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 "clang/AST/APValue.h"
20 #include "clang/AST/ASTContext.h"
21 #include "clang/AST/RecordLayout.h"
22 #include "clang/AST/StmtVisitor.h"
23 #include "clang/Basic/Builtins.h"
24 #include "llvm/IR/Constants.h"
25 #include "llvm/IR/DataLayout.h"
26 #include "llvm/IR/Function.h"
27 #include "llvm/IR/GlobalVariable.h"
28 using namespace clang;
29 using namespace CodeGen;
30
31 //===----------------------------------------------------------------------===//
32 // ConstStructBuilder
33 //===----------------------------------------------------------------------===//
34
35 namespace {
36 class ConstExprEmitter;
37 class ConstStructBuilder {
38 CodeGenModule &CGM;
39 CodeGenFunction *CGF;
40
41 bool Packed;
42 CharUnits NextFieldOffsetInChars;
43 CharUnits LLVMStructAlignment;
44 SmallVector<llvm::Constant *, 32> Elements;
45 public:
46 static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CFG,
47 ConstExprEmitter *Emitter,
48 llvm::ConstantStruct *Base,
49 InitListExpr *Updater);
50 static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF,
51 InitListExpr *ILE);
52 static llvm::Constant *BuildStruct(CodeGenModule &CGM, CodeGenFunction *CGF,
53 const APValue &Value, QualType ValTy);
54
55 private:
ConstStructBuilder(CodeGenModule & CGM,CodeGenFunction * CGF)56 ConstStructBuilder(CodeGenModule &CGM, CodeGenFunction *CGF)
57 : CGM(CGM), CGF(CGF), Packed(false),
58 NextFieldOffsetInChars(CharUnits::Zero()),
59 LLVMStructAlignment(CharUnits::One()) { }
60
61 void AppendField(const FieldDecl *Field, uint64_t FieldOffset,
62 llvm::Constant *InitExpr);
63
64 void AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst);
65
66 void AppendBitField(const FieldDecl *Field, uint64_t FieldOffset,
67 llvm::ConstantInt *InitExpr);
68
69 void AppendPadding(CharUnits PadSize);
70
71 void AppendTailPadding(CharUnits RecordSize);
72
73 void ConvertStructToPacked();
74
75 bool Build(InitListExpr *ILE);
76 bool Build(ConstExprEmitter *Emitter, llvm::ConstantStruct *Base,
77 InitListExpr *Updater);
78 void Build(const APValue &Val, const RecordDecl *RD, bool IsPrimaryBase,
79 const CXXRecordDecl *VTableClass, CharUnits BaseOffset);
80 llvm::Constant *Finalize(QualType Ty);
81
getAlignment(const llvm::Constant * C) const82 CharUnits getAlignment(const llvm::Constant *C) const {
83 if (Packed) return CharUnits::One();
84 return CharUnits::fromQuantity(
85 CGM.getDataLayout().getABITypeAlignment(C->getType()));
86 }
87
getSizeInChars(const llvm::Constant * C) const88 CharUnits getSizeInChars(const llvm::Constant *C) const {
89 return CharUnits::fromQuantity(
90 CGM.getDataLayout().getTypeAllocSize(C->getType()));
91 }
92 };
93
94 void ConstStructBuilder::
AppendField(const FieldDecl * Field,uint64_t FieldOffset,llvm::Constant * InitCst)95 AppendField(const FieldDecl *Field, uint64_t FieldOffset,
96 llvm::Constant *InitCst) {
97 const ASTContext &Context = CGM.getContext();
98
99 CharUnits FieldOffsetInChars = Context.toCharUnitsFromBits(FieldOffset);
100
101 AppendBytes(FieldOffsetInChars, InitCst);
102 }
103
104 void ConstStructBuilder::
AppendBytes(CharUnits FieldOffsetInChars,llvm::Constant * InitCst)105 AppendBytes(CharUnits FieldOffsetInChars, llvm::Constant *InitCst) {
106
107 assert(NextFieldOffsetInChars <= FieldOffsetInChars
108 && "Field offset mismatch!");
109
110 CharUnits FieldAlignment = getAlignment(InitCst);
111
112 // Round up the field offset to the alignment of the field type.
113 CharUnits AlignedNextFieldOffsetInChars =
114 NextFieldOffsetInChars.RoundUpToAlignment(FieldAlignment);
115
116 if (AlignedNextFieldOffsetInChars < FieldOffsetInChars) {
117 // We need to append padding.
118 AppendPadding(FieldOffsetInChars - NextFieldOffsetInChars);
119
120 assert(NextFieldOffsetInChars == FieldOffsetInChars &&
121 "Did not add enough padding!");
122
123 AlignedNextFieldOffsetInChars =
124 NextFieldOffsetInChars.RoundUpToAlignment(FieldAlignment);
125 }
126
127 if (AlignedNextFieldOffsetInChars > FieldOffsetInChars) {
128 assert(!Packed && "Alignment is wrong even with a packed struct!");
129
130 // Convert the struct to a packed struct.
131 ConvertStructToPacked();
132
133 // After we pack the struct, we may need to insert padding.
134 if (NextFieldOffsetInChars < FieldOffsetInChars) {
135 // We need to append padding.
136 AppendPadding(FieldOffsetInChars - NextFieldOffsetInChars);
137
138 assert(NextFieldOffsetInChars == FieldOffsetInChars &&
139 "Did not add enough padding!");
140 }
141 AlignedNextFieldOffsetInChars = NextFieldOffsetInChars;
142 }
143
144 // Add the field.
145 Elements.push_back(InitCst);
146 NextFieldOffsetInChars = AlignedNextFieldOffsetInChars +
147 getSizeInChars(InitCst);
148
149 if (Packed)
150 assert(LLVMStructAlignment == CharUnits::One() &&
151 "Packed struct not byte-aligned!");
152 else
153 LLVMStructAlignment = std::max(LLVMStructAlignment, FieldAlignment);
154 }
155
AppendBitField(const FieldDecl * Field,uint64_t FieldOffset,llvm::ConstantInt * CI)156 void ConstStructBuilder::AppendBitField(const FieldDecl *Field,
157 uint64_t FieldOffset,
158 llvm::ConstantInt *CI) {
159 const ASTContext &Context = CGM.getContext();
160 const uint64_t CharWidth = Context.getCharWidth();
161 uint64_t NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars);
162 if (FieldOffset > NextFieldOffsetInBits) {
163 // We need to add padding.
164 CharUnits PadSize = Context.toCharUnitsFromBits(
165 llvm::RoundUpToAlignment(FieldOffset - NextFieldOffsetInBits,
166 Context.getTargetInfo().getCharAlign()));
167
168 AppendPadding(PadSize);
169 }
170
171 uint64_t FieldSize = Field->getBitWidthValue(Context);
172
173 llvm::APInt FieldValue = CI->getValue();
174
175 // Promote the size of FieldValue if necessary
176 // FIXME: This should never occur, but currently it can because initializer
177 // constants are cast to bool, and because clang is not enforcing bitfield
178 // width limits.
179 if (FieldSize > FieldValue.getBitWidth())
180 FieldValue = FieldValue.zext(FieldSize);
181
182 // Truncate the size of FieldValue to the bit field size.
183 if (FieldSize < FieldValue.getBitWidth())
184 FieldValue = FieldValue.trunc(FieldSize);
185
186 NextFieldOffsetInBits = Context.toBits(NextFieldOffsetInChars);
187 if (FieldOffset < NextFieldOffsetInBits) {
188 // Either part of the field or the entire field can go into the previous
189 // byte.
190 assert(!Elements.empty() && "Elements can't be empty!");
191
192 unsigned BitsInPreviousByte = NextFieldOffsetInBits - FieldOffset;
193
194 bool FitsCompletelyInPreviousByte =
195 BitsInPreviousByte >= FieldValue.getBitWidth();
196
197 llvm::APInt Tmp = FieldValue;
198
199 if (!FitsCompletelyInPreviousByte) {
200 unsigned NewFieldWidth = FieldSize - BitsInPreviousByte;
201
202 if (CGM.getDataLayout().isBigEndian()) {
203 Tmp = Tmp.lshr(NewFieldWidth);
204 Tmp = Tmp.trunc(BitsInPreviousByte);
205
206 // We want the remaining high bits.
207 FieldValue = FieldValue.trunc(NewFieldWidth);
208 } else {
209 Tmp = Tmp.trunc(BitsInPreviousByte);
210
211 // We want the remaining low bits.
