CGExprConstant.cpp revision 344779 
1//===--- CGExprConstant.cpp - Emit LLVM Code from Constant Expressions ----===//
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 contains code to emit Constant Expr nodes as LLVM code.
11//
12//===----------------------------------------------------------------------===//
13
14#include "CodeGenFunction.h"
15#include "CGCXXABI.h"
16#include "CGObjCRuntime.h"
17#include "CGRecordLayout.h"
18#include "CodeGenModule.h"
19#include "ConstantEmitter.h"
20#include "TargetInfo.h"
21#include "clang/AST/APValue.h"
22#include "clang/AST/ASTContext.h"
23#include "clang/AST/RecordLayout.h"
24#include "clang/AST/StmtVisitor.h"
25#include "clang/Basic/Builtins.h"
26#include "llvm/IR/Constants.h"
27#include "llvm/IR/DataLayout.h"
28#include "llvm/IR/Function.h"
29#include "llvm/IR/GlobalVariable.h"
30using namespace clang;
31using namespace CodeGen;
32
33//===----------------------------------------------------------------------===//
34//                            ConstStructBuilder
35//===----------------------------------------------------------------------===//
36
37namespace {
38class ConstExprEmitter;
39class ConstStructBuilder {
40  CodeGenModule &CGM;
41  ConstantEmitter &Emitter;
42
43  bool Packed;
44  CharUnits NextFieldOffsetInChars;
45  CharUnits LLVMStructAlignment;
46  SmallVector<llvm::Constant *, 32> Elements;
47public:
48  static llvm::Constant *BuildStruct(ConstantEmitter &Emitter,
49                                     ConstExprEmitter *ExprEmitter,
50                                     llvm::Constant *Base,
51                                     InitListExpr *Updater,
52                                     QualType ValTy);
53  static llvm::Constant *BuildStruct(ConstantEmitter &Emitter,
54                                     InitListExpr *ILE, QualType StructTy);
55  static llvm::Constant *BuildStruct(ConstantEmitter &Emitter,
56                                     const APValue &Value, QualType ValTy);
57
58private:
59  ConstStructBuilder(ConstantEmitter &emitter)
60    : CGM(emitter.CGM), Emitter(emitter), Packed(false),
61    NextFieldOffsetInChars(CharUnits::Zero()),
62    LLVMStructAlignment(CharUnits::One()) { }
63
64  void AppendField(const FieldDecl *Field, uint64_t FieldOffset,
65                   llvm::Constant *InitExpr);
66
67  void AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst);
68
69  void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset,
70                      llvm::ConstantInt *InitExpr);
71
72  void AppendPadding(CharUnits PadSize);
73
74  void AppendTailPadding(CharUnits RecordSize);
75
76  void ConvertStructToPacked();
77
78  bool Build(InitListExpr *ILE);
79  bool Build(ConstExprEmitter *Emitter, llvm::Constant *Base,
80             InitListExpr *Updater);
81  bool Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase,
82             const CXXRecordDecl *VTableClass, CharUnits BaseOffset);
83  llvm::Constant *Finalize(QualType Ty);
84
85  CharUnits getAlignment(const llvm::Constant *C) const {
86    if (Packed)  return CharUnits::One();
87    return CharUnits::fromQuantity(
88        CGM.getDataLayout().getABITypeAlignment(C->getType()));
89  }
90
91  CharUnits getSizeInChars(const llvm::Constant *C) const {
92    return CharUnits::fromQuantity(
93        CGM.getDataLayout().getTypeAllocSize(C->getType()));
94  }
95};
96
97void ConstStructBuilder::
98AppendField(const FieldDecl *Field, uint64_t FieldOffset,
99            llvm::Constant *InitCst) {
100  const ASTContext &Context = CGM.getContext();
101
102  CharUnits FieldOffsetInChars = Context.toCharUnitsFromBits(FieldOffset);
103
104  AppendBytes(FieldOffsetInChars, InitCst);
105}
106
107void ConstStructBuilder::
108AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst) {
109
110  assert(NextFieldOffsetInChars <= FieldOffsetInChars
111         && "Field offset mismatch!");
112
113  CharUnits FieldAlignment = getAlignment(InitCst);
114
115  // Round up the field offset to the alignment of the field type.
116  CharUnits AlignedNextFieldOffsetInChars =
117      NextFieldOffsetInChars.alignTo(FieldAlignment);
118
119  if (AlignedNextFieldOffsetInChars < FieldOffsetInChars) {
120    // We need to append padding.
121    AppendPadding(FieldOffsetInChars - NextFieldOffsetInChars);
122
123    assert(NextFieldOffsetInChars == FieldOffsetInChars &&
124           "Did not add enough padding!");
125
126    AlignedNextFieldOffsetInChars =
127        NextFieldOffsetInChars.alignTo(FieldAlignment);
128  }
129
130  if (AlignedNextFieldOffsetInChars > FieldOffsetInChars) {
131    assert(!Packed && "Alignment is wrong even with a packed struct!");
132
133    // Convert the struct to a packed struct.
134    ConvertStructToPacked();
135
136    // After we pack the struct, we may need to insert padding.
137    if (NextFieldOffsetInChars < FieldOffsetInChars) {
138      // We need to append padding.
139      AppendPadding(FieldOffsetInChars - NextFieldOffsetInChars);
140
141      assert(NextFieldOffsetInChars == FieldOffsetInChars &&
142             "Did not add enough padding!");
143    }
144    AlignedNextFieldOffsetInChars = NextFieldOffsetInChars;
145  }
146
147  // Add the field.
148  Elements.push_back(InitCst);
149  NextFieldOffsetInChars = AlignedNextFieldOffsetInChars +
150                           getSizeInChars(InitCst);
151
152  if (Packed)
153    assert(LLVMStructAlignment == CharUnits::One() &&
154           "Packed struct not byte-aligned!");
155  else
156    LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment);
157}
158
159void ConstStructBuilder::AppendBitField(const FieldDecl *Field,
160                                        uint64_t FieldOffset,
161                                        llvm::ConstantInt *CI) {
162  const ASTContext &Context = CGM.getContext();
163  const uint64_t CharWidth = Context.getCharWidth();
164  uint64_t NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars);
165  if (FieldOffset > NextFieldOffsetInBits) {
166    // We need to add padding.
167    CharUnits PadSize = Context.toCharUnitsFromBits(
168        llvm::alignTo(FieldOffset - NextFieldOffsetInBits,
169                      Context.getTargetInfo().getCharAlign()));
170
171    AppendPadding(PadSize);
172  }
173
174  uint64_t FieldSize = Field->getBitWidthValue(Context);
175
176  llvm::APInt FieldValue = CI->getValue();
177
178  // Promote the size of FieldValue if necessary
179  // FIXME: This should never occur, but currently it can because initializer
180  // constants are cast to bool, and because clang is not enforcing bitfield
181  // width limits.
182  if (FieldSize > FieldValue.getBitWidth())
183    FieldValue = FieldValue.zext(FieldSize);
184
185  // Truncate the size of FieldValue to the bit field size.
186  if (FieldSize < FieldValue.getBitWidth())
187    FieldValue = FieldValue.trunc(FieldSize);
188
189  NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars);
190  if (FieldOffset < NextFieldOffsetInBits) {
191    // Either part of the field or the entire field can go into the previous
192    // byte.
193    assert(!Elements.empty() && "Elements can't be empty!");
194
195    unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset;
196
197    bool FitsCompletelyInPreviousByte =
198      BitsInPreviousByte >= FieldValue.getBitWidth();
199
200    llvm::APInt Tmp = FieldValue;
201
202    if (!FitsCompletelyInPreviousByte) {
203      unsigned NewFieldWidth = FieldSize - BitsInPreviousByte;
204
205      if (CGM.getDataLayout().isBigEndian()) {
206        Tmp.lshrInPlace(NewFieldWidth);
207        Tmp = Tmp.trunc(BitsInPreviousByte);
208
209        // We want the remaining high bits.
210        FieldValue = FieldValue.trunc(NewFieldWidth);
211      } else {
212        Tmp = Tmp.trunc(BitsInPreviousByte);
213
214        // We want the remaining low bits.
215        FieldValue.lshrInPlace(BitsInPreviousByte);
216        FieldValue = FieldValue.trunc(NewFieldWidth);
217      }
218    }
219
220    Tmp = Tmp.zext(CharWidth);
221    if (CGM.getDataLayout().isBigEndian()) {
222      if (FitsCompletelyInPreviousByte)
223        Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth());
224    } else {
225      Tmp = Tmp.shl(CharWidth - BitsInPreviousByte);
226    }
227
228    // 'or' in the bits that go into the previous byte.
229    llvm::Value *LastElt = Elements.back();
230    if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt))
231      Tmp |= Val->getValue();
232    else {
233      assert(isa<llvm::UndefValue>(LastElt));
234      // If there is an undef field that we're adding to, it can either be a
235      // scalar undef (in which case, we just replace it with our field) or it
236      // is an array.  If it is an array, we have to pull one byte off the
237      // array so that the other undef bytes stay around.
238      if (!isa<llvm::IntegerType>(LastElt->getType())) {
239        // The undef padding will be a multibyte array, create a new smaller
240        // padding and then an hole for our i8 to get plopped into.
241        assert(isa<llvm::ArrayType>(LastElt->getType()) &&
242               "Expected array padding of undefs");
243        llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType());
244        assert(AT->getElementType()->isIntegerTy(CharWidth) &&
245               AT->getNumElements() != 0 &&
246               "Expected non-empty array padding of undefs");
247
248        // Remove the padding array.
249        NextFieldOffsetInChars -= CharUnits::fromQuantity(AT->getNumElements());
250        Elements.pop_back();
251
252        // Add the padding back in two chunks.
253        AppendPadding(CharUnits::fromQuantity(AT->getNumElements()-1));
254        AppendPadding(CharUnits::One());
255        assert(isa<llvm::UndefValue>(Elements.back()) &&
256               Elements.back()->getType()->isIntegerTy(CharWidth) &&
257               "Padding addition didn't work right");
258      }
259    }
260
261    Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp);
262
263    if (FitsCompletelyInPreviousByte)
264      return;
265  }
266
267  while (FieldValue.getBitWidth() > CharWidth) {
268    llvm::APInt Tmp;
269
270    if (CGM.getDataLayout().isBigEndian()) {
271      // We want the high bits.
272      Tmp =
273        FieldValue.lshr(FieldValue.getBitWidth() - CharWidth).trunc(CharWidth);
274    } else {
275      // We want the low bits.
276      Tmp = FieldValue.trunc(CharWidth);
277
278      FieldValue.lshrInPlace(CharWidth);
279    }
280
281    Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp));
282    ++NextFieldOffsetInChars;
283
284    FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth);
285  }
286
287  assert(FieldValue.getBitWidth() > 0 &&
288         "Should have at least one bit left!");
289  assert(FieldValue.getBitWidth() <= CharWidth &&
290         "Should not have more than a byte left!");
291
292  if (FieldValue.getBitWidth() < CharWidth) {
293    if (CGM.getDataLayout().isBigEndian()) {
294      unsigned BitWidth = FieldValue.getBitWidth();
295
296      FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth);
297    } else
298      FieldValue = FieldValue.zext(CharWidth);
299  }
300
301  // Append the last element.
