C++ AllocaInst::isArrayAllocation方法代码示例

bool CallAnalyzer::visitAlloca(AllocaInst &I) {
  // Check whether inlining will turn a dynamic alloca into a static
  // alloca, and handle that case.
  if (I.isArrayAllocation()) {
    if (Constant *Size = SimplifiedValues.lookup(I.getArraySize())) {
      ConstantInt *AllocSize = dyn_cast<ConstantInt>(Size);
      assert(AllocSize && "Allocation size not a constant int?");
      Type *Ty = I.getAllocatedType();
      AllocatedSize += Ty->getPrimitiveSizeInBits() * AllocSize->getZExtValue();
      return Base::visitAlloca(I);
    }
  }

  // Accumulate the allocated size.
  if (I.isStaticAlloca()) {
    Type *Ty = I.getAllocatedType();
    AllocatedSize += (DL ? DL->getTypeAllocSize(Ty) :
                      Ty->getPrimitiveSizeInBits());
  }

  // We will happily inline static alloca instructions.
  if (I.isStaticAlloca())
    return Base::visitAlloca(I);

  // FIXME: This is overly conservative. Dynamic allocas are inefficient for
  // a variety of reasons, and so we would like to not inline them into
  // functions which don't currently have a dynamic alloca. This simply
  // disables inlining altogether in the presence of a dynamic alloca.
  HasDynamicAlloca = true;
  return false;
}

SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitAllocaInst(AllocaInst &I) {
  if (!I.getAllocatedType()->isSized())
    return unknown();

  // must be a VLA
  assert(I.isArrayAllocation());
  Value *ArraySize = I.getArraySize();
  Value *Size = ConstantInt::get(ArraySize->getType(),
                                 TD->getTypeAllocSize(I.getAllocatedType()));
  Size = Builder.CreateMul(Size, ArraySize);
  return std::make_pair(Size, Zero);
}

void AllocaMergingBase::analyzeBlock(const cheerp::Registerize& registerize, BasicBlock& BB,
				AllocaInfos& allocaInfos)
{
	for(Instruction& I: BB)
	{
		if(I.getOpcode() == Instruction::Alloca)
		{
			AllocaInst* AI = cast<AllocaInst>(&I);
			if(AI->isArrayAllocation())
				continue;
			allocaInfos.push_back(std::make_pair(AI, registerize.getLiveRangeForAlloca(AI)));
		}
	}
}

SizeOffsetType ObjectSizeOffsetVisitor::visitAllocaInst(AllocaInst &I) {
  if (!I.getAllocatedType()->isSized())
    return unknown();

  APInt Size(IntTyBits, DL.getTypeAllocSize(I.getAllocatedType()));
  if (!I.isArrayAllocation())
    return std::make_pair(align(Size, I.getAlignment()), Zero);

  Value *ArraySize = I.getArraySize();
  if (const ConstantInt *C = dyn_cast<ConstantInt>(ArraySize)) {
    APInt NumElems = C->getValue();
    if (!CheckedZextOrTrunc(NumElems))
      return unknown();

    bool Overflow;
    Size = Size.umul_ov(NumElems, Overflow);
    return Overflow ? unknown() : std::make_pair(align(Size, I.getAlignment()),
                                                 Zero);
  }
  return unknown();
}

void AMDGPUPromoteAlloca::handleAlloca(AllocaInst &I) {
  // Array allocations are probably not worth handling, since an allocation of
  // the array type is the canonical form.
  if (!I.isStaticAlloca() || I.isArrayAllocation())
    return;

  IRBuilder<> Builder(&I);

  // First try to replace the alloca with a vector
  Type *AllocaTy = I.getAllocatedType();

  DEBUG(dbgs() << "Trying to promote " << I << '\n');

  if (tryPromoteAllocaToVector(&I))
    return;

  DEBUG(dbgs() << " alloca is not a candidate for vectorization.\n");

  const Function &ContainingFunction = *I.getParent()->getParent();