212 FieldValue = FieldValue.lshr(BitsInPreviousByte);
213 FieldValue = FieldValue.trunc(NewFieldWidth);
214 }
215 }
216
217 Tmp = Tmp.zext(CharWidth);
218 if (CGM.getDataLayout().isBigEndian()) {
219 if (FitsCompletelyInPreviousByte)
220 Tmp = Tmp.shl(BitsInPreviousByte - FieldValue.getBitWidth());
221 } else {
222 Tmp = Tmp.shl(CharWidth - BitsInPreviousByte);
223 }
224
225 // 'or' in the bits that go into the previous byte.
226 llvm::Value *LastElt = Elements.back();
227 if (llvm::ConstantInt *Val = dyn_cast<llvm::ConstantInt>(LastElt))
228 Tmp |= Val->getValue();
229 else {
230 assert(isa<llvm::UndefValue>(LastElt));
231 // If there is an undef field that we're adding to, it can either be a
232 // scalar undef (in which case, we just replace it with our field) or it
233 // is an array. If it is an array, we have to pull one byte off the
234 // array so that the other undef bytes stay around.
235 if (!isa<llvm::IntegerType>(LastElt->getType())) {
236 // The undef padding will be a multibyte array, create a new smaller
237 // padding and then an hole for our i8 to get plopped into.
238 assert(isa<llvm::ArrayType>(LastElt->getType()) &&
239 "Expected array padding of undefs");
240 llvm::ArrayType *AT = cast<llvm::ArrayType>(LastElt->getType());
241 assert(AT->getElementType()->isIntegerTy(CharWidth) &&
242 AT->getNumElements() != 0 &&
243 "Expected non-empty array padding of undefs");
244
245 // Remove the padding array.
246 NextFieldOffsetInChars -= CharUnits::fromQuantity(AT->getNumElements());
247 Elements.pop_back();
248
249 // Add the padding back in two chunks.
250 AppendPadding(CharUnits::fromQuantity(AT->getNumElements()-1));
251 AppendPadding(CharUnits::One());
252 assert(isa<llvm::UndefValue>(Elements.back()) &&
253 Elements.back()->getType()->isIntegerTy(CharWidth) &&
254 "Padding addition didn't work right");
255 }
256 }
257
258 Elements.back() = llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp);
259
260 if (FitsCompletelyInPreviousByte)
261 return;
262 }
263
264 while (FieldValue.getBitWidth() > CharWidth) {
265 llvm::APInt Tmp;
266
267 if (CGM.getDataLayout().isBigEndian()) {
268 // We want the high bits.
269 Tmp =
270 FieldValue.lshr(FieldValue.getBitWidth() - CharWidth).trunc(CharWidth);
271 } else {
272 // We want the low bits.
273 Tmp = FieldValue.trunc(CharWidth);
274
275 FieldValue = FieldValue.lshr(CharWidth);
276 }
277
278 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(), Tmp));
279 ++NextFieldOffsetInChars;
280
281 FieldValue = FieldValue.trunc(FieldValue.getBitWidth() - CharWidth);
282 }
283
284 assert(FieldValue.getBitWidth() > 0 &&
285 "Should have at least one bit left!");
286 assert(FieldValue.getBitWidth() <= CharWidth &&
287 "Should not have more than a byte left!");
288
289 if (FieldValue.getBitWidth() < CharWidth) {
290 if (CGM.getDataLayout().isBigEndian()) {
291 unsigned BitWidth = FieldValue.getBitWidth();
292
293 FieldValue = FieldValue.zext(CharWidth) << (CharWidth - BitWidth);
294 } else
295 FieldValue = FieldValue.zext(CharWidth);
296 }
297
298 // Append the last element.
299 Elements.push_back(llvm::ConstantInt::get(CGM.getLLVMContext(),
300 FieldValue));
301 ++NextFieldOffsetInChars;
302 }
303
AppendPadding(CharUnits PadSize)304 void ConstStructBuilder::AppendPadding(CharUnits PadSize) {
305 if (PadSize.isZero())
306 return;
307
308 llvm::Type *Ty = CGM.Int8Ty;
309 if (PadSize > CharUnits::One())
310 Ty = llvm::ArrayType::get(Ty, PadSize.getQuantity());
311
312 llvm::Constant *C = llvm::UndefValue::get(Ty);
313 Elements.push_back(C);
314 assert(getAlignment(C) == CharUnits::One() &&
315 "Padding must have 1 byte alignment!");
316
317 NextFieldOffsetInChars += getSizeInChars(C);
318 }
319
AppendTailPadding(CharUnits RecordSize)320 void ConstStructBuilder::AppendTailPadding(CharUnits RecordSize) {
321 assert(NextFieldOffsetInChars <= RecordSize &&
322 "Size mismatch!");
323
324 AppendPadding(RecordSize - NextFieldOffsetInChars);
325 }
326
ConvertStructToPacked()327 void ConstStructBuilder::ConvertStructToPacked() {
328 SmallVector<llvm::Constant *, 16> PackedElements;
329 CharUnits ElementOffsetInChars = CharUnits::Zero();
330
331 for (unsigned i = 0, e = Elements.size(); i != e; ++i) {
332 llvm::Constant *C = Elements[i];
333
334 CharUnits ElementAlign = CharUnits::fromQuantity(
335 CGM.getDataLayout().getABITypeAlignment(C->getType()));
336 CharUnits AlignedElementOffsetInChars =
337 ElementOffsetInChars.RoundUpToAlignment(ElementAlign);
338
339 if (AlignedElementOffsetInChars > ElementOffsetInChars) {
340 // We need some padding.
341 CharUnits NumChars =
342 AlignedElementOffsetInChars - ElementOffsetInChars;
343
344 llvm::Type *Ty = CGM.Int8Ty;
345 if (NumChars > CharUnits::One())
346 Ty = llvm::ArrayType::get(Ty, NumChars.getQuantity());
347
348 llvm::Constant *Padding = llvm::UndefValue::get(Ty);
349 PackedElements.push_back(Padding);
350 ElementOffsetInChars += getSizeInChars(Padding);
351 }
352
353 PackedElements.push_back(C);
354 ElementOffsetInChars += getSizeInChars(C);
355 }
356
357 assert(ElementOffsetInChars == NextFieldOffsetInChars &&
358 "Packing the struct changed its size!");
359
360 Elements.swap(PackedElements);
361 LLVMStructAlignment = CharUnits::One();
362 Packed = true;
363 }
364
Build(InitListExpr * ILE)365 bool ConstStructBuilder::Build(InitListExpr *ILE) {
366 RecordDecl *RD = ILE->getType()->getAs<RecordType>()->getDecl();
367 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
368
369 unsigned FieldNo = 0;
370 unsigned ElementNo = 0;
371
372 for (RecordDecl::field_iterator Field = RD->field_begin(),
373 FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
374 // If this is a union, skip all the fields that aren't being initialized.
375 if (RD->isUnion() && ILE->getInitializedFieldInUnion() != *Field)
376 continue;
377
378 // Don't emit anonymous bitfields, they just affect layout.
379 if (Field->isUnnamedBitfield())
380 continue;
381
382 // Get the initializer. A struct can include fields without initializers,
383 // we just use explicit null values for them.
384 llvm::Constant *EltInit;
385 if (ElementNo < ILE->getNumInits())
386 EltInit = CGM.EmitConstantExpr(ILE->getInit(ElementNo++),
387 Field->getType(), CGF);
388 else
389 EltInit = CGM.EmitNullConstant(Field->getType());
390
391 if (!EltInit)
392 return false;
393
394 if (!Field->isBitField()) {
395 // Handle non-bitfield members.
396 AppendField(*Field, Layout.getFieldOffset(FieldNo), EltInit);
397 } else {
398 // Otherwise we have a bitfield.
399 if (auto *CI = dyn_cast<llvm::ConstantInt>(EltInit)) {
400 AppendBitField(*Field, Layout.getFieldOffset(FieldNo), CI);
401 } else {
402 // We are trying to initialize a bitfield with a non-trivial constant,
403 // this must require run-time code.
404 return false;
405 }
406 }
407 }
408
409 return true;
410 }
411
412 namespace {
413 struct BaseInfo {
BaseInfo__anon3adcc1930111::__anon3adcc1930211::BaseInfo414 BaseInfo(const CXXRecordDecl *Decl, CharUnits Offset, unsigned Index)
415 : Decl(Decl), Offset(Offset), Index(Index) {
416 }
417
418 const CXXRecordDecl *Decl;
419 CharUnits Offset;
420 unsigned Index;
421
operator <__anon3adcc1930111::__anon3adcc1930211::BaseInfo422 bool operator<(const BaseInfo &O) const { return Offset < O.Offset; }
423 };
424 }
425
Build(const APValue & Val,const RecordDecl * RD,bool IsPrimaryBase,const CXXRecordDecl * VTableClass,CharUnits Offset)426 void ConstStructBuilder::Build(const APValue &Val, const RecordDecl *RD,
427 bool IsPrimaryBase,
428 const CXXRecordDecl *VTableClass,
429 CharUnits Offset) {
430 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
431
432 if (const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD)) {
433 // Add a vtable pointer, if we need one and it hasn't already been added.
