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#include "llvm/Support/DataTypes.h"
26
27namespace llvm {
28
29class Value;
30class Type;
31class IntegerType;
32class StructType;
33class StructLayout;
34class GlobalVariable;
35class LLVMContext;
36template<typename T>
37class ArrayRef;
38
39/// Enum used to categorize the alignment types stored by TargetAlignElem
40enum AlignTypeEnum {
41  INTEGER_ALIGN = 'i',               ///< Integer type alignment
42  VECTOR_ALIGN = 'v',                ///< Vector type alignment
43  FLOAT_ALIGN = 'f',                 ///< Floating point type alignment
44  AGGREGATE_ALIGN = 'a',             ///< Aggregate alignment
45  STACK_ALIGN = 's'                  ///< Stack objects alignment
46};
47
48/// Target alignment element.
49///
50/// Stores the alignment data associated with a given alignment type (pointer,
51/// integer, vector, float) and type bit width.
52///
53/// @note The unusual order of elements in the structure attempts to reduce
54/// padding and make the structure slightly more cache friendly.
55struct TargetAlignElem {
56  unsigned AlignType    : 8;  ///< Alignment type (AlignTypeEnum)
57  unsigned TypeBitWidth : 24; ///< Type bit width
58  unsigned ABIAlign     : 16; ///< ABI alignment for this type/bitw
59  unsigned PrefAlign    : 16; ///< Pref. alignment for this type/bitw
60
61  /// Initializer
62  static TargetAlignElem get(AlignTypeEnum align_type, unsigned abi_align,
63                             unsigned pref_align, uint32_t bit_width);
64  /// Equality predicate
65  bool operator==(const TargetAlignElem &rhs) const;
66};
67
68/// TargetData - This class holds a parsed version of the target data layout
69/// string in a module and provides methods for querying it.  The target data
70/// layout string is specified *by the target* - a frontend generating LLVM IR
71/// is required to generate the right target data for the target being codegen'd
72/// to.  If some measure of portability is desired, an empty string may be
73/// specified in the module.
74class TargetData : public ImmutablePass {
75private:
76  bool          LittleEndian;          ///< Defaults to false
77  unsigned      PointerMemSize;        ///< Pointer size in bytes
78  unsigned      PointerABIAlign;       ///< Pointer ABI alignment
79  unsigned      PointerPrefAlign;      ///< Pointer preferred alignment
80  unsigned      StackNaturalAlign;     ///< Stack natural alignment
81
82  SmallVector<unsigned char, 8> LegalIntWidths; ///< Legal Integers.
83
84  /// Alignments- Where the primitive type alignment data is stored.
85  ///
86  /// @sa init().
87  /// @note Could support multiple size pointer alignments, e.g., 32-bit
88  /// pointers vs. 64-bit pointers by extending TargetAlignment, but for now,
89  /// we don't.
90  SmallVector<TargetAlignElem, 16> Alignments;
91
92  /// InvalidAlignmentElem - This member is a signal that a requested alignment
93  /// type and bit width were not found in the SmallVector.
94  static const TargetAlignElem InvalidAlignmentElem;
95
96  // The StructType -> StructLayout map.
97  mutable void *LayoutMap;
98
99  //! Set/initialize target alignments
100  void setAlignment(AlignTypeEnum align_type, unsigned abi_align,
101                    unsigned pref_align, uint32_t bit_width);
102  unsigned getAlignmentInfo(AlignTypeEnum align_type, uint32_t bit_width,
103                            bool ABIAlign, Type *Ty) const;
104  //! Internal helper method that returns requested alignment for type.
105  unsigned getAlignment(Type *Ty, bool abi_or_pref) const;
106
107  /// Valid alignment predicate.
108  ///
109  /// Predicate that tests a TargetAlignElem reference returned by get() against
110  /// InvalidAlignmentElem.
111  bool validAlignment(const TargetAlignElem &align) const {
112    return &align != &InvalidAlignmentElem;
113  }
114
115  /// Initialise a TargetData object with default values, ensure that the
116  /// target data pass is registered.
117  void init();
118
119public:
120  /// Default ctor.
121  ///
122  /// @note This has to exist, because this is a pass, but it should never be
123  /// used.
124  TargetData();
125
126  /// Constructs a TargetData from a specification string. See init().
127  explicit TargetData(StringRef TargetDescription)
128    : ImmutablePass(ID) {
129    std::string errMsg = parseSpecifier(TargetDescription, this);
130    assert(errMsg == "" && "Invalid target data layout string.");
131    (void)errMsg;
132  }
133
134  /// Parses a target data specification string. Returns an error message
135  /// if the string is malformed, or the empty string on success. Optionally
136  /// initialises a TargetData object if passed a non-null pointer.
137  static std::string parseSpecifier(StringRef TargetDescription, TargetData* td = 0);
138
139  /// Initialize target data from properties stored in the module.
