lib/Target/TargetData.cpp

//===-- TargetData.cpp - Data size & alignment routines --------------------==//
// 
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
// 
//===----------------------------------------------------------------------===//
//
// This file defines target properties related to datatype size/offset/alignment
// information.
//
// This structure should be created once, filled in if the defaults are not
// correct and then passed around by const&.  None of the members functions
// require modification to the object.
//
//===----------------------------------------------------------------------===//

#include "llvm/Target/TargetData.h"
#include "llvm/Module.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Constants.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
using namespace llvm;

// Handle the Pass registration stuff necessary to use TargetData's.
namespace {
  // Register the default SparcV9 implementation...
  RegisterPass<TargetData> X("targetdata", "Target Data Layout");
}

static inline void getTypeInfo(const Type *Ty, const TargetData *TD,
			       uint64_t &Size, unsigned char &Alignment);

//===----------------------------------------------------------------------===//
// Support for StructLayout
//===----------------------------------------------------------------------===//

StructLayout::StructLayout(const StructType *ST, const TargetData &TD) {
  StructAlignment = 0;
  StructSize = 0;

  // Loop over each of the elements, placing them in memory...
  for (StructType::element_iterator TI = ST->element_begin(), 
	 TE = ST->element_end(); TI != TE; ++TI) {
    const Type *Ty = *TI;
    unsigned char A;
    unsigned TyAlign;
    uint64_t TySize;
    getTypeInfo(Ty, &TD, TySize, A);
    TyAlign = A;

    // Add padding if necessary to make the data element aligned properly...
    if (StructSize % TyAlign != 0)
      StructSize = (StructSize/TyAlign + 1) * TyAlign;   // Add padding...

    // Keep track of maximum alignment constraint
    StructAlignment = std::max(TyAlign, StructAlignment);

    MemberOffsets.push_back(StructSize);
    StructSize += TySize;                 // Consume space for this data item
  }

  // Empty structures have alignment of 1 byte.
  if (StructAlignment == 0) StructAlignment = 1;

  // Add padding to the end of the struct so that it could be put in an array
  // and all array elements would be aligned correctly.
  if (StructSize % StructAlignment != 0)
    StructSize = (StructSize/StructAlignment + 1) * StructAlignment;
}

//===----------------------------------------------------------------------===//
//                       TargetData Class Implementation
//===----------------------------------------------------------------------===//

TargetData::TargetData(const std::string &TargetName,
                       bool isLittleEndian, unsigned char PtrSize,
                       unsigned char PtrAl, unsigned char DoubleAl,
                       unsigned char FloatAl, unsigned char LongAl, 
                       unsigned char IntAl, unsigned char ShortAl,
                       unsigned char ByteAl) {

  // If this assert triggers, a pass "required" TargetData information, but the
  // top level tool did not provide one for it.  We do not want to default
  // construct, or else we might end up using a bad endianness or pointer size!
  //
  assert(!TargetName.empty() &&
         "ERROR: Tool did not specify a target data to use!");

  LittleEndian     = isLittleEndian;
  PointerSize      = PtrSize;
  PointerAlignment = PtrAl;
  DoubleAlignment  = DoubleAl;
  assert(DoubleAlignment == PtrAl &&
         "Double alignment and pointer alignment agree for now!");
  FloatAlignment   = FloatAl;
  LongAlignment    = LongAl;
  IntAlignment     = IntAl;
  ShortAlignment   = ShortAl;
  ByteAlignment    = ByteAl;
}

TargetData::TargetData(const std::string &ToolName, const Module *M) {
  LittleEndian     = M->getEndianness() != Module::BigEndian;
  PointerSize      = M->getPointerSize() != Module::Pointer64 ? 4 : 8;
  PointerAlignment = PointerSize;
  DoubleAlignment  = PointerSize;
  FloatAlignment   = 4;
  LongAlignment    = 8;
  IntAlignment     = 4;
  ShortAlignment   = 2;
  ByteAlignment    = 1;
}

static std::map<std::pair<const TargetData*,const StructType*>,
                StructLayout> *Layouts = 0;