434 if (CD->isDynamicClass() && !IsPrimaryBase) {
435 llvm::Constant *VTableAddressPoint =
436 CGM.getCXXABI().getVTableAddressPointForConstExpr(
437 BaseSubobject(CD, Offset), VTableClass);
438 AppendBytes(Offset, VTableAddressPoint);
439 }
440
441 // Accumulate and sort bases, in order to visit them in address order, which
442 // may not be the same as declaration order.
443 SmallVector<BaseInfo, 8> Bases;
444 Bases.reserve(CD->getNumBases());
445 unsigned BaseNo = 0;
446 for (CXXRecordDecl::base_class_const_iterator Base = CD->bases_begin(),
447 BaseEnd = CD->bases_end(); Base != BaseEnd; ++Base, ++BaseNo) {
448 assert(!Base->isVirtual() && "should not have virtual bases here");
449 const CXXRecordDecl *BD = Base->getType()->getAsCXXRecordDecl();
450 CharUnits BaseOffset = Layout.getBaseClassOffset(BD);
451 Bases.push_back(BaseInfo(BD, BaseOffset, BaseNo));
452 }
453 std::stable_sort(Bases.begin(), Bases.end());
454
455 for (unsigned I = 0, N = Bases.size(); I != N; ++I) {
456 BaseInfo &Base = Bases[I];
457
458 bool IsPrimaryBase = Layout.getPrimaryBase() == Base.Decl;
459 Build(Val.getStructBase(Base.Index), Base.Decl, IsPrimaryBase,
460 VTableClass, Offset + Base.Offset);
461 }
462 }
463
464 unsigned FieldNo = 0;
465 uint64_t OffsetBits = CGM.getContext().toBits(Offset);
466
467 for (RecordDecl::field_iterator Field = RD->field_begin(),
468 FieldEnd = RD->field_end(); Field != FieldEnd; ++Field, ++FieldNo) {
469 // If this is a union, skip all the fields that aren't being initialized.
470 if (RD->isUnion() && Val.getUnionField() != *Field)
471 continue;
472
473 // Don't emit anonymous bitfields, they just affect layout.
474 if (Field->isUnnamedBitfield())
475 continue;
476
477 // Emit the value of the initializer.
478 const APValue &FieldValue =
479 RD->isUnion() ? Val.getUnionValue() : Val.getStructField(FieldNo);
480 llvm::Constant *EltInit =
481 CGM.EmitConstantValueForMemory(FieldValue, Field->getType(), CGF);
482 assert(EltInit && "EmitConstantValue can't fail");
483
484 if (!Field->isBitField()) {
485 // Handle non-bitfield members.
486 AppendField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits, EltInit);
487 } else {
488 // Otherwise we have a bitfield.
489 AppendBitField(*Field, Layout.getFieldOffset(FieldNo) + OffsetBits,
490 cast<llvm::ConstantInt>(EltInit));
491 }
492 }
493 }
494
Finalize(QualType Ty)495 llvm::Constant *ConstStructBuilder::Finalize(QualType Ty) {
496 RecordDecl *RD = Ty->getAs<RecordType>()->getDecl();
497 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
498
499 CharUnits LayoutSizeInChars = Layout.getSize();
500
501 if (NextFieldOffsetInChars > LayoutSizeInChars) {
502 // If the struct is bigger than the size of the record type,
503 // we must have a flexible array member at the end.
504 assert(RD->hasFlexibleArrayMember() &&
505 "Must have flexible array member if struct is bigger than type!");
506
507 // No tail padding is necessary.
508 } else {
509 // Append tail padding if necessary.
510 CharUnits LLVMSizeInChars =
511 NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment);
512
513 if (LLVMSizeInChars != LayoutSizeInChars)
514 AppendTailPadding(LayoutSizeInChars);
515
516 LLVMSizeInChars =
517 NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment);
518
519 // Check if we need to convert the struct to a packed struct.
520 if (NextFieldOffsetInChars <= LayoutSizeInChars &&
521 LLVMSizeInChars > LayoutSizeInChars) {
522 assert(!Packed && "Size mismatch!");
523
524 ConvertStructToPacked();
525 assert(NextFieldOffsetInChars <= LayoutSizeInChars &&
526 "Converting to packed did not help!");
527 }
528
529 LLVMSizeInChars =
530 NextFieldOffsetInChars.RoundUpToAlignment(LLVMStructAlignment);
531
532 assert(LayoutSizeInChars == LLVMSizeInChars &&
533 "Tail padding mismatch!");
534 }
535
536 // Pick the type to use. If the type is layout identical to the ConvertType
537 // type then use it, otherwise use whatever the builder produced for us.
538 llvm::StructType *STy =
539 llvm::ConstantStruct::getTypeForElements(CGM.getLLVMContext(),
540 Elements, Packed);
541 llvm::Type *ValTy = CGM.getTypes().ConvertType(Ty);
542 if (llvm::StructType *ValSTy = dyn_cast<llvm::StructType>(ValTy)) {
543 if (ValSTy->isLayoutIdentical(STy))
544 STy = ValSTy;
545 }
546
547 llvm::Constant *Result = llvm::ConstantStruct::get(STy, Elements);
548
549 assert(NextFieldOffsetInChars.RoundUpToAlignment(getAlignment(Result)) ==
550 getSizeInChars(Result) && "Size mismatch!");
551
552 return Result;
553 }
554
BuildStruct(CodeGenModule & CGM,CodeGenFunction * CGF,ConstExprEmitter * Emitter,llvm::ConstantStruct * Base,InitListExpr * Updater)555 llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM,
556 CodeGenFunction *CGF,
557 ConstExprEmitter *Emitter,
558 llvm::ConstantStruct *Base,
559 InitListExpr *Updater) {
560 ConstStructBuilder Builder(CGM, CGF);
561 if (!Builder.Build(Emitter, Base, Updater))
562 return nullptr;
563 return Builder.Finalize(Updater->getType());
564 }
565
BuildStruct(CodeGenModule & CGM,CodeGenFunction * CGF,InitListExpr * ILE)566 llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM,
567 CodeGenFunction *CGF,
568 InitListExpr *ILE) {
569 ConstStructBuilder Builder(CGM, CGF);
570
571 if (!Builder.Build(ILE))
572 return nullptr;
573
574 return Builder.Finalize(ILE->getType());
575 }
576
BuildStruct(CodeGenModule & CGM,CodeGenFunction * CGF,const APValue & Val,QualType ValTy)577 llvm::Constant *ConstStructBuilder::BuildStruct(CodeGenModule &CGM,
578 CodeGenFunction *CGF,
579 const APValue &Val,
580 QualType ValTy) {
581 ConstStructBuilder Builder(CGM, CGF);
582
583 const RecordDecl *RD = ValTy->castAs<RecordType>()->getDecl();
584 const CXXRecordDecl *CD = dyn_cast<CXXRecordDecl>(RD);
585 Builder.Build(Val, RD, false, CD, CharUnits::Zero());
586
587 return Builder.Finalize(ValTy);
588 }
589
590
591 //===----------------------------------------------------------------------===//
592 // ConstExprEmitter
593 //===----------------------------------------------------------------------===//
594
595 /// This class only needs to handle two cases:
596 /// 1) Literals (this is used by APValue emission to emit literals).
597 /// 2) Arrays, structs and unions (outside C++11 mode, we don't currently
598 /// constant fold these types).