140  explicit TargetData(const Module *M);
141
142  TargetData(const TargetData &TD) :
143    ImmutablePass(ID),
144    LittleEndian(TD.isLittleEndian()),
145    PointerMemSize(TD.PointerMemSize),
146    PointerABIAlign(TD.PointerABIAlign),
147    PointerPrefAlign(TD.PointerPrefAlign),
148    LegalIntWidths(TD.LegalIntWidths),
149    Alignments(TD.Alignments),
150    LayoutMap(0)
151  { }
152
153  ~TargetData();  // Not virtual, do not subclass this class
154
155  /// Target endianness...
156  bool isLittleEndian() const { return LittleEndian; }
157  bool isBigEndian() const { return !LittleEndian; }
158
159  /// getStringRepresentation - Return the string representation of the
160  /// TargetData.  This representation is in the same format accepted by the
161  /// string constructor above.
162  std::string getStringRepresentation() const;
163
164  /// isLegalInteger - This function returns true if the specified type is
165  /// known to be a native integer type supported by the CPU.  For example,
166  /// i64 is not native on most 32-bit CPUs and i37 is not native on any known
167  /// one.  This returns false if the integer width is not legal.
168  ///
169  /// The width is specified in bits.
170  ///
171  bool isLegalInteger(unsigned Width) const {
172    for (unsigned i = 0, e = (unsigned)LegalIntWidths.size(); i != e; ++i)
173      if (LegalIntWidths[i] == Width)
174        return true;
175    return false;
176  }
177
178  bool isIllegalInteger(unsigned Width) const {
179    return !isLegalInteger(Width);
180  }
181
182  /// Returns true if the given alignment exceeds the natural stack alignment.
183  bool exceedsNaturalStackAlignment(unsigned Align) const {
184    return (StackNaturalAlign != 0) && (Align > StackNaturalAlign);
185  }
186
187  /// fitsInLegalInteger - This function returns true if the specified type fits
188  /// in a native integer type supported by the CPU.  For example, if the CPU
189  /// only supports i32 as a native integer type, then i27 fits in a legal
190  // integer type but i45 does not.
191  bool fitsInLegalInteger(unsigned Width) const {
192    for (unsigned i = 0, e = (unsigned)LegalIntWidths.size(); i != e; ++i)
193      if (Width <= LegalIntWidths[i])
194        return true;
195    return false;
196  }
197
198  /// Target pointer alignment
199  unsigned getPointerABIAlignment() const { return PointerABIAlign; }
200  /// Return target's alignment for stack-based pointers
201  unsigned getPointerPrefAlignment() const { return PointerPrefAlign; }
202  /// Target pointer size
203  unsigned getPointerSize()         const { return PointerMemSize; }
204  /// Target pointer size, in bits
205  unsigned getPointerSizeInBits()   const { return 8*PointerMemSize; }
206
207  /// Size examples:
208  ///
209  /// Type        SizeInBits  StoreSizeInBits  AllocSizeInBits[*]
210  /// ----        ----------  ---------------  ---------------
211  ///  i1            1           8                8
212  ///  i8            8           8                8
213  ///  i19          19          24               32
214  ///  i32          32          32               32
215  ///  i100        100         104              128
216  ///  i128        128         128              128
217  ///  Float        32          32               32
218  ///  Double       64          64               64
219  ///  X86_FP80     80          80               96
220  ///
221  /// [*] The alloc size depends on the alignment, and thus on the target.
222  ///     These values are for x86-32 linux.
223
224  /// getTypeSizeInBits - Return the number of bits necessary to hold the
225  /// specified type.  For example, returns 36 for i36 and 80 for x86_fp80.
226  uint64_t getTypeSizeInBits(Type* Ty) const;
227
228  /// getTypeStoreSize - Return the maximum number of bytes that may be
229  /// overwritten by storing the specified type.  For example, returns 5
230  /// for i36 and 10 for x86_fp80.
231  uint64_t getTypeStoreSize(Type *Ty) const {
232    return (getTypeSizeInBits(Ty)+7)/8;
233  }
234
235  /// getTypeStoreSizeInBits - Return the maximum number of bits that may be
236  /// overwritten by storing the specified type; always a multiple of 8.  For
237  /// example, returns 40 for i36 and 80 for x86_fp80.
238  uint64_t getTypeStoreSizeInBits(Type *Ty) const {
239    return 8*getTypeStoreSize(Ty);
240  }
241
242  /// getTypeAllocSize - Return the offset in bytes between successive objects
243  /// of the specified type, including alignment padding.  This is the amount
244  /// that alloca reserves for this type.  For example, returns 12 or 16 for
245  /// x86_fp80, depending on alignment.
246  uint64_t getTypeAllocSize(Type* Ty) const {
247    // Round up to the next alignment boundary.
