction;
802};
803} // end anonymous namespace
804
805// Try to fold some different type of calls here.
806// Currently we're only working with the checking functions, memcpy_chk,
807// mempcpy_chk, memmove_chk, memset_chk, strcpy_chk, stpcpy_chk, strncpy_chk,
808// strcat_chk and strncat_chk.
809Instruction *InstCombiner::tryOptimizeCall(CallInst *CI, const TargetData *TD) {
810  if (CI->getCalledFunction() == 0) return 0;
811
812  InstCombineFortifiedLibCalls Simplifier(this);
813  Simplifier.fold(CI, TD);
814  return Simplifier.NewInstruction;
815}
816
817// visitCallSite - Improvements for call and invoke instructions.
818//
819Instruction *InstCombiner::visitCallSite(CallSite CS) {
820  bool Changed = false;
821
822  // If the callee is a constexpr cast of a function, attempt to move the cast
823  // to the arguments of the call/invoke.
824  if (transformConstExprCastCall(CS)) return 0;
825
826  Value *Callee = CS.getCalledValue();
827
828  if (Function *CalleeF = dyn_cast<Function>(Callee))
829    // If the call and callee calling conventions don't match, this call must
830    // be unreachable, as the call is undefined.
831    if (CalleeF->getCallingConv() != CS.getCallingConv() &&
832        // Only do this for calls to a function with a body.  A prototype may
833        // not actually end up matching the implementation's calling conv for a
834        // variety of reasons (e.g. it may be written in assembly).
835        !CalleeF->isDeclaration()) {
836      Instruction *OldCall = CS.getInstruction();
837      new StoreInst(ConstantInt::getTrue(Callee->getContext()),
838                UndefValue::get(Type::getInt1PtrTy(Callee->getContext())),
839                                  OldCall);
840      // If OldCall dues not return void then replaceAllUsesWith undef.
841      // This allows ValueHandlers and custom metadata to adjust itself.
842      if (!OldCall->getType()->isVoidTy())
843        OldCall->replaceAllUsesWith(UndefValue::get(OldCall->getType()));
844      if (isa<CallInst>(OldCall))
845        return EraseInstFromFunction(*OldCall);
846
847      // We cannot remove an invoke, because it would change the CFG, just
848      // change the callee to a null pointer.
849      cast<InvokeInst>(OldCall)->setCalledFunction(
850                                    Constant::getNullValue(CalleeF->getType()));
851      return 0;
852    }
853
854  if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
855    // This instruction is not reachable, just remove it.  We insert a store to
856    // undef so that we know that this code is not reachable, despite the fact
857    // that we can't modify the CFG here.
858    new StoreInst(ConstantInt::getTrue(Callee->getContext()),
859               UndefValue::get(Type::getInt1PtrTy(Callee->getContext())),
860                  CS.getInstruction());
861
862    // If CS does not return void then replaceAllUsesWith undef.
863    // This allows ValueHandlers and custom metadata to adjust itself.
864    if (!CS.getInstruction()->getType()->isVoidTy())
865      CS.getInstruction()->
866        replaceAllUsesWith(UndefValue::get(CS.getInstruction()->getType()));
867
868    if (InvokeInst *II = dyn_cast<InvokeInst>(CS.getInstruction())) {
869      // Don't break the CFG, insert a dummy cond branch.
870      BranchInst::Create(II->getNormalDest(), II->getUnwindDest(),
871                         ConstantInt::getTrue(Callee->getContext()), II);
872    }
873    return EraseInstFromFunction(*CS.getInstruction());
874  }
875
876  if (BitCastInst *BC = dyn_cast<BitCastInst>(Callee))
877    if (IntrinsicInst *In = dyn_cast<IntrinsicInst>(BC->getOperand(0)))
878      if (In->getIntrinsicID() == Intrinsic::init_trampoline)
879        return transformCallThroughTrampoline(CS);
880
881  const PointerType *PTy = cast<PointerType>(Callee->getType());
882  const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
883  if (FTy->isVarArg()) {
884    int ix = FTy->getNumParams() + (isa<InvokeInst>(Callee) ? 3 : 1);
885    // See if we can optimize any arguments passed through the varargs area of
886    // the call.
887    for (CallSite::arg_iterator I = CS.arg_begin()+FTy->getNumParams(),
888           E = CS.arg_end(); I != E; ++I, ++ix) {
889      CastInst *CI = dyn_cast<CastInst>(*I);
890      if (CI && isSafeToEliminateVarargsCast(CS, CI, TD, ix)) {
891        *I = CI->getOperand(0);
892        Changed = true;
893      }
894    }
895  }
896
897  if (isa<InlineAsm>(Callee) && !CS.doesNotThrow()) {
898    // Inline asm calls cannot throw - mark them 'nounwind'.