599 class ConstExprEmitter :
600 public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
601 CodeGenModule &CGM;
602 CodeGenFunction *CGF;
603 llvm::LLVMContext &VMContext;
604 public:
ConstExprEmitter(CodeGenModule & cgm,CodeGenFunction * cgf)605 ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf)
606 : CGM(cgm), CGF(cgf), VMContext(cgm.getLLVMContext()) {
607 }
608
609 //===--------------------------------------------------------------------===//
610 // Visitor Methods
611 //===--------------------------------------------------------------------===//
612
VisitStmt(Stmt * S)613 llvm::Constant *VisitStmt(Stmt *S) {
614 return nullptr;
615 }
616
VisitParenExpr(ParenExpr * PE)617 llvm::Constant *VisitParenExpr(ParenExpr *PE) {
618 return Visit(PE->getSubExpr());
619 }
620
621 llvm::Constant *
VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr * PE)622 VisitSubstNonTypeTemplateParmExpr(SubstNonTypeTemplateParmExpr *PE) {
623 return Visit(PE->getReplacement());
624 }
625
VisitGenericSelectionExpr(GenericSelectionExpr * GE)626 llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
627 return Visit(GE->getResultExpr());
628 }
629
VisitChooseExpr(ChooseExpr * CE)630 llvm::Constant *VisitChooseExpr(ChooseExpr *CE) {
631 return Visit(CE->getChosenSubExpr());
632 }
633
VisitCompoundLiteralExpr(CompoundLiteralExpr * E)634 llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
635 return Visit(E->getInitializer());
636 }
637
VisitCastExpr(CastExpr * E)638 llvm::Constant *VisitCastExpr(CastExpr* E) {
639 if (const auto *ECE = dyn_cast<ExplicitCastExpr>(E))
640 CGM.EmitExplicitCastExprType(ECE, CGF);
641 Expr *subExpr = E->getSubExpr();
642 llvm::Constant *C = CGM.EmitConstantExpr(subExpr, subExpr->getType(), CGF);
643 if (!C) return nullptr;
644
645 llvm::Type *destType = ConvertType(E->getType());
646
647 switch (E->getCastKind()) {
648 case CK_ToUnion: {
649 // GCC cast to union extension
650 assert(E->getType()->isUnionType() &&
651 "Destination type is not union type!");
652
653 // Build a struct with the union sub-element as the first member,
654 // and padded to the appropriate size
655 SmallVector<llvm::Constant*, 2> Elts;
656 SmallVector<llvm::Type*, 2> Types;
657 Elts.push_back(C);
658 Types.push_back(C->getType());
659 unsigned CurSize = CGM.getDataLayout().getTypeAllocSize(C->getType());
660 unsigned TotalSize = CGM.getDataLayout().getTypeAllocSize(destType);
661
662 assert(CurSize <= TotalSize && "Union size mismatch!");
663 if (unsigned NumPadBytes = TotalSize - CurSize) {
664 llvm::Type *Ty = CGM.Int8Ty;
665 if (NumPadBytes > 1)
666 Ty = llvm::ArrayType::get(Ty, NumPadBytes);
667
668 Elts.push_back(llvm::UndefValue::get(Ty));
669 Types.push_back(Ty);
670 }
671
672 llvm::StructType* STy =
673 llvm::StructType::get(C->getType()->getContext(), Types, false);
674 return llvm::ConstantStruct::get(STy, Elts);
675 }
676
677 case CK_AddressSpaceConversion:
678 return llvm::ConstantExpr::getAddrSpaceCast(C, destType);
679
680 case CK_LValueToRValue:
681 case CK_AtomicToNonAtomic:
682 case CK_NonAtomicToAtomic:
683 case CK_NoOp:
684 case CK_ConstructorConversion:
685 return C;
686
687 case CK_Dependent: llvm_unreachable("saw dependent cast!");
688
689 case CK_BuiltinFnToFnPtr:
690 llvm_unreachable("builtin functions are handled elsewhere");
691
692 case CK_ReinterpretMemberPointer:
693 case CK_DerivedToBaseMemberPointer:
694 case CK_BaseToDerivedMemberPointer:
695 return CGM.getCXXABI().EmitMemberPointerConversion(E, C);
696
697 // These will never be supported.
698 case CK_ObjCObjectLValueCast:
699 case CK_ARCProduceObject:
700 case CK_ARCConsumeObject:
701 case CK_ARCReclaimReturnedObject:
702 case CK_ARCExtendBlockObject:
703 case CK_CopyAndAutoreleaseBlockObject:
704 return nullptr;
705
706 // These don't need to be handled here because Evaluate knows how to
707 // evaluate them in the cases where they can be folded.
708 case CK_BitCast:
709 case CK_ToVoid:
710 case CK_Dynamic:
711 case CK_LValueBitCast:
712 case CK_NullToMemberPointer:
713 case CK_UserDefinedConversion:
714 case CK_CPointerToObjCPointerCast:
715 case CK_BlockPointerToObjCPointerCast:
716 case CK_AnyPointerToBlockPointerCast:
717 case CK_ArrayToPointerDecay:
718 case CK_FunctionToPointerDecay:
719 case CK_BaseToDerived:
720 case CK_DerivedToBase:
721 case CK_UncheckedDerivedToBase:
722 case CK_MemberPointerToBoolean:
723 case CK_VectorSplat:
724 case CK_FloatingRealToComplex:
725 case CK_FloatingComplexToReal:
726 case CK_FloatingComplexToBoolean:
727 case CK_FloatingComplexCast:
728 case CK_FloatingComplexToIntegralComplex:
729 case CK_IntegralRealToComplex:
730 case CK_IntegralComplexToReal:
731 case CK_IntegralComplexToBoolean:
732 case CK_IntegralComplexCast:
733 case CK_IntegralComplexToFloatingComplex:
734 case CK_PointerToIntegral:
735 case CK_PointerToBoolean:
736 case CK_NullToPointer:
737 case CK_IntegralCast:
738 case CK_IntegralToPointer:
739 case CK_IntegralToBoolean:
740 case CK_IntegralToFloating:
741 case CK_FloatingToIntegral:
742 case CK_FloatingToBoolean:
743 case CK_FloatingCast:
744 case CK_ZeroToOCLEvent:
745 return nullptr;
746 }
747 llvm_unreachable("Invalid CastKind");
748 }
749
VisitCXXDefaultArgExpr(CXXDefaultArgExpr * DAE)750 llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
751 return Visit(DAE->getExpr());
752 }
753
VisitCXXDefaultInitExpr(CXXDefaultInitExpr * DIE)754 llvm::Constant *VisitCXXDefaultInitExpr(CXXDefaultInitExpr *DIE) {
755 // No need for a DefaultInitExprScope: we don't handle 'this' in a
756 // constant expression.
757 return Visit(DIE->getExpr());
758 }
759
VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr * E)760 llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) {
761 return Visit(E->GetTemporaryExpr());
762 }
763
EmitArrayInitialization(InitListExpr * ILE)764 llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
765 if (ILE->isStringLiteralInit())
766 return Visit(ILE->getInit(0));
767
768 llvm::ArrayType *AType =
769 cast<llvm::ArrayType>(ConvertType(ILE->getType()));
770 llvm::Type *ElemTy = AType->getElementType();
771 unsigned NumInitElements = ILE->getNumInits();
772 unsigned NumElements = AType->getNumElements();
773
774 // Initialising an array requires us to automatically
775 // initialise any elements that have not been initialised explicitly
776 unsigned NumInitableElts = std::min(NumInitElements, NumElements);
777
778 // Initialize remaining array elements.
779 // FIXME: This doesn't handle member pointers correctly!
780 llvm::Constant *fillC;
781 if (Expr *filler = ILE->getArrayFiller())
782 fillC = CGM.EmitConstantExpr(filler, filler->getType(), CGF);
783 else
784 fillC = llvm::Constant::getNullValue(ElemTy);
785 if (!fillC)
786 return nullptr;
787
788 // Try to use a ConstantAggregateZero if we can.
789 if (fillC->isNullValue() && !NumInitableElts)
790 return llvm::ConstantAggregateZero::get(AType);
791
792 // Copy initializer elements.
