TargetData.h revision 3b5b4cd1a50e3fe8748a8626cca3c643f5681f5a 
1//===-- llvm/Target/TargetData.h - Data size & alignment info ---*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file defines target properties related to datatype size/offset/alignment
11// information.  It uses lazy annotations to cache information about how
12// structure types are laid out and used.
13//
14// This structure should be created once, filled in if the defaults are not
15// correct and then passed around by const&.  None of the members functions
16// require modification to the object.
17//
18//===----------------------------------------------------------------------===//
19
20#ifndef LLVM_TARGET_TARGETDATA_H
21#define LLVM_TARGET_TARGETDATA_H
22
23#include "llvm/Pass.h"
24#include "llvm/Support/DataTypes.h"
25#include "llvm/ADT/SmallVector.h"
26#include <string>
27
28namespace llvm {
29
30class Value;
31class Type;
32class StructType;
33class StructLayout;
34class GlobalVariable;
35
36/// Enum used to categorize the alignment types stored by TargetAlignElem
37enum AlignTypeEnum {
38  INTEGER_ALIGN = 'i',               ///< Integer type alignment
39  VECTOR_ALIGN = 'v',                ///< Vector type alignment
40  FLOAT_ALIGN = 'f',                 ///< Floating point type alignment
41  AGGREGATE_ALIGN = 'a',             ///< Aggregate alignment
42  STACK_ALIGN = 's'                  ///< Stack objects alignment
43};
44/// Target alignment element.
45///
46/// Stores the alignment data associated with a given alignment type (pointer,
47/// integer, vector, float) and type bit width.
48///
49/// @note The unusual order of elements in the structure attempts to reduce
50/// padding and make the structure slightly more cache friendly.
51struct TargetAlignElem {
52  AlignTypeEnum       AlignType : 8;  //< Alignment type (AlignTypeEnum)
53  unsigned char       ABIAlign;       //< ABI alignment for this type/bitw
54  unsigned char       PrefAlign;      //< Pref. alignment for this type/bitw
55  uint32_t            TypeBitWidth;   //< Type bit width
56
57  /// Initializer
58  static TargetAlignElem get(AlignTypeEnum align_type, unsigned char abi_align,
59                             unsigned char pref_align, uint32_t bit_width);
60  /// Equality predicate
61  bool operator==(const TargetAlignElem &rhs) const;
62  /// output stream operator
63  std::ostream &dump(std::ostream &os) const;
64};
65
66class TargetData : public ImmutablePass {
67private:
68  bool          LittleEndian;          ///< Defaults to false
69  unsigned char PointerMemSize;        ///< Pointer size in bytes
70  unsigned char PointerABIAlign;       ///< Pointer ABI alignment
71  unsigned char PointerPrefAlign;      ///< Pointer preferred alignment
72
73  //! Where the primitive type alignment data is stored.
74  /*!
75   @sa init().
76   @note Could support multiple size pointer alignments, e.g., 32-bit pointers
77   vs. 64-bit pointers by extending TargetAlignment, but for now, we don't.
78   */
79  SmallVector<TargetAlignElem, 16> Alignments;
80  //! Alignment iterator shorthand
81  typedef SmallVector<TargetAlignElem, 16>::iterator align_iterator;
82  //! Constant alignment iterator shorthand
83  typedef SmallVector<TargetAlignElem, 16>::const_iterator align_const_iterator;
84  //! Invalid alignment.
85  /*!
86    This member is a signal that a requested alignment type and bit width were
87    not found in the SmallVector.
88   */
89  static const TargetAlignElem InvalidAlignmentElem;
90
91  //! Set/initialize target alignments
92  void setAlignment(AlignTypeEnum align_type, unsigned char abi_align,
93                    unsigned char pref_align, uint32_t bit_width);
94  unsigned getAlignmentInfo(AlignTypeEnum align_type, uint32_t bit_width,
95                            bool ABIAlign) const;
96  //! Internal helper method that returns requested alignment for type.
97  unsigned char getAlignment(const Type *Ty, bool abi_or_pref) const;
98
99  /// Valid alignment predicate.
100  ///
101  /// Predicate that tests a TargetAlignElem reference returned by get() against
102  /// InvalidAlignmentElem.
103  inline bool validAlignment(const TargetAlignElem &align) const {
104    return (&align != &InvalidAlignmentElem);
105  }
106
107public:
108  /// Default ctor.
109  ///
110  /// @note This has to exist, because this is a pass, but it should never be
111  /// used.
112  TargetData() : ImmutablePass(intptr_t(&ID)) {
113    assert(0 && "ERROR: Bad TargetData ctor used.  "
114           "Tool did not specify a TargetData to use?");
115    abort();
116  }
117
118  /// Constructs a TargetData from a specification string. See init().
119  explicit TargetData(const std::string &TargetDescription)
120    : ImmutablePass(intptr_t(&ID)) {
121    init(TargetDescription);
122  }
123
124  /// Initialize target data from properties stored in the module.
125  explicit TargetData(const Module *M);
126
127  TargetData(const TargetData &TD) :
128    ImmutablePass(intptr_t(&ID)),
129    LittleEndian(TD.isLittleEndian()),
130    PointerMemSize(TD.PointerMemSize),
131    PointerABIAlign(TD.PointerABIAlign),
132    PointerPrefAlign(TD.PointerPrefAlign),
133    Alignments(TD.Alignments)
134  { }
135
136  ~TargetData();  // Not virtual, do not subclass this class
137
138  //! Parse a target data layout string and initialize TargetData alignments.