  // FIXME: We should also try to get this value from the reqd_work_group_size
  // function attribute if it is available.
  unsigned WorkGroupSize = AMDGPU::getMaximumWorkGroupSize(ContainingFunction);

  int AllocaSize =
      WorkGroupSize * Mod->getDataLayout().getTypeAllocSize(AllocaTy);

  if (AllocaSize > LocalMemAvailable) {
    DEBUG(dbgs() << " Not enough local memory to promote alloca.\n");
    return;
  }

  std::vector<Value*> WorkList;

  if (!collectUsesWithPtrTypes(&I, WorkList)) {
    DEBUG(dbgs() << " Do not know how to convert all uses\n");
    return;
  }

  DEBUG(dbgs() << "Promoting alloca to local memory\n");
  LocalMemAvailable -= AllocaSize;

  Function *F = I.getParent()->getParent();

  Type *GVTy = ArrayType::get(I.getAllocatedType(), WorkGroupSize);
  GlobalVariable *GV = new GlobalVariable(
      *Mod, GVTy, false, GlobalValue::InternalLinkage,
      UndefValue::get(GVTy),
      Twine(F->getName()) + Twine('.') + I.getName(),
      nullptr,
      GlobalVariable::NotThreadLocal,
      AMDGPUAS::LOCAL_ADDRESS);
  GV->setUnnamedAddr(true);
  GV->setAlignment(I.getAlignment());

  Value *TCntY, *TCntZ;

  std::tie(TCntY, TCntZ) = getLocalSizeYZ(Builder);
  Value *TIdX = getWorkitemID(Builder, 0);
  Value *TIdY = getWorkitemID(Builder, 1);
  Value *TIdZ = getWorkitemID(Builder, 2);

  Value *Tmp0 = Builder.CreateMul(TCntY, TCntZ, "", true, true);
  Tmp0 = Builder.CreateMul(Tmp0, TIdX);
  Value *Tmp1 = Builder.CreateMul(TIdY, TCntZ, "", true, true);
  Value *TID = Builder.CreateAdd(Tmp0, Tmp1);
  TID = Builder.CreateAdd(TID, TIdZ);

  Value *Indices[] = {
    Constant::getNullValue(Type::getInt32Ty(Mod->getContext())),
    TID
  };

  Value *Offset = Builder.CreateInBoundsGEP(GVTy, GV, Indices);
  I.mutateType(Offset->getType());
  I.replaceAllUsesWith(Offset);
  I.eraseFromParent();

  for (Value *V : WorkList) {
    CallInst *Call = dyn_cast<CallInst>(V);
    if (!Call) {
      Type *EltTy = V->getType()->getPointerElementType();
      PointerType *NewTy = PointerType::get(EltTy, AMDGPUAS::LOCAL_ADDRESS);

      // The operand's value should be corrected on its own.
      if (isa<AddrSpaceCastInst>(V))
        continue;

      // FIXME: It doesn't really make sense to try to do this for all
      // instructions.
      V->mutateType(NewTy);
      continue;
    }

    IntrinsicInst *Intr = dyn_cast<IntrinsicInst>(Call);
    if (!Intr) {
      // FIXME: What is this for? It doesn't make sense to promote arbitrary
      // function calls. If the call is to a defined function that can also be
      // promoted, we should be able to do this once that function is also
      // rewritten.
//.........这里部分代码省略.........

// emit code to unpack a raw value from a box into registers or a stack slot
static Value *emit_unbox(jl_codectx_t &ctx, Type *to, const jl_cgval_t &x, jl_value_t *jt, Value *dest, bool volatile_store)
{
    assert(to != T_void);
    // TODO: fully validate that x.typ == jt?
    if (x.isghost) {
        // this can happen when a branch yielding a different type ends
        // up being dead code, and type inference knows that the other
        // branch's type is the only one that matters.
        if (type_is_ghost(to)) {
            return NULL;
        }
        //emit_error(ctx, "emit_unbox: a type mismatch error in occurred during codegen");
        return UndefValue::get(to); // type mismatch error
    }

    Constant *c = x.constant ? julia_const_to_llvm(x.constant) : NULL;
    if (!x.ispointer() || c) { // already unboxed, but sometimes need conversion
        Value *unboxed = emit_unboxed_coercion(ctx, to, c ? c : x.V);
        if (!dest)
            return unboxed;
        Type *dest_ty = unboxed->getType()->getPointerTo();
        if (dest->getType() != dest_ty)
            dest = emit_bitcast(ctx, dest, dest_ty);
        ctx.builder.CreateStore(unboxed, dest, volatile_store);
        return NULL;
    }