248    return RoundUpAlignment(getTypeStoreSize(Ty), getABITypeAlignment(Ty));
249  }
250
251  /// getTypeAllocSizeInBits - Return the offset in bits between successive
252  /// objects of the specified type, including alignment padding; always a
253  /// multiple of 8.  This is the amount that alloca reserves for this type.
254  /// For example, returns 96 or 128 for x86_fp80, depending on alignment.
255  uint64_t getTypeAllocSizeInBits(Type* Ty) const {
256    return 8*getTypeAllocSize(Ty);
257  }
258
259  /// getABITypeAlignment - Return the minimum ABI-required alignment for the
260  /// specified type.
261  unsigned getABITypeAlignment(Type *Ty) const;
262
263  /// getABIIntegerTypeAlignment - Return the minimum ABI-required alignment for
264  /// an integer type of the specified bitwidth.
265  unsigned getABIIntegerTypeAlignment(unsigned BitWidth) const;
266
267
268  /// getCallFrameTypeAlignment - Return the minimum ABI-required alignment
269  /// for the specified type when it is part of a call frame.
270  unsigned getCallFrameTypeAlignment(Type *Ty) const;
271
272
273  /// getPrefTypeAlignment - Return the preferred stack/global alignment for
274  /// the specified type.  This is always at least as good as the ABI alignment.
275  unsigned getPrefTypeAlignment(Type *Ty) const;
276
277  /// getPreferredTypeAlignmentShift - Return the preferred alignment for the
278  /// specified type, returned as log2 of the value (a shift amount).
279  ///
280  unsigned getPreferredTypeAlignmentShift(Type *Ty) const;
281
282  /// getIntPtrType - Return an unsigned integer type that is the same size or
283  /// greater to the host pointer size.
284  ///
285  IntegerType *getIntPtrType(LLVMContext &C) const;
286
287  /// getIndexedOffset - return the offset from the beginning of the type for
288  /// the specified indices.  This is used to implement getelementptr.
289  ///
290  uint64_t getIndexedOffset(Type *Ty, ArrayRef<Value *> Indices) const;
291
292  /// getStructLayout - Return a StructLayout object, indicating the alignment
293  /// of the struct, its size, and the offsets of its fields.  Note that this
294  /// information is lazily cached.
295  const StructLayout *getStructLayout(StructType *Ty) const;
296
297  /// getPreferredAlignment - Return the preferred alignment of the specified
298  /// global.  This includes an explicitly requested alignment (if the global
299  /// has one).
300  unsigned getPreferredAlignment(const GlobalVariable *GV) const;
301
302  /// getPreferredAlignmentLog - Return the preferred alignment of the
303  /// specified global, returned in log form.  This includes an explicitly
304  /// requested alignment (if the global has one).
305  unsigned getPreferredAlignmentLog(const GlobalVariable *GV) const;
306
307  /// RoundUpAlignment - Round the specified value up to the next alignment
308  /// boundary specified by Alignment.  For example, 7 rounded up to an
309  /// alignment boundary of 4 is 8.  8 rounded up to the alignment boundary of 4
310  /// is 8 because it is already aligned.
311  template <typename UIntTy>
312  static UIntTy RoundUpAlignment(UIntTy Val, unsigned Alignment) {
313    assert((Alignment & (Alignment-1)) == 0 && "Alignment must be power of 2!");
314    return (Val + (Alignment-1)) & ~UIntTy(Alignment-1);
315  }
316
317  static char ID; // Pass identification, replacement for typeid
318};
319
320/// StructLayout - used to lazily calculate structure layout information for a
321/// target machine, based on the TargetData structure.
322///
323class StructLayout {
324  uint64_t StructSize;
325  unsigned StructAlignment;
326  unsigned NumElements;
327  uint64_t MemberOffsets[1];  // variable sized array!
328public:
329
330  uint64_t getSizeInBytes() const {
331    return StructSize;
332  }
333
334  uint64_t getSizeInBits() const {
335    return 8*StructSize;
336  }
337
338  unsigned getAlignment() const {
339    return StructAlignment;
340  }
341
342  /// getElementContainingOffset - Given a valid byte offset into the structure,
343  /// return the structure index that contains it.
344  ///
345  unsigned getElementContainingOffset(uint64_t Offset) const;
346
347  uint64_t getElementOffset(unsigned Idx) const {
348    assert(Idx < NumElements && "Invalid element idx!");
349    return MemberOffsets[Idx];
350  }
351
352  uint64_t getElementOffsetInBits(unsigned Idx) const {
353    return getElementOffset(Idx)*8;
354  }
355
356private:
357  friend class TargetData;   // Only TargetData can create this class
358  StructLayout(StructType *ST, const TargetData &TD);
359};
360
361} // End llvm namespace
362
363#endif
364