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    GlobalReg     // This is a register l-value, use getGlobalReg()
115  } LVType;
116
117  llvm::Value *V;
118
119  union {
120    // Index into a vector subscript: V[i]
121    llvm::Value *VectorIdx;
122
123    // ExtVector element subset: V.xyx
124    llvm::Constant *VectorElts;
125
126    // BitField start bit and size
127    const CGBitFieldInfo *BitFieldInfo;
128  };
129
130  QualType Type;
131
132  // 'const' is unused here
133  Qualifiers Quals;
134
135  // The alignment to use when accessing this lvalue.  (For vector elements,
136  // this is the alignment of the whole vector.)
137  int64_t Alignment;
138
139  // objective-c's ivar
140  bool Ivar:1;
141
142  // objective-c's ivar is an array
143  bool ObjIsArray:1;
144
145  // LValue is non-gc'able for any reason, including being a parameter or local
146  // variable.
147  bool NonGC: 1;
148
149  // Lvalue is a global reference of an objective-c object
150  bool GlobalObjCRef : 1;
151
152  // Lvalue is a thread local reference
153  bool ThreadLocalRef : 1;
154
155  // Lvalue has ARC imprecise lifetime.  We store this inverted to try
156  // to make the default bitfield pattern all-zeroes.
157  bool ImpreciseLifetime : 1;
158
159  Expr *BaseIvarExp;
160
161  /// Used by struct-path-aware TBAA.
162  QualType TBAABaseType;
163  /// Offset relative to the base type.
164  uint64_t TBAAOffset;
165
166  /// TBAAInfo - TBAA information to attach to dereferences of this LValue.
167  llvm::MDNode *TBAAInfo;
168
169private:
170  void Initialize(QualType Type, Qualifiers Quals,
171                  CharUnits Alignment,
172                  llvm::MDNode *TBAAInfo = nullptr) {
173    this->Type = Type;
174    this->Quals = Quals;
175    this->Alignment = Alignment.getQuantity();
176    assert(this->Alignment == Alignment.getQuantity() &&
177           "Alignment exceeds allowed max!");
178
179    // Initialize Objective-C flags.
180    this->Ivar = this->ObjIsArray = this->NonGC = this->GlobalObjCRef = false;
181    this->ImpreciseLifetime = false;
182    this->ThreadLocalRef = false;
183    this->BaseIvarExp = nullptr;
184
185    // Initialize fields for TBAA.
186    this->TBAABaseType = Type;
187    this->TBAAOffset = 0;
188    this->TBAAInfo = TBAAInfo;
189  }
190
191public:
192  bool isSimple() const { return LVType == Simple; }
193  bool isVectorElt() const { return LVType == VectorElt; }
194  bool isBitField() const { return LVType == BitField; }
195  bool isExtVectorElt() const { return LVType == ExtVectorElt; }
196  bool isGlobalReg() const { return LVType == GlobalReg; }
197
198  bool isVolatileQualified() const { return Quals.hasVolatile(); }
199  bool isRestrictQualified() const { return Quals.hasRestrict(); }
200  unsigned getVRQualifiers() const {
201    return Quals.getCVRQualifiers() & ~Qualifiers::Const;
202  }
203
204  QualType getType() const { return Type; }
205
206  Qualifiers::ObjCLifetime getObjCLifetime() const {
207    return Quals.getObjCLifetime();
208  }
209
210  bool isObjCIvar() const { return Ivar; }
211  void setObjCIvar(bool Value) { Ivar = Value; }
212
213  bool isObjCArray() const { return ObjIsArray; }
214  void setObjCArray(bool Value) { ObjIsArray = Value; }
215
216  bool isNonGC () const { return NonGC; }
217  void setNonGC(bool Value) { NonGC = Value; }
218
219  bool isGlobalObjCRef() const { return GlobalObjCRef; }
220  void setGlobalObjCRef(bool Value) { GlobalObjCRef = Value; }
221
222  bool isThreadLocalRef() const { return ThreadLocalRef; }
223  void setThreadLocalRef(bool Value) { ThreadLocalRef = Value;}
224
225  ARCPreciseLifetime_t isARCPreciseLifetime() const {
226    return ARCPreciseLifetime_t(!ImpreciseLifetime);
227  }
228  void setARCPreciseLifetime(ARCPreciseLifetime_t value) {
229    ImpreciseLifetime = (value == ARCImpreciseLifetime);
230  }
231
232  bool isObjCWeak() const {
233    return Quals.getObjCGCAttr() == Qualifiers::Weak;
234  }
235  bool isObjCStrong() const {
236    return Quals.getObjCGCAttr() == Qualifiers::Strong;
237  }
238
239  bool isVolatile() const {
240    return Quals.hasVolatile();
241  }
242
243  Expr *getBaseIvarExp() const { return BaseIvarExp; }
244  void setBaseIvarExp(Expr *V) { BaseIvarExp = V; }
245
246  QualType getTBAABaseType() const { return TBAABaseType; }
247  void setTBAABaseType(QualType T) { TBAABaseType = T; }
248
249  uint64_t getTBAAOffset() const { return TBAAOffset; }
250  void setTBAAOffset(uint64_t O) { TBAAOffset = O; }
251
252  llvm::MDNode *getTBAAInfo() const { return TBAAInfo; }
253  void setTBAAInfo(llvm::MDNode *N) { TBAAInfo = N; }
254
255  const Qualifiers &getQuals() const { return Quals; }
256  Qualifiers &getQuals() { return Quals; }
257
258  unsigned getAddressSpace() const { return Quals.getAddressSpace(); }
259
260  CharUnits getAlignment() const { return CharUnits::fromQuantity(Alignment); }
261  void setAlignment(CharUnits A) { Alignment = A.getQuantity(); }
262
263  // simple lvalue
264  llvm::Value *getAddress() const { assert(isSimple()); return V; }
265  void setAddress(llvm::Value *address) {
266    assert(isSimple());
267    V = address;
268  }
269
270  // vector elt lvalue
271  llvm::Value *getVectorAddr() const { assert(isVectorElt()); return V; }
272  llvm::Value *getVectorIdx() const { assert(isVectorElt()); return VectorIdx; }
273
274  // extended vector elements.