    // bools stored as int8, so an extra Trunc is needed to get an int1
    Value *p = x.constant ? literal_pointer_val(ctx, x.constant) : x.V;
    Type *ptype = (to == T_int1 ? T_pint8 : to->getPointerTo());

    Value *unboxed = NULL;
    if (to == T_int1)
        unboxed = ctx.builder.CreateTrunc(tbaa_decorate(x.tbaa, ctx.builder.CreateLoad(maybe_bitcast(ctx, p, ptype))), T_int1);
    else if (jt == (jl_value_t*)jl_bool_type)
        unboxed = ctx.builder.CreateZExt(ctx.builder.CreateTrunc(tbaa_decorate(x.tbaa, ctx.builder.CreateLoad(maybe_bitcast(ctx, p, ptype))), T_int1), to);
    if (unboxed) {
        if (!dest)
            return unboxed;
        ctx.builder.CreateStore(unboxed, dest);
        return NULL;
    }

    unsigned alignment = julia_alignment(jt, 0);
    if (dest) {
        MDNode *tbaa = x.tbaa;
        // the memcpy intrinsic does not allow to specify different alias tags
        // for the load part (x.tbaa) and the store part (tbaa_stack).
        // since the tbaa lattice has to be a tree we have unfortunately
        // x.tbaa ∪ tbaa_stack = tbaa_root if x.tbaa != tbaa_stack
        if (tbaa != tbaa_stack)
            tbaa = NULL;
        emit_memcpy(ctx, dest, p, jl_datatype_size(jt), alignment, volatile_store, tbaa);
        return NULL;
    }
    else {
        if (p->getType() != ptype && isa<AllocaInst>(p)) {
            // LLVM's mem2reg can't handle coercion if the load/store type does
            // not match the type of the alloca. As such, it is better to
            // perform the load using the alloca's type and then perform the
            // appropriate coercion manually.
            AllocaInst *AI = cast<AllocaInst>(p);
            Type *AllocType = AI->getAllocatedType();
#if JL_LLVM_VERSION >= 40000
            const DataLayout &DL = jl_data_layout;
#else
            const DataLayout &DL = jl_ExecutionEngine->getDataLayout();
#endif
            if (!AI->isArrayAllocation() &&
                    (AllocType->isFloatingPointTy() || AllocType->isIntegerTy() || AllocType->isPointerTy()) &&
                    (to->isFloatingPointTy() || to->isIntegerTy() || to->isPointerTy()) &&
                    DL.getTypeSizeInBits(AllocType) == DL.getTypeSizeInBits(to)) {
                Instruction *load = ctx.builder.CreateAlignedLoad(p, alignment);
                return emit_unboxed_coercion(ctx, to, tbaa_decorate(x.tbaa, load));
            }
        }
        p = maybe_bitcast(ctx, p, ptype);
        Instruction *load = ctx.builder.CreateAlignedLoad(p, alignment);
        return tbaa_decorate(x.tbaa, load);
    }
}

/// If it is possible to inline the specified call site,
/// do so and update the CallGraph for this operation.
///
/// This function also does some basic book-keeping to update the IR.  The
/// InlinedArrayAllocas map keeps track of any allocas that are already
/// available from other functions inlined into the caller.  If we are able to
/// inline this call site we attempt to reuse already available allocas or add
/// any new allocas to the set if not possible.
static bool InlineCallIfPossible(CallSite CS, InlineFunctionInfo &IFI,
                                 InlinedArrayAllocasTy &InlinedArrayAllocas,
                                 int InlineHistory, bool InsertLifetime) {
  Function *Callee = CS.getCalledFunction();
  Function *Caller = CS.getCaller();

  // Try to inline the function.  Get the list of static allocas that were
  // inlined.
  if (!InlineFunction(CS, IFI, InsertLifetime))
    return false;

  AdjustCallerSSPLevel(Caller, Callee);

