//===--- ConstantInitBuilder.cpp - Global initializer builder -------------===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This file defines out-of-line routines for building initializers for

// global variables, in particular the kind of globals that are implicitly

// introduced by various language ABIs.

//

//===----------------------------------------------------------------------===//

#include "clang/CodeGen/ConstantInitBuilder.h"

#include "CodeGenModule.h"

using namespace clang;

using namespace CodeGen;

llvm::Type *ConstantInitFuture::getType() const {

  assert(Data && "dereferencing null future");

  if (Data.is<llvm::Constant*>()) {

    return Data.get<llvm::Constant*>()->getType();

  } else {

    return Data.get<ConstantInitBuilderBase*>()->Buffer[0]->getType();

  }

}

void ConstantInitFuture::abandon() {

  assert(Data && "abandoning null future");

  if (auto builder = Data.dyn_cast<ConstantInitBuilderBase*>()) {

    builder->abandon(0);

  }

  Data = nullptr;

}

void ConstantInitFuture::installInGlobal(llvm::GlobalVariable *GV) {

  assert(Data && "installing null future");

  if (Data.is<llvm::Constant*>()) {

    GV->setInitializer(Data.get<llvm::Constant*>());

  } else {

    auto &builder = *Data.get<ConstantInitBuilderBase*>();

    assert(builder.Buffer.size() == 1);

    builder.setGlobalInitializer(GV, builder.Buffer[0]);

    builder.Buffer.clear();

    Data = nullptr;

  }

}

ConstantInitFuture

ConstantInitBuilderBase::createFuture(llvm::Constant *initializer) {

  assert(Buffer.empty() && "buffer not current empty");

  Buffer.push_back(initializer);

  return ConstantInitFuture(this);

}

// Only used in this file.

inline ConstantInitFuture::ConstantInitFuture(ConstantInitBuilderBase *builder)

    : Data(builder) {

  assert(!builder->Frozen);

  assert(builder->Buffer.size() == 1);

  assert(builder->Buffer[0] != nullptr);

}

llvm::GlobalVariable *

ConstantInitBuilderBase::createGlobal(llvm::Constant *initializer,

                                      const llvm::Twine &name,

                                      CharUnits alignment,

                                      bool constant,

                                      llvm::GlobalValue::LinkageTypes linkage,

                                      unsigned addressSpace) {

  auto GV = new llvm::GlobalVariable(CGM.getModule(),

                                     initializer->getType(),

                                     constant,

                                     linkage,

                                     initializer,

                                     name,

                                     /*insert before*/ nullptr,

                                     llvm::GlobalValue::NotThreadLocal,

                                     addressSpace);

  GV->setAlignment(alignment.getAsAlign());

  resolveSelfReferences(GV);

  return GV;

}

void ConstantInitBuilderBase::setGlobalInitializer(llvm::GlobalVariable *GV,

                                                   llvm::Constant *initializer){

  GV->setInitializer(initializer);

  if (!SelfReferences.empty())

    resolveSelfReferences(GV);

}

void ConstantInitBuilderBase::resolveSelfReferences(llvm::GlobalVariable *GV) {

  for (auto &entry : SelfReferences) {

    llvm::Constant *resolvedReference =

      llvm::ConstantExpr::getInBoundsGetElementPtr(

        GV->getValueType(), GV, entry.Indices);

    auto dummy = entry.Dummy;

    dummy->replaceAllUsesWith(resolvedReference);

    dummy->eraseFromParent();

  }

  SelfReferences.clear();

}

void ConstantInitBuilderBase::abandon(size_t newEnd) {

  // Remove all the entries we've added.

  Buffer.erase(Buffer.begin() + newEnd, Buffer.end());

  // If we're abandoning all the way to the beginning, destroy

  // all the self-references, because we might not get another

  // opportunity.

  if (newEnd == 0) {

    for (auto &entry : SelfReferences) {

      auto dummy = entry.Dummy;

      dummy->replaceAllUsesWith(llvm::PoisonValue::get(dummy->getType()));

      dummy->eraseFromParent();

    }

    SelfReferences.clear();

  }

}

void ConstantAggregateBuilderBase::addSize(CharUnits size) {

  add(Builder.CGM.getSize(size));

}

llvm::Constant *

ConstantAggregateBuilderBase::getRelativeOffset(llvm::IntegerType *offsetType,

                                                llvm::Constant *target) {

  return getRelativeOffsetToPosition(offsetType, target,

                                     Builder.Buffer.size() - Begin);

}

llvm::Constant *ConstantAggregateBuilderBase::getRelativeOffsetToPosition(

    llvm::IntegerType *offsetType, llvm::Constant *target, size_t position) {

  // Compute the address of the relative-address slot.

  auto base = getAddrOfPosition(offsetType, position);

  // Subtract.

  base = llvm::ConstantExpr::getPtrToInt(base, Builder.CGM.IntPtrTy);

  target = llvm::ConstantExpr::getPtrToInt(target, Builder.CGM.IntPtrTy);

  llvm::Constant *offset = llvm::ConstantExpr::getSub(target, base);

  // Truncate to the relative-address type if necessary.

  if (Builder.CGM.IntPtrTy != offsetType) {

    offset = llvm::ConstantExpr::getTrunc(offset, offsetType);

  }

  return offset;

}

llvm::Constant *

ConstantAggregateBuilderBase::getAddrOfPosition(llvm::Type *type,

                                                size_t position) {

  // Make a global variable.  We will replace this with a GEP to this

  // position after installing the initializer.