275  llvm::Value *getExtVectorAddr() const { assert(isExtVectorElt()); return V; }
276  llvm::Constant *getExtVectorElts() const {
277    assert(isExtVectorElt());
278    return VectorElts;
279  }
280
281  // bitfield lvalue
282  llvm::Value *getBitFieldAddr() const {
283    assert(isBitField());
284    return V;
285  }
286  const CGBitFieldInfo &getBitFieldInfo() const {
287    assert(isBitField());
288    return *BitFieldInfo;
289  }
290
291  // global register lvalue
292  llvm::Value *getGlobalReg() const { assert(isGlobalReg()); return V; }
293
294  static LValue MakeAddr(llvm::Value *address, QualType type,
295                         CharUnits alignment, ASTContext &Context,
296                         llvm::MDNode *TBAAInfo = nullptr) {
297    Qualifiers qs = type.getQualifiers();
298    qs.setObjCGCAttr(Context.getObjCGCAttrKind(type));
299
300    LValue R;
301    R.LVType = Simple;
302    R.V = address;
303    R.Initialize(type, qs, alignment, TBAAInfo);
304    return R;
305  }
306
307  static LValue MakeVectorElt(llvm::Value *Vec, llvm::Value *Idx,
308                              QualType type, CharUnits Alignment) {
309    LValue R;
310    R.LVType = VectorElt;
311    R.V = Vec;
312    R.VectorIdx = Idx;
313    R.Initialize(type, type.getQualifiers(), Alignment);
314    return R;
315  }
316
317  static LValue MakeExtVectorElt(llvm::Value *Vec, llvm::Constant *Elts,
318                                 QualType type, CharUnits Alignment) {
319    LValue R;
320    R.LVType = ExtVectorElt;
321    R.V = Vec;
322    R.VectorElts = Elts;
323    R.Initialize(type, type.getQualifiers(), Alignment);
324    return R;
325  }
326
327  /// \brief Create a new object to represent a bit-field access.
328  ///
329  /// \param Addr - The base address of the bit-field sequence this
330  /// bit-field refers to.
331  /// \param Info - The information describing how to perform the bit-field
332  /// access.
333  static LValue MakeBitfield(llvm::Value *Addr,
334                             const CGBitFieldInfo &Info,
335                             QualType type, CharUnits Alignment) {
336    LValue R;
337    R.LVType = BitField;
338    R.V = Addr;
339    R.BitFieldInfo = &Info;
340    R.Initialize(type, type.getQualifiers(), Alignment);
341    return R;
342  }
343
344  static LValue MakeGlobalReg(llvm::Value *Reg,
345                              QualType type,
346                              CharUnits Alignment) {
347    LValue R;
348    R.LVType = GlobalReg;
349    R.V = Reg;
350    R.Initialize(type, type.getQualifiers(), Alignment);
351    return R;
352  }
353
354  RValue asAggregateRValue() const {
355    // FIMXE: Alignment
356    return RValue::getAggregate(getAddress(), isVolatileQualified());
357  }
358};
359
360/// An aggregate value slot.
361class AggValueSlot {
362  /// The address.
363  llvm::Value *Addr;
364
365  // Qualifiers
366  Qualifiers Quals;
367
368  unsigned short Alignment;
369
370  /// DestructedFlag - This is set to true if some external code is
371  /// responsible for setting up a destructor for the slot.  Otherwise
372  /// the code which constructs it should push the appropriate cleanup.
373  bool DestructedFlag : 1;
374
375  /// ObjCGCFlag - This is set to true if writing to the memory in the
376  /// slot might require calling an appropriate Objective-C GC
377  /// barrier.  The exact interaction here is unnecessarily mysterious.