302  Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(),
303                                            FieldValue));
304  ++NextFieldOffsetInChars;
305}
306
307void ConstStructBuilder::AppendPadding(CharUnits PadSize) {
308  if (PadSize.isZero())
309    return;
310
311  llvm::Type *Ty = CGM.Int8Ty;
312  if (PadSize > CharUnits::One())
313    Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity());
314
315  llvm::Constant *C = llvm::UndefValue::get(Ty);
316  Elements.push_back(C);
317  assert(getAlignment(C) == CharUnits::One() &&
318         "Padding must have 1 byte alignment!");
319
320  NextFieldOffsetInChars += getSizeInChars(C);
321}
322
323void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) {
324  assert(NextFieldOffsetInChars <= RecordSize &&
325         "Size mismatch!");
326
327  AppendPadding(RecordSize - NextFieldOffsetInChars);
328}
329
330void ConstStructBuilder::ConvertStructToPacked() {
331  SmallVector<llvm::Constant *, 16> PackedElements;
332  CharUnits ElementOffsetInChars = CharUnits::Zero();
333
334  for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
335    llvm::Constant *C = Elements[i];
336
337    CharUnits ElementAlign = CharUnits::fromQuantity(
338      CGM.getDataLayout().getABITypeAlignment(C->getType()));
339    CharUnits AlignedElementOffsetInChars =
340        ElementOffsetInChars.alignTo(ElementAlign);
341
342    if (AlignedElementOffsetInChars > ElementOffsetInChars) {
343      // We need some padding.
344      CharUnits NumChars =
345        AlignedElementOffsetInChars - ElementOffsetInChars;
346
347      llvm::Type *Ty = CGM.Int8Ty;
348      if (NumChars > CharUnits::One())
349        Ty = llvm::ArrayType::get(Ty, NumChars.getQuantity());
350
351      llvm::Constant *Padding = llvm::UndefValue::get(Ty);
352      PackedElements.push_back(Padding);
353      ElementOffsetInChars += getSizeInChars(Padding);
354    }
355
356    PackedElements.push_back(C);
357    ElementOffsetInChars += getSizeInChars(C);
358  }
359
360  assert(ElementOffsetInChars == NextFieldOffsetInChars &&
361         "Packing the struct changed its size!");
362
363  Elements.swap(PackedElements);
364  LLVMStructAlignment = CharUnits::One();
365  Packed = true;
366}
367
368bool ConstStructBuilder::Build(InitListExpr *ILE) {
369  RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl();
370  const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
371
372  unsigned FieldNo = 0;
373  unsigned ElementNo = 0;
374
375  // Bail out if we have base classes. We could support these, but they only
376  // arise in C++1z where we will have already constant folded most interesting
377  // cases. FIXME: There are still a few more cases we can handle this way.
378  if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD))
379    if (CXXRD->getNumBases())
380      return false;
381
382  for (RecordDecl::field_iterator Field = RD->field_begin(),
383       FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
384    // If this is a union, skip all the fields that aren't being initialized.
385    if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field)
386      continue;
387
388    // Don't emit anonymous bitfields, they just affect layout.
389    if (Field->isUnnamedBitfield())
390      continue;
391
392    // Get the initializer.  A struct can include fields without initializers,
393    // we just use explicit null values for them.
394    llvm::Constant *EltInit;
395    if (ElementNo < ILE->getNumInits())
396      EltInit = Emitter.tryEmitPrivateForMemory(ILE->getInit(ElementNo++),
397                                                Field->getType());
398    else
399      EltInit = Emitter.emitNullForMemory(Field->getType());
400
401    if (!EltInit)
402      return false;
403
404    if (!Field->isBitField()) {
405      // Handle non-bitfield members.
406      AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit);
407    } else {
408      // Otherwise we have a bitfield.
409      if (auto *CI = dyn_cast<llvm::ConstantInt>(EltInit)) {
410        AppendBitField(*Field, Layout.getFieldOffset(FieldNo), CI);
411      } else {
412        // We are trying to initialize a bitfield with a non-trivial constant,
413        // this must require run-time code.
414        return false;
415      }
416    }
417  }
418
419  return true;
420}
421
422namespace {
423struct BaseInfo {
424  BaseInfo(const CXXRecordDecl *Decl, CharUnits Offset, unsigned Index)
425    : Decl(Decl), Offset(Offset), Index(Index) {
426  }
427
428  const CXXRecordDecl *Decl;
429  CharUnits Offset;
430  unsigned Index;
431
432  bool operator<(const BaseInfo &O) const { return Offset < O.Offset; }
433};
434}
435
436bool ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD,
437                               bool IsPrimaryBase,
438                               const CXXRecordDecl *VTableClass,
439                               CharUnits Offset) {
440  const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
441
442  if (const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD)) {
443    // Add a vtable pointer, if we need one and it hasn't already been added.
444    if (CD->isDynamicClass() && !IsPrimaryBase) {
445      llvm::Constant *VTableAddressPoint =
446          CGM.getCXXABI().getVTableAddressPointForConstExpr(
447              BaseSubobject(CD, Offset), VTableClass);
448      AppendBytes(Offset, VTableAddressPoint);
449    }
450
451    // Accumulate and sort bases, in order to visit them in address order, which
452    // may not be the same as declaration order.
453    SmallVector<BaseInfo, 8> Bases;
454    Bases.reserve(CD->getNumBases());
455    unsigned BaseNo = 0;
456    for (CXXRecordDecl::base_class_const_iterator Base = CD->bases_begin(),
457         BaseEnd = CD->bases_end(); Base != BaseEnd; ++Base, ++BaseNo) {
458      assert(!Base->isVirtual() && "should not have virtual bases here");
459      const CXXRecordDecl *BD = Base->getType()->getAsCXXRecordDecl();
460      CharUnits BaseOffset = Layout.getBaseClassOffset(BD);
461      Bases.push_back(BaseInfo(BD, BaseOffset, BaseNo));
462    }
463    std::stable_sort(Bases.begin(), Bases.end());
464
465    for (unsigned I = 0, N = Bases.size(); I != N; ++I) {
466      BaseInfo &Base = Bases[I];
467
468      bool IsPrimaryBase = Layout.getPrimaryBase() == Base.Decl;
469      Build(Val.getStructBase(Base.Index), Base.Decl, IsPrimaryBase,
470            VTableClass, Offset + Base.Offset);
471    }
472  }
473
474  unsigned FieldNo = 0;
475  uint64_t OffsetBits = CGM.getContext().toBits(Offset);
476
477  for (RecordDecl::field_iterator Field = RD->field_begin(),
478       FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
479    // If this is a union, skip all the fields that aren't being initialized.
480    if (RD->isUnion() && Val.getUnionField() != *Field)
481      continue;
482
483    // Don't emit anonymous bitfields, they just affect layout.
484    if (Field->isUnnamedBitfield())
485      continue;
486
487    // Emit the value of the initializer.
488    const APValue &FieldValue =
489      RD->isUnion() ? Val.getUnionValue() : Val.getStructField(FieldNo);
490    llvm::Constant *EltInit =
491      Emitter.tryEmitPrivateForMemory(FieldValue, Field->getType());
492    if (!EltInit)
493      return false;
494
495    if (!Field->isBitField()) {
496      // Handle non-bitfield members.
497      AppendField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, EltInit);
498    } else {
499      // Otherwise we have a bitfield.
500      AppendBitField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits,
501                     cast<llvm::ConstantInt>(EltInit));
502    }
503  }
504
505  return true;
506}
507
508llvm::Constant *ConstStructBuilder::Finalize(QualType Ty) {
509  RecordDecl *RD = Ty->getAs<RecordType>()->getDecl();
510  const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
511
512  CharUnits LayoutSizeInChars = Layout.getSize();
513
514  if (NextFieldOffsetInChars > LayoutSizeInChars) {
515    // If the struct is bigger than the size of the record type,
516    // we must have a flexible array member at the end.
517    assert(RD->hasFlexibleArrayMember() &&
518           "Must have flexible array member if struct is bigger than type!");
519
520    // No tail padding is necessary.
521  } else {
522    // Append tail padding if necessary.
523    CharUnits LLVMSizeInChars =
524        NextFieldOffsetInChars.alignTo(LLVMStructAlignment);
525
526    if (LLVMSizeInChars != LayoutSizeInChars)
527      AppendTailPadding(LayoutSizeInChars);
528
529    LLVMSizeInChars = NextFieldOffsetInChars.alignTo(LLVMStructAlignment);
530
531    // Check if we need to convert the struct to a packed struct.
532    if (NextFieldOffsetInChars <= LayoutSizeInChars &&
533        LLVMSizeInChars > LayoutSizeInChars) {
534      assert(!Packed && "Size mismatch!");
535
536      ConvertStructToPacked();
537      assert(NextFieldOffsetInChars <= LayoutSizeInChars &&
538             "Converting to packed did not help!");
539    }
540
541    LLVMSizeInChars = NextFieldOffsetInChars.alignTo(LLVMStructAlignment);
542
543    assert(LayoutSizeInChars == LLVMSizeInChars &&
544           "Tail padding mismatch!");
545  }
546
547  // Pick the type to use.  If the type is layout identical to the ConvertType
548  // type then use it, otherwise use whatever the builder produced for us.
