CGExprConstant.cpp revision bd012ff1fa088181646a784f385b28867372d434 
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 "CodeGenModule.h"
16#include "clang/AST/AST.h"
17#include "llvm/Constants.h"
18#include "llvