TargetData.h revision 2e07494170d5f56805b7a6c1b70808fc2a157052 
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/ADT/SmallVector.h"
25
26namespace llvm {
27
28class Value;
29class Type;
30class IntegerType;
31class StructType;
32class StructLayout;
33class GlobalVariable;
34class LLVMContext;
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  /// Alignments- Where the primitive type alignment data is stored.
74  ///
75  /// @sa init().
76  /// @note Could support multiple size pointer alignments, e.g., 32-bit
77  /// pointers vs. 64-bit pointers by extending TargetAlignment, but for now,
78  /// we don't.
79  SmallVector<TargetAlignElem, 16> Alignments;
80
81
82
83  /*!
84    This member is a signal that a requested alignment type and bit width were
85    not found in the SmallVector.
86   */
87  static const TargetAlignElem InvalidAlignmentElem;
88
89  // Opaque pointer for the StructType -> StructLayout map.
90  mutable void *LayoutMap;
91
92  //! Set/initialize target alignments
93  void setAlignment(AlignTypeEnum align_type, unsigned char abi_align,
94                    unsigned char pref_align, uint32_t bit_width);
95  unsigned getAlignmentInfo(AlignTypeEnum align_type, uint32_t bit_width,
96                            bool ABIAlign, const Type *Ty) const;
97  //! Internal helper method that returns requested alignment for type.
98  unsigned char getAlignment(const Type *Ty, bool abi_or_pref) const;
99
100  /// Valid alignment predicate.
101  ///
102  /// Predicate that tests a TargetAlignElem reference returned by get() against
103  /// InvalidAlignmentElem.
104  bool validAlignment(const TargetAlignElem &align) const {
105    return &align != &InvalidAlignmentElem;
106  }
107
108public:
109  /// Default ctor.
110  ///
111  /// @note This has to exist, because this is a pass, but it should never be
112  /// used.
113  TargetData();
114
115  /// Constructs a TargetData from a specification string. See init().
116  explicit TargetData(StringRef TargetDescription)
117    : ImmutablePass(&ID) {
118    init(TargetDescription);
119  }
120
121  /// Initialize target data from properties stored in the module.
122  explicit TargetData(const Module *M);
123
124  TargetData(const TargetData &TD) :
125    ImmutablePass(&ID),
126    LittleEndian(TD.isLittleEndian()),
127    PointerMemSize(TD.PointerMemSize),
128    PointerABIAlign(TD.PointerABIAlign),
129    PointerPrefAlign(TD.PointerPrefAlign),
130    Alignments(TD.Alignments),
131    LayoutMap(0)
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(StringRef 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  /// Size examples:
157  ///
158  /// Type        SizeInBits  StoreSizeInBits  AllocSizeInBits[*]
159  /// ----        ----------  ---------------  ---------------
160  ///  i1            1           8                8
161  ///  i8            8           8                8
162  ///  i19          19          24               32
163  ///  i32          32          32               32
164  ///  i100        100         104              128
165  ///  i128        128         128              128
166  ///  Float        32          32               32
167  ///  Double       64          64               64
168  ///  X86_FP80     80          80               96
169  ///
170  /// [*] The alloc size depends on the alignment, and thus on the target.
171  ///     These values are for x86-32 linux.
172
173  /// getTypeSizeInBits - Return the number of bits necessary to hold the
174  /// specified type.  For example, returns 36 for i36 and 80 for x86_fp80.
175  uint64_t getTypeSizeInBits(const Type* Ty) const;
176
177  /// getTypeStoreSize - Return the maximum number of bytes that may be
178  /// overwritten by storing the specified type.  For example, returns 5
179  /// for i36 and 10 for x86_fp80.
180  uint64_t getTypeStoreSize(const Type *Ty) const {
181    return (getTypeSizeInBits(Ty)+7)/8;
182  }
183
184  /// getTypeStoreSizeInBits - Return the maximum number of bits that may be
185  /// overwritten by storing the specified type; always a multiple of 8.  For
186  /// example, returns 40 for i36 and 80 for x86_fp80.
187  uint64_t getTypeStoreSizeInBits(const Type *Ty) const {
188    return 8*getTypeStoreSize(Ty);
189  }
190
191  /// getTypeAllocSize - Return the offset in bytes between successive objects
192  /// of the specified type, including alignment padding.  This is the amount
193  /// that alloca reserves for this type.  For example, returns 12 or 16 for
194  /// x86_fp80, depending on alignment.
195  uint64_t getTypeAllocSize(const Type* Ty) const {
196    // Round up to the next alignment boundary.
197    return RoundUpAlignment(getTypeStoreSize(Ty), getABITypeAlignment(Ty));
198  }
199
200  /// getTypeAllocSizeInBits - Return the offset in bits between successive
201  /// objects of the specified type, including alignment padding; always a
202  /// multiple of 8.  This is the amount that alloca reserves for this type.