549  llvm::StructType *STy =
550      llvm::ConstantStruct::getTypeForElements(CGM.getLLVMContext(),
551                                               Elements, Packed);
552  llvm::Type *ValTy = CGM.getTypes().ConvertType(Ty);
553  if (llvm::StructType *ValSTy = dyn_cast<llvm::StructType>(ValTy)) {
554    if (ValSTy->isLayoutIdentical(STy))
555      STy = ValSTy;
556  }
557
558  llvm::Constant *Result = llvm::ConstantStruct::get(STy, Elements);
559
560  assert(NextFieldOffsetInChars.alignTo(getAlignment(Result)) ==
561             getSizeInChars(Result) &&
562         "Size mismatch!");
563
564  return Result;
565}
566
567llvm::Constant *ConstStructBuilder::BuildStruct(ConstantEmitter &Emitter,
568                                                ConstExprEmitter *ExprEmitter,
569                                                llvm::Constant *Base,
570                                                InitListExpr *Updater,
571                                                QualType ValTy) {
572  ConstStructBuilder Builder(Emitter);
573  if (!Builder.Build(ExprEmitter, Base, Updater))
574    return nullptr;
575  return Builder.Finalize(ValTy);
576}
577
578llvm::Constant *ConstStructBuilder::BuildStruct(ConstantEmitter &Emitter,
579                                                InitListExpr *ILE,
580                                                QualType ValTy) {
581  ConstStructBuilder Builder(Emitter);
582
583  if (!Builder.Build(ILE))
584    return nullptr;
585
586  return Builder.Finalize(ValTy);
587}
588
589llvm::Constant *ConstStructBuilder::BuildStruct(ConstantEmitter &Emitter,
590                                                const APValue &Val,
591                                                QualType ValTy) {
592  ConstStructBuilder Builder(Emitter);
593
594  const RecordDecl *RD = ValTy->castAs<RecordType>()->getDecl();
595  const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD);
596  if (!Builder.Build(Val, RD, false, CD, CharUnits::Zero()))
597    return nullptr;
598
599  return Builder.Finalize(ValTy);
600}
601
602
603//===----------------------------------------------------------------------===//
604//                             ConstExprEmitter
605//===----------------------------------------------------------------------===//
606
607static ConstantAddress tryEmitGlobalCompoundLiteral(CodeGenModule &CGM,
608                                                    CodeGenFunction *CGF,
609                                              const CompoundLiteralExpr *E) {
610  CharUnits Align = CGM.getContext().getTypeAlignInChars(E->getType());
611  if (llvm::GlobalVariable *Addr =
612          CGM.getAddrOfConstantCompoundLiteralIfEmitted(E))
613    return ConstantAddress(Addr, Align);
614
615  LangAS addressSpace = E->getType().getAddressSpace();
616
617  ConstantEmitter emitter(CGM, CGF);
618  llvm::Constant *C = emitter.tryEmitForInitializer(E->getInitializer(),
619                                                    addressSpace, E->getType());
620  if (!C) {
621    assert(!E->isFileScope() &&
622           "file-scope compound literal did not have constant initializer!");
623    return ConstantAddress::invalid();
624  }
625
626  auto GV = new llvm::GlobalVariable(CGM.getModule(), C->getType(),
627                                     CGM.isTypeConstant(E->getType(), true),
628                                     llvm::GlobalValue::InternalLinkage,
629                                     C, ".compoundliteral", nullptr,
630                                     llvm::GlobalVariable::NotThreadLocal,
631                    CGM.getContext().getTargetAddressSpace(addressSpace));
632  emitter.finalize(GV);
633  GV->setAlignment(Align.getQuantity());
634  CGM.setAddrOfConstantCompoundLiteral(E, GV);
635  return ConstantAddress(GV, Align);
636}
637
638static llvm::Constant *
639EmitArrayConstant(CodeGenModule &CGM, const ConstantArrayType *DestType,
640                  llvm::Type *CommonElementType, unsigned ArrayBound,
641                  SmallVectorImpl<llvm::Constant *> &Elements,
642                  llvm::Constant *Filler) {
643  // Figure out how long the initial prefix of non-zero elements is.
644  unsigned NonzeroLength = ArrayBound;
645  if (Elements.size() < NonzeroLength && Filler->isNullValue())
646    NonzeroLength = Elements.size();
647  if (NonzeroLength == Elements.size()) {
648    while (NonzeroLength > 0 && Elements[NonzeroLength - 1]->isNullValue())
649      --NonzeroLength;
650  }
651
652  if (NonzeroLength == 0) {
653    return llvm::ConstantAggregateZero::get(
654        CGM.getTypes().ConvertType(QualType(DestType, 0)));
655  }
656
657  // Add a zeroinitializer array filler if we have lots of trailing zeroes.
658  unsigned TrailingZeroes = ArrayBound - NonzeroLength;
659  if (TrailingZeroes >= 8) {
660    assert(Elements.size() >= NonzeroLength &&
661           "missing initializer for non-zero element");
662
663    // If all the elements had the same type up to the trailing zeroes, emit a
664    // struct of two arrays (the nonzero data and the zeroinitializer).
665    if (CommonElementType && NonzeroLength >= 8) {
666      llvm::Constant *Initial = llvm::ConstantArray::get(
667          llvm::ArrayType::get(CommonElementType, NonzeroLength),
668          makeArrayRef(Elements).take_front(NonzeroLength));
669      Elements.resize(2);
670      Elements[0] = Initial;
671    } else {
672      Elements.resize(NonzeroLength + 1);
673    }
674
675    auto *FillerType =
676        CommonElementType
677            ? CommonElementType
678            : CGM.getTypes().ConvertType(DestType->getElementType());
679    FillerType = llvm::ArrayType::get(FillerType, TrailingZeroes);
680    Elements.back() = llvm::ConstantAggregateZero::get(FillerType);
681    CommonElementType = nullptr;
682  } else if (Elements.size() != ArrayBound) {
683    // Otherwise pad to the right size with the filler if necessary.
684    Elements.resize(ArrayBound, Filler);
685    if (Filler->getType() != CommonElementType)
686      CommonElementType = nullptr;
687  }
688
689  // If all elements have the same type, just emit an array constant.
690  if (CommonElementType)
691    return llvm::ConstantArray::get(
692        llvm::ArrayType::get(CommonElementType, ArrayBound), Elements);
693
694  // We have mixed types. Use a packed struct.
695  llvm::SmallVector<llvm::Type *, 16> Types;
696  Types.reserve(Elements.size());
697  for (llvm::Constant *Elt : Elements)
698    Types.push_back(Elt->getType());
699  llvm::StructType *SType =
700      llvm::StructType::get(CGM.getLLVMContext(), Types, true);
701  return llvm::ConstantStruct::get(SType, Elements);
702}
703
704/// This class only needs to handle two cases:
705/// 1) Literals (this is used by APValue emission to emit literals).
706/// 2) Arrays, structs and unions (outside C++11 mode, we don't currently
707///    constant fold these types).
708class ConstExprEmitter :
709  public StmtVisitor<ConstExprEmitter, llvm::Constant*, QualType> {
710  CodeGenModule &CGM;
711  ConstantEmitter &Emitter;
712  llvm::LLVMContext &VMContext;
713public:
714  ConstExprEmitter(ConstantEmitter &emitter)
715    : CGM(emitter.CGM), Emitter(emitter), VMContext(CGM.getLLVMContext()) {
716  }
717
718  //===--------------------------------------------------------------------===//
719  //                            Visitor Methods
720  //===--------------------------------------------------------------------===//
721
722  llvm::Constant *VisitStmt(Stmt *S, QualType T) {
723    return nullptr;
724  }
725
726  llvm::Constant *VisitConstantExpr(ConstantExpr *CE, QualType T) {
727    return Visit(CE->getSubExpr(), T);
728  }
729
730  llvm::Constant *VisitParenExpr(ParenExpr *PE, QualType T) {
731    return Visit(PE->getSubExpr(), T);
732  }
733
734  llvm::Constant *
735  VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE,
736                                    QualType T) {
737    return Visit(PE->getReplacement(), T);
738  }
739
740  llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE,
741                                            QualType T) {
742    return Visit(GE->getResultExpr(), T);
743  }
744
745  llvm::Constant *VisitChooseExpr(ChooseExpr *CE, QualType T) {
746    return Visit(CE->getChosenSubExpr(), T);
747  }
748
749  llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E, QualType T) {
750    return Visit(E->getInitializer(), T);
751  }
752
753  llvm::Constant *VisitCastExpr(CastExpr *E, QualType destType) {
754    if (const auto *ECE = dyn_cast<ExplicitCastExpr>(E))
755      CGM.EmitExplicitCastExprType(ECE, Emitter.CGF);
756    Expr *subExpr = E->getSubExpr();
757
758    switch (E->getCastKind()) {
759    case CK_ToUnion: {
760      // GCC cast to union extension
761      assert(E->getType()->isUnionType() &&
762             "Destination type is not union type!");
763
764      auto field = E->getTargetUnionField();
765
766      auto C = Emitter.tryEmitPrivateForMemory(subExpr, field->getType());
767      if (!C) return nullptr;
768
769      auto destTy = ConvertType(destType);
770      if (C->getType() == destTy) return C;
771
772      // Build a struct with the union sub-element as the first member,
773      // and padded to the appropriate size.
774      SmallVector<llvm::Constant*, 2> Elts;
775      SmallVector<llvm::Type*, 2> Types;
776      Elts.push_back(C);
777      Types.push_back(C->getType());
778      unsigned CurSize = CGM.getDataLayout().getTypeAllocSize(C->getType());
779      unsigned TotalSize = CGM.getDataLayout().getTypeAllocSize(destTy);
780
781      assert(CurSize <= TotalSize && "Union size mismatch!");
782      if (unsigned NumPadBytes = TotalSize - CurSize) {
783        llvm::Type *Ty = CGM.Int8Ty;
784        if (NumPadBytes > 1)
785          Ty = llvm::ArrayType::get(Ty, NumPadBytes);
786
787        Elts.push_back(llvm::UndefValue::get(Ty));
788        Types.push_back(Ty);
789      }
790
791      llvm::StructType *STy = llvm::StructType::get(VMContext, Types, false);
792      return llvm::ConstantStruct::get(STy, Elts);
793    }
794
795    case CK_AddressSpaceConversion: {
796      auto C = Emitter.tryEmitPrivate(subExpr, subExpr->getType());
797      if (!C) return nullptr;
798      LangAS destAS = E->getType()->getPointeeType().getAddressSpace();
799      LangAS srcAS = subExpr->getType()->getPointeeType().getAddressSpace();
800      llvm::Type *destTy = ConvertType(E->getType());
801      return CGM.getTargetCodeGenInfo().performAddrSpaceCast(CGM, C, srcAS,
802                                                             destAS, destTy);
803    }
804
805    case CK_LValueToRValue:
806    case CK_AtomicToNonAtomic:
807    case CK_NonAtomicToAtomic:
808    case CK_NoOp:
809    case CK_ConstructorConversion:
810      return Visit(subExpr, destType);
811
812    case CK_IntToOCLSampler:
813      llvm_unreachable("global sampler variables are not generated");
814
815    case CK_Dependent: llvm_unreachable("saw dependent cast!");
816
817    case CK_BuiltinFnToFnPtr:
818      llvm_unreachable("builtin functions are handled elsewhere");
819
820    case CK_ReinterpretMemberPointer:
821    case CK_DerivedToBaseMemberPointer:
822    case CK_BaseToDerivedMemberPointer: {
823      auto C = Emitter.tryEmitPrivate(subExpr, subExpr->getType());
824      if (!C) return nullptr;
825      return CGM.getCXXABI().EmitMemberPointerConversion(E, C);
826    }
827
828    // These will never be supported.
829    case CK_ObjCObjectLValueCast:
830    case CK_ARCProduceObject:
831    case CK_ARCConsumeObject:
832    case CK_ARCReclaimReturnedObject:
833    case CK_ARCExtendBlockObject:
834    case CK_CopyAndAutoreleaseBlockObject:
835      return nullptr;
836
837    // These don't need to be handled here because Evaluate knows how to
838    // evaluate them in the cases where they can be folded.