899    CS.setDoesNotThrow();
900    Changed = true;
901  }
902
903  // Try to optimize the call if possible, we require TargetData for most of
904  // this.  None of these calls are seen as possibly dead so go ahead and
905  // delete the instruction now.
906  if (CallInst *CI = dyn_cast<CallInst>(CS.getInstruction())) {
907    Instruction *I = tryOptimizeCall(CI, TD);
908    // If we changed something return the result, etc. Otherwise let
909    // the fallthrough check.
910    if (I) return EraseInstFromFunction(*I);
911  }
912
913  return Changed ? CS.getInstruction() : 0;
914}
915
916// transformConstExprCastCall - If the callee is a constexpr cast of a function,
917// attempt to move the cast to the arguments of the call/invoke.
918//
919bool InstCombiner::transformConstExprCastCall(CallSite CS) {
920  if (!isa<ConstantExpr>(CS.getCalledValue())) return false;
921  ConstantExpr *CE = cast<ConstantExpr>(CS.getCalledValue());
922  if (CE->getOpcode() != Instruction::BitCast ||
923      !isa<Function>(CE->getOperand(0)))
924    return false;
925  Function *Callee = cast<Function>(CE->getOperand(0));
926  Instruction *Caller = CS.getInstruction();
927  const AttrListPtr &CallerPAL = CS.getAttributes();
928
929  // Okay, this is a cast from a function to a different type.  Unless doing so
930  // would cause a type conversion of one of our arguments, change this call to
931  // be a direct call with arguments casted to the appropriate types.
932  //
933  const FunctionType *FT = Callee->getFunctionType();
934  const Type *OldRetTy = Caller->getType();
935  const Type *NewRetTy = FT->getReturnType();
936
937  if (NewRetTy->isStructTy())
938    return false; // TODO: Handle multiple return values.
939
940  // Check to see if we are changing the return type...
941  if (OldRetTy != NewRetTy) {
942    if (Callee->isDeclaration() &&
943        // Conversion is ok if changing from one pointer type to another or from
944        // a pointer to an integer of the same size.
945        !((OldRetTy->isPointerTy() || !TD ||
946           OldRetTy == TD->getIntPtrType(Caller->getContext())) &&
947          (NewRetTy->isPointerTy() || !TD ||
948           NewRetTy == TD->getIntPtrType(Caller->getContext()))))
949      return false;   // Cannot transform this return value.
950
951    if (!Caller->use_empty() &&
952        // void -> non-void is handled specially
953        !NewRetTy->isVoidTy() && !CastInst::isCastable(NewRetTy, OldRetTy))
954      return false;   // Cannot transform this return value.
955
956    if (!CallerPAL.isEmpty() && !Caller->use_empty()) {
957      Attributes RAttrs = CallerPAL.getRetAttributes();
958      if (RAttrs & Attribute::typeIncompatible(NewRetTy))
959        return false;   // Attribute not compatible with transformed value.
960    }
961
962    // If the callsite is an invoke instruction, and the return value is used by
963    // a PHI node in a successor, we cannot change the return type of the call
964    // because there is no place to put the cast instruction (without breaking
965    // the critical edge).  Bail out in this case.
966    if (!Caller->use_empty())
967      if (InvokeInst *II = dyn_cast<InvokeInst>(Caller))
968        for (Value::use_iterator UI = II->use_begin(), E = II->use_end();
969             UI != E; ++UI)
970          if (PHINode *PN = dyn_cast<PHINode>(*UI))
971            if (PN->getParent() == II->getNormalDest() ||
972                PN->getParent() == II->getUnwindDest())
973              return false;
974  }
975
976  unsigned NumActualArgs = unsigned(CS.arg_end()-CS.arg_begin());
977  unsigned NumCommonArgs = std::min(FT->getNumParams(), NumActualArgs);
978
979  CallSite::arg_iterator AI = CS.arg_begin();
980  for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
981    const Type *ParamTy = FT->getParamType(i);
982    const Type *ActTy = (*AI)->getType();
983
984    if (!CastInst::isCastable(ActTy, ParamTy))
985      return false;   // Cannot transform this parameter value.
986
987    if (CallerPAL.getParamAttributes(i + 1)
988        & Attribute::typeIncompatible(ParamTy))
989      return false;   // Attribute not compatible with transformed value.
990
991    // Converting from one pointer type to another or between a pointer and an
992    // integer of the same size is safe even if we do not have a body.
