ldc/ir/iraggr.cpp

//===-- iraggr.cpp --------------------------------------------------------===//
//
//                         LDC – the LLVM D compiler
//
// This file is distributed under the BSD-style LDC license. See the LICENSE
// file for details.
//
//===----------------------------------------------------------------------===//

#include "gen/llvm.h"
#include "aggregate.h"
#include "declaration.h"
#include "init.h"
#include "mtype.h"
#include "target.h"
#include "gen/irstate.h"
#include "gen/llvmhelpers.h"
#include "gen/logger.h"
#include "gen/mangling.h"
#include "gen/tollvm.h"
#include "ir/iraggr.h"
#include "irdsymbol.h"
#include "ir/irtypeclass.h"
#include "ir/irtypestruct.h"
#include <algorithm>

//////////////////////////////////////////////////////////////////////////////

IrAggr::IrAggr(AggregateDeclaration *aggr)
    : aggrdecl(aggr), type(aggr->type),
      // above still need to be looked at
      init_type(LLStructType::create(
          gIR->context(), std::string(aggr->toPrettyChars()) + "_init")) {}

//////////////////////////////////////////////////////////////////////////////

LLGlobalVariable *IrAggr::getInitSymbol() {
  if (init) {
    return init;
  }

  // create the initZ symbol
  auto initname = getMangledInitSymbolName(aggrdecl);

  init =
      getOrCreateGlobal(aggrdecl->loc, gIR->module, init_type, true,
                        llvm::GlobalValue::ExternalLinkage, nullptr, initname);

  // set alignment
  init->setAlignment(DtoAlignment(type));

  return init;
}

//////////////////////////////////////////////////////////////////////////////

llvm::Constant *IrAggr::getDefaultInit() {
  if (constInit) {
    return constInit;
  }

  IF_LOG Logger::println("Building default initializer for %s",
                         aggrdecl->toPrettyChars());
  LOG_SCOPE;

  DtoType(type);
  VarInitMap noExplicitInitializers;
  constInit = createInitializerConstant(noExplicitInitializers, init_type);
  return constInit;
}

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

// helper function that adds zero bytes to a vector of constants
// FIXME A similar function is in ir/irtypeaggr.cpp
static inline size_t
add_zeros(llvm::SmallVectorImpl<llvm::Constant *> &constants,
          size_t startOffset, size_t endOffset) {
  assert(startOffset <= endOffset);
  const size_t paddingSize = endOffset - startOffset;
  if (paddingSize) {
    llvm::ArrayType *pad = llvm::ArrayType::get(
        llvm::Type::getInt8Ty(gIR->context()), paddingSize);
    constants.push_back(llvm::Constant::getNullValue(pad));
  }
  return paddingSize ? 1 : 0;
}

//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////

typedef std::pair<VarDeclaration *, llvm::Constant *> VarInitConst;

static bool struct_init_data_sort(const VarInitConst &a,
                                  const VarInitConst &b) {
  return (a.first && b.first) ? a.first->offset < b.first->offset : false;
}

// helper function that returns the static default initializer of a variable
LLConstant *get_default_initializer(VarDeclaration *vd) {
  if (vd->_init) {
    // Issue 9057 workaround caused by issue 14666 fix, see DMD upstream
    // commit 069f570005.
    if (vd->sem < Semantic2Done && vd->_scope) {
      vd->semantic2(vd->_scope);
    }
    return DtoConstInitializer(vd->_init->loc, vd->type, vd->_init);
  }

  if (vd->type->size(vd->loc) == 0) {
    // We need to be able to handle void[0] struct members even if void has
    // no default initializer.
    return llvm::ConstantPointerNull::get(DtoPtrToType(vd->type));
  }
  return DtoConstExpInit(vd->loc, vd->type, vd->type->defaultInit(vd->loc));
}