793 std::vector<llvm::Constant*> Elts;
794 Elts.reserve(NumInitableElts + NumElements);
795
796 bool RewriteType = false;
797 for (unsigned i = 0; i < NumInitableElts; ++i) {
798 Expr *Init = ILE->getInit(i);
799 llvm::Constant *C = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
800 if (!C)
801 return nullptr;
802 RewriteType |= (C->getType() != ElemTy);
803 Elts.push_back(C);
804 }
805
806 RewriteType |= (fillC->getType() != ElemTy);
807 Elts.resize(NumElements, fillC);
808
809 if (RewriteType) {
810 // FIXME: Try to avoid packing the array
811 std::vector<llvm::Type*> Types;
812 Types.reserve(NumInitableElts + NumElements);
813 for (unsigned i = 0, e = Elts.size(); i < e; ++i)
814 Types.push_back(Elts[i]->getType());
815 llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
816 Types, true);
817 return llvm::ConstantStruct::get(SType, Elts);
818 }
819
820 return llvm::ConstantArray::get(AType, Elts);
821 }
822
EmitRecordInitialization(InitListExpr * ILE)823 llvm::Constant *EmitRecordInitialization(InitListExpr *ILE) {
824 return ConstStructBuilder::BuildStruct(CGM, CGF, ILE);
825 }
826
VisitImplicitValueInitExpr(ImplicitValueInitExpr * E)827 llvm::Constant *VisitImplicitValueInitExpr(ImplicitValueInitExpr* E) {
828 return CGM.EmitNullConstant(E->getType());
829 }
830
VisitInitListExpr(InitListExpr * ILE)831 llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
832 if (ILE->getType()->isArrayType())
833 return EmitArrayInitialization(ILE);
834
835 if (ILE->getType()->isRecordType())
836 return EmitRecordInitialization(ILE);
837
838 return nullptr;
839 }
840
EmitDesignatedInitUpdater(llvm::Constant * Base,InitListExpr * Updater)841 llvm::Constant *EmitDesignatedInitUpdater(llvm::Constant *Base,
842 InitListExpr *Updater) {
843 QualType ExprType = Updater->getType();
844
845 if (ExprType->isArrayType()) {
846 llvm::ArrayType *AType = cast<llvm::ArrayType>(ConvertType(ExprType));
847 llvm::Type *ElemType = AType->getElementType();
848
849 unsigned NumInitElements = Updater->getNumInits();
850 unsigned NumElements = AType->getNumElements();
851
852 std::vector<llvm::Constant *> Elts;
853 Elts.reserve(NumElements);
854
855 if (llvm::ConstantDataArray *DataArray =
856 dyn_cast<llvm::ConstantDataArray>(Base))
857 for (unsigned i = 0; i != NumElements; ++i)
858 Elts.push_back(DataArray->getElementAsConstant(i));
859 else if (llvm::ConstantArray *Array =
860 dyn_cast<llvm::ConstantArray>(Base))
861 for (unsigned i = 0; i != NumElements; ++i)
862 Elts.push_back(Array->getOperand(i));
863 else
864 return nullptr; // FIXME: other array types not implemented
865
866 llvm::Constant *fillC = nullptr;
867 if (Expr *filler = Updater->getArrayFiller())
868 if (!isa<NoInitExpr>(filler))
869 fillC = CGM.EmitConstantExpr(filler, filler->getType(), CGF);
870 bool RewriteType = (fillC && fillC->getType() != ElemType);
871
872 for (unsigned i = 0; i != NumElements; ++i) {
873 Expr *Init = nullptr;
874 if (i < NumInitElements)
875 Init = Updater->getInit(i);
876
877 if (!Init && fillC)
878 Elts[i] = fillC;
879 else if (!Init || isa<NoInitExpr>(Init))
880 ; // Do nothing.
881 else if (InitListExpr *ChildILE = dyn_cast<InitListExpr>(Init))
882 Elts[i] = EmitDesignatedInitUpdater(Elts[i], ChildILE);
883 else
884 Elts[i] = CGM.EmitConstantExpr(Init, Init->getType(), CGF);
885
886 if (!Elts[i])
887 return nullptr;
888 RewriteType |= (Elts[i]->getType() != ElemType);
889 }
890
891 if (RewriteType) {
892 std::vector<llvm::Type *> Types;
893 Types.reserve(NumElements);
894 for (unsigned i = 0; i != NumElements; ++i)
895 Types.push_back(Elts[i]->getType());
896 llvm::StructType *SType = llvm::StructType::get(AType->getContext(),
897 Types, true);
898 return llvm::ConstantStruct::get(SType, Elts);
899 }
900
901 return llvm::ConstantArray::get(AType, Elts);
902 }
903
904 if (ExprType->isRecordType())
905 return ConstStructBuilder::BuildStruct(CGM, CGF, this,
906 dyn_cast<llvm::ConstantStruct>(Base), Updater);
907
908 return nullptr;
909 }
910
VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr * E)911 llvm::Constant *VisitDesignatedInitUpdateExpr(DesignatedInitUpdateExpr *E) {
912 return EmitDesignatedInitUpdater(
913 CGM.EmitConstantExpr(E->getBase(), E->getType(), CGF),
914 E->getUpdater());
915 }
916
VisitCXXConstructExpr(CXXConstructExpr * E)917 llvm::Constant *VisitCXXConstructExpr(CXXConstructExpr *E) {
918 if (!E->getConstructor()->isTrivial())
919 return nullptr;
920
921 QualType Ty = E->getType();
922
923 // FIXME: We should not have to call getBaseElementType here.
924 const RecordType *RT =
925 CGM.getContext().getBaseElementType(Ty)->getAs<RecordType>();
926 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
927
928 // If the class doesn't have a trivial destructor, we can't emit it as a
929 // constant expr.
930 if (!RD->hasTrivialDestructor())
931 return nullptr;
932
933 // Only copy and default constructors can be trivial.
934
935
936 if (E->getNumArgs()) {
937 assert(E->getNumArgs() == 1 && "trivial ctor with > 1 argument");
938 assert(E->getConstructor()->isCopyOrMoveConstructor() &&
939 "trivial ctor has argument but isn't a copy/move ctor");
940
941 Expr *Arg = E->getArg(0);
942 assert(CGM.getContext().hasSameUnqualifiedType(Ty, Arg->getType()) &&
943 "argument to copy ctor is of wrong type");
944
945 return Visit(Arg);
946 }
947
948 return CGM.EmitNullConstant(Ty);
949 }
950
VisitStringLiteral(StringLiteral * E)951 llvm::Constant *VisitStringLiteral(StringLiteral *E) {
952 return CGM.GetConstantArrayFromStringLiteral(E);
953 }
954
VisitObjCEncodeExpr(ObjCEncodeExpr * E)955 llvm::Constant *VisitObjCEncodeExpr(ObjCEncodeExpr *E) {
956 // This must be an @encode initializing an array in a static initializer.
957 // Don't emit it as the address of the string, emit the string data itself
958 // as an inline array.
959 std::string Str;
960 CGM.getContext().getObjCEncodingForType(E->getEncodedType(), Str);
961 QualType T = E->getType();
962 if (T->getTypeClass() == Type::TypeOfExpr)
963 T = cast<TypeOfExprType>(T)->getUnderlyingExpr()->getType();
964 const ConstantArrayType *CAT = cast<ConstantArrayType>(T);
965
966 // Resize the string to the right size, adding zeros at the end, or
967 // truncating as needed.
968 Str.resize(CAT->getSize().getZExtValue(), '\0');
969 return llvm::ConstantDataArray::getString(VMContext, Str, false);
970 }
971
VisitUnaryExtension(const UnaryOperator * E)972 llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) {
973 return Visit(E->getSubExpr());
974 }
975
976 // Utility methods
ConvertType(QualType T)977 llvm::Type *ConvertType(QualType T) {
978 return CGM.getTypes().ConvertType(T);
979 }
980
981 public:
EmitLValue(APValue::LValueBase LVBase)982 ConstantAddress EmitLValue(APValue::LValueBase LVBase) {
983 if (const ValueDecl *Decl = LVBase.dyn_cast<const ValueDecl*>()) {
984 if (Decl->hasAttr<WeakRefAttr>())
985 return CGM.GetWeakRefReference(Decl);
986 if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
987 return ConstantAddress(CGM.GetAddrOfFunction(FD), CharUnits::One());
988 if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
989 // We can never refer to a variable with local storage.
990 if (!VD->hasLocalStorage()) {
991 CharUnits Align = CGM.getContext().getDeclAlign(VD);
992 if (VD->isFileVarDecl() || VD->hasExternalStorage())
993 return ConstantAddress(CGM.GetAddrOfGlobalVar(VD), Align);
994 else if (VD->isLocalVarDecl()) {
995 auto Ptr = CGM.getOrCreateStaticVarDecl(
996 *VD, CGM.getLLVMLinkageVarDefinition(VD, /*isConstant=*/false));
997 return ConstantAddress(Ptr, Align);
998 }
999 }
1000 }
1001 return ConstantAddress::invalid();
1002 }
1003
1004 Expr *E = const_cast<Expr*>(LVBase.get<const Expr*>());
1005 switch (E->getStmtClass()) {
1006 default: break;
1007 case Expr::CompoundLiteralExprClass: {
1008 // Note that due to the nature of compound literals, this is guaranteed
1009 // to be the only use of the variable, so we just generate it here.
1010 CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
1011 llvm::Constant* C = CGM.EmitConstantExpr(CLE->getInitializer(),
1012 CLE->getType(), CGF);
1013 // FIXME: "Leaked" on failure.