839    case CK_BitCast:
840    case CK_ToVoid:
841    case CK_Dynamic:
842    case CK_LValueBitCast:
843    case CK_NullToMemberPointer:
844    case CK_UserDefinedConversion:
845    case CK_CPointerToObjCPointerCast:
846    case CK_BlockPointerToObjCPointerCast:
847    case CK_AnyPointerToBlockPointerCast:
848    case CK_ArrayToPointerDecay:
849    case CK_FunctionToPointerDecay:
850    case CK_BaseToDerived:
851    case CK_DerivedToBase:
852    case CK_UncheckedDerivedToBase:
853    case CK_MemberPointerToBoolean:
854    case CK_VectorSplat:
855    case CK_FloatingRealToComplex:
856    case CK_FloatingComplexToReal:
857    case CK_FloatingComplexToBoolean:
858    case CK_FloatingComplexCast:
859    case CK_FloatingComplexToIntegralComplex:
860    case CK_IntegralRealToComplex:
861    case CK_IntegralComplexToReal:
862    case CK_IntegralComplexToBoolean:
863    case CK_IntegralComplexCast:
864    case CK_IntegralComplexToFloatingComplex:
865    case CK_PointerToIntegral:
866    case CK_PointerToBoolean:
867    case CK_NullToPointer:
868    case CK_IntegralCast:
869    case CK_BooleanToSignedIntegral:
870    case CK_IntegralToPointer:
871    case CK_IntegralToBoolean:
872    case CK_IntegralToFloating:
873    case CK_FloatingToIntegral:
874    case CK_FloatingToBoolean:
875    case CK_FloatingCast:
876    case CK_FixedPointCast:
877    case CK_FixedPointToBoolean:
878    case CK_ZeroToOCLOpaqueType:
879      return nullptr;
880    }
881    llvm_unreachable("Invalid CastKind");
882  }
883
884  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE, QualType T) {
885    return Visit(DAE->getExpr(), T);
886  }
887
888  llvm::Constant *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE, QualType T) {
889    // No need for a DefaultInitExprScope: we don't handle 'this' in a
890    // constant expression.
891    return Visit(DIE->getExpr(), T);
892  }
893
894  llvm::Constant *VisitExprWithCleanups(ExprWithCleanups *E, QualType T) {
895    if (!E->cleanupsHaveSideEffects())
896      return Visit(E->getSubExpr(), T);
897    return nullptr;
898  }
899
900  llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E,
901                                                QualType T) {
902    return Visit(E->GetTemporaryExpr(), T);
903  }
904
905  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE, QualType T) {
906    auto *CAT = CGM.getContext().getAsConstantArrayType(ILE->getType());
907    assert(CAT && "can't emit array init for non-constant-bound array");
908    unsigned NumInitElements = ILE->getNumInits();
909    unsigned NumElements = CAT->getSize().getZExtValue();
910
911    // Initialising an array requires us to automatically
912    // initialise any elements that have not been initialised explicitly
913    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
914
915    QualType EltType = CAT->getElementType();
916
917    // Initialize remaining array elements.
918    llvm::Constant *fillC = nullptr;
919    if (Expr *filler = ILE->getArrayFiller()) {
920      fillC = Emitter.tryEmitAbstractForMemory(filler, EltType);
921      if (!fillC)
922        return nullptr;
923    }
924
925    // Copy initializer elements.
926    SmallVector<llvm::Constant*, 16> Elts;
927    if (fillC && fillC->isNullValue())
928      Elts.reserve(NumInitableElts + 1);
929    else
930      Elts.reserve(NumElements);
931
932    llvm::Type *CommonElementType = nullptr;
933    for (unsigned i = 0; i < NumInitableElts; ++i) {
934      Expr *Init = ILE->getInit(i);
935      llvm::Constant *C = Emitter.tryEmitPrivateForMemory(Init, EltType);
936      if (!C)
937        return nullptr;
938      if (i == 0)
939        CommonElementType = C->getType();
940      else if (C->getType() != CommonElementType)
941        CommonElementType = nullptr;
942      Elts.push_back(C);
943    }
944
945    return EmitArrayConstant(CGM, CAT, CommonElementType, NumElements, Elts,
946                             fillC);
947  }
948
949  llvm::Constant *EmitRecordInitialization(InitListExpr *ILE, QualType T) {
950    return ConstStructBuilder::BuildStruct(Emitter, ILE, T);
951  }
952
953  llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E,
954                                             QualType T) {
955    return CGM.EmitNullConstant(T);
956  }
957
958  llvm::Constant *VisitInitListExpr(InitListExpr *ILE, QualType T) {
959    if (ILE->isTransparent())
960      return Visit(ILE->getInit(0), T);
961
962    if (ILE->getType()->isArrayType())
963      return EmitArrayInitialization(ILE, T);
964
965    if (ILE->getType()->isRecordType())
966      return EmitRecordInitialization(ILE, T);
967
968    return nullptr;
969  }
970
971  llvm::Constant *EmitDesignatedInitUpdater(llvm::Constant *Base,
972                                            InitListExpr *Updater,
973                                            QualType destType) {
974    if (auto destAT = CGM.getContext().getAsArrayType(destType)) {
975      llvm::ArrayType *AType = cast<llvm::ArrayType>(ConvertType(destType));
976      llvm::Type *ElemType = AType->getElementType();
977
978      unsigned NumInitElements = Updater->getNumInits();
979      unsigned NumElements = AType->getNumElements();
980
981      std::vector<llvm::Constant *> Elts;
982      Elts.reserve(NumElements);
983
984      QualType destElemType = destAT->getElementType();
985
986      if (auto DataArray = dyn_cast<llvm::ConstantDataArray>(Base))
987        for (unsigned i = 0; i != NumElements; ++i)
988          Elts.push_back(DataArray->getElementAsConstant(i));
989      else if (auto Array = dyn_cast<llvm::ConstantArray>(Base))
990        for (unsigned i = 0; i != NumElements; ++i)
991          Elts.push_back(Array->getOperand(i));
992      else
993        return nullptr; // FIXME: other array types not implemented
994
995      llvm::Constant *fillC = nullptr;
996      if (Expr *filler = Updater->getArrayFiller())
997        if (!isa<NoInitExpr>(filler))
998          fillC = Emitter.tryEmitAbstractForMemory(filler, destElemType);
999      bool RewriteType = (fillC && fillC->getType() != ElemType);
1000
1001      for (unsigned i = 0; i != NumElements; ++i) {
1002        Expr *Init = nullptr;
1003        if (i < NumInitElements)
1004          Init = Updater->getInit(i);
1005
1006        if (!Init && fillC)
1007          Elts[i] = fillC;
1008        else if (!Init || isa<NoInitExpr>(Init))
1009          ; // Do nothing.
1010        else if (InitListExpr *ChildILE = dyn_cast<InitListExpr>(Init))
1011          Elts[i] = EmitDesignatedInitUpdater(Elts[i], ChildILE, destElemType);
1012        else
1013          Elts[i] = Emitter.tryEmitPrivateForMemory(Init, destElemType);
1014
1015       if (!Elts[i])
1016          return nullptr;
1017        RewriteType |= (Elts[i]->getType() != ElemType);
1018      }
1019
1020      if (RewriteType) {
1021        std::vector<llvm::Type *> Types;
1022        Types.reserve(NumElements);
1023        for (unsigned i = 0; i != NumElements; ++i)
1024          Types.push_back(Elts[i]->getType());
1025        llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
1026                                                        Types, true);
1027        return llvm::ConstantStruct::get(SType, Elts);
1028      }
1029
1030      return llvm::ConstantArray::get(AType, Elts);
1031    }
1032
1033    if (destType->isRecordType())
1034      return ConstStructBuilder::BuildStruct(Emitter, this, Base, Updater,
1035                                             destType);
1036
1037    return nullptr;
1038  }
1039
1040  llvm::Constant *VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E,
1041                                                QualType destType) {
1042    auto C = Visit(E->getBase(), destType);
1043    if (!C) return nullptr;
1044    return EmitDesignatedInitUpdater(C, E->getUpdater(), destType);
1045  }
1046
1047  llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E, QualType Ty) {
1048    if (!E->getConstructor()->isTrivial())
1049      return nullptr;
1050
1051    // FIXME: We should not have to call getBaseElementType here.
1052    const RecordType *RT =
1053      CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>();
1054    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1055
1056    // If the class doesn't have a trivial destructor, we can't emit it as a
1057    // constant expr.
1058    if (!RD->hasTrivialDestructor())
1059      return nullptr;
1060
1061    // Only copy and default constructors can be trivial.
1062
1063
1064    if (E->getNumArgs()) {
1065      assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument");
1066      assert(E->getConstructor()->isCopyOrMoveConstructor() &&
1067             "trivial ctor has argument but isn't a copy/move ctor");
1068
1069      Expr *Arg = E->getArg(0);
1070      assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) &&
1071             "argument to copy ctor is of wrong type");
1072
1073      return Visit(Arg, Ty);
1074    }
1075
1076    return CGM.EmitNullConstant(Ty);
1077  }
1078
1079  llvm::Constant *VisitStringLiteral(StringLiteral *E, QualType T) {
1080    return CGM.GetConstantArrayFromStringLiteral(E);
1081  }
1082
1083  llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E, QualType T) {
1084    // This must be an @encode initializing an array in a static initializer.
1085    // Don't emit it as the address of the string, emit the string data itself
1086    // as an inline array.
1087    std::string Str;
1088    CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str);
1089    const ConstantArrayType *CAT = CGM.getContext().getAsConstantArrayType(T);
1090
1091    // Resize the string to the right size, adding zeros at the end, or
1092    // truncating as needed.
1093    Str.resize(CAT->getSize().getZExtValue(), '\0');
1094    return llvm::ConstantDataArray::getString(VMContext, Str, false);
1095  }
1096
1097  llvm::Constant *VisitUnaryExtension(const UnaryOperator *E, QualType T) {
1098    return Visit(E->getSubExpr(), T);
1099  }
1100
1101  // Utility methods
1102  llvm::Type *ConvertType(QualType T) {
1103    return CGM.getTypes().ConvertType(T);
1104  }
1105};
1106
1107}  // end anonymous namespace.
1108
1109bool ConstStructBuilder::Build(ConstExprEmitter *ExprEmitter,
1110                               llvm::Constant *Base,
1111                               InitListExpr *Updater) {
1112  assert(Base && "base expression should not be empty");
1113
1114  QualType ExprType = Updater->getType();
1115  RecordDecl *RD = ExprType->getAs<RecordType>()->getDecl();
1116  const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
1117  const llvm::StructLayout *BaseLayout = CGM.getDataLayout().getStructLayout(
1118      cast<llvm::StructType>(Base->getType()));
1119  unsigned FieldNo = -1;
1120  unsigned ElementNo = 0;
1121
1122  // Bail out if we have base classes. We could support these, but they only
1123  // arise in C++1z where we will have already constant folded most interesting
1124  // cases. FIXME: There are still a few more cases we can handle this way.
1125  if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD))
1126    if (CXXRD->getNumBases())
1127      return false;
1128
1129  for (FieldDecl *Field : RD->fields()) {
1130    ++FieldNo;
1131
1132    if (RD->isUnion() && Updater->getInitializedFieldInUnion() != Field)
1133      continue;
1134
1135    // Skip anonymous bitfields.
1136    if (Field->isUnnamedBitfield())
1137      continue;
1138
1139    llvm::Constant *EltInit = Base->getAggregateElement(ElementNo);
1140
1141    // Bail out if the type of the ConstantStruct does not have the same layout
1142    // as the type of the InitListExpr.