993    bool isConvertible = ActTy == ParamTy ||
994      (TD && ((ParamTy->isPointerTy() ||
995      ParamTy == TD->getIntPtrType(Caller->getContext())) &&
996              (ActTy->isPointerTy() ||
997              ActTy == TD->getIntPtrType(Caller->getContext()))));
998    if (Callee->isDeclaration() && !isConvertible) return false;
999  }
1000
1001  if (FT->getNumParams() < NumActualArgs && !FT->isVarArg() &&
1002      Callee->isDeclaration())
1003    return false;   // Do not delete arguments unless we have a function body.
1004
1005  if (FT->getNumParams() < NumActualArgs && FT->isVarArg() &&
1006      !CallerPAL.isEmpty())
1007    // In this case we have more arguments than the new function type, but we
1008    // won't be dropping them.  Check that these extra arguments have attributes
1009    // that are compatible with being a vararg call argument.
1010    for (unsigned i = CallerPAL.getNumSlots(); i; --i) {
1011      if (CallerPAL.getSlot(i - 1).Index <= FT->getNumParams())
1012        break;
1013      Attributes PAttrs = CallerPAL.getSlot(i - 1).Attrs;
1014      if (PAttrs & Attribute::VarArgsIncompatible)
1015        return false;
1016    }
1017
1018  // Okay, we decided that this is a safe thing to do: go ahead and start
1019  // inserting cast instructions as necessary...
1020  std::vector<Value*> Args;
1021  Args.reserve(NumActualArgs);
1022  SmallVector<AttributeWithIndex, 8> attrVec;
1023  attrVec.reserve(NumCommonArgs);
1024
1025  // Get any return attributes.
1026  Attributes RAttrs = CallerPAL.getRetAttributes();
1027
1028  // If the return value is not being used, the type may not be compatible
1029  // with the existing attributes.  Wipe out any problematic attributes.
1030  RAttrs &= ~Attribute::typeIncompatible(NewRetTy);
1031
1032  // Add the new return attributes.
1033  if (RAttrs)
1034    attrVec.push_back(AttributeWithIndex::get(0, RAttrs));
1035
1036  AI = CS.arg_begin();
1037  for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
1038    const Type *ParamTy = FT->getParamType(i);
1039    if ((*AI)->getType() == ParamTy) {
1040      Args.push_back(*AI);
1041    } else {
1042      Instruction::CastOps opcode = CastInst::getCastOpcode(*AI,
1043          false, ParamTy, false);
1044      Args.push_back(Builder->CreateCast(opcode, *AI, ParamTy, "tmp"));
1045    }
1046
1047    // Add any parameter attributes.
1048    if (Attributes PAttrs = CallerPAL.getParamAttributes(i + 1))
1049      attrVec.push_back(AttributeWithIndex::get(i + 1, PAttrs));
1050  }
1051
1052  // If the function takes more arguments than the call was taking, add them
1053  // now.
1054  for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
1055    Args.push_back(Constant::getNullValue(FT->getParamType(i)));
1056
1057  // If we are removing arguments to the function, emit an obnoxious warning.
1058  if (FT->getNumParams() < NumActualArgs) {
1059    if (!FT->isVarArg()) {
1060      errs() << "WARNING: While resolving call to function '"
1061             << Callee->getName() << "' arguments were dropped!\n";
1062    } else {
1063      // Add all of the arguments in their promoted form to the arg list.
1064      for (unsigned i = FT->getNumParams(); i != NumActualArgs; ++i, ++AI) {
1065        const Type *PTy = getPromotedType((*AI)->getType());
1066        if (PTy != (*AI)->getType()) {
1067          // Must promote to pass through va_arg area!
1068          Instruction::CastOps opcode =
1069            CastInst::getCastOpcode(*AI, false, PTy, false);
1070          Args.push_back(Builder->CreateCast(opcode, *AI, PTy, "tmp"));
1071        } else {
1072          Args.push_back(*AI);
1073        }
1074
1075        // Add any parameter attributes.
