TargetData.h revision 7ed47a13356daed2a34cd2209a31f92552e3bdd8 
1//===-- llvm/Target/TargetData.h - Data size & alignment info ---*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// 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  /// getTypeSizeInBits - Return the number of bits necessary to hold the
159  /// specified type.  For example, returns 36 for i36 and 80 for x86_fp80.
160  uint64_t getTypeSizeInBits(const Type* Ty) const;
161
162  /// getTypeStoreSize - Return the maximum number of bytes that may be
163  /// overwritten by storing the specified type.  For example, returns 5
164  /// for i36 and 10 for x86_fp80.
165  uint64_t getTypeStoreSize(const Type *Ty) const {
166    return (getTypeSizeInBits(Ty)+7)/8;
167  }
168
169  /// getTypeStoreSizeInBits - Return the maximum number of bits that may be
170  /// overwritten by storing the specified type; always a multiple of 8.  For
171  /// example, returns 40 for i36 and 80 for x86_fp80.
172  uint64_t getTypeStoreSizeInBits(const Type *Ty) const {
173    return 8*getTypeStoreSize(Ty);
174  }
175
176  /// getABITypeSize - Return the offset in bytes between successive objects
177  /// of the specified type, including alignment padding.  This is the amount
178  /// that alloca reserves for this type.  For example, returns 12 or 16 for
179  /// x86_fp80, depending on alignment.
180  uint64_t getABITypeSize(const Type* Ty) const {
181    unsigned char Align = getABITypeAlignment(Ty);
182    return (getTypeStoreSize(Ty) + Align - 1)/Align*Align;
183  }
184
185  /// getABITypeSizeInBits - Return the offset in bits between successive
186  /// objects of the specified type, including alignment padding; always a
187  /// multiple of 8.  This is the amount that alloca reserves for this type.
188  /// For example, returns 96 or 128 for x86_fp80, depending on alignment.
189  uint64_t getABITypeSizeInBits(const Type* Ty) const {
190    return 8*getABITypeSize(Ty);
191  }
192
193  /// getABITypeAlignment - Return the minimum ABI-required alignment for the
194  /// specified type.
195  unsigned char getABITypeAlignment(const Type *Ty) const;
196
197  /// getCallFrameTypeAlignment - Return the minimum ABI-required alignment
198  /// for the specified type when it is part of a call frame.
199  unsigned char getCallFrameTypeAlignment(const Type *Ty) const;
200
201
202  /// getPrefTypeAlignment - Return the preferred stack/global alignment for
203  /// the specified type.
204  unsigned char getPrefTypeAlignment(const Type *Ty) const;
205
206  /// getPreferredTypeAlignmentShift - Return the preferred alignment for the
207  /// specified type, returned as log2 of the value (a shift amount).
208  ///
209  unsigned char getPreferredTypeAlignmentShift(const Type *Ty) const;
210
211  /// getIntPtrType - Return an unsigned integer type that is the same size or
212  /// greater to the host pointer size.
213  ///
214  const Type *getIntPtrType() const;
215
216  /// getIndexedOffset - return the offset from the beginning of the type for the
217  /// specified indices.  This is used to implement getelementptr.
218  ///
219  uint64_t getIndexedOffset(const Type *Ty,
220                            Value* const* Indices, unsigned NumIndices) const;
221
222  /// getStructLayout - Return a StructLayout object, indicating the alignment
223  /// of the struct, its size, and the offsets of its fields.  Note that this
224  /// information is lazily cached.
225  const StructLayout *getStructLayout(const StructType *Ty) const;
226
227  /// InvalidateStructLayoutInfo - TargetData speculatively caches StructLayout
228  /// objects.  If a TargetData object is alive when types are being refined and
229  /// removed, this method must be called whenever a StructType is removed to
230  /// avoid a dangling pointer in this cache.
231  void InvalidateStructLayoutInfo(const StructType *Ty) const;
232
233  /// getPreferredAlignmentLog - Return the preferred alignment of the
234  /// specified global, returned in log form.  This includes an explicitly
235  /// requested alignment (if the global has one).
236  unsigned getPreferredAlignmentLog(const GlobalVariable *GV) const;
237
238  static char ID; // Pass identification, replacement for typeid
239};
240
241/// StructLayout - used to lazily calculate structure layout information for a
242/// target machine, based on the TargetData structure.
243///
244class StructLayout {
245  uint64_t StructSize;
246  unsigned StructAlignment;
247  unsigned NumElements;
248  uint64_t MemberOffsets[1];  // variable sized array!
249public:
250
251  uint64_t getSizeInBytes() const {
252    return StructSize;
253  }
254
255  uint64_t getSizeInBits() const {
256    return 8*StructSize;
257  }
258
259  unsigned getAlignment() const {
260    return StructAlignment;
261  }
262
263  /// getElementContainingOffset - Given a valid offset into the structure,
264  /// return the structure index that contains it.
265  ///
266  unsigned getElementContainingOffset(uint64_t Offset) const;
267
268  uint64_t getElementOffset(unsigned Idx) const {
269    assert(Idx < NumElements && "Invalid element idx!");
270    return MemberOffsets[Idx];
271  }
272
273  uint64_t getElementOffsetInBits(unsigned Idx) const {
274    return getElementOffset(Idx)*8;
275  }
276
277private:
278  friend class TargetData;   // Only TargetData can create this class
279  StructLayout(const StructType *ST, const TargetData &TD);
280};
281
282} // End llvm namespace
283
284#endif
285