139  void init(const std::string &TargetDescription);
140
141  /// Target endianness...
142  bool          isLittleEndian()       const { return     LittleEndian; }
143  bool          isBigEndian()          const { return    !LittleEndian; }
144
145  /// getStringRepresentation - Return the string representation of the
146  /// TargetData.  This representation is in the same format accepted by the
147  /// string constructor above.
148  std::string getStringRepresentation() const;
149  /// Target pointer alignment
150  unsigned char getPointerABIAlignment() const { return PointerABIAlign; }
151  /// Return target's alignment for stack-based pointers
152  unsigned char getPointerPrefAlignment() const { return PointerPrefAlign; }
153  /// Target pointer size
154  unsigned char getPointerSize()         const { return PointerMemSize; }
155  /// Target pointer size, in bits
156  unsigned char getPointerSizeInBits()   const { return 8*PointerMemSize; }
157
158  /// getTypeSize - Return the number of bytes necessary to hold the specified
159  /// type.
160  uint64_t getTypeSize(const Type *Ty) const;
161
162  /// getABITypeSize - Return the number of bytes allocated for the specified
163  /// type when used as an element in a larger object, including alignment
164  /// padding.
165  uint64_t getABITypeSize(const Type *Ty) const {
166    unsigned char Align = getABITypeAlignment(Ty);
167    return (getTypeSize(Ty) + Align - 1)/Align*Align;
168  }
169
170  /// getTypeSizeInBits - Return the number of bits necessary to hold the
171  /// specified type.
172  uint64_t getTypeSizeInBits(const Type* Ty) const;
173
174  /// getABITypeSizeInBits - Return the number of bytes allocated for the
175  /// specified type when used as an element in a larger object, including
176  ///  alignment padding.
177  uint64_t getABITypeSizeInBits(const Type* Ty) const;
178
179  /// getABITypeAlignment - Return the minimum ABI-required alignment for the
180  /// specified type.
181  unsigned char getABITypeAlignment(const Type *Ty) const;
182
183  /// getCallFrameTypeAlignment - Return the minimum ABI-required alignment
184  /// for the specified type when it is part of a call frame.
185  unsigned char getCallFrameTypeAlignment(const Type *Ty) const;
186
187
188  /// getPrefTypeAlignment - Return the preferred stack/global alignment for
189  /// the specified type.
190  unsigned char getPrefTypeAlignment(const Type *Ty) const;
191
192  /// getPreferredTypeAlignmentShift - Return the preferred alignment for the
193  /// specified type, returned as log2 of the value (a shift amount).
194  ///
195  unsigned char getPreferredTypeAlignmentShift(const Type *Ty) const;
196
197  /// getIntPtrType - Return an unsigned integer type that is the same size or
198  /// greater to the host pointer size.
199  ///
200  const Type *getIntPtrType() const;
201
202  /// getIndexedOffset - return the offset from the beginning of the type for the
203  /// specified indices.  This is used to implement getelementptr.
204  ///
205  uint64_t getIndexedOffset(const Type *Ty,
206                            Value* const* Indices, unsigned NumIndices) const;
207
208  /// getStructLayout - Return a StructLayout object, indicating the alignment
209  /// of the struct, its size, and the offsets of its fields.  Note that this
210  /// information is lazily cached.
211  const StructLayout *getStructLayout(const StructType *Ty) const;
212
213  /// InvalidateStructLayoutInfo - TargetData speculatively caches StructLayout
214  /// objects.  If a TargetData object is alive when types are being refined and
215  /// removed, this method must be called whenever a StructType is removed to
216  /// avoid a dangling pointer in this cache.
217  void InvalidateStructLayoutInfo(const StructType *Ty) const;
218
219  /// getPreferredAlignmentLog - Return the preferred alignment of the
220  /// specified global, returned in log form.  This includes an explicitly
221  /// requested alignment (if the global has one).
222  unsigned getPreferredAlignmentLog(const GlobalVariable *GV) const;
223
224  static char ID; // Pass identification, replacement for typeid
225};
226
227/// StructLayout - used to lazily calculate structure layout information for a
228/// target machine, based on the TargetData structure.
229///
230class StructLayout {
231  uint64_t StructSize;
232  unsigned StructAlignment;
233  unsigned NumElements;
234  uint64_t MemberOffsets[1];  // variable sized array!
235public:
236
237  uint64_t getSizeInBytes() const {
238    return StructSize;
239  }
240
241  unsigned getAlignment() const {
242    return StructAlignment;
243  }
244
245  /// getElementContainingOffset - Given a valid offset into the structure,
246  /// return the structure index that contains it.
247  ///
248  unsigned getElementContainingOffset(uint64_t Offset) const;
249
250  uint64_t getElementOffset(unsigned Idx) const {
251    assert(Idx < NumElements && "Invalid element idx!");
252    return MemberOffsets[Idx];
253  }
254
255private:
256  friend class TargetData;   // Only TargetData can create this class
257  StructLayout(const StructType *ST, const TargetData &TD);
258};
259
260} // End llvm namespace
261
262#endif
263