1143    if (CGM.getTypes().ConvertType(Field->getType()) != EltInit->getType() ||
1144        Layout.getFieldOffset(ElementNo) !=
1145          BaseLayout->getElementOffsetInBits(ElementNo))
1146      return false;
1147
1148    // Get the initializer. If we encounter an empty field or a NoInitExpr,
1149    // we use values from the base expression.
1150    Expr *Init = nullptr;
1151    if (ElementNo < Updater->getNumInits())
1152      Init = Updater->getInit(ElementNo);
1153
1154    if (!Init || isa<NoInitExpr>(Init))
1155      ; // Do nothing.
1156    else if (InitListExpr *ChildILE = dyn_cast<InitListExpr>(Init))
1157      EltInit = ExprEmitter->EmitDesignatedInitUpdater(EltInit, ChildILE,
1158                                                       Field->getType());
1159    else
1160      EltInit = Emitter.tryEmitPrivateForMemory(Init, Field->getType());
1161
1162    ++ElementNo;
1163
1164    if (!EltInit)
1165      return false;
1166
1167    if (!Field->isBitField())
1168      AppendField(Field, Layout.getFieldOffset(FieldNo), EltInit);
1169    else if (llvm::ConstantInt *CI = dyn_cast<llvm::ConstantInt>(EltInit))
1170      AppendBitField(Field, Layout.getFieldOffset(FieldNo), CI);
1171    else
1172      // Initializing a bitfield with a non-trivial constant?
1173      return false;
1174  }
1175
1176  return true;
1177}
1178
1179llvm::Constant *ConstantEmitter::validateAndPopAbstract(llvm::Constant *C,
1180                                                        AbstractState saved) {
1181  Abstract = saved.OldValue;
1182
1183  assert(saved.OldPlaceholdersSize == PlaceholderAddresses.size() &&
1184         "created a placeholder while doing an abstract emission?");
1185
1186  // No validation necessary for now.
1187  // No cleanup to do for now.
1188  return C;
1189}
1190
1191llvm::Constant *
1192ConstantEmitter::tryEmitAbstractForInitializer(const VarDecl &D) {
1193  auto state = pushAbstract();
1194  auto C = tryEmitPrivateForVarInit(D);
1195  return validateAndPopAbstract(C, state);
1196}
1197
1198llvm::Constant *
1199ConstantEmitter::tryEmitAbstract(const Expr *E, QualType destType) {
1200  auto state = pushAbstract();
1201  auto C = tryEmitPrivate(E, destType);
1202  return validateAndPopAbstract(C, state);
1203}
1204
1205llvm::Constant *
1206ConstantEmitter::tryEmitAbstract(const APValue &value, QualType destType) {
1207  auto state = pushAbstract();
1208  auto C = tryEmitPrivate(value, destType);
1209  return validateAndPopAbstract(C, state);
1210}
1211
1212llvm::Constant *
1213ConstantEmitter::emitAbstract(const Expr *E, QualType destType) {
1214  auto state = pushAbstract();
1215  auto C = tryEmitPrivate(E, destType);
1216  C = validateAndPopAbstract(C, state);
1217  if (!C) {
1218    CGM.Error(E->getExprLoc(),
1219              "internal error: could not emit constant value \"abstractly\"");
1220    C = CGM.EmitNullConstant(destType);
1221  }
1222  return C;
1223}
1224
1225llvm::Constant *
1226ConstantEmitter::emitAbstract(SourceLocation loc, const APValue &value,
1227                              QualType destType) {
1228  auto state = pushAbstract();
1229  auto C = tryEmitPrivate(value, destType);
1230  C = validateAndPopAbstract(C, state);
1231  if (!C) {
1232    CGM.Error(loc,
1233              "internal error: could not emit constant value \"abstractly\"");
1234    C = CGM.EmitNullConstant(destType);
1235  }
1236  return C;
1237}
1238
1239llvm::Constant *ConstantEmitter::tryEmitForInitializer(const VarDecl &D) {
1240  initializeNonAbstract(D.getType().getAddressSpace());
1241  return markIfFailed(tryEmitPrivateForVarInit(D));
1242}
1243
1244llvm::Constant *ConstantEmitter::tryEmitForInitializer(const Expr *E,
1245                                                       LangAS destAddrSpace,
1246                                                       QualType destType) {
1247  initializeNonAbstract(destAddrSpace);
1248  return markIfFailed(tryEmitPrivateForMemory(E, destType));
1249}
1250
1251llvm::Constant *ConstantEmitter::emitForInitializer(const APValue &value,
1252                                                    LangAS destAddrSpace,
1253                                                    QualType destType) {
1254  initializeNonAbstract(destAddrSpace);
1255  auto C = tryEmitPrivateForMemory(value, destType);
1256  assert(C && "couldn't emit constant value non-abstractly?");
1257  return C;
1258}
1259
1260llvm::GlobalValue *ConstantEmitter::getCurrentAddrPrivate() {
1261  assert(!Abstract && "cannot get current address for abstract constant");
1262
1263
1264
1265  // Make an obviously ill-formed global that should blow up compilation
1266  // if it survives.
1267  auto global = new llvm::GlobalVariable(CGM.getModule(), CGM.Int8Ty, true,
1268                                         llvm::GlobalValue::PrivateLinkage,
1269                                         /*init*/ nullptr,
1270                                         /*name*/ "",
1271                                         /*before*/ nullptr,
1272                                         llvm::GlobalVariable::NotThreadLocal,
1273                                         CGM.getContext().getTargetAddressSpace(DestAddressSpace));
1274
1275  PlaceholderAddresses.push_back(std::make_pair(nullptr, global));
1276
1277  return global;
1278}
1279
1280void ConstantEmitter::registerCurrentAddrPrivate(llvm::Constant *signal,
1281                                           llvm::GlobalValue *placeholder) {
1282  assert(!PlaceholderAddresses.empty());
1283  assert(PlaceholderAddresses.back().first == nullptr);
1284  assert(PlaceholderAddresses.back().second == placeholder);
1285  PlaceholderAddresses.back().first = signal;
1286}
1287
1288namespace {
1289  struct ReplacePlaceholders {
1290    CodeGenModule &CGM;
1291
1292    /// The base address of the global.
1293    llvm::Constant *Base;
1294    llvm::Type *BaseValueTy = nullptr;
1295
1296    /// The placeholder addresses that were registered during emission.
1297    llvm::DenseMap<llvm::Constant*, llvm::GlobalVariable*> PlaceholderAddresses;
1298
1299    /// The locations of the placeholder signals.
1300    llvm::DenseMap<llvm::GlobalVariable*, llvm::Constant*> Locations;
1301
1302    /// The current index stack.  We use a simple unsigned stack because
1303    /// we assume that placeholders will be relatively sparse in the
1304    /// initializer, but we cache the index values we find just in case.
1305    llvm::SmallVector<unsigned, 8> Indices;
1306    llvm::SmallVector<llvm::Constant*, 8> IndexValues;
1307
1308    ReplacePlaceholders(CodeGenModule &CGM, llvm::Constant *base,
1309                        ArrayRef<std::pair<llvm::Constant*,
1310                                           llvm::GlobalVariable*>> addresses)
1311        : CGM(CGM), Base(base),
1312          PlaceholderAddresses(addresses.begin(), addresses.end()) {
1313    }
1314
1315    void replaceInInitializer(llvm::Constant *init) {
1316      // Remember the type of the top-most initializer.
1317      BaseValueTy = init->getType();
1318
1319      // Initialize the stack.
1320      Indices.push_back(0);
1321      IndexValues.push_back(nullptr);
1322
1323      // Recurse into the initializer.
1324      findLocations(init);
1325
1326      // Check invariants.
1327      assert(IndexValues.size() == Indices.size() && "mismatch");
1328      assert(Indices.size() == 1 && "didn't pop all indices");
1329
1330      // Do the replacement; this basically invalidates 'init'.
1331      assert(Locations.size() == PlaceholderAddresses.size() &&
1332             "missed a placeholder?");
1333
1334      // We're iterating over a hashtable, so this would be a source of
1335      // non-determinism in compiler output *except* that we're just
1336      // messing around with llvm::Constant structures, which never itself
1337      // does anything that should be visible in compiler output.
1338      for (auto &entry : Locations) {
1339        assert(entry.first->getParent() == nullptr && "not a placeholder!");
1340        entry.first->replaceAllUsesWith(entry.second);
1341        entry.first->eraseFromParent();
1342      }
1343    }
1344
1345  private:
1346    void findLocations(llvm::Constant *init) {
1347      // Recurse into aggregates.
1348      if (auto agg = dyn_cast<llvm::ConstantAggregate>(init)) {
1349        for (unsigned i = 0, e = agg->getNumOperands(); i != e; ++i) {
1350          Indices.push_back(i);
1351          IndexValues.push_back(nullptr);
1352
1353          findLocations(agg->getOperand(i));
1354
1355          IndexValues.pop_back();
1356          Indices.pop_back();
1357        }
1358        return;
1359      }
1360
1361      // Otherwise, check for registered constants.
1362      while (true) {
1363        auto it = PlaceholderAddresses.find(init);
1364        if (it != PlaceholderAddresses.end()) {
1365          setLocation(it->second);
1366          break;
1367        }
1368
1369        // Look through bitcasts or other expressions.
1370        if (auto expr = dyn_cast<llvm::ConstantExpr>(init)) {
1371          init = expr->getOperand(0);
1372        } else {
1373          break;
1374        }
1375      }
1376    }
1377
1378    void setLocation(llvm::GlobalVariable *placeholder) {
1379      assert(Locations.find(placeholder) == Locations.end() &&
1380             "already found location for placeholder!");
1381
1382      // Lazily fill in IndexValues with the values from Indices.
1383      // We do this in reverse because we should always have a strict
1384      // prefix of indices from the start.
1385      assert(Indices.size() == IndexValues.size());
1386      for (size_t i = Indices.size() - 1; i != size_t(-1); --i) {
1387        if (IndexValues[i]) {
1388#ifndef NDEBUG
1389          for (size_t j = 0; j != i + 1; ++j) {
1390            assert(IndexValues[j] &&
1391                   isa<llvm::ConstantInt>(IndexValues[j]) &&
1392                   cast<llvm::ConstantInt>(IndexValues[j])->getZExtValue()
1393                     == Indices[j]);
1394          }
1395#endif
1396          break;
1397        }
1398
1399        IndexValues[i] = llvm::ConstantInt::get(CGM.Int32Ty, Indices[i]);
1400      }
1401
1402      // Form a GEP and then bitcast to the placeholder type so that the
1403      // replacement will succeed.
1404      llvm::Constant *location =
1405        llvm::ConstantExpr::getInBoundsGetElementPtr(BaseValueTy,
1406                                                     Base, IndexValues);
1407      location = llvm::ConstantExpr::getBitCast(location,
1408                                                placeholder->getType());
1409
1410      Locations.insert({placeholder, location});
1411    }
1412  };
1413}
1414
1415void ConstantEmitter::finalize(llvm::GlobalVariable *global) {
1416  assert(InitializedNonAbstract &&
1417         "finalizing emitter that was used for abstract emission?");
1418  assert(!Finalized && "finalizing emitter multiple times");
1419  assert(global->getInitializer());
1420
1421  // Note that we might also be Failed.