378  bool ObjCGCFlag : 1;
379
380  /// ZeroedFlag - This is set to true if the memory in the slot is
381  /// known to be zero before the assignment into it.  This means that
382  /// zero fields don't need to be set.
383  bool ZeroedFlag : 1;
384
385  /// AliasedFlag - This is set to true if the slot might be aliased
386  /// and it's not undefined behavior to access it through such an
387  /// alias.  Note that it's always undefined behavior to access a C++
388  /// object that's under construction through an alias derived from
389  /// outside the construction process.
390  ///
391  /// This flag controls whether calls that produce the aggregate
392  /// value may be evaluated directly into the slot, or whether they
393  /// must be evaluated into an unaliased temporary and then memcpy'ed
394  /// over.  Since it's invalid in general to memcpy a non-POD C++
395  /// object, it's important that this flag never be set when
396  /// evaluating an expression which constructs such an object.
397  bool AliasedFlag : 1;
398
399public:
400  enum IsAliased_t { IsNotAliased, IsAliased };
401  enum IsDestructed_t { IsNotDestructed, IsDestructed };
402  enum IsZeroed_t { IsNotZeroed, IsZeroed };
403  enum NeedsGCBarriers_t { DoesNotNeedGCBarriers, NeedsGCBarriers };
404
405  /// ignored - Returns an aggregate value slot indicating that the
406  /// aggregate value is being ignored.
407  static AggValueSlot ignored() {
408    return forAddr(nullptr, CharUnits(), Qualifiers(), IsNotDestructed,
409                   DoesNotNeedGCBarriers, IsNotAliased);
410  }
411
412  /// forAddr - Make a slot for an aggregate value.
413  ///
414  /// \param quals - The qualifiers that dictate how the slot should
415  /// be initialied. Only 'volatile' and the Objective-C lifetime
416  /// qualifiers matter.
417  ///
418  /// \param isDestructed - true if something else is responsible
419  ///   for calling destructors on this object
420  /// \param needsGC - true if the slot is potentially located
421  ///   somewhere that ObjC GC calls should be emitted for
422  static AggValueSlot forAddr(llvm::Value *addr, CharUnits align,
423                              Qualifiers quals,
424                              IsDestructed_t isDestructed,
425                              NeedsGCBarriers_t needsGC,
426                              IsAliased_t isAliased,
427                              IsZeroed_t isZeroed = IsNotZeroed) {
428    AggValueSlot AV;
429    AV.Addr = addr;
430    AV.Alignment = align.getQuantity();
431    AV.Quals = quals;
432    AV.DestructedFlag = isDestructed;
433    AV.ObjCGCFlag = needsGC;
434    AV.ZeroedFlag = isZeroed;
435    AV.AliasedFlag = isAliased;
436    return AV;
437  }
438
439  static AggValueSlot forLValue(const LValue &LV,
440                                IsDestructed_t isDestructed,
441                                NeedsGCBarriers_t needsGC,
442                                IsAliased_t isAliased,
443                                IsZeroed_t isZeroed = IsNotZeroed) {
444    return forAddr(LV.getAddress(), LV.getAlignment(),
445                   LV.getQuals(), isDestructed, needsGC, isAliased, isZeroed);
446  }
447
448  IsDestructed_t isExternallyDestructed() const {
449    return IsDestructed_t(DestructedFlag);
450  }
451  void setExternallyDestructed(bool destructed = true) {
452    DestructedFlag = destructed;
453  }
454
455  Qualifiers getQualifiers() const { return Quals; }
456
457  bool isVolatile() const {
458    return Quals.hasVolatile();
459  }
460
461  void setVolatile(bool flag) {
462    Quals.setVolatile(flag);
463  }
464
465  Qualifiers::ObjCLifetime getObjCLifetime() const {
466    return Quals.getObjCLifetime();
467  }
468
469  NeedsGCBarriers_t requiresGCollection() const {
470    return NeedsGCBarriers_t(ObjCGCFlag);
471  }
472
473  llvm::Value *getAddr() const {
474    return Addr;
475  }
476
477  bool isIgnored() const {
478    return Addr == nullptr;
479  }
480
481  CharUnits getAlignment() const {
482    return CharUnits::fromQuantity(Alignment);
483  }
484
485  IsAliased_t isPotentiallyAliased() const {
486    return IsAliased_t(AliasedFlag);
487  }
488
489  // FIXME: Alignment?
490  RValue asRValue() const {
491    return RValue::getAggregate(getAddr(), isVolatile());
492  }
493
494  void setZeroed(bool V = true) { ZeroedFlag = V; }
495  IsZeroed_t isZeroed() const {
496    return IsZeroed_t(ZeroedFlag);
497  }
498};
499
500}  // end namespace CodeGen
501}  // end namespace clang
502
503#endif
504