CGValue.h revision 99c6418e37380abbc7042ea82634bb4f7f674e15 
1//===-- CGValue.h - LLVM CodeGen wrappers for llvm::Value* ------*- 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// These classes implement wrappers around llvm::Value in order to
11// fully represent the range of values for C L- and R- values.
12//
13//===----------------------------------------------------------------------===//
14
15#ifndef CLANG_CODEGEN_CGVALUE_H
16#define CLANG_CODEGEN_CGVALUE_H
17
18#include "clang/AST/ASTContext.h"
19#include "clang/AST/CharUnits.h"
20#include "clang/AST/Type.h"
21#include "llvm/IR/Value.h"
22
23namespace llvm {
24  class Constant;
25  class MDNode;
26}
27
28namespace clang {
29namespace CodeGen {
30  class AggValueSlot;
31  struct CGBitFieldInfo;
32
33/// RValue - This trivial value class is used to represent the result of an
34/// expression that is evaluated.  It can be one of three things: either a
35/// simple LLVM SSA value, a pair of SSA values for complex numbers, or the
36/// address of an aggregate value in memory.
37class RValue {
38  enum Flavor { Scalar, Complex, Aggregate };
39
40  // Stores first value and flavor.
41  llvm::PointerIntPair<llvm::Value *, 2, Flavor> V1;
42  // Stores second value and volatility.
43  llvm::PointerIntPair<llvm::Value *, 1, bool> V2;
44
45public:
46  bool isScalar() const { return V1.getInt() == Scalar; }
47  bool isComplex() const { return V1.getInt() == Complex; }
48  bool isAggregate() const { return V1.getInt() == Aggregate; }
49
50  bool isVolatileQualified() const { return V2.getInt(); }
51
52  /// getScalarVal() - Return the Value* of this scalar value.
53  llvm::Value *getScalarVal() const {
54    assert(isScalar() && "Not a scalar!");
55    return V1.getPointer();
56  }
57
58  /// getComplexVal - Return the real/imag components of this complex value.
59  ///
60  std::pair<llvm::Value *, llvm::Value *> getComplexVal() const {
61    return std::make_pair(V1.getPointer(), V2.getPointer());
62  }
63
64  /// getAggregateAddr() - Return the Value* of the address of the aggregate.
65  llvm::Value *getAggregateAddr() const {
66    assert(isAggregate() && "Not an aggregate!");
67    return V1.getPointer();
68  }
69
70  static RValue get(llvm::Value *V) {
71    RValue ER;
72    ER.V1.setPointer(V);
73    ER.V1.setInt(Scalar);
74    ER.V2.setInt(false);
75    return ER;
76  }
77  static RValue getComplex(llvm::Value *V1, llvm::Value *V2) {
78    RValue ER;
79    ER.V1.setPointer(V1);
80    ER.V2.setPointer(V2);
81    ER.V1.setInt(Complex);
82    ER.V2.setInt(false);
83    return ER;
84  }
85  static RValue getComplex(const std::pair<llvm::Value *, llvm::Value *> &C) {
86    return getComplex(C.first, C.second);
87  }
88  // FIXME: Aggregate rvalues need to retain information about whether they are
89  // volatile or not.  Remove default to find all places that probably get this
90  // wrong.
91  static RValue getAggregate(llvm::Value *V, bool Volatile = false) {
92    RValue ER;
93    ER.V1.setPointer(V);
94    ER.V1.setInt(Aggregate);
95    ER.V2.setInt(Volatile);
96    return ER;
97  }
98};
99
100/// Does an ARC strong l-value have precise lifetime?
101enum ARCPreciseLifetime_t {
102  ARCImpreciseLifetime, ARCPreciseLifetime
103};
104
105/// LValue - This represents an lvalue references.  Because C/C++ allow
106/// bitfields, this is not a simple LLVM pointer, it may be a pointer plus a
107/// bitrange.
108class LValue {
109  enum {
110    Simple,       // This is a normal l-value, use getAddress().
111    VectorElt,    // This is a vector element l-value (V[i]), use getVector*
112    BitField,     // This is a bitfield l-value, use getBitfield*.
113    ExtVectorElt  // This is an extended vector subset, use getExtVectorComp
114  } LVType;
115
116  llvm::Value *V;
117
118  union {
119    // Index into a vector subscript: V[i]
120    llvm::Value *VectorIdx;
121
122    // ExtVector element subset: V.xyx
123    llvm::Constant *VectorElts;
124
125    // BitField start bit and size
126    const CGBitFieldInfo *BitFieldInfo;
127  };
128
129  QualType Type;
130
131  // 'const' is unused here
132  Qualifiers Quals;
133
134  // The alignment to use when accessing this lvalue.  (For vector elements,
135  // this is the alignment of the whole vector.)
