TargetData.h revision edc1d159841fd279d58177bfd6ac4bc1f616d91a 
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};
43/// Target alignment element.
44///
45/// Stores the alignment data associated with a given alignment type (pointer,
46/// integer, packed/vector, float) and type bit width.
47///
48/// @note The unusual order of elements in the structure attempts to reduce
49/// padding and make the structure slightly more cache friendly.
50struct TargetAlignElem {
51  AlignTypeEnum       AlignType : 8;  //< Alignment type (AlignTypeEnum)
52  unsigned char       ABIAlign;       //< ABI alignment for this type/bitw
53  unsigned char       PrefAlign;      //< Pref. alignment for this type/bitw
54  uint32_t            TypeBitWidth;   //< Type bit width
55
56  /// Initializer
57  static TargetAlignElem get(AlignTypeEnum align_type, unsigned char abi_align,
58                             unsigned char pref_align, uint32_t bit_width);
59  /// Equality predicate
60  bool operator==(const TargetAlignElem &rhs) const;
61  /// output stream operator
62  std::ostream &dump(std::ostream &os) const;
63};
64
65class TargetData : public ImmutablePass {
66private:
67  bool          LittleEndian;          ///< Defaults to false
68  unsigned char PointerMemSize;        ///< Pointer size in bytes
69  unsigned char PointerABIAlign;       ///< Pointer ABI alignment
70  unsigned char PointerPrefAlign;      ///< Pointer preferred alignment
71
72  //! Where the primitive type alignment data is stored.
73  /*!
74   @sa init().
75   @note Could support multiple size pointer alignments, e.g., 32-bit pointers
76   vs. 64-bit pointers by extending TargetAlignment, but for now, we don't.
77   */
78  SmallVector<TargetAlignElem, 16> Alignments;
79  //! Alignment iterator shorthand
80  typedef SmallVector<TargetAlignElem, 16>::iterator align_iterator;
81  //! Constant alignment iterator shorthand
82  typedef SmallVector<TargetAlignElem, 16>::const_iterator align_const_iterator;
83  //! Invalid alignment.
84  /*!
85    This member is a signal that a requested alignment type and bit width were
86    not found in the SmallVector.
87   */
88  static const TargetAlignElem InvalidAlignmentElem;
89
90  //! Set/initialize target alignments
91  void setAlignment(AlignTypeEnum align_type, unsigned char abi_align,
92                    unsigned char pref_align, uint32_t bit_width);
93  unsigned getAlignmentInfo(AlignTypeEnum align_type, uint32_t bit_width,
94                            bool ABIAlign) const;
95  //! Internal helper method that returns requested alignment for type.
96  unsigned char getAlignment(const Type *Ty, bool abi_or_pref) const;
97
98  /// Valid alignment predicate.
99  ///
100  /// Predicate that tests a TargetAlignElem reference returned by get() against
101  /// InvalidAlignmentElem.
102  inline bool validAlignment(const TargetAlignElem &align) const {
103    return (&align != &InvalidAlignmentElem);
104  }
105
106public:
107  /// Default ctor.
108  ///
109  /// @note This has to exist, because this is a pass, but it should never be
110  /// used.
111  TargetData() {
112    assert(0 && "ERROR: Bad TargetData ctor used.  "
113           "Tool did not specify a TargetData to use?");
114    abort();
115  }
116
117  /// Constructs a TargetData from a specification string. See init().
118  TargetData(const std::string &TargetDescription) {
119    init(TargetDescription);
120  }
121
122  /// Initialize target data from properties stored in the module.
123  TargetData(const Module *M);
124
125  TargetData(const TargetData &TD) :
126    ImmutablePass(),
127    LittleEndian(TD.isLittleEndian()),
128    PointerMemSize(TD.PointerMemSize),
129    PointerABIAlign(TD.PointerABIAlign),
130    PointerPrefAlign(TD.PointerPrefAlign),
131    Alignments(TD.Alignments)
132  { }
133
134  ~TargetData();  // Not virtual, do not subclass this class
135
136  //! Parse a target data layout string and initialize TargetData alignments.
137  void init(const std::string &TargetDescription);
138
139  /// Target endianness...