  // Look at all of the allocas that we inlined through this call site.  If we
  // have already inlined other allocas through other calls into this function,
  // then we know that they have disjoint lifetimes and that we can merge them.
  //
  // There are many heuristics possible for merging these allocas, and the
  // different options have different tradeoffs.  One thing that we *really*
  // don't want to hurt is SRoA: once inlining happens, often allocas are no
  // longer address taken and so they can be promoted.
  //
  // Our "solution" for that is to only merge allocas whose outermost type is an
  // array type.  These are usually not promoted because someone is using a
  // variable index into them.  These are also often the most important ones to
  // merge.
  //
  // A better solution would be to have real memory lifetime markers in the IR
  // and not have the inliner do any merging of allocas at all.  This would
  // allow the backend to do proper stack slot coloring of all allocas that
  // *actually make it to the backend*, which is really what we want.
  //
  // Because we don't have this information, we do this simple and useful hack.
  //
  SmallPtrSet<AllocaInst*, 16> UsedAllocas;
  
  // When processing our SCC, check to see if CS was inlined from some other
  // call site.  For example, if we're processing "A" in this code:
  //   A() { B() }
  //   B() { x = alloca ... C() }
  //   C() { y = alloca ... }
  // Assume that C was not inlined into B initially, and so we're processing A
  // and decide to inline B into A.  Doing this makes an alloca available for
  // reuse and makes a callsite (C) available for inlining.  When we process
  // the C call site we don't want to do any alloca merging between X and Y
  // because their scopes are not disjoint.  We could make this smarter by
  // keeping track of the inline history for each alloca in the
  // InlinedArrayAllocas but this isn't likely to be a significant win.
  if (InlineHistory != -1)  // Only do merging for top-level call sites in SCC.
    return true;
  
  // Loop over all the allocas we have so far and see if they can be merged with
  // a previously inlined alloca.  If not, remember that we had it.
  for (unsigned AllocaNo = 0, e = IFI.StaticAllocas.size();
       AllocaNo != e; ++AllocaNo) {
    AllocaInst *AI = IFI.StaticAllocas[AllocaNo];
    
    // Don't bother trying to merge array allocations (they will usually be
    // canonicalized to be an allocation *of* an array), or allocations whose
    // type is not itself an array (because we're afraid of pessimizing SRoA).
    ArrayType *ATy = dyn_cast<ArrayType>(AI->getAllocatedType());
    if (!ATy || AI->isArrayAllocation())
      continue;
    
    // Get the list of all available allocas for this array type.
    std::vector<AllocaInst*> &AllocasForType = InlinedArrayAllocas[ATy];
    
    // Loop over the allocas in AllocasForType to see if we can reuse one.  Note
    // that we have to be careful not to reuse the same "available" alloca for
    // multiple different allocas that we just inlined, we use the 'UsedAllocas'
    // set to keep track of which "available" allocas are being used by this
    // function.  Also, AllocasForType can be empty of course!
    bool MergedAwayAlloca = false;
    for (unsigned i = 0, e = AllocasForType.size(); i != e; ++i) {
      AllocaInst *AvailableAlloca = AllocasForType[i];

      unsigned Align1 = AI->getAlignment(),
               Align2 = AvailableAlloca->getAlignment();
      
      // The available alloca has to be in the right function, not in some other
      // function in this SCC.
      if (AvailableAlloca->getParent() != AI->getParent())
        continue;
      
      // If the inlined function already uses this alloca then we can't reuse
      // it.
      if (!UsedAllocas.insert(AvailableAlloca).second)
        continue;
      
      // Otherwise, we *can* reuse it, RAUW AI into AvailableAlloca and declare
      // success!
      DEBUG(dbgs() << "    ***MERGED ALLOCA: " << *AI << "\n\t\tINTO: "
//.........这里部分代码省略.........

// FIXME: Should try to pick the most likely to be profitable allocas first.
bool AMDGPUPromoteAlloca::handleAlloca(AllocaInst &I, bool SufficientLDS) {
  // Array allocations are probably not worth handling, since an allocation of
  // the array type is the canonical form.
  if (!I.isStaticAlloca() || I.isArrayAllocation())
    return false;

  IRBuilder<> Builder(&I);

  // First try to replace the alloca with a vector
  Type *AllocaTy = I.getAllocatedType();

  DEBUG(dbgs() << "Trying to promote " << I << '\n');

  if (tryPromoteAllocaToVector(&I, AS))
    return true; // Promoted to vector.