136  int64_t Alignment;
137
138  // objective-c's ivar
139  bool Ivar:1;
140
141  // objective-c's ivar is an array
142  bool ObjIsArray:1;
143
144  // LValue is non-gc'able for any reason, including being a parameter or local
145  // variable.
146  bool NonGC: 1;
147
148  // Lvalue is a global reference of an objective-c object
149  bool GlobalObjCRef : 1;
150
151  // Lvalue is a thread local reference
152  bool ThreadLocalRef : 1;
153
154  // Lvalue has ARC imprecise lifetime.  We store this inverted to try
155  // to make the default bitfield pattern all-zeroes.
156  bool ImpreciseLifetime : 1;
157
158  Expr *BaseIvarExp;
159
160  /// TBAAInfo - TBAA information to attach to dereferences of this LValue.
161  llvm::MDNode *TBAAInfo;
162
163private:
164  void Initialize(QualType Type, Qualifiers Quals,
165                  CharUnits Alignment,
166                  llvm::MDNode *TBAAInfo = 0) {
167    this->Type = Type;
168    this->Quals = Quals;
169    this->Alignment = Alignment.getQuantity();
170    assert(this->Alignment == Alignment.getQuantity() &&
171           "Alignment exceeds allowed max!");
172
173    // Initialize Objective-C flags.
174    this->Ivar = this->ObjIsArray = this->NonGC = this->GlobalObjCRef = false;
175    this->ImpreciseLifetime = false;
176    this->ThreadLocalRef = false;
177    this->BaseIvarExp = 0;
178    this->TBAAInfo = TBAAInfo;
179  }
180
181public:
182  bool isSimple() const { return LVType == Simple; }
183  bool isVectorElt() const { return LVType == VectorElt; }
184  bool isBitField() const { return LVType == BitField; }
185  bool isExtVectorElt() const { return LVType == ExtVectorElt; }
186
187  bool isVolatileQualified() const { return Quals.hasVolatile(); }
188  bool isRestrictQualified() const { return Quals.hasRestrict(); }
189  unsigned getVRQualifiers() const {
190    return Quals.getCVRQualifiers() & ~Qualifiers::Const;
191  }
192
193  QualType getType() const { return Type; }
194
195  Qualifiers::ObjCLifetime getObjCLifetime() const {
196    return Quals.getObjCLifetime();
197  }
198
199  bool isObjCIvar() const { return Ivar; }
200  void setObjCIvar(bool Value) { Ivar = Value; }
201
202  bool isObjCArray() const { return ObjIsArray; }
203  void setObjCArray(bool Value) { ObjIsArray = Value; }
204
205  bool isNonGC () const { return NonGC; }
206  void setNonGC(bool Value) { NonGC = Value; }
207
208  bool isGlobalObjCRef() const { return GlobalObjCRef; }
209  void setGlobalObjCRef(bool Value) { GlobalObjCRef = Value; }
210
211  bool isThreadLocalRef() const { return ThreadLocalRef; }
212  void setThreadLocalRef(bool Value) { ThreadLocalRef = Value;}
213
214  ARCPreciseLifetime_t isARCPreciseLifetime() const {
215    return ARCPreciseLifetime_t(!ImpreciseLifetime);
216  }
217  void setARCPreciseLifetime(ARCPreciseLifetime_t value) {
218    ImpreciseLifetime = (value == ARCImpreciseLifetime);
219  }
220
221  bool isObjCWeak() const {
222    return Quals.getObjCGCAttr() == Qualifiers::Weak;
223  }
224  bool isObjCStrong() const {
225    return Quals.getObjCGCAttr() == Qualifiers::Strong;
226  }
227
228  bool isVolatile() const {
229    return Quals.hasVolatile();
230  }
231
232  Expr *getBaseIvarExp() const { return BaseIvarExp; }
233  void setBaseIvarExp(Expr *V) { BaseIvarExp = V; }
234
235  llvm::MDNode *getTBAAInfo() const { return TBAAInfo; }
236  void setTBAAInfo(llvm::MDNode *N) { TBAAInfo = N; }
237
238  const Qualifiers &getQuals() const { return Quals; }
239  Qualifiers &getQuals() { return Quals; }
240
241  unsigned getAddressSpace() const { return Quals.getAddressSpace(); }
242
243  CharUnits getAlignment() const { return CharUnits::fromQuantity(Alignment); }
244  void setAlignment(CharUnits A) { Alignment = A.getQuantity(); }
245
246  // simple lvalue
247  llvm::Value *getAddress() const { assert(isSimple()); return V; }
248  void setAddress(llvm::Value *address) {
249    assert(isSimple());
250    V = address;
251  }
252
253  // vector elt lvalue
254  llvm::Value *getVectorAddr() const { assert(isVectorElt()); return V; }
255  llvm::Value *getVectorIdx() const { assert(isVectorElt()); return VectorIdx; }
256
257  // extended vector elements.