140  bool          isLittleEndian()       const { return     LittleEndian; }
141  bool          isBigEndian()          const { return    !LittleEndian; }
142
143  /// getStringRepresentation - Return the string representation of the
144  /// TargetData.  This representation is in the same format accepted by the
145  /// string constructor above.
146  std::string getStringRepresentation() const;
147  /// Target pointer alignment
148  unsigned char getPointerABIAlignment() const { return PointerABIAlign; }
149  /// Return target's alignment for stack-based pointers
150  unsigned char getPointerPrefAlignment() const { return PointerPrefAlign; }
151  /// Target pointer size
152  unsigned char getPointerSize()         const { return PointerMemSize; }
153  /// Target pointer size, in bits
154  unsigned char getPointerSizeInBits()   const { return 8*PointerMemSize; }
155
156  /// getTypeSize - Return the number of bytes necessary to hold the specified
157  /// type.
158  uint64_t getTypeSize(const Type *Ty) const;
159
160  /// getTypeSizeInBits - Return the number of bits necessary to hold the
161  /// specified type.
162  uint64_t getTypeSizeInBits(const Type* Ty) const;
163
164  /// getABITypeAlignment - Return the minimum ABI-required alignment for the
165  /// specified type.
166  unsigned char getABITypeAlignment(const Type *Ty) const;
167
168  /// getPrefTypeAlignment - Return the preferred stack/global alignment for
169  /// the specified type.
170  unsigned char getPrefTypeAlignment(const Type *Ty) const;
171
172  /// getPreferredTypeAlignmentShift - Return the preferred alignment for the
173  /// specified type, returned as log2 of the value (a shift amount).
174  ///
175  unsigned char getPreferredTypeAlignmentShift(const Type *Ty) const;
176
177  /// getIntPtrType - Return an unsigned integer type that is the same size or
178  /// greater to the host pointer size.
179  ///
180  const Type *getIntPtrType() const;
181
182  /// getIndexedOffset - return the offset from the beginning of the type for the
183  /// specified indices.  This is used to implement getelementptr.
184  ///
185  uint64_t getIndexedOffset(const Type *Ty,
186                            Value* const* Indices, unsigned NumIndices) const;
187
188  /// getStructLayout - Return a StructLayout object, indicating the alignment
189  /// of the struct, its size, and the offsets of its fields.  Note that this
190  /// information is lazily cached.
191  const StructLayout *getStructLayout(const StructType *Ty) const;
192
193  /// InvalidateStructLayoutInfo - TargetData speculatively caches StructLayout
194  /// objects.  If a TargetData object is alive when types are being refined and
195  /// removed, this method must be called whenever a StructType is removed to
196  /// avoid a dangling pointer in this cache.
197  void InvalidateStructLayoutInfo(const StructType *Ty) const;
198
199  /// getPreferredAlignmentLog - Return the preferred alignment of the
200  /// specified global, returned in log form.  This includes an explicitly
201  /// requested alignment (if the global has one).
202  unsigned getPreferredAlignmentLog(const GlobalVariable *GV) const;
203};
204
205/// StructLayout - used to lazily calculate structure layout information for a
206/// target machine, based on the TargetData structure.
207///
208class StructLayout {
209  uint64_t StructSize;
210  unsigned StructAlignment;
211  unsigned NumElements;
212  uint64_t MemberOffsets[1];  // variable sized array!
213public:
214
215  uint64_t getSizeInBytes() const {
216    return StructSize;
217  }
218
219  unsigned getAlignment() const {
220    return StructAlignment;
221  }
222
223  /// getElementContainingOffset - Given a valid offset into the structure,
224  /// return the structure index that contains it.
225  ///
226  unsigned getElementContainingOffset(uint64_t Offset) const;
227
228  uint64_t getElementOffset(unsigned Idx) const {
229    assert(Idx < NumElements && "Invalid element idx!");
230    return MemberOffsets[Idx];
231  }
232
233private:
234  friend class TargetData;   // Only TargetData can create this class
235  StructLayout(const StructType *ST, const TargetData &TD);
236};
237
238} // End llvm namespace
239
240#endif
241