  const Function &ContainingFunction = *I.getParent()->getParent();
  CallingConv::ID CC = ContainingFunction.getCallingConv();

  // Don't promote the alloca to LDS for shader calling conventions as the work
  // item ID intrinsics are not supported for these calling conventions.
  // Furthermore not all LDS is available for some of the stages.
  switch (CC) {
  case CallingConv::AMDGPU_KERNEL:
  case CallingConv::SPIR_KERNEL:
    break;
  default:
    DEBUG(dbgs() << " promote alloca to LDS not supported with calling convention.\n");
    return false;
  }

  // Not likely to have sufficient local memory for promotion.
  if (!SufficientLDS)
    return false;

  const AMDGPUSubtarget &ST =
    TM->getSubtarget<AMDGPUSubtarget>(ContainingFunction);
  unsigned WorkGroupSize = ST.getFlatWorkGroupSizes(ContainingFunction).second;

  const DataLayout &DL = Mod->getDataLayout();

  unsigned Align = I.getAlignment();
  if (Align == 0)
    Align = DL.getABITypeAlignment(I.getAllocatedType());

  // FIXME: This computed padding is likely wrong since it depends on inverse
  // usage order.
  //
  // FIXME: It is also possible that if we're allowed to use all of the memory
  // could could end up using more than the maximum due to alignment padding.

  uint32_t NewSize = alignTo(CurrentLocalMemUsage, Align);
  uint32_t AllocSize = WorkGroupSize * DL.getTypeAllocSize(AllocaTy);
  NewSize += AllocSize;

  if (NewSize > LocalMemLimit) {
    DEBUG(dbgs() << "  " << AllocSize
          << " bytes of local memory not available to promote\n");
    return false;
  }

  CurrentLocalMemUsage = NewSize;

  std::vector<Value*> WorkList;

  if (!collectUsesWithPtrTypes(&I, &I, WorkList)) {
    DEBUG(dbgs() << " Do not know how to convert all uses\n");
    return false;
  }

  DEBUG(dbgs() << "Promoting alloca to local memory\n");

  Function *F = I.getParent()->getParent();

  Type *GVTy = ArrayType::get(I.getAllocatedType(), WorkGroupSize);
  GlobalVariable *GV = new GlobalVariable(
      *Mod, GVTy, false, GlobalValue::InternalLinkage,
      UndefValue::get(GVTy),
      Twine(F->getName()) + Twine('.') + I.getName(),
      nullptr,
      GlobalVariable::NotThreadLocal,
      AS.LOCAL_ADDRESS);
  GV->setUnnamedAddr(GlobalValue::UnnamedAddr::Global);
  GV->setAlignment(I.getAlignment());

  Value *TCntY, *TCntZ;

  std::tie(TCntY, TCntZ) = getLocalSizeYZ(Builder);
  Value *TIdX = getWorkitemID(Builder, 0);
  Value *TIdY = getWorkitemID(Builder, 1);
  Value *TIdZ = getWorkitemID(Builder, 2);

  Value *Tmp0 = Builder.CreateMul(TCntY, TCntZ, "", true, true);
  Tmp0 = Builder.CreateMul(Tmp0, TIdX);
  Value *Tmp1 = Builder.CreateMul(TIdY, TCntZ, "", true, true);
  Value *TID = Builder.CreateAdd(Tmp0, Tmp1);
  TID = Builder.CreateAdd(TID, TIdZ);

  Value *Indices[] = {
//.........这里部分代码省略.........

/// InlineCallIfPossible - If it is possible to inline the specified call site,
/// do so and update the CallGraph for this operation.
///
/// This function also does some basic book-keeping to update the IR.  The
/// InlinedArrayAllocas map keeps track of any allocas that are already
/// available from other  functions inlined into the caller.  If we are able to
/// inline this call site we attempt to reuse already available allocas or add
/// any new allocas to the set if not possible.
static bool InlineCallIfPossible(CallSite CS, InlineFunctionInfo &IFI,
                                 InlinedArrayAllocasTy &InlinedArrayAllocas) {
  Function *Callee = CS.getCalledFunction();
  Function *Caller = CS.getCaller();

  // Try to inline the function.  Get the list of static allocas that were
  // inlined.
  if (!InlineFunction(CS, IFI))
    return false;