258  llvm::Value *getExtVectorAddr() const { assert(isExtVectorElt()); return V; }
259  llvm::Constant *getExtVectorElts() const {
260    assert(isExtVectorElt());
261    return VectorElts;
262  }
263
264  // bitfield lvalue
265  llvm::Value *getBitFieldAddr() const {
266    assert(isBitField());
267    return V;
268  }
269  const CGBitFieldInfo &getBitFieldInfo() const {
270    assert(isBitField());
271    return *BitFieldInfo;
272  }
273
274  static LValue MakeAddr(llvm::Value *address, QualType type,
275                         CharUnits alignment, ASTContext &Context,
276                         llvm::MDNode *TBAAInfo = 0) {
277    Qualifiers qs = type.getQualifiers();
278    qs.setObjCGCAttr(Context.getObjCGCAttrKind(type));
279
280    LValue R;
281    R.LVType = Simple;
282    R.V = address;
283    R.Initialize(type, qs, alignment, TBAAInfo);
284    return R;
285  }
286
287  static LValue MakeVectorElt(llvm::Value *Vec, llvm::Value *Idx,
288                              QualType type, CharUnits Alignment) {
289    LValue R;
290    R.LVType = VectorElt;
291    R.V = Vec;
292    R.VectorIdx = Idx;
293    R.Initialize(type, type.getQualifiers(), Alignment);
294    return R;
295  }
296
297  static LValue MakeExtVectorElt(llvm::Value *Vec, llvm::Constant *Elts,
298                                 QualType type, CharUnits Alignment) {
299    LValue R;
300    R.LVType = ExtVectorElt;
301    R.V = Vec;
302    R.VectorElts = Elts;
303    R.Initialize(type, type.getQualifiers(), Alignment);
304    return R;
305  }
306
307  /// \brief Create a new object to represent a bit-field access.
308  ///
309  /// \param Addr - The base address of the bit-field sequence this
310  /// bit-field refers to.
311  /// \param Info - The information describing how to perform the bit-field
312  /// access.
313  static LValue MakeBitfield(llvm::Value *Addr,
314                             const CGBitFieldInfo &Info,
315                             QualType type, CharUnits Alignment) {
316    LValue R;
317    R.LVType = BitField;
318    R.V = Addr;
319    R.BitFieldInfo = &Info;
320    R.Initialize(type, type.getQualifiers(), Alignment);
321    return R;
322  }
323
324  RValue asAggregateRValue() const {
325    // FIMXE: Alignment
326    return RValue::getAggregate(getAddress(), isVolatileQualified());
327  }
328};
329
330/// An aggregate value slot.
331class AggValueSlot {
332  /// The address.
333  llvm::Value *Addr;
334
335  // Qualifiers
336  Qualifiers Quals;
337
338  unsigned short Alignment;
339
340  /// DestructedFlag - This is set to true if some external code is
341  /// responsible for setting up a destructor for the slot.  Otherwise
342  /// the code which constructs it should push the appropriate cleanup.
343  bool DestructedFlag : 1;
344
345  /// ObjCGCFlag - This is set to true if writing to the memory in the
346  /// slot might require calling an appropriate Objective-C GC
347  /// barrier.  The exact interaction here is unnecessarily mysterious.
348  bool ObjCGCFlag : 1;
349
350  /// ZeroedFlag - This is set to true if the memory in the slot is
351  /// known to be zero before the assignment into it.  This means that
352  /// zero fields don't need to be set.
353  bool ZeroedFlag : 1;
354
355  /// AliasedFlag - This is set to true if the slot might be aliased
356  /// and it's not undefined behavior to access it through such an
357  /// alias.  Note that it's always undefined behavior to access a C++
358  /// object that's under construction through an alias derived from
359  /// outside the construction process.
360  ///
361  /// This flag controls whether calls that produce the aggregate
362  /// value may be evaluated directly into the slot, or whether they
363  /// must be evaluated into an unaliased temporary and then memcpy'ed
364  /// over.  Since it's invalid in general to memcpy a non-POD C++
365  /// object, it's important that this flag never be set when
366  /// evaluating an expression which constructs such an object.
367  bool AliasedFlag : 1;
368
369  /// ValueOfAtomicFlag - This is set to true if the slot is the value
370  /// subobject of an object the size of an _Atomic(T).  The specific
371  /// guarantees this makes are:
372  ///   - the address is guaranteed to be a getelementptr into the
373  ///     padding struct and
374  ///   - it is okay to store something the width of an _Atomic(T)
375  ///     into the address.