1422  Finalized = true;
1423
1424  if (!PlaceholderAddresses.empty()) {
1425    ReplacePlaceholders(CGM, global, PlaceholderAddresses)
1426      .replaceInInitializer(global->getInitializer());
1427    PlaceholderAddresses.clear(); // satisfy
1428  }
1429}
1430
1431ConstantEmitter::~ConstantEmitter() {
1432  assert((!InitializedNonAbstract || Finalized || Failed) &&
1433         "not finalized after being initialized for non-abstract emission");
1434  assert(PlaceholderAddresses.empty() && "unhandled placeholders");
1435}
1436
1437static QualType getNonMemoryType(CodeGenModule &CGM, QualType type) {
1438  if (auto AT = type->getAs<AtomicType>()) {
1439    return CGM.getContext().getQualifiedType(AT->getValueType(),
1440                                             type.getQualifiers());
1441  }
1442  return type;
1443}
1444
1445llvm::Constant *ConstantEmitter::tryEmitPrivateForVarInit(const VarDecl &D) {
1446  // Make a quick check if variable can be default NULL initialized
1447  // and avoid going through rest of code which may do, for c++11,
1448  // initialization of memory to all NULLs.
1449  if (!D.hasLocalStorage()) {
1450    QualType Ty = CGM.getContext().getBaseElementType(D.getType());
1451    if (Ty->isRecordType())
1452      if (const CXXConstructExpr *E =
1453          dyn_cast_or_null<CXXConstructExpr>(D.getInit())) {
1454        const CXXConstructorDecl *CD = E->getConstructor();
1455        if (CD->isTrivial() && CD->isDefaultConstructor())
1456          return CGM.EmitNullConstant(D.getType());
1457      }
1458    InConstantContext = true;
1459  }
1460
1461  QualType destType = D.getType();
1462
1463  // Try to emit the initializer.  Note that this can allow some things that
1464  // are not allowed by tryEmitPrivateForMemory alone.
1465  if (auto value = D.evaluateValue()) {
1466    return tryEmitPrivateForMemory(*value, destType);
1467  }
1468
1469  // FIXME: Implement C++11 [basic.start.init]p2: if the initializer of a
1470  // reference is a constant expression, and the reference binds to a temporary,
1471  // then constant initialization is performed. ConstExprEmitter will
1472  // incorrectly emit a prvalue constant in this case, and the calling code
1473  // interprets that as the (pointer) value of the reference, rather than the
1474  // desired value of the referee.
1475  if (destType->isReferenceType())
1476    return nullptr;
1477
1478  const Expr *E = D.getInit();
1479  assert(E && "No initializer to emit");
1480
1481  auto nonMemoryDestType = getNonMemoryType(CGM, destType);
1482  auto C =
1483    ConstExprEmitter(*this).Visit(const_cast<Expr*>(E), nonMemoryDestType);
1484  return (C ? emitForMemory(C, destType) : nullptr);
1485}
1486
1487llvm::Constant *
1488ConstantEmitter::tryEmitAbstractForMemory(const Expr *E, QualType destType) {
1489  auto nonMemoryDestType = getNonMemoryType(CGM, destType);
1490  auto C = tryEmitAbstract(E, nonMemoryDestType);
1491  return (C ? emitForMemory(C, destType) : nullptr);
1492}
1493
1494llvm::Constant *
1495ConstantEmitter::tryEmitAbstractForMemory(const APValue &value,
1496                                          QualType destType) {
1497  auto nonMemoryDestType = getNonMemoryType(CGM, destType);
1498  auto C = tryEmitAbstract(value, nonMemoryDestType);
1499  return (C ? emitForMemory(C, destType) : nullptr);
1500}
1501
1502llvm::Constant *ConstantEmitter::tryEmitPrivateForMemory(const Expr *E,
1503                                                         QualType destType) {
1504  auto nonMemoryDestType = getNonMemoryType(CGM, destType);
1505  llvm::Constant *C = tryEmitPrivate(E, nonMemoryDestType);
1506  return (C ? emitForMemory(C, destType) : nullptr);
1507}
1508
1509llvm::Constant *ConstantEmitter::tryEmitPrivateForMemory(const APValue &value,
1510                                                         QualType destType) {
1511  auto nonMemoryDestType = getNonMemoryType(CGM, destType);
1512  auto C = tryEmitPrivate(value, nonMemoryDestType);
1513  return (C ? emitForMemory(C, destType) : nullptr);
1514}
1515
1516llvm::Constant *ConstantEmitter::emitForMemory(CodeGenModule &CGM,
1517                                               llvm::Constant *C,
1518                                               QualType destType) {
1519  // For an _Atomic-qualified constant, we may need to add tail padding.
1520  if (auto AT = destType->getAs<AtomicType>()) {
1521    QualType destValueType = AT->getValueType();
1522    C = emitForMemory(CGM, C, destValueType);
1523
1524    uint64_t innerSize = CGM.getContext().getTypeSize(destValueType);
1525    uint64_t outerSize = CGM.getContext().getTypeSize(destType);
1526    if (innerSize == outerSize)
1527      return C;
1528
1529    assert(innerSize < outerSize && "emitted over-large constant for atomic");
1530    llvm::Constant *elts[] = {
1531      C,
1532      llvm::ConstantAggregateZero::get(
1533          llvm::ArrayType::get(CGM.Int8Ty, (outerSize - innerSize) / 8))
1534    };
1535    return llvm::ConstantStruct::getAnon(elts);
1536  }
1537
1538  // Zero-extend bool.
1539  if (C->getType()->isIntegerTy(1)) {
1540    llvm::Type *boolTy = CGM.getTypes().ConvertTypeForMem(destType);
1541    return llvm::ConstantExpr::getZExt(C, boolTy);
1542  }
1543
1544  return C;
1545}
1546
1547llvm::Constant *ConstantEmitter::tryEmitPrivate(const Expr *E,
1548                                                QualType destType) {
1549  Expr::EvalResult Result;
1550
1551  bool Success = false;
1552
1553  if (destType->isReferenceType())
1554    Success = E->EvaluateAsLValue(Result, CGM.getContext());
1555  else
1556    Success = E->EvaluateAsRValue(Result, CGM.getContext(), InConstantContext);
1557
1558  llvm::Constant *C;
1559  if (Success && !Result.HasSideEffects)
1560    C = tryEmitPrivate(Result.Val, destType);
1561  else
1562    C = ConstExprEmitter(*this).Visit(const_cast<Expr*>(E), destType);
1563
1564  return C;
1565}
1566
1567llvm::Constant *CodeGenModule::getNullPointer(llvm::PointerType *T, QualType QT) {
1568  return getTargetCodeGenInfo().getNullPointer(*this, T, QT);
1569}
1570
1571namespace {
1572/// A struct which can be used to peephole certain kinds of finalization
1573/// that normally happen during l-value emission.
1574struct ConstantLValue {
1575  llvm::Constant *Value;
1576  bool HasOffsetApplied;
1577
1578  /*implicit*/ ConstantLValue(llvm::Constant *value,
1579                              bool hasOffsetApplied = false)
1580    : Value(value), HasOffsetApplied(false) {}
1581
1582  /*implicit*/ ConstantLValue(ConstantAddress address)
1583    : ConstantLValue(address.getPointer()) {}
1584};
1585
1586/// A helper class for emitting constant l-values.
1587class ConstantLValueEmitter : public ConstStmtVisitor<ConstantLValueEmitter,
1588                                                      ConstantLValue> {
1589  CodeGenModule &CGM;
1590  ConstantEmitter &Emitter;
1591  const APValue &Value;
1592  QualType DestType;
1593
1594  // Befriend StmtVisitorBase so that we don't have to expose Visit*.
1595  friend StmtVisitorBase;
1596
1597public:
1598  ConstantLValueEmitter(ConstantEmitter &emitter, const APValue &value,
1599                        QualType destType)
1600    : CGM(emitter.CGM), Emitter(emitter), Value(value), DestType(destType) {}
1601
1602  llvm::Constant *tryEmit();
1603
1604private:
1605  llvm::Constant *tryEmitAbsolute(llvm::Type *destTy);
1606  ConstantLValue tryEmitBase(const APValue::LValueBase &base);
1607
1608  ConstantLValue VisitStmt(const Stmt *S) { return nullptr; }
1609  ConstantLValue VisitConstantExpr(const ConstantExpr *E);
1610  ConstantLValue VisitCompoundLiteralExpr(const CompoundLiteralExpr *E);
1611  ConstantLValue VisitStringLiteral(const StringLiteral *E);
1612  ConstantLValue VisitObjCEncodeExpr(const ObjCEncodeExpr *E);
1613  ConstantLValue VisitObjCStringLiteral(const ObjCStringLiteral *E);
1614  ConstantLValue VisitPredefinedExpr(const PredefinedExpr *E);
1615  ConstantLValue VisitAddrLabelExpr(const AddrLabelExpr *E);
1616  ConstantLValue VisitCallExpr(const CallExpr *E);
1617  ConstantLValue VisitBlockExpr(const BlockExpr *E);
1618  ConstantLValue VisitCXXTypeidExpr(const CXXTypeidExpr *E);
1619  ConstantLValue VisitCXXUuidofExpr(const CXXUuidofExpr *E);
1620  ConstantLValue VisitMaterializeTemporaryExpr(
1621                                         const MaterializeTemporaryExpr *E);
1622
1623  bool hasNonZeroOffset() const {
1624    return !Value.getLValueOffset().isZero();
1625  }
1626
1627  /// Return the value offset.
1628  llvm::Constant *getOffset() {
1629    return llvm::ConstantInt::get(CGM.Int64Ty,
1630                                  Value.getLValueOffset().getQuantity());
1631  }
1632
1633  /// Apply the value offset to the given constant.
1634  llvm::Constant *applyOffset(llvm::Constant *C) {
1635    if (!hasNonZeroOffset())
1636      return C;
1637
1638    llvm::Type *origPtrTy = C->getType();
1639    unsigned AS = origPtrTy->getPointerAddressSpace();
1640    llvm::Type *charPtrTy = CGM.Int8Ty->getPointerTo(AS);
1641    C = llvm::ConstantExpr::getBitCast(C, charPtrTy);
1642    C = llvm::ConstantExpr::getGetElementPtr(CGM.Int8Ty, C, getOffset());
1643    C = llvm::ConstantExpr::getPointerCast(C, origPtrTy);
1644    return C;
1645  }
1646};
1647
1648}
1649
1650llvm::Constant *ConstantLValueEmitter::tryEmit() {
1651  const APValue::LValueBase &base = Value.getLValueBase();
1652
1653  // Certain special array initializers are represented in APValue
1654  // as l-values referring to the base expression which generates the
1655  // array.  This happens with e.g. string literals.  These should
1656  // probably just get their own representation kind in APValue.
1657  if (DestType->isArrayType()) {
1658    assert(!hasNonZeroOffset() && "offset on array initializer");
1659    auto expr = const_cast<Expr*>(base.get<const Expr*>());
1660    return ConstExprEmitter(Emitter).Visit(expr, DestType);
1661  }
1662
1663  // Otherwise, the destination type should be a pointer or reference
1664  // type, but it might also be a cast thereof.