  // If the inlined function had a higher stack protection level than the
  // calling function, then bump up the caller's stack protection level.
  if (Callee->hasFnAttr(Attribute::StackProtectReq))
    Caller->addFnAttr(Attribute::StackProtectReq);
  else if (Callee->hasFnAttr(Attribute::StackProtect) &&
           !Caller->hasFnAttr(Attribute::StackProtectReq))
    Caller->addFnAttr(Attribute::StackProtect);

  
  // Look at all of the allocas that we inlined through this call site.  If we
  // have already inlined other allocas through other calls into this function,
  // then we know that they have disjoint lifetimes and that we can merge them.
  //
  // There are many heuristics possible for merging these allocas, and the
  // different options have different tradeoffs.  One thing that we *really*
  // don't want to hurt is SRoA: once inlining happens, often allocas are no
  // longer address taken and so they can be promoted.
  //
  // Our "solution" for that is to only merge allocas whose outermost type is an
  // array type.  These are usually not promoted because someone is using a
  // variable index into them.  These are also often the most important ones to
  // merge.
  //
  // A better solution would be to have real memory lifetime markers in the IR
  // and not have the inliner do any merging of allocas at all.  This would
  // allow the backend to do proper stack slot coloring of all allocas that
  // *actually make it to the backend*, which is really what we want.
  //
  // Because we don't have this information, we do this simple and useful hack.
  //
  SmallPtrSet<AllocaInst*, 16> UsedAllocas;
  
  // Loop over all the allocas we have so far and see if they can be merged with
  // a previously inlined alloca.  If not, remember that we had it.
  for (unsigned AllocaNo = 0, e = IFI.StaticAllocas.size();
       AllocaNo != e; ++AllocaNo) {
    AllocaInst *AI = IFI.StaticAllocas[AllocaNo];
    
    // Don't bother trying to merge array allocations (they will usually be
    // canonicalized to be an allocation *of* an array), or allocations whose
    // type is not itself an array (because we're afraid of pessimizing SRoA).
    const ArrayType *ATy = dyn_cast<ArrayType>(AI->getAllocatedType());
    if (ATy == 0 || AI->isArrayAllocation())
      continue;
    
    // Get the list of all available allocas for this array type.
    std::vector<AllocaInst*> &AllocasForType = InlinedArrayAllocas[ATy];
    
    // Loop over the allocas in AllocasForType to see if we can reuse one.  Note
    // that we have to be careful not to reuse the same "available" alloca for
    // multiple different allocas that we just inlined, we use the 'UsedAllocas'
    // set to keep track of which "available" allocas are being used by this
    // function.  Also, AllocasForType can be empty of course!
    bool MergedAwayAlloca = false;
    for (unsigned i = 0, e = AllocasForType.size(); i != e; ++i) {
      AllocaInst *AvailableAlloca = AllocasForType[i];
      
      // The available alloca has to be in the right function, not in some other
      // function in this SCC.
      if (AvailableAlloca->getParent() != AI->getParent())
        continue;
      
      // If the inlined function already uses this alloca then we can't reuse
      // it.
      if (!UsedAllocas.insert(AvailableAlloca))
        continue;
      
      // Otherwise, we *can* reuse it, RAUW AI into AvailableAlloca and declare
      // success!
      DEBUG(dbgs() << "    ***MERGED ALLOCA: " << *AI);
      
      AI->replaceAllUsesWith(AvailableAlloca);
      AI->eraseFromParent();
      MergedAwayAlloca = true;
      ++NumMergedAllocas;
      break;
    }

    // If we already nuked the alloca, we're done with it.
    if (MergedAwayAlloca)
      continue;

//.........这里部分代码省略.........