1076        if (Attributes PAttrs = CallerPAL.getParamAttributes(i + 1))
1077          attrVec.push_back(AttributeWithIndex::get(i + 1, PAttrs));
1078      }
1079    }
1080  }
1081
1082  if (Attributes FnAttrs =  CallerPAL.getFnAttributes())
1083    attrVec.push_back(AttributeWithIndex::get(~0, FnAttrs));
1084
1085  if (NewRetTy->isVoidTy())
1086    Caller->setName("");   // Void type should not have a name.
1087
1088  const AttrListPtr &NewCallerPAL = AttrListPtr::get(attrVec.begin(),
1089                                                     attrVec.end());
1090
1091  Instruction *NC;
1092  if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1093    NC = InvokeInst::Create(Callee, II->getNormalDest(), II->getUnwindDest(),
1094                            Args.begin(), Args.end(),
1095                            Caller->getName(), Caller);
1096    cast<InvokeInst>(NC)->setCallingConv(II->getCallingConv());
1097    cast<InvokeInst>(NC)->setAttributes(NewCallerPAL);
1098  } else {
1099    NC = CallInst::Create(Callee, Args.begin(), Args.end(),
1100                          Caller->getName(), Caller);
1101    CallInst *CI = cast<CallInst>(Caller);
1102    if (CI->isTailCall())
1103      cast<CallInst>(NC)->setTailCall();
1104    cast<CallInst>(NC)->setCallingConv(CI->getCallingConv());
1105    cast<CallInst>(NC)->setAttributes(NewCallerPAL);
1106  }
1107
1108  // Insert a cast of the return type as necessary.
1109  Value *NV = NC;
1110  if (OldRetTy != NV->getType() && !Caller->use_empty()) {
1111    if (!NV->getType()->isVoidTy()) {
1112      Instruction::CastOps opcode = CastInst::getCastOpcode(NC, false,
1113                                                            OldRetTy, false);
1114      NV = NC = CastInst::Create(opcode, NC, OldRetTy, "tmp");
1115
1116      // If this is an invoke instruction, we should insert it after the first
1117      // non-phi, instruction in the normal successor block.
1118      if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1119        BasicBlock::iterator I = II->getNormalDest()->getFirstNonPHI();
1120        InsertNewInstBefore(NC, *I);
1121      } else {
1122        // Otherwise, it's a call, just insert cast right after the call instr
1123        InsertNewInstBefore(NC, *Caller);
1124      }
1125      Worklist.AddUsersToWorkList(*Caller);
1126    } else {
1127      NV = UndefValue::get(Caller->getType());
1128    }
1129  }
1130
1131
1132  if (!Caller->use_empty())
1133    Caller->replaceAllUsesWith(NV);
1134
1135  EraseInstFromFunction(*Caller);
1136  return true;
1137}
1138
1139// transformCallThroughTrampoline - Turn a call to a function created by the
1140// init_trampoline intrinsic into a direct call to the underlying function.
1141//
1142Instruction *InstCombiner::transformCallThroughTrampoline(CallSite CS) {
1143  Value *Callee = CS.getCalledValue();
1144  const PointerType *PTy = cast<PointerType>(Callee->getType());
1145  const FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
1146  const AttrListPtr &Attrs = CS.getAttributes();
1147
1148  // If the call already has the 'nest' attribute somewhere then give up -
1149  // otherwise 'nest' would occur twice after splicing in the chain.
1150  if (Attrs.hasAttrSomewhere(Attribute::Nest))
1151    return 0;
1152
1153  IntrinsicInst *Tramp =
1154    cast<IntrinsicInst>(cast<BitCastInst>(Callee)->getOperand(0));
1155
1156  Function *NestF =cast<Function>(Tramp->getArgOperand(1)->stripPointerCasts());
1157  const PointerType *NestFPTy = cast<PointerType>(NestF->getType());
1158  const FunctionType *NestFTy = cast<FunctionType>(NestFPTy->getElementType());
1159
1160  const AttrListPtr &NestAttrs = NestF->getAttributes();
1161  if (!NestAttrs.isEmpty()) {
1162    unsigned NestIdx = 1;
1163    const Type *NestTy = 0;
1164    Attributes NestAttr = Attribute::None;
1165
1166    // Look for a parameter marked with the 'nest' attribute.
1167    for (FunctionType::param_iterator I = NestFTy->param_begin(),
1168         E = NestFTy->param_end(); I != E; ++NestIdx, ++I)
1169      if (NestAttrs.paramHasAttr(NestIdx, Attribute::Nest)) {
1170        // Record the parameter type and any other attributes.
1171        NestTy = *I;
1172        NestAttr = NestAttrs.getParamAttributes(NestIdx);
1173        break;
1174      }
1175
1176    if (NestTy) {
1177      Instruction *Caller = CS.getInstruction();
1178      std::vector<Value*> NewArgs;
1179      NewArgs.reserve(unsigned(CS.arg_end()-CS.arg_begin())+1);
1180
1181      SmallVector<AttributeWithIndex, 8> NewAttrs;
1182      NewAttrs.reserve(Attrs.getNumSlots() + 1);
1183
1184      // Insert the nest argument into the call argument list, which may
1185      // mean appending it.  Likewise for attributes.