1014 if (!C) return ConstantAddress::invalid();
1015
1016 CharUnits Align = CGM.getContext().getTypeAlignInChars(E->getType());
1017
1018 auto GV = new llvm::GlobalVariable(CGM.getModule(), C->getType(),
1019 E->getType().isConstant(CGM.getContext()),
1020 llvm::GlobalValue::InternalLinkage,
1021 C, ".compoundliteral", nullptr,
1022 llvm::GlobalVariable::NotThreadLocal,
1023 CGM.getContext().getTargetAddressSpace(E->getType()));
1024 GV->setAlignment(Align.getQuantity());
1025 return ConstantAddress(GV, Align);
1026 }
1027 case Expr::StringLiteralClass:
1028 return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E));
1029 case Expr::ObjCEncodeExprClass:
1030 return CGM.GetAddrOfConstantStringFromObjCEncode(cast<ObjCEncodeExpr>(E));
1031 case Expr::ObjCStringLiteralClass: {
1032 ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E);
1033 ConstantAddress C =
1034 CGM.getObjCRuntime().GenerateConstantString(SL->getString());
1035 return C.getElementBitCast(ConvertType(E->getType()));
1036 }
1037 case Expr::PredefinedExprClass: {
1038 unsigned Type = cast<PredefinedExpr>(E)->getIdentType();
1039 if (CGF) {
1040 LValue Res = CGF->EmitPredefinedLValue(cast<PredefinedExpr>(E));
1041 return cast<ConstantAddress>(Res.getAddress());
1042 } else if (Type == PredefinedExpr::PrettyFunction) {
1043 return CGM.GetAddrOfConstantCString("top level", ".tmp");
1044 }
1045
1046 return CGM.GetAddrOfConstantCString("", ".tmp");
1047 }
1048 case Expr::AddrLabelExprClass: {
1049 assert(CGF && "Invalid address of label expression outside function.");
1050 llvm::Constant *Ptr =
1051 CGF->GetAddrOfLabel(cast<AddrLabelExpr>(E)->getLabel());
1052 Ptr = llvm::ConstantExpr::getBitCast(Ptr, ConvertType(E->getType()));
1053 return ConstantAddress(Ptr, CharUnits::One());
1054 }
1055 case Expr::CallExprClass: {
1056 CallExpr* CE = cast<CallExpr>(E);
1057 unsigned builtin = CE->getBuiltinCallee();
1058 if (builtin !=
1059 Builtin::BI__builtin___CFStringMakeConstantString &&
1060 builtin !=
1061 Builtin::BI__builtin___NSStringMakeConstantString)
1062 break;
1063 const Expr *Arg = CE->getArg(0)->IgnoreParenCasts();
1064 const StringLiteral *Literal = cast<StringLiteral>(Arg);
1065 if (builtin ==
1066 Builtin::BI__builtin___NSStringMakeConstantString) {
1067 return CGM.getObjCRuntime().GenerateConstantString(Literal);
1068 }
1069 // FIXME: need to deal with UCN conversion issues.
1070 return CGM.GetAddrOfConstantCFString(Literal);
1071 }
1072 case Expr::BlockExprClass: {
1073 std::string FunctionName;
1074 if (CGF)
1075 FunctionName = CGF->CurFn->getName();
1076 else
1077 FunctionName = "global";
1078
1079 // This is not really an l-value.
1080 llvm::Constant *Ptr =
1081 CGM.GetAddrOfGlobalBlock(cast<BlockExpr>(E), FunctionName.c_str());
1082 return ConstantAddress(Ptr, CGM.getPointerAlign());
1083 }
1084 case Expr::CXXTypeidExprClass: {
1085 CXXTypeidExpr *Typeid = cast<CXXTypeidExpr>(E);
1086 QualType T;
1087 if (Typeid->isTypeOperand())
1088 T = Typeid->getTypeOperand(CGM.getContext());
1089 else
1090 T = Typeid->getExprOperand()->getType();
1091 return ConstantAddress(CGM.GetAddrOfRTTIDescriptor(T),
1092 CGM.getPointerAlign());
1093 }
1094 case Expr::CXXUuidofExprClass: {
1095 return CGM.GetAddrOfUuidDescriptor(cast<CXXUuidofExpr>(E));
1096 }
1097 case Expr::MaterializeTemporaryExprClass: {
1098 MaterializeTemporaryExpr *MTE = cast<MaterializeTemporaryExpr>(E);
1099 assert(MTE->getStorageDuration() == SD_Static);
1100 SmallVector<const Expr *, 2> CommaLHSs;
1101 SmallVector<SubobjectAdjustment, 2> Adjustments;
1102 const Expr *Inner = MTE->GetTemporaryExpr()
1103 ->skipRValueSubobjectAdjustments(CommaLHSs, Adjustments);
1104 return CGM.GetAddrOfGlobalTemporary(MTE, Inner);
1105 }
1106 }
1107
1108 return ConstantAddress::invalid();
1109 }
1110 };
1111
1112 } // end anonymous namespace.
1113
Build(ConstExprEmitter * Emitter,llvm::ConstantStruct * Base,InitListExpr * Updater)1114 bool ConstStructBuilder::Build(ConstExprEmitter *Emitter,
1115 llvm::ConstantStruct *Base,
1116 InitListExpr *Updater) {
1117 assert(Base && "base expression should not be empty");
1118
1119 QualType ExprType = Updater->getType();
1120 RecordDecl *RD = ExprType->getAs<RecordType>()->getDecl();
1121 const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
1122 const llvm::StructLayout *BaseLayout = CGM.getDataLayout().getStructLayout(
1123 Base->getType());
1124 unsigned FieldNo = -1;
1125 unsigned ElementNo = 0;
1126
1127 for (FieldDecl *Field : RD->fields()) {
1128 ++FieldNo;
1129
1130 if (RD->isUnion() && Updater->getInitializedFieldInUnion() != Field)
1131 continue;
1132
1133 // Skip anonymous bitfields.
1134 if (Field->isUnnamedBitfield())
1135 continue;
1136
1137 llvm::Constant *EltInit = Base->getOperand(ElementNo);
1138
1139 // Bail out if the type of the ConstantStruct does not have the same layout
1140 // as the type of the InitListExpr.
1141 if (CGM.getTypes().ConvertType(Field->getType()) != EltInit->getType() ||
1142 Layout.getFieldOffset(ElementNo) !=
1143 BaseLayout->getElementOffsetInBits(ElementNo))
1144 return false;
1145
1146 // Get the initializer. If we encounter an empty field or a NoInitExpr,
1147 // we use values from the base expression.
1148 Expr *Init = nullptr;
1149 if (ElementNo < Updater->getNumInits())
1150 Init = Updater->getInit(ElementNo);
1151
1152 if (!Init || isa<NoInitExpr>(Init))
1153 ; // Do nothing.
1154 else if (InitListExpr *ChildILE = dyn_cast<InitListExpr>(Init))
1155 EltInit = Emitter->EmitDesignatedInitUpdater(EltInit, ChildILE);
1156 else
1157 EltInit = CGM.EmitConstantExpr(Init, Field->getType(), CGF);
1158
1159 ++ElementNo;
1160
1161 if (!EltInit)
1162 return false;
1163
1164 if (!Field->isBitField())
1165 AppendField(Field, Layout.getFieldOffset(FieldNo), EltInit);
1166 else if (llvm::ConstantInt *CI = dyn_cast<llvm::ConstantInt>(EltInit))
1167 AppendBitField(Field, Layout.getFieldOffset(FieldNo), CI);
1168 else
1169 // Initializing a bitfield with a non-trivial constant?
1170 return false;
1171 }
1172
1173 return true;
1174 }
1175
EmitConstantInit(const VarDecl & D,CodeGenFunction * CGF)1176 llvm::Constant *CodeGenModule::EmitConstantInit(const VarDecl &D,
1177 CodeGenFunction *CGF) {
1178 // Make a quick check if variable can be default NULL initialized
1179 // and avoid going through rest of code which may do, for c++11,
1180 // initialization of memory to all NULLs.
1181 if (!D.hasLocalStorage()) {
1182 QualType Ty = D.getType();
1183 if (Ty->isArrayType())
1184 Ty = Context.getBaseElementType(Ty);
1185 if (Ty->isRecordType())
1186 if (const CXXConstructExpr *E =
1187 dyn_cast_or_null<CXXConstructExpr>(D.getInit())) {
1188 const CXXConstructorDecl *CD = E->getConstructor();
1189 if (CD->isTrivial() && CD->isDefaultConstructor())
1190 return EmitNullConstant(D.getType());
1191 }
1192 }
1193
1194 if (const APValue *Value = D.evaluateValue())
1195 return EmitConstantValueForMemory(*Value, D.getType(), CGF);
1196
1197 // FIXME: Implement C++11 [basic.start.init]p2: if the initializer of a
1198 // reference is a constant expression, and the reference binds to a temporary,
1199 // then constant initialization is performed. ConstExprEmitter will
1200 // incorrectly emit a prvalue constant in this case, and the calling code
1201 // interprets that as the (pointer) value of the reference, rather than the
1202 // desired value of the referee.