1665  //
1666  // FIXME: the chain of casts required should be reflected in the APValue.
1667  // We need this in order to correctly handle things like a ptrtoint of a
1668  // non-zero null pointer and addrspace casts that aren't trivially
1669  // represented in LLVM IR.
1670  auto destTy = CGM.getTypes().ConvertTypeForMem(DestType);
1671  assert(isa<llvm::IntegerType>(destTy) || isa<llvm::PointerType>(destTy));
1672
1673  // If there's no base at all, this is a null or absolute pointer,
1674  // possibly cast back to an integer type.
1675  if (!base) {
1676    return tryEmitAbsolute(destTy);
1677  }
1678
1679  // Otherwise, try to emit the base.
1680  ConstantLValue result = tryEmitBase(base);
1681
1682  // If that failed, we're done.
1683  llvm::Constant *value = result.Value;
1684  if (!value) return nullptr;
1685
1686  // Apply the offset if necessary and not already done.
1687  if (!result.HasOffsetApplied) {
1688    value = applyOffset(value);
1689  }
1690
1691  // Convert to the appropriate type; this could be an lvalue for
1692  // an integer.  FIXME: performAddrSpaceCast
1693  if (isa<llvm::PointerType>(destTy))
1694    return llvm::ConstantExpr::getPointerCast(value, destTy);
1695
1696  return llvm::ConstantExpr::getPtrToInt(value, destTy);
1697}
1698
1699/// Try to emit an absolute l-value, such as a null pointer or an integer
1700/// bitcast to pointer type.
1701llvm::Constant *
1702ConstantLValueEmitter::tryEmitAbsolute(llvm::Type *destTy) {
1703  auto offset = getOffset();
1704
1705  // If we're producing a pointer, this is easy.
1706  if (auto destPtrTy = cast<llvm::PointerType>(destTy)) {
1707    if (Value.isNullPointer()) {
1708      // FIXME: integer offsets from non-zero null pointers.
1709      return CGM.getNullPointer(destPtrTy, DestType);
1710    }
1711
1712    // Convert the integer to a pointer-sized integer before converting it
1713    // to a pointer.
1714    // FIXME: signedness depends on the original integer type.
1715    auto intptrTy = CGM.getDataLayout().getIntPtrType(destPtrTy);
1716    llvm::Constant *C = offset;
1717    C = llvm::ConstantExpr::getIntegerCast(getOffset(), intptrTy,
1718                                           /*isSigned*/ false);
1719    C = llvm::ConstantExpr::getIntToPtr(C, destPtrTy);
1720    return C;
1721  }
1722
1723  // Otherwise, we're basically returning an integer constant.
1724
1725  // FIXME: this does the wrong thing with ptrtoint of a null pointer,
1726  // but since we don't know the original pointer type, there's not much
1727  // we can do about it.
1728
1729  auto C = getOffset();
1730  C = llvm::ConstantExpr::getIntegerCast(C, destTy, /*isSigned*/ false);
1731  return C;
1732}
1733
1734ConstantLValue
1735ConstantLValueEmitter::tryEmitBase(const APValue::LValueBase &base) {
1736  // Handle values.
1737  if (const ValueDecl *D = base.dyn_cast<const ValueDecl*>()) {
1738    if (D->hasAttr<WeakRefAttr>())
1739      return CGM.GetWeakRefReference(D).getPointer();
1740
1741    if (auto FD = dyn_cast<FunctionDecl>(D))
1742      return CGM.GetAddrOfFunction(FD);
1743
1744    if (auto VD = dyn_cast<VarDecl>(D)) {
1745      // We can never refer to a variable with local storage.
1746      if (!VD->hasLocalStorage()) {
1747        if (VD->isFileVarDecl() || VD->hasExternalStorage())
1748          return CGM.GetAddrOfGlobalVar(VD);
1749
1750        if (VD->isLocalVarDecl()) {
1751          return CGM.getOrCreateStaticVarDecl(
1752              *VD, CGM.getLLVMLinkageVarDefinition(VD, /*isConstant=*/false));
1753        }
1754      }
1755    }
1756
1757    return nullptr;
1758  }
1759
1760  // Otherwise, it must be an expression.
1761  return Visit(base.get<const Expr*>());
1762}
1763
1764ConstantLValue
1765ConstantLValueEmitter::VisitConstantExpr(const ConstantExpr *E) {
1766  return Visit(E->getSubExpr());
1767}
1768
1769ConstantLValue
1770ConstantLValueEmitter::VisitCompoundLiteralExpr(const CompoundLiteralExpr *E) {
1771  return tryEmitGlobalCompoundLiteral(CGM, Emitter.CGF, E);
1772}
1773
1774ConstantLValue
1775ConstantLValueEmitter::VisitStringLiteral(const StringLiteral *E) {
1776  return CGM.GetAddrOfConstantStringFromLiteral(E);
1777}
1778
1779ConstantLValue
1780ConstantLValueEmitter::VisitObjCEncodeExpr(const ObjCEncodeExpr *E) {
1781  return CGM.GetAddrOfConstantStringFromObjCEncode(E);
1782}
1783
1784ConstantLValue
1785ConstantLValueEmitter::VisitObjCStringLiteral(const ObjCStringLiteral *E) {
1786  auto C = CGM.getObjCRuntime().GenerateConstantString(E->getString());
1787  return C.getElementBitCast(CGM.getTypes().ConvertTypeForMem(E->getType()));
1788}
1789
1790ConstantLValue
1791ConstantLValueEmitter::VisitPredefinedExpr(const PredefinedExpr *E) {
1792  if (auto CGF = Emitter.CGF) {
1793    LValue Res = CGF->EmitPredefinedLValue(E);
1794    return cast<ConstantAddress>(Res.getAddress());
1795  }
1796
1797  auto kind = E->getIdentKind();
1798  if (kind == PredefinedExpr::PrettyFunction) {
1799    return CGM.GetAddrOfConstantCString("top level", ".tmp");
1800  }
1801
1802  return CGM.GetAddrOfConstantCString("", ".tmp");
1803}
1804
1805ConstantLValue
1806ConstantLValueEmitter::VisitAddrLabelExpr(const AddrLabelExpr *E) {
1807  assert(Emitter.CGF && "Invalid address of label expression outside function");
1808  llvm::Constant *Ptr = Emitter.CGF->GetAddrOfLabel(E->getLabel());
1809  Ptr = llvm::ConstantExpr::getBitCast(Ptr,
1810                                   CGM.getTypes().ConvertType(E->getType()));
1811  return Ptr;
1812}
1813
1814ConstantLValue
1815ConstantLValueEmitter::VisitCallExpr(const CallExpr *E) {
1816  unsigned builtin = E->getBuiltinCallee();
1817  if (builtin != Builtin::BI__builtin___CFStringMakeConstantString &&
1818      builtin != Builtin::BI__builtin___NSStringMakeConstantString)
1819    return nullptr;
1820
1821  auto literal = cast<StringLiteral>(E->getArg(0)->IgnoreParenCasts());
1822  if (builtin == Builtin::BI__builtin___NSStringMakeConstantString) {
1823    return CGM.getObjCRuntime().GenerateConstantString(literal);
1824  } else {
1825    // FIXME: need to deal with UCN conversion issues.
1826    return CGM.GetAddrOfConstantCFString(literal);
1827  }
1828}
1829
1830ConstantLValue
1831ConstantLValueEmitter::VisitBlockExpr(const BlockExpr *E) {
1832  StringRef functionName;
1833  if (auto CGF = Emitter.CGF)
1834    functionName = CGF->CurFn->getName();
1835  else
1836    functionName = "global";
1837
1838  return CGM.GetAddrOfGlobalBlock(E, functionName);
1839}
1840
1841ConstantLValue
1842ConstantLValueEmitter::VisitCXXTypeidExpr(const CXXTypeidExpr *E) {
1843  QualType T;
1844  if (E->isTypeOperand())
1845    T = E->getTypeOperand(CGM.getContext());
1846  else
1847    T = E->getExprOperand()->getType();
1848  return CGM.GetAddrOfRTTIDescriptor(T);
1849}
1850
1851ConstantLValue
1852ConstantLValueEmitter::VisitCXXUuidofExpr(const CXXUuidofExpr *E) {
1853  return CGM.GetAddrOfUuidDescriptor(E);
1854}
1855
1856ConstantLValue
1857ConstantLValueEmitter::VisitMaterializeTemporaryExpr(
1858                                            const MaterializeTemporaryExpr *E) {
1859  assert(E->getStorageDuration() == SD_Static);
1860  SmallVector<const Expr *, 2> CommaLHSs;
1861  SmallVector<SubobjectAdjustment, 2> Adjustments;
1862  const Expr *Inner = E->GetTemporaryExpr()
1863      ->skipRValueSubobjectAdjustments(CommaLHSs, Adjustments);
1864  return CGM.GetAddrOfGlobalTemporary(E, Inner);
1865}
1866
1867llvm::Constant *ConstantEmitter::tryEmitPrivate(const APValue &Value,
1868                                                QualType DestType) {
1869  switch (Value.getKind()) {
1870  case APValue::Uninitialized:
1871    llvm_unreachable("Constant expressions should be initialized.");
1872  case APValue::LValue:
1873    return ConstantLValueEmitter(*this, Value, DestType).tryEmit();
1874  case APValue::Int:
1875    return llvm::ConstantInt::get(CGM.getLLVMContext(), Value.getInt());
1876  case APValue::ComplexInt: {
1877    llvm::Constant *Complex[2];
1878
1879    Complex[0] = llvm::ConstantInt::get(CGM.getLLVMContext(),
1880                                        Value.getComplexIntReal());
1881    Complex[1] = llvm::ConstantInt::get(CGM.getLLVMContext(),
1882                                        Value.getComplexIntImag());
1883
1884    // FIXME: the target may want to specify that this is packed.
1885    llvm::StructType *STy =
1886        llvm::StructType::get(Complex[0]->getType(), Complex[1]->getType());
1887    return llvm::ConstantStruct::get(STy, Complex);
1888  }
1889  case APValue::Float: {
1890    const llvm::APFloat &Init = Value.getFloat();
1891    if (&Init.getSemantics() == &llvm::APFloat::IEEEhalf() &&
1892        !CGM.getContext().getLangOpts().NativeHalfType &&
1893        CGM.getContext().getTargetInfo().useFP16ConversionIntrinsics())
1894      return llvm::ConstantInt::get(CGM.getLLVMContext(),
1895                                    Init.bitcastToAPInt());
1896    else
1897      return llvm::ConstantFP::get(CGM.getLLVMContext(), Init);
1898  }
1899  case APValue::ComplexFloat: {
1900    llvm::Constant *Complex[2];
1901
1902    Complex[0] = llvm::ConstantFP::get(CGM.getLLVMContext(),
1903                                       Value.getComplexFloatReal());
1904    Complex[1] = llvm::ConstantFP::get(CGM.getLLVMContext(),
1905                                       Value.getComplexFloatImag());
1906
1907    // FIXME: the target may want to specify that this is packed.