// return a constant array of type arrTypeD initialized with a constant value,
// or that constant value
static llvm::Constant *FillSArrayDims(Type *arrTypeD, llvm::Constant *init) {
  // Check whether we actually need to expand anything.
  // KLUDGE: We don't have the initializer type here, so we can only check
  // the size without doing an expensive recursive D <-> LLVM type comparison.
  // The better way to solve this would be to just fix the initializer
  // codegen in any place where a scalar initializer might still be generated.
  if (gDataLayout->getTypeStoreSize(init->getType()) >= arrTypeD->size()) {
    return init;
  }

  if (arrTypeD->ty == Tsarray) {
    init = FillSArrayDims(arrTypeD->nextOf(), init);
    size_t dim = static_cast<TypeSArray *>(arrTypeD)->dim->toUInteger();
    llvm::ArrayType *arrty = llvm::ArrayType::get(init->getType(), dim);
    return llvm::ConstantArray::get(arrty,
                                    std::vector<llvm::Constant *>(dim, init));
  }
  return init;
}

llvm::Constant *
IrAggr::createInitializerConstant(const VarInitMap &explicitInitializers,
                                  llvm::StructType *initializerType) {
  IF_LOG Logger::println("Creating initializer constant for %s",
                         aggrdecl->toChars());
  LOG_SCOPE;

  llvm::SmallVector<llvm::Constant *, 16> constants;

  unsigned offset = 0;
  if (type->ty == Tclass) {
    // add vtbl
    constants.push_back(getVtblSymbol());
    offset += Target::ptrsize;

    // add monitor (except for C++ classes)
    if (!aggrdecl->isClassDeclaration()->isCPPclass()) {
      constants.push_back(getNullValue(getVoidPtrType()));
      offset += Target::ptrsize;
    }
  }

  // Add the initializers for the member fields. While we are traversing the
  // class hierarchy, use the opportunity to populate interfacesWithVtbls if
  // we haven't done so previously (due to e.g. ClassReferenceExp, we can
  // have multiple initializer constants for a single class).
  addFieldInitializers(constants, explicitInitializers, aggrdecl, offset,
                       interfacesWithVtbls.empty());

  // tail padding?
  const size_t structsize = aggrdecl->size(Loc());
  if (offset < structsize) {
    add_zeros(constants, offset, structsize);
  }

  // get initializer type
  if (!initializerType || initializerType->isOpaque()) {
    llvm::SmallVector<llvm::Type *, 16> types;
    types.reserve(constants.size());
    for (auto c : constants) {
      types.push_back(c->getType());
    }
    if (!initializerType) {
      initializerType = LLStructType::get(gIR->context(), types, isPacked());
    } else {
      initializerType->setBody(types, isPacked());
    }
  }

  // build constant
  assert(!constants.empty());
  llvm::Constant *c = LLConstantStruct::get(initializerType, constants);
  IF_LOG Logger::cout() << "final initializer: " << *c << std::endl;
  return c;
}

void IrAggr::addFieldInitializers(
    llvm::SmallVectorImpl<llvm::Constant *> &constants,
    const VarInitMap &explicitInitializers, AggregateDeclaration *decl,
    unsigned &offset, bool populateInterfacesWithVtbls) {

  if (ClassDeclaration *cd = decl->isClassDeclaration()) {
    if (cd->baseClass) {
      addFieldInitializers(constants, explicitInitializers, cd->baseClass,
                           offset, populateInterfacesWithVtbls);
    }

    // has interface vtbls?
    if (cd->vtblInterfaces && cd->vtblInterfaces->dim > 0) {
      // Align interface infos to pointer size.
      unsigned aligned =
          (offset + Target::ptrsize - 1) & ~(Target::ptrsize - 1);
      if (offset < aligned) {
        add_zeros(constants, offset, aligned);
        offset = aligned;
      }

      // false when it's not okay to use functions from super classes
      bool newinsts = (cd == aggrdecl->isClassDeclaration());

      size_t inter_idx = interfacesWithVtbls.size();

      offset = (offset + Target::ptrsize - 1) & ~(Target::ptrsize - 1);

      for (auto bc : *cd->vtblInterfaces) {
        constants.push_back(getInterfaceVtbl(bc, newinsts, inter_idx));
        offset += Target::ptrsize;
        inter_idx++;

        if (populateInterfacesWithVtbls) {
          interfacesWithVtbls.push_back(bc);
        }
      }
    }
  }

  // Build up vector with one-to-one mapping to field indices.
  const size_t n = decl->fields.dim;
  llvm::SmallVector<VarInitConst, 16> data(n);