1203 if (D.getType()->isReferenceType())
1204 return nullptr;
1205
1206 const Expr *E = D.getInit();
1207 assert(E && "No initializer to emit");
1208
1209 llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
1210 if (C && C->getType()->isIntegerTy(1)) {
1211 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
1212 C = llvm::ConstantExpr::getZExt(C, BoolTy);
1213 }
1214 return C;
1215 }
1216
EmitConstantExpr(const Expr * E,QualType DestType,CodeGenFunction * CGF)1217 llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
1218 QualType DestType,
1219 CodeGenFunction *CGF) {
1220 Expr::EvalResult Result;
1221
1222 bool Success = false;
1223
1224 if (DestType->isReferenceType())
1225 Success = E->EvaluateAsLValue(Result, Context);
1226 else
1227 Success = E->EvaluateAsRValue(Result, Context);
1228
1229 llvm::Constant *C = nullptr;
1230 if (Success && !Result.HasSideEffects)
1231 C = EmitConstantValue(Result.Val, DestType, CGF);
1232 else
1233 C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
1234
1235 if (C && C->getType()->isIntegerTy(1)) {
1236 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
1237 C = llvm::ConstantExpr::getZExt(C, BoolTy);
1238 }
1239 return C;
1240 }
1241
EmitConstantValue(const APValue & Value,QualType DestType,CodeGenFunction * CGF)1242 llvm::Constant *CodeGenModule::EmitConstantValue(const APValue &Value,
1243 QualType DestType,
1244 CodeGenFunction *CGF) {
1245 // For an _Atomic-qualified constant, we may need to add tail padding.
1246 if (auto *AT = DestType->getAs<AtomicType>()) {
1247 QualType InnerType = AT->getValueType();
1248 auto *Inner = EmitConstantValue(Value, InnerType, CGF);
1249
1250 uint64_t InnerSize = Context.getTypeSize(InnerType);
1251 uint64_t OuterSize = Context.getTypeSize(DestType);
1252 if (InnerSize == OuterSize)
1253 return Inner;
1254
1255 assert(InnerSize < OuterSize && "emitted over-large constant for atomic");
1256 llvm::Constant *Elts[] = {
1257 Inner,
1258 llvm::ConstantAggregateZero::get(
1259 llvm::ArrayType::get(Int8Ty, (OuterSize - InnerSize) / 8))
1260 };
1261 return llvm::ConstantStruct::getAnon(Elts);
1262 }
1263
1264 switch (Value.getKind()) {
1265 case APValue::Uninitialized:
1266 llvm_unreachable("Constant expressions should be initialized.");
1267 case APValue::LValue: {
1268 llvm::Type *DestTy = getTypes().ConvertTypeForMem(DestType);
1269 llvm::Constant *Offset =
1270 llvm::ConstantInt::get(Int64Ty, Value.getLValueOffset().getQuantity());
1271
1272 llvm::Constant *C = nullptr;
1273 if (APValue::LValueBase LVBase = Value.getLValueBase()) {
1274 // An array can be represented as an lvalue referring to the base.
1275 if (isa<llvm::ArrayType>(DestTy)) {
1276 assert(Offset->isNullValue() && "offset on array initializer");
1277 return ConstExprEmitter(*this, CGF).Visit(
1278 const_cast<Expr*>(LVBase.get<const Expr*>()));
1279 }
1280
1281 C = ConstExprEmitter(*this, CGF).EmitLValue(LVBase).getPointer();
1282
1283 // Apply offset if necessary.
1284 if (!Offset->isNullValue()) {
1285 unsigned AS = C->getType()->getPointerAddressSpace();
1286 llvm::Type *CharPtrTy = Int8Ty->getPointerTo(AS);
1287 llvm::Constant *Casted = llvm::ConstantExpr::getBitCast(C, CharPtrTy);
1288 Casted = llvm::ConstantExpr::getGetElementPtr(Int8Ty, Casted, Offset);
1289 C = llvm::ConstantExpr::getPointerCast(Casted, C->getType());
1290 }
1291
1292 // Convert to the appropriate type; this could be an lvalue for
1293 // an integer.
1294 if (isa<llvm::PointerType>(DestTy))
1295 return llvm::ConstantExpr::getPointerCast(C, DestTy);
1296
1297 return llvm::ConstantExpr::getPtrToInt(C, DestTy);
1298 } else {
1299 C = Offset;
1300
1301 // Convert to the appropriate type; this could be an lvalue for
1302 // an integer.
1303 if (isa<llvm::PointerType>(DestTy))
1304 return llvm::ConstantExpr::getIntToPtr(C, DestTy);
1305
1306 // If the types don't match this should only be a truncate.
1307 if (C->getType() != DestTy)
1308 return llvm::ConstantExpr::getTrunc(C, DestTy);
1309
1310 return C;
1311 }
1312 }
1313 case APValue::Int:
1314 return llvm::ConstantInt::get(VMContext, Value.getInt());
1315 case APValue::ComplexInt: {
1316 llvm::Constant *Complex[2];
1317
1318 Complex[0] = llvm::ConstantInt::get(VMContext,
1319 Value.getComplexIntReal());
1320 Complex[1] = llvm::ConstantInt::get(VMContext,
1321 Value.getComplexIntImag());
1322
1323 // FIXME: the target may want to specify that this is packed.
1324 llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(),
1325 Complex[1]->getType(),
1326 nullptr);
1327 return llvm::ConstantStruct::get(STy, Complex);
1328 }
1329 case APValue::Float: {
1330 const llvm::APFloat &Init = Value.getFloat();
1331 if (&Init.getSemantics() == &llvm::APFloat::IEEEhalf &&
1332 !Context.getLangOpts().NativeHalfType &&
1333 !Context.getLangOpts().HalfArgsAndReturns)
1334 return llvm::ConstantInt::get(VMContext, Init.bitcastToAPInt());
1335 else
1336 return llvm::ConstantFP::get(VMContext, Init);
1337 }
1338 case APValue::ComplexFloat: {
1339 llvm::Constant *Complex[2];
1340
1341 Complex[0] = llvm::ConstantFP::get(VMContext,
1342 Value.getComplexFloatReal());
1343 Complex[1] = llvm::ConstantFP::get(VMContext,
1344 Value.getComplexFloatImag());
1345
1346 // FIXME: the target may want to specify that this is packed.
1347 llvm::StructType *STy = llvm::StructType::get(Complex[0]->getType(),
1348 Complex[1]->getType(),
1349 nullptr);
1350 return llvm::ConstantStruct::get(STy, Complex);
1351 }
1352 case APValue::Vector: {
1353 unsigned NumElts = Value.getVectorLength();
1354 SmallVector<llvm::Constant *, 4> Inits(NumElts);
1355
1356 for (unsigned I = 0; I != NumElts; ++I) {
1357 const APValue &Elt = Value.getVectorElt(I);
1358 if (Elt.isInt())
1359 Inits[I] = llvm::ConstantInt::get(VMContext, Elt.getInt());
1360 else if (Elt.isFloat())
1361 Inits[I] = llvm::ConstantFP::get(VMContext, Elt.getFloat());
1362 else
1363 llvm_unreachable("unsupported vector element type");
1364 }
1365 return llvm::ConstantVector::get(Inits);
1366 }
1367 case APValue::AddrLabelDiff: {
1368 const AddrLabelExpr *LHSExpr = Value.getAddrLabelDiffLHS();
1369 const AddrLabelExpr *RHSExpr = Value.getAddrLabelDiffRHS();
1370 llvm::Constant *LHS = EmitConstantExpr(LHSExpr, LHSExpr->getType(), CGF);
1371 llvm::Constant *RHS = EmitConstantExpr(RHSExpr, RHSExpr->getType(), CGF);
1372
1373 // Compute difference
1374 llvm::Type *ResultType = getTypes().ConvertType(DestType);
1375 LHS = llvm::ConstantExpr::getPtrToInt(LHS, IntPtrTy);
1376 RHS = llvm::ConstantExpr::getPtrToInt(RHS, IntPtrTy);
1377 llvm::Constant *AddrLabelDiff = llvm::ConstantExpr::getSub(LHS, RHS);
1378
1379 // LLVM is a bit sensitive about the exact format of the
1380 // address-of-label difference; make sure to truncate after
1381 // the subtraction.
1382 return llvm::ConstantExpr::getTruncOrBitCast(AddrLabelDiff, ResultType);
1383 }
1384 case APValue::Struct:
1385 case APValue::Union:
1386 return ConstStructBuilder::BuildStruct(*this, CGF, Value, DestType);
1387 case APValue::Array: {
1388 const ArrayType *CAT = Context.getAsArrayType(DestType);
1389 unsigned NumElements = Value.getArraySize();
1390 unsigned NumInitElts = Value.getArrayInitializedElts();
1391
1392 // Emit array filler, if there is one.
1393 llvm::Constant *Filler = nullptr;
1394 if (Value.hasArrayFiller())
1395 Filler = EmitConstantValueForMemory(Value.getArrayFiller(),
1396 CAT->getElementType(), CGF);
1397
1398 // Emit initializer elements.
1399 llvm::Type *CommonElementType =
1400 getTypes().ConvertType(CAT->getElementType());
1401
1402 // Try to use a ConstantAggregateZero if we can.