  auto dummy = new llvm::GlobalVariable(Builder.CGM.getModule(), type, true,

                                        llvm::GlobalVariable::PrivateLinkage,

                                        nullptr, "");

  Builder.SelfReferences.emplace_back(dummy);

  auto &entry = Builder.SelfReferences.back();

  (void)getGEPIndicesTo(entry.Indices, position + Begin);

  return dummy;

}

llvm::Constant *

ConstantAggregateBuilderBase::getAddrOfCurrentPosition(llvm::Type *type) {

  // Make a global variable.  We will replace this with a GEP to this

  // position after installing the initializer.

  auto dummy =

    new llvm::GlobalVariable(Builder.CGM.getModule(), type, true,

                             llvm::GlobalVariable::PrivateLinkage,

                             nullptr, "");

  Builder.SelfReferences.emplace_back(dummy);

  auto &entry = Builder.SelfReferences.back();

  (void) getGEPIndicesToCurrentPosition(entry.Indices);

  return dummy;

}

void ConstantAggregateBuilderBase::getGEPIndicesTo(

                               llvm::SmallVectorImpl<llvm::Constant*> &indices,

                               size_t position) const {

  // Recurse on the parent builder if present.

  if (Parent) {

    Parent->getGEPIndicesTo(indices, Begin);

  // Otherwise, add an index to drill into the first level of pointer.

  } else {

    assert(indices.empty());

    indices.push_back(llvm::ConstantInt::get(Builder.CGM.Int32Ty, 0));

  }

  assert(position >= Begin);

  // We have to use i32 here because struct GEPs demand i32 indices.

  // It's rather unlikely to matter in practice.

  indices.push_back(llvm::ConstantInt::get(Builder.CGM.Int32Ty,

                                           position - Begin));

}

ConstantAggregateBuilderBase::PlaceholderPosition

ConstantAggregateBuilderBase::addPlaceholderWithSize(llvm::Type *type) {

  // Bring the offset up to the last field.

  CharUnits offset = getNextOffsetFromGlobal();

  // Create the placeholder.

  auto position = addPlaceholder();

  // Advance the offset past that field.

  auto &layout = Builder.CGM.getDataLayout();

  if (!Packed)

    offset = offset.alignTo(CharUnits::fromQuantity(

                                layout.getABITypeAlignment(type)));

  offset += CharUnits::fromQuantity(layout.getTypeStoreSize(type));

  CachedOffsetEnd = Builder.Buffer.size();

  CachedOffsetFromGlobal = offset;

  return position;

}

CharUnits ConstantAggregateBuilderBase::getOffsetFromGlobalTo(size_t end) const{

  size_t cacheEnd = CachedOffsetEnd;

  assert(cacheEnd <= end);

  // Fast path: if the cache is valid, just use it.

  if (cacheEnd == end) {

    return CachedOffsetFromGlobal;

  }

  // If the cached range ends before the index at which the current

  // aggregate starts, recurse for the parent.

  CharUnits offset;

  if (cacheEnd < Begin) {

    assert(cacheEnd == 0);

    assert(Parent && "Begin != 0 for root builder");

    cacheEnd = Begin;

    offset = Parent->getOffsetFromGlobalTo(Begin);

  } else {

    offset = CachedOffsetFromGlobal;

  }

  // Perform simple layout on the elements in cacheEnd..<end.

  if (cacheEnd != end) {

    auto &layout = Builder.CGM.getDataLayout();

    do {

      llvm::Constant *element = Builder.Buffer[cacheEnd];

      assert(element != nullptr &&

             "cannot compute offset when a placeholder is present");

      llvm::Type *elementType = element->getType();

      if (!Packed)

        offset = offset.alignTo(CharUnits::fromQuantity(

                                  layout.getABITypeAlignment(elementType)));

      offset += CharUnits::fromQuantity(layout.getTypeStoreSize(elementType));

    } while (++cacheEnd != end);

  }

  // Cache and return.

  CachedOffsetEnd = cacheEnd;

  CachedOffsetFromGlobal = offset;

  return offset;

}

llvm::Constant *ConstantAggregateBuilderBase::finishArray(llvm::Type *eltTy) {

  markFinished();

  auto &buffer = getBuffer();

  assert((Begin < buffer.size() ||

          (Begin == buffer.size() && eltTy))

         && "didn't add any array elements without element type");

  auto elts = llvm::makeArrayRef(buffer).slice(Begin);

  if (!eltTy) 
eltTy = elts[0]->getType()25
;

  auto type = llvm::ArrayType::get(eltTy, elts.size());

  auto constant = llvm::ConstantArray::get(type, elts);

  buffer.erase(buffer.begin() + Begin, buffer.end());

  return constant;

}

llvm::Constant *

ConstantAggregateBuilderBase::finishStruct(llvm::StructType *ty) {

  markFinished();

  auto &buffer = getBuffer();

  auto elts = llvm::makeArrayRef(buffer).slice(Begin);

  if (ty == nullptr && 
elts.empty()6.86k
)

    ty = llvm::StructType::get(Builder.CGM.getLLVMContext(), {}, Packed);

  llvm::Constant *constant;

  if (ty) {

    assert(ty->isPacked() == Packed);

    constant = llvm::ConstantStruct::get(ty, elts);

  } else {

    constant = llvm::ConstantStruct::getAnon(elts, Packed);

  }

  buffer.erase(buffer.begin() + Begin, buffer.end());

  return constant;

}