1908    llvm::StructType *STy =
1909        llvm::StructType::get(Complex[0]->getType(), Complex[1]->getType());
1910    return llvm::ConstantStruct::get(STy, Complex);
1911  }
1912  case APValue::Vector: {
1913    unsigned NumElts = Value.getVectorLength();
1914    SmallVector<llvm::Constant *, 4> Inits(NumElts);
1915
1916    for (unsigned I = 0; I != NumElts; ++I) {
1917      const APValue &Elt = Value.getVectorElt(I);
1918      if (Elt.isInt())
1919        Inits[I] = llvm::ConstantInt::get(CGM.getLLVMContext(), Elt.getInt());
1920      else if (Elt.isFloat())
1921        Inits[I] = llvm::ConstantFP::get(CGM.getLLVMContext(), Elt.getFloat());
1922      else
1923        llvm_unreachable("unsupported vector element type");
1924    }
1925    return llvm::ConstantVector::get(Inits);
1926  }
1927  case APValue::AddrLabelDiff: {
1928    const AddrLabelExpr *LHSExpr = Value.getAddrLabelDiffLHS();
1929    const AddrLabelExpr *RHSExpr = Value.getAddrLabelDiffRHS();
1930    llvm::Constant *LHS = tryEmitPrivate(LHSExpr, LHSExpr->getType());
1931    llvm::Constant *RHS = tryEmitPrivate(RHSExpr, RHSExpr->getType());
1932    if (!LHS || !RHS) return nullptr;
1933
1934    // Compute difference
1935    llvm::Type *ResultType = CGM.getTypes().ConvertType(DestType);
1936    LHS = llvm::ConstantExpr::getPtrToInt(LHS, CGM.IntPtrTy);
1937    RHS = llvm::ConstantExpr::getPtrToInt(RHS, CGM.IntPtrTy);
1938    llvm::Constant *AddrLabelDiff = llvm::ConstantExpr::getSub(LHS, RHS);
1939
1940    // LLVM is a bit sensitive about the exact format of the
1941    // address-of-label difference; make sure to truncate after
1942    // the subtraction.
1943    return llvm::ConstantExpr::getTruncOrBitCast(AddrLabelDiff, ResultType);
1944  }
1945  case APValue::Struct:
1946  case APValue::Union:
1947    return ConstStructBuilder::BuildStruct(*this, Value, DestType);
1948  case APValue::Array: {
1949    const ConstantArrayType *CAT =
1950        CGM.getContext().getAsConstantArrayType(DestType);
1951    unsigned NumElements = Value.getArraySize();
1952    unsigned NumInitElts = Value.getArrayInitializedElts();
1953
1954    // Emit array filler, if there is one.
1955    llvm::Constant *Filler = nullptr;
1956    if (Value.hasArrayFiller()) {
1957      Filler = tryEmitAbstractForMemory(Value.getArrayFiller(),
1958                                        CAT->getElementType());
1959      if (!Filler)
1960        return nullptr;
1961    }
1962
1963    // Emit initializer elements.
1964    SmallVector<llvm::Constant*, 16> Elts;
1965    if (Filler && Filler->isNullValue())
1966      Elts.reserve(NumInitElts + 1);
1967    else
1968      Elts.reserve(NumElements);
1969
1970    llvm::Type *CommonElementType = nullptr;
1971    for (unsigned I = 0; I < NumInitElts; ++I) {
1972      llvm::Constant *C = tryEmitPrivateForMemory(
1973          Value.getArrayInitializedElt(I), CAT->getElementType());
1974      if (!C) return nullptr;
1975
1976      if (I == 0)
1977        CommonElementType = C->getType();
1978      else if (C->getType() != CommonElementType)
1979        CommonElementType = nullptr;
1980      Elts.push_back(C);
1981    }
1982
1983    // This means that the array type is probably "IncompleteType" or some
1984    // type that is not ConstantArray.
1985    if (CAT == nullptr && CommonElementType == nullptr && !NumInitElts) {
1986      const ArrayType *AT = CGM.getContext().getAsArrayType(DestType);
1987      CommonElementType = CGM.getTypes().ConvertType(AT->getElementType());
1988      llvm::ArrayType *AType = llvm::ArrayType::get(CommonElementType,
1989                                                    NumElements);
1990      return llvm::ConstantAggregateZero::get(AType);
1991    }
1992
1993    return EmitArrayConstant(CGM, CAT, CommonElementType, NumElements, Elts,
1994                             Filler);
1995  }
1996  case APValue::MemberPointer:
1997    return CGM.getCXXABI().EmitMemberPointer(Value, DestType);
1998  }
1999  llvm_unreachable("Unknown APValue kind");
2000}
2001
2002llvm::GlobalVariable *CodeGenModule::getAddrOfConstantCompoundLiteralIfEmitted(
2003    const CompoundLiteralExpr *E) {
2004  return EmittedCompoundLiterals.lookup(E);
2005}
2006
2007void CodeGenModule::setAddrOfConstantCompoundLiteral(
2008    const CompoundLiteralExpr *CLE, llvm::GlobalVariable *GV) {
2009  bool Ok = EmittedCompoundLiterals.insert(std::make_pair(CLE, GV)).second;
2010  (void)Ok;
2011  assert(Ok && "CLE has already been emitted!");
2012}
2013
2014ConstantAddress
2015CodeGenModule::GetAddrOfConstantCompoundLiteral(const CompoundLiteralExpr *E) {
2016  assert(E->isFileScope() && "not a file-scope compound literal expr");
2017  return tryEmitGlobalCompoundLiteral(*this, nullptr, E);
2018}
2019
2020llvm::Constant *
2021CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) {
2022  // Member pointer constants always have a very particular form.
2023  const MemberPointerType *type = cast<MemberPointerType>(uo->getType());
2024  const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl();
2025
2026  // A member function pointer.
2027  if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(decl))
2028    return getCXXABI().EmitMemberFunctionPointer(method);
2029
2030  // Otherwise, a member data pointer.
2031  uint64_t fieldOffset = getContext().getFieldOffset(decl);
2032  CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset);
2033  return getCXXABI().EmitMemberDataPointer(type, chars);
2034}
2035
2036static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
2037                                               llvm::Type *baseType,
2038                                               const CXXRecordDecl *base);
2039
2040static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
2041                                        const RecordDecl *record,
2042                                        bool asCompleteObject) {
2043  const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record);
2044  llvm::StructType *structure =
2045    (asCompleteObject ? layout.getLLVMType()
2046                      : layout.getBaseSubobjectLLVMType());
2047
2048  unsigned numElements = structure->getNumElements();
2049  std::vector<llvm::Constant *> elements(numElements);
2050
2051  auto CXXR = dyn_cast<CXXRecordDecl>(record);
2052  // Fill in all the bases.
2053  if (CXXR) {
2054    for (const auto &I : CXXR->bases()) {
2055      if (I.isVirtual()) {
2056        // Ignore virtual bases; if we're laying out for a complete
2057        // object, we'll lay these out later.
2058        continue;
2059      }
2060
2061      const CXXRecordDecl *base =
2062        cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl());
2063
2064      // Ignore empty bases.
2065      if (base->isEmpty() ||
2066          CGM.getContext().getASTRecordLayout(base).getNonVirtualSize()
2067              .isZero())
2068        continue;
2069
2070      unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base);
2071      llvm::Type *baseType = structure->getElementType(fieldIndex);
2072      elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
2073    }
2074  }
2075
2076  // Fill in all the fields.
2077  for (const auto *Field : record->fields()) {
2078    // Fill in non-bitfields. (Bitfields always use a zero pattern, which we
2079    // will fill in later.)
2080    if (!Field->isBitField()) {
2081      unsigned fieldIndex = layout.getLLVMFieldNo(Field);
2082      elements[fieldIndex] = CGM.EmitNullConstant(Field->getType());
2083    }
2084
2085    // For unions, stop after the first named field.
2086    if (record->isUnion()) {
2087      if (Field->getIdentifier())
2088        break;
2089      if (const auto *FieldRD = Field->getType()->getAsRecordDecl())
2090        if (FieldRD->findFirstNamedDataMember())
2091          break;
2092    }
2093  }
2094
2095  // Fill in the virtual bases, if we're working with the complete object.
2096  if (CXXR && asCompleteObject) {
2097    for (const auto &I : CXXR->vbases()) {
2098      const CXXRecordDecl *base =
2099        cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl());
2100
2101      // Ignore empty bases.
2102      if (base->isEmpty())
2103        continue;
2104
2105      unsigned fieldIndex = layout.getVirtualBaseIndex(base);
2106
2107      // We might have already laid this field out.
2108      if (elements[fieldIndex]) continue;
2109
2110      llvm::Type *baseType = structure->getElementType(fieldIndex);
2111      elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
2112    }
2113  }
2114
2115  // Now go through all other fields and zero them out.
2116  for (unsigned i = 0; i != numElements; ++i) {
2117    if (!elements[i])
2118      elements[i] = llvm::Constant::getNullValue(structure->getElementType(i));
2119  }
2120
2121  return llvm::ConstantStruct::get(structure, elements);
2122}
2123
2124/// Emit the null constant for a base subobject.
2125static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
2126                                               llvm::Type *baseType,
2127                                               const CXXRecordDecl *base) {
2128  const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base);
2129
2130  // Just zero out bases that don't have any pointer to data members.
2131  if (baseLayout.isZeroInitializableAsBase())
2132    return llvm::Constant::getNullValue(baseType);
2133
2134  // Otherwise, we can just use its null constant.
2135  return EmitNullConstant(CGM, base, /*asCompleteObject=*/false);
2136}
2137
2138llvm::Constant *ConstantEmitter::emitNullForMemory(CodeGenModule &CGM,
2139                                                   QualType T) {
2140  return emitForMemory(CGM, CGM.EmitNullConstant(T), T);
2141}
2142
2143llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
2144  if (T->getAs<PointerType>())
2145    return getNullPointer(
2146        cast<llvm::PointerType>(getTypes().ConvertTypeForMem(T)), T);
2147
2148  if (getTypes().isZeroInitializable(T))
2149    return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
2150
2151  if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) {
2152    llvm::ArrayType *ATy =
2153      cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T));
2154
2155    QualType ElementTy = CAT->getElementType();
2156
2157    llvm::Constant *Element =
2158      ConstantEmitter::emitNullForMemory(*this, ElementTy);
2159    unsigned NumElements = CAT->getSize().getZExtValue();
2160    SmallVector<llvm::Constant *, 8> Array(NumElements, Element);
2161    return llvm::ConstantArray::get(ATy, Array);
2162  }
2163
2164  if (const RecordType *RT = T->getAs<RecordType>())
2165    return ::EmitNullConstant(*this, RT->getDecl(), /*complete object*/ true);
2166
2167  assert(T->isMemberDataPointerType() &&
2168         "Should only see pointers to data members here!");
2169
2170  return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>());
2171}
2172
2173llvm::Constant *
2174CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) {
2175  return ::EmitNullConstant(*this, Record, false);
2176}
2177