TargetData::~TargetData() {
  if (Layouts) {
    // Remove any layouts for this TD.
    std::map<std::pair<const TargetData*,
      const StructType*>, StructLayout>::iterator
      I = Layouts->lower_bound(std::make_pair(this, (const StructType*)0));
    while (I != Layouts->end() && I->first.first == this)
      Layouts->erase(I++);
    if (Layouts->empty()) {
      delete Layouts;
      Layouts = 0;
    }
  }
}

const StructLayout *TargetData::getStructLayout(const StructType *Ty) const {
  if (Layouts == 0)
    Layouts = new std::map<std::pair<const TargetData*,const StructType*>,
                           StructLayout>();
  std::map<std::pair<const TargetData*,const StructType*>,
                     StructLayout>::iterator
    I = Layouts->lower_bound(std::make_pair(this, Ty));
  if (I != Layouts->end() && I->first.first == this && I->first.second == Ty)
    return &I->second;
  else {
    return &Layouts->insert(I, std::make_pair(std::make_pair(this, Ty),
                                              StructLayout(Ty, *this)))->second;
  }
}

static inline void getTypeInfo(const Type *Ty, const TargetData *TD,
			       uint64_t &Size, unsigned char &Alignment) {
  assert(Ty->isSized() && "Cannot getTypeInfo() on a type that is unsized!");
  switch (Ty->getPrimitiveID()) {
  case Type::VoidTyID:
  case Type::BoolTyID:
  case Type::UByteTyID:
  case Type::SByteTyID:  Size = 1; Alignment = TD->getByteAlignment(); return;
  case Type::UShortTyID:
  case Type::ShortTyID:  Size = 2; Alignment = TD->getShortAlignment(); return;
  case Type::UIntTyID:
  case Type::IntTyID:    Size = 4; Alignment = TD->getIntAlignment(); return;
  case Type::ULongTyID:
  case Type::LongTyID:   Size = 8; Alignment = TD->getLongAlignment(); return;
  case Type::FloatTyID:  Size = 4; Alignment = TD->getFloatAlignment(); return;
  case Type::DoubleTyID: Size = 8; Alignment = TD->getDoubleAlignment(); return;
  case Type::LabelTyID:
  case Type::PointerTyID:
    Size = TD->getPointerSize(); Alignment = TD->getPointerAlignment();
    return;
  case Type::ArrayTyID: {
    const ArrayType *ATy = (const ArrayType *)Ty;
    getTypeInfo(ATy->getElementType(), TD, Size, Alignment);
    Size *= ATy->getNumElements();
    return;
  }
  case Type::StructTyID: {
    // Get the layout annotation... which is lazily created on demand.
    const StructLayout *Layout = TD->getStructLayout((const StructType*)Ty);
    Size = Layout->StructSize; Alignment = Layout->StructAlignment;
    return;
  }
    
  case Type::TypeTyID:
  default:
    assert(0 && "Bad type for getTypeInfo!!!");
    return;
  }
}

uint64_t TargetData::getTypeSize(const Type *Ty) const {
  uint64_t Size;
  unsigned char Align;
  getTypeInfo(Ty, this, Size, Align);
  return Size;
}

unsigned char TargetData::getTypeAlignment(const Type *Ty) const {
  uint64_t Size;
  unsigned char Align;
  getTypeInfo(Ty, this, Size, Align);
  return Align;
}

/// getIntPtrType - Return an unsigned integer type that is the same size or
/// greater to the host pointer size.
const Type *TargetData::getIntPtrType() const {
  switch (getPointerSize()) {
  default: assert(0 && "Unknown pointer size!");
  case 2: return Type::UShortTy;
  case 4: return Type::UIntTy;
  case 8: return Type::ULongTy;
  }
}


uint64_t TargetData::getIndexedOffset(const Type *ptrTy,
				      const std::vector<Value*> &Idx) const {
  const Type *Ty = ptrTy;
  assert(isa<PointerType>(Ty) && "Illegal argument for getIndexedOffset()");
  uint64_t Result = 0;

  generic_gep_type_iterator<std::vector<Value*>::const_iterator>
    TI = gep_type_begin(ptrTy, Idx.begin(), Idx.end());
  for (unsigned CurIDX = 0; CurIDX != Idx.size(); ++CurIDX, ++TI) {
    if (const StructType *STy = dyn_cast<StructType>(*TI)) {
      assert(Idx[CurIDX]->getType() == Type::UIntTy && "Illegal struct idx");
      unsigned FieldNo = cast<ConstantUInt>(Idx[CurIDX])->getValue();

      // Get structure layout information...
      const StructLayout *Layout = getStructLayout(STy);

      // Add in the offset, as calculated by the structure layout info...
      assert(FieldNo < Layout->MemberOffsets.size() &&"FieldNo out of range!");
      Result += Layout->MemberOffsets[FieldNo];

      // Update Ty to refer to current element
      Ty = STy->getElementType(FieldNo);
    } else {
      // Update Ty to refer to current element
      Ty = cast<SequentialType>(Ty)->getElementType();

      // Get the array index and the size of each array element.
      int64_t arrayIdx = cast<ConstantInt>(Idx[CurIDX])->getRawValue();
      Result += arrayIdx * (int64_t)getTypeSize(Ty);
    }
  }

  return Result;
}