203  /// For example, returns 96 or 128 for x86_fp80, depending on alignment.
204  uint64_t getTypeAllocSizeInBits(const Type* Ty) const {
205    return 8*getTypeAllocSize(Ty);
206  }
207
208  /// getABITypeAlignment - Return the minimum ABI-required alignment for the
209  /// specified type.
210  unsigned char getABITypeAlignment(const Type *Ty) const;
211
212  /// getCallFrameTypeAlignment - Return the minimum ABI-required alignment
213  /// for the specified type when it is part of a call frame.
214  unsigned char getCallFrameTypeAlignment(const Type *Ty) const;
215
216
217  /// getPrefTypeAlignment - Return the preferred stack/global alignment for
218  /// the specified type.  This is always at least as good as the ABI alignment.
219  unsigned char getPrefTypeAlignment(const Type *Ty) const;
220
221  /// getPreferredTypeAlignmentShift - Return the preferred alignment for the
222  /// specified type, returned as log2 of the value (a shift amount).
223  ///
224  unsigned char getPreferredTypeAlignmentShift(const Type *Ty) const;
225
226  /// getIntPtrType - Return an unsigned integer type that is the same size or
227  /// greater to the host pointer size.
228  ///
229  const IntegerType *getIntPtrType(LLVMContext &C) const;
230
231  /// getIndexedOffset - return the offset from the beginning of the type for
232  /// the specified indices.  This is used to implement getelementptr.
233  ///
234  uint64_t getIndexedOffset(const Type *Ty,
235                            Value* const* Indices, unsigned NumIndices) const;
236
237  /// getStructLayout - Return a StructLayout object, indicating the alignment
238  /// of the struct, its size, and the offsets of its fields.  Note that this
239  /// information is lazily cached.
240  const StructLayout *getStructLayout(const StructType *Ty) const;
241
242  /// InvalidateStructLayoutInfo - TargetData speculatively caches StructLayout
243  /// objects.  If a TargetData object is alive when types are being refined and
244  /// removed, this method must be called whenever a StructType is removed to
245  /// avoid a dangling pointer in this cache.
246  void InvalidateStructLayoutInfo(const StructType *Ty) const;
247
248  /// getPreferredAlignment - Return the preferred alignment of the specified
249  /// global.  This includes an explicitly requested alignment (if the global
250  /// has one).
251  unsigned getPreferredAlignment(const GlobalVariable *GV) const;
252
253  /// getPreferredAlignmentLog - Return the preferred alignment of the
254  /// specified global, returned in log form.  This includes an explicitly
255  /// requested alignment (if the global has one).
256  unsigned getPreferredAlignmentLog(const GlobalVariable *GV) const;
257
258  /// RoundUpAlignment - Round the specified value up to the next alignment
259  /// boundary specified by Alignment.  For example, 7 rounded up to an
260  /// alignment boundary of 4 is 8.  8 rounded up to the alignment boundary of 4
261  /// is 8 because it is already aligned.
262  template <typename UIntTy>
263  static UIntTy RoundUpAlignment(UIntTy Val, unsigned Alignment) {
264    assert((Alignment & (Alignment-1)) == 0 && "Alignment must be power of 2!");
265    return (Val + (Alignment-1)) & ~UIntTy(Alignment-1);
266  }
267
268  static char ID; // Pass identification, replacement for typeid
269};
270
271/// StructLayout - used to lazily calculate structure layout information for a
272/// target machine, based on the TargetData structure.
273///
274class StructLayout {
275  uint64_t StructSize;
276  unsigned StructAlignment;
277  unsigned NumElements;
278  uint64_t MemberOffsets[1];  // variable sized array!
279public:
280
281  uint64_t getSizeInBytes() const {
282    return StructSize;
283  }
284
285  uint64_t getSizeInBits() const {
286    return 8*StructSize;
287  }
288
289  unsigned getAlignment() const {
290    return StructAlignment;
291  }
292
293  /// getElementContainingOffset - Given a valid byte offset into the structure,
294  /// return the structure index that contains it.
295  ///
296  unsigned getElementContainingOffset(uint64_t Offset) const;
297
298  uint64_t getElementOffset(unsigned Idx) const {
299    assert(Idx < NumElements && "Invalid element idx!");
300    return MemberOffsets[Idx];
301  }
302
303  uint64_t getElementOffsetInBits(unsigned Idx) const {
304    return getElementOffset(Idx)*8;
305  }
306
307private:
308  friend class TargetData;   // Only TargetData can create this class
309  StructLayout(const StructType *ST, const TargetData &TD);
310};
311
312} // End llvm namespace
313
314#endif
315