  // Fill in explicit initializers.
  for (size_t i = 0; i < n; ++i) {
    VarDeclaration *vd = decl->fields[i];
    auto expl = explicitInitializers.find(vd);
    if (expl != explicitInitializers.end()) {
      const unsigned vd_begin = vd->offset;
      const unsigned vd_end = vd_begin + vd->type->size();

      // Make sure it doesn't overlap any prior initializers (needed for
      // unions). This effectively initializes only the first member with an
      // explicit initializer of a union.
      // Only classes and structs can contain unions / overlapping fields.
      if (type->ty == Tstruct || type->ty == Tclass) {
        bool overlaps = false;
        for (size_t j = 0; j < i; ++j) {
          if (!data[j].first) {
            continue;
          }

          const unsigned f_begin = decl->fields[j]->offset;
          const unsigned f_end = f_begin + decl->fields[j]->type->size();
          if (vd_begin >= f_end || vd_end <= f_begin) {
            continue;
          }

          overlaps = true;
          break;
        }
        if (overlaps)
          continue;
      }

      data[i] = *expl;
    }
  }

  // Fill in implicit initializers
  for (size_t i = 0; i < n; i++) {
    if (data[i].first) {
      continue;
    }

    VarDeclaration *vd = decl->fields[i];

    /* Skip void initializers for unions. DMD bug 3991:
        union X
        {
            int   a = void;
            dchar b = 'a';
        }
    */
    // FIXME: decl->isUnionDeclaration() is always false, the FE lowers
    // UnionDeclarations.
    if (decl->isUnionDeclaration() && vd->_init &&
        vd->_init->isVoidInitializer()) {
      continue;
    }

    unsigned vd_begin = vd->offset;
    unsigned vd_end = vd_begin + vd->type->size();

    /* Skip zero size fields like zero-length static arrays, LDC issue 812:
        class B {
            ubyte[0] test;
        }
    */
    if (vd_begin == vd_end) {
      continue;
    }

    // make sure it doesn't overlap any explicit initializers.
    bool overlaps = false;
    if (type->ty == Tstruct || type->ty == Tclass) {
      // Only classes and structs can have overlapping fields.
      for (size_t j = 0; j < n; ++j) {
        if (i == j || !data[j].first) {
          continue;
        }

        VarDeclaration *it = decl->fields[j];
        unsigned f_begin = it->offset;
        unsigned f_end = f_begin + it->type->size();

        if (vd_begin >= f_end || vd_end <= f_begin) {
          continue;
        }

        overlaps = true;
        break;
      }
    }
    // add if no overlap found
    if (!overlaps) {
      IF_LOG Logger::println("Implicit initializer: %s @+%u", vd->toChars(),
                             vd->offset);
      LOG_SCOPE;

      data[i].first = vd;
      data[i].second = get_default_initializer(vd);
    }
  }

  // Sort data array by offset.
  // TODO: Figure out whether this is really necessary, fields should already
  // be in offset order. Not having do do this would mean we could use a plain
  // llvm::Constant* vector for initializers and avoid all the VarInitConst
  // business.
  std::sort(data.begin(), data.end(), struct_init_data_sort);

  // build array of constants and make sure explicit zero padding is inserted
  // when necessary.
  for (size_t i = 0; i < n; i++) {
    VarDeclaration *vd = data[i].first;
    if (vd == nullptr) {
      continue;
    }

    // Explicitly zero the padding as per TDPL §7.1.1. Otherwise, it would
    // be left uninitialized by LLVM.
    if (offset < vd->offset) {
      add_zeros(constants, offset, vd->offset);
      offset = vd->offset;
    }

    IF_LOG Logger::println("adding field %s", vd->toChars());

    constants.push_back(FillSArrayDims(vd->type, data[i].second));
    offset += getMemberSize(vd->type);
  }
}

IrAggr *getIrAggr(AggregateDeclaration *decl, bool create) {
  if (!isIrAggrCreated(decl) && create) {
    assert(decl->ir->irAggr == NULL);
    decl->ir->irAggr = new IrAggr(decl);
    decl->ir->m_type = IrDsymbol::AggrType;
  }
  assert(decl->ir->irAggr != NULL);
  return decl->ir->irAggr;
}

bool isIrAggrCreated(AggregateDeclaration *decl) {
  int t = decl->ir->type();
  assert(t == IrDsymbol::AggrType || t == IrDsymbol::NotSet);
  return t == IrDsymbol::AggrType;
}