1403 if (Filler && Filler->isNullValue() && !NumInitElts) {
1404 llvm::ArrayType *AType =
1405 llvm::ArrayType::get(CommonElementType, NumElements);
1406 return llvm::ConstantAggregateZero::get(AType);
1407 }
1408
1409 std::vector<llvm::Constant*> Elts;
1410 Elts.reserve(NumElements);
1411 for (unsigned I = 0; I < NumElements; ++I) {
1412 llvm::Constant *C = Filler;
1413 if (I < NumInitElts)
1414 C = EmitConstantValueForMemory(Value.getArrayInitializedElt(I),
1415 CAT->getElementType(), CGF);
1416 else
1417 assert(Filler && "Missing filler for implicit elements of initializer");
1418 if (I == 0)
1419 CommonElementType = C->getType();
1420 else if (C->getType() != CommonElementType)
1421 CommonElementType = nullptr;
1422 Elts.push_back(C);
1423 }
1424
1425 if (!CommonElementType) {
1426 // FIXME: Try to avoid packing the array
1427 std::vector<llvm::Type*> Types;
1428 Types.reserve(NumElements);
1429 for (unsigned i = 0, e = Elts.size(); i < e; ++i)
1430 Types.push_back(Elts[i]->getType());
1431 llvm::StructType *SType = llvm::StructType::get(VMContext, Types, true);
1432 return llvm::ConstantStruct::get(SType, Elts);
1433 }
1434
1435 llvm::ArrayType *AType =
1436 llvm::ArrayType::get(CommonElementType, NumElements);
1437 return llvm::ConstantArray::get(AType, Elts);
1438 }
1439 case APValue::MemberPointer:
1440 return getCXXABI().EmitMemberPointer(Value, DestType);
1441 }
1442 llvm_unreachable("Unknown APValue kind");
1443 }
1444
1445 llvm::Constant *
EmitConstantValueForMemory(const APValue & Value,QualType DestType,CodeGenFunction * CGF)1446 CodeGenModule::EmitConstantValueForMemory(const APValue &Value,
1447 QualType DestType,
1448 CodeGenFunction *CGF) {
1449 llvm::Constant *C = EmitConstantValue(Value, DestType, CGF);
1450 if (C->getType()->isIntegerTy(1)) {
1451 llvm::Type *BoolTy = getTypes().ConvertTypeForMem(DestType);
1452 C = llvm::ConstantExpr::getZExt(C, BoolTy);
1453 }
1454 return C;
1455 }
1456
1457 ConstantAddress
GetAddrOfConstantCompoundLiteral(const CompoundLiteralExpr * E)1458 CodeGenModule::GetAddrOfConstantCompoundLiteral(const CompoundLiteralExpr *E) {
1459 assert(E->isFileScope() && "not a file-scope compound literal expr");
1460 return ConstExprEmitter(*this, nullptr).EmitLValue(E);
1461 }
1462
1463 llvm::Constant *
getMemberPointerConstant(const UnaryOperator * uo)1464 CodeGenModule::getMemberPointerConstant(const UnaryOperator *uo) {
1465 // Member pointer constants always have a very particular form.
1466 const MemberPointerType *type = cast<MemberPointerType>(uo->getType());
1467 const ValueDecl *decl = cast<DeclRefExpr>(uo->getSubExpr())->getDecl();
1468
1469 // A member function pointer.
1470 if (const CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(decl))
1471 return getCXXABI().EmitMemberFunctionPointer(method);
1472
1473 // Otherwise, a member data pointer.
1474 uint64_t fieldOffset = getContext().getFieldOffset(decl);
1475 CharUnits chars = getContext().toCharUnitsFromBits((int64_t) fieldOffset);
1476 return getCXXABI().EmitMemberDataPointer(type, chars);
1477 }
1478
1479 static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
1480 llvm::Type *baseType,
1481 const CXXRecordDecl *base);
1482
EmitNullConstant(CodeGenModule & CGM,const CXXRecordDecl * record,bool asCompleteObject)1483 static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
1484 const CXXRecordDecl *record,
1485 bool asCompleteObject) {
1486 const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record);
1487 llvm::StructType *structure =
1488 (asCompleteObject ? layout.getLLVMType()
1489 : layout.getBaseSubobjectLLVMType());
1490
1491 unsigned numElements = structure->getNumElements();
1492 std::vector<llvm::Constant *> elements(numElements);
1493
1494 // Fill in all the bases.
1495 for (const auto &I : record->bases()) {
1496 if (I.isVirtual()) {
1497 // Ignore virtual bases; if we're laying out for a complete
1498 // object, we'll lay these out later.
1499 continue;
1500 }
1501
1502 const CXXRecordDecl *base =
1503 cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl());
1504
1505 // Ignore empty bases.
1506 if (base->isEmpty())
1507 continue;
1508
1509 unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base);
1510 llvm::Type *baseType = structure->getElementType(fieldIndex);
1511 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
1512 }
1513
1514 // Fill in all the fields.
1515 for (const auto *Field : record->fields()) {
1516 // Fill in non-bitfields. (Bitfields always use a zero pattern, which we
1517 // will fill in later.)
1518 if (!Field->isBitField()) {
1519 unsigned fieldIndex = layout.getLLVMFieldNo(Field);
1520 elements[fieldIndex] = CGM.EmitNullConstant(Field->getType());
1521 }
1522
1523 // For unions, stop after the first named field.
1524 if (record->isUnion()) {
1525 if (Field->getIdentifier())
1526 break;
1527 if (const auto *FieldRD =
1528 dyn_cast_or_null<RecordDecl>(Field->getType()->getAsTagDecl()))
1529 if (FieldRD->findFirstNamedDataMember())
1530 break;
1531 }
1532 }
1533
1534 // Fill in the virtual bases, if we're working with the complete object.
1535 if (asCompleteObject) {
1536 for (const auto &I : record->vbases()) {
1537 const CXXRecordDecl *base =
1538 cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl());
1539
1540 // Ignore empty bases.
1541 if (base->isEmpty())
1542 continue;
1543
1544 unsigned fieldIndex = layout.getVirtualBaseIndex(base);
1545
1546 // We might have already laid this field out.
1547 if (elements[fieldIndex]) continue;
1548
1549 llvm::Type *baseType = structure->getElementType(fieldIndex);
1550 elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
1551 }
1552 }
1553
1554 // Now go through all other fields and zero them out.
1555 for (unsigned i = 0; i != numElements; ++i) {
1556 if (!elements[i])
1557 elements[i] = llvm::Constant::getNullValue(structure->getElementType(i));
1558 }
1559
1560 return llvm::ConstantStruct::get(structure, elements);
1561 }
1562
1563 /// Emit the null constant for a base subobject.
EmitNullConstantForBase(CodeGenModule & CGM,llvm::Type * baseType,const CXXRecordDecl * base)1564 static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
1565 llvm::Type *baseType,
1566 const CXXRecordDecl *base) {
1567 const CGRecordLayout &baseLayout = CGM.getTypes().getCGRecordLayout(base);
1568
1569 // Just zero out bases that don't have any pointer to data members.
1570 if (baseLayout.isZeroInitializableAsBase())
1571 return llvm::Constant::getNullValue(baseType);
1572
1573 // Otherwise, we can just use its null constant.
1574 return EmitNullConstant(CGM, base, /*asCompleteObject=*/false);
1575 }
1576
EmitNullConstant(QualType T)1577 llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
1578 if (getTypes().isZeroInitializable(T))
1579 return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
1580
1581 if (const ConstantArrayType *CAT = Context.getAsConstantArrayType(T)) {
1582 llvm::ArrayType *ATy =
1583 cast<llvm::ArrayType>(getTypes().ConvertTypeForMem(T));
1584
1585 QualType ElementTy = CAT->getElementType();
1586
1587 llvm::Constant *Element = EmitNullConstant(ElementTy);
1588 unsigned NumElements = CAT->getSize().getZExtValue();
1589 SmallVector<llvm::Constant *, 8> Array(NumElements, Element);
1590 return llvm::ConstantArray::get(ATy, Array);
1591 }
1592
1593 if (const RecordType *RT = T->getAs<RecordType>()) {
1594 const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
1595 return ::EmitNullConstant(*this, RD, /*complete object*/ true);
1596 }
1597
1598 assert(T->isMemberDataPointerType() &&
1599 "Should only see pointers to data members here!");
1600
1601 return getCXXABI().EmitNullMemberPointer(T->castAs<MemberPointerType>());
1602 }
1603
1604 llvm::Constant *
EmitNullConstantForBase(const CXXRecordDecl * Record)1605 CodeGenModule::EmitNullConstantForBase(const CXXRecordDecl *Record) {
1606 return ::EmitNullConstant(*this, Record, false);
1607 }
1608