/// Look at all of the allocas that we inlined through this call site.  If we
/// have already inlined other allocas through other calls into this function,
/// then we know that they have disjoint lifetimes and that we can merge them.
///
/// There are many heuristics possible for merging these allocas, and the
/// different options have different tradeoffs.  One thing that we *really*
/// don't want to hurt is SRoA: once inlining happens, often allocas are no
/// longer address taken and so they can be promoted.
///
/// Our "solution" for that is to only merge allocas whose outermost type is an
/// array type.  These are usually not promoted because someone is using a
/// variable index into them.  These are also often the most important ones to
/// merge.
///
/// A better solution would be to have real memory lifetime markers in the IR
/// and not have the inliner do any merging of allocas at all.  This would
/// allow the backend to do proper stack slot coloring of all allocas that
/// *actually make it to the backend*, which is really what we want.
///
/// Because we don't have this information, we do this simple and useful hack.
static void mergeInlinedArrayAllocas(
    Function *Caller, InlineFunctionInfo &IFI,
    InlinedArrayAllocasTy &InlinedArrayAllocas, int InlineHistory) {
  SmallPtrSet<AllocaInst *, 16> UsedAllocas;

  // When processing our SCC, check to see if CS was inlined from some other
  // call site.  For example, if we're processing "A" in this code:
  //   A() { B() }
  //   B() { x = alloca ... C() }
  //   C() { y = alloca ... }
  // Assume that C was not inlined into B initially, and so we're processing A
  // and decide to inline B into A.  Doing this makes an alloca available for
  // reuse and makes a callsite (C) available for inlining.  When we process
  // the C call site we don't want to do any alloca merging between X and Y
  // because their scopes are not disjoint.  We could make this smarter by
  // keeping track of the inline history for each alloca in the
  // InlinedArrayAllocas but this isn't likely to be a significant win.
  if (InlineHistory != -1) // Only do merging for top-level call sites in SCC.
    return;

  // Loop over all the allocas we have so far and see if they can be merged with
  // a previously inlined alloca.  If not, remember that we had it.
  for (unsigned AllocaNo = 0, e = IFI.StaticAllocas.size(); AllocaNo != e;
       ++AllocaNo) {
    AllocaInst *AI = IFI.StaticAllocas[AllocaNo];

    // Don't bother trying to merge array allocations (they will usually be
    // canonicalized to be an allocation *of* an array), or allocations whose
    // type is not itself an array (because we're afraid of pessimizing SRoA).
    ArrayType *ATy = dyn_cast<ArrayType>(AI->getAllocatedType());
    if (!ATy || AI->isArrayAllocation())
      continue;

    // Get the list of all available allocas for this array type.
    std::vector<AllocaInst *> &AllocasForType = InlinedArrayAllocas[ATy];

    // Loop over the allocas in AllocasForType to see if we can reuse one.  Note
    // that we have to be careful not to reuse the same "available" alloca for
    // multiple different allocas that we just inlined, we use the 'UsedAllocas'
    // set to keep track of which "available" allocas are being used by this
    // function.  Also, AllocasForType can be empty of course!
    bool MergedAwayAlloca = false;
    for (AllocaInst *AvailableAlloca : AllocasForType) {
      unsigned Align1 = AI->getAlignment(),
               Align2 = AvailableAlloca->getAlignment();

      // The available alloca has to be in the right function, not in some other
      // function in this SCC.
      if (AvailableAlloca->getParent() != AI->getParent())
        continue;

      // If the inlined function already uses this alloca then we can't reuse
      // it.
      if (!UsedAllocas.insert(AvailableAlloca).second)
        continue;

      // Otherwise, we *can* reuse it, RAUW AI into AvailableAlloca and declare
      // success!
      LLVM_DEBUG(dbgs() << "    ***MERGED ALLOCA: " << *AI
                        << "\n\t\tINTO: " << *AvailableAlloca << '\n');

      // Move affected dbg.declare calls immediately after the new alloca to
      // avoid the situation when a dbg.declare precedes its alloca.
      if (auto *L = LocalAsMetadata::getIfExists(AI))
        if (auto *MDV = MetadataAsValue::getIfExists(AI->getContext(), L))
          for (User *U : MDV->users())
            if (DbgDeclareInst *DDI = dyn_cast<DbgDeclareInst>(U))
              DDI->moveBefore(AvailableAlloca->getNextNode());

      AI->replaceAllUsesWith(AvailableAlloca);

      if (Align1 != Align2) {
        if (!Align1 || !Align2) {
          const DataLayout &DL = Caller->getParent()->getDataLayout();
          unsigned TypeAlign = DL.getABITypeAlignment(AI->getAllocatedType());

          Align1 = Align1 ? Align1 : TypeAlign;
          Align2 = Align2 ? Align2 : TypeAlign;
        }

//.........这里部分代码省略.........