376  /// Tracking this allows us to avoid some obviously unnecessary
377  /// memcpys.
378  bool ValueOfAtomicFlag : 1;
379
380public:
381  enum IsAliased_t { IsNotAliased, IsAliased };
382  enum IsDestructed_t { IsNotDestructed, IsDestructed };
383  enum IsZeroed_t { IsNotZeroed, IsZeroed };
384  enum NeedsGCBarriers_t { DoesNotNeedGCBarriers, NeedsGCBarriers };
385  enum IsValueOfAtomic_t { IsNotValueOfAtomic, IsValueOfAtomic };
386
387  /// ignored - Returns an aggregate value slot indicating that the
388  /// aggregate value is being ignored.
389  static AggValueSlot ignored() {
390    return forAddr(0, CharUnits(), Qualifiers(), IsNotDestructed,
391                   DoesNotNeedGCBarriers, IsNotAliased);
392  }
393
394  /// forAddr - Make a slot for an aggregate value.
395  ///
396  /// \param quals - The qualifiers that dictate how the slot should
397  /// be initialied. Only 'volatile' and the Objective-C lifetime
398  /// qualifiers matter.
399  ///
400  /// \param isDestructed - true if something else is responsible
401  ///   for calling destructors on this object
402  /// \param needsGC - true if the slot is potentially located
403  ///   somewhere that ObjC GC calls should be emitted for
404  static AggValueSlot forAddr(llvm::Value *addr, CharUnits align,
405                              Qualifiers quals,
406                              IsDestructed_t isDestructed,
407                              NeedsGCBarriers_t needsGC,
408                              IsAliased_t isAliased,
409                              IsZeroed_t isZeroed = IsNotZeroed,
410                              IsValueOfAtomic_t isValueOfAtomic
411                                = IsNotValueOfAtomic) {
412    AggValueSlot AV;
413    AV.Addr = addr;
414    AV.Alignment = align.getQuantity();
415    AV.Quals = quals;
416    AV.DestructedFlag = isDestructed;
417    AV.ObjCGCFlag = needsGC;
418    AV.ZeroedFlag = isZeroed;
419    AV.AliasedFlag = isAliased;
420    AV.ValueOfAtomicFlag = isValueOfAtomic;
421    return AV;
422  }
423
424  static AggValueSlot forLValue(const LValue &LV,
425                                IsDestructed_t isDestructed,
426                                NeedsGCBarriers_t needsGC,
427                                IsAliased_t isAliased,
428                                IsZeroed_t isZeroed = IsNotZeroed,
429                                IsValueOfAtomic_t isValueOfAtomic
430                                  = IsNotValueOfAtomic) {
431    return forAddr(LV.getAddress(), LV.getAlignment(),
432                   LV.getQuals(), isDestructed, needsGC, isAliased, isZeroed,
433                   isValueOfAtomic);
434  }
435
436  IsDestructed_t isExternallyDestructed() const {
437    return IsDestructed_t(DestructedFlag);
438  }
439  void setExternallyDestructed(bool destructed = true) {
440    DestructedFlag = destructed;
441  }
442
443  Qualifiers getQualifiers() const { return Quals; }
444
445  bool isVolatile() const {
446    return Quals.hasVolatile();
447  }
448
449  void setVolatile(bool flag) {
450    Quals.setVolatile(flag);
451  }
452
453  Qualifiers::ObjCLifetime getObjCLifetime() const {
454    return Quals.getObjCLifetime();
455  }
456
457  NeedsGCBarriers_t requiresGCollection() const {
458    return NeedsGCBarriers_t(ObjCGCFlag);
459  }
460
461  llvm::Value *getAddr() const {
462    return Addr;
463  }
464
465  IsValueOfAtomic_t isValueOfAtomic() const {
466    return IsValueOfAtomic_t(ValueOfAtomicFlag);
467  }
468
469  llvm::Value *getPaddedAtomicAddr() const;
470
471  bool isIgnored() const {
472    return Addr == 0;
473  }
474
475  CharUnits getAlignment() const {
476    return CharUnits::fromQuantity(Alignment);
477  }
478
479  IsAliased_t isPotentiallyAliased() const {
480    return IsAliased_t(AliasedFlag);
481  }
482
483  // FIXME: Alignment?
484  RValue asRValue() const {
485    return RValue::getAggregate(getAddr(), isVolatile());
486  }
487
488  void setZeroed(bool V = true) { ZeroedFlag = V; }
489  IsZeroed_t isZeroed() const {
490    return IsZeroed_t(ZeroedFlag);
491  }
492};
493
494}  // end namespace CodeGen
495}  // end namespace clang
496
497#endif
498