1186
1187      // Add any result attributes.
1188      if (Attributes Attr = Attrs.getRetAttributes())
1189        NewAttrs.push_back(AttributeWithIndex::get(0, Attr));
1190
1191      {
1192        unsigned Idx = 1;
1193        CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
1194        do {
1195          if (Idx == NestIdx) {
1196            // Add the chain argument and attributes.
1197            Value *NestVal = Tramp->getArgOperand(2);
1198            if (NestVal->getType() != NestTy)
1199              NestVal = new BitCastInst(NestVal, NestTy, "nest", Caller);
1200            NewArgs.push_back(NestVal);
1201            NewAttrs.push_back(AttributeWithIndex::get(NestIdx, NestAttr));
1202          }
1203
1204          if (I == E)
1205            break;
1206
1207          // Add the original argument and attributes.
1208          NewArgs.push_back(*I);
1209          if (Attributes Attr = Attrs.getParamAttributes(Idx))
1210            NewAttrs.push_back
1211              (AttributeWithIndex::get(Idx + (Idx >= NestIdx), Attr));
1212
1213          ++Idx, ++I;
1214        } while (1);
1215      }
1216
1217      // Add any function attributes.
1218      if (Attributes Attr = Attrs.getFnAttributes())
1219        NewAttrs.push_back(AttributeWithIndex::get(~0, Attr));
1220
1221      // The trampoline may have been bitcast to a bogus type (FTy).
1222      // Handle this by synthesizing a new function type, equal to FTy
1223      // with the chain parameter inserted.
1224
1225      std::vector<const Type*> NewTypes;
1226      NewTypes.reserve(FTy->getNumParams()+1);
1227
1228      // Insert the chain's type into the list of parameter types, which may
1229      // mean appending it.
1230      {
1231        unsigned Idx = 1;
1232        FunctionType::param_iterator I = FTy->param_begin(),
1233          E = FTy->param_end();
1234
1235        do {
1236          if (Idx == NestIdx)
1237            // Add the chain's type.
1238            NewTypes.push_back(NestTy);
1239
1240          if (I == E)
1241            break;
1242
1243          // Add the original type.
1244          NewTypes.push_back(*I);
1245
1246          ++Idx, ++I;
1247        } while (1);
1248      }
1249
1250      // Replace the trampoline call with a direct call.  Let the generic
1251      // code sort out any function type mismatches.
1252      FunctionType *NewFTy = FunctionType::get(FTy->getReturnType(), NewTypes,
1253                                                FTy->isVarArg());
1254      Constant *NewCallee =
1255        NestF->getType() == PointerType::getUnqual(NewFTy) ?
1256        NestF : ConstantExpr::getBitCast(NestF,
1257                                         PointerType::getUnqual(NewFTy));
1258      const AttrListPtr &NewPAL = AttrListPtr::get(NewAttrs.begin(),
1259                                                   NewAttrs.end());
1260
1261      Instruction *NewCaller;
1262      if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
1263        NewCaller = InvokeInst::Create(NewCallee,
1264                                       II->getNormalDest(), II->getUnwindDest(),
1265                                       NewArgs.begin(), NewArgs.end(),
1266                                       Caller->getName(), Caller);
1267        cast<InvokeInst>(NewCaller)->setCallingConv(II->getCallingConv());
1268        cast<InvokeInst>(NewCaller)->setAttributes(NewPAL);
1269      } else {
1270        NewCaller = CallInst::Create(NewCallee, NewArgs.begin(), NewArgs.end(),
1271                                     Caller->getName(), Caller);
1272        if (cast<CallInst>(Caller)->isTailCall())
1273          cast<CallInst>(NewCaller)->setTailCall();
1274        cast<CallInst>(NewCaller)->
1275          setCallingConv(cast<CallInst>(Caller)->getCallingConv());
1276        cast<CallInst>(NewCaller)->setAttributes(NewPAL);
1277      }
1278      if (!Caller->getType()->isVoidTy())
1279        Caller->replaceAllUsesWith(NewCaller);
1280      Caller->eraseFromParent();
1281      Worklist.Remove(Caller);
1282      return 0;
1283    }
1284  }
1285
1286  // Replace the trampoline call with a direct call.  Since there is no 'nest'
1287  // parameter, there is no need to adjust the argument list.  Let the generic
1288  // code sort out any function type mismatches.
1289  Constant *NewCallee =
1290    NestF->getType() == PTy ? NestF :
1291                              ConstantExpr::getBitCast(NestF, PTy);
1292  CS.setCalledFunction(NewCallee);
1293  return CS.getInstruction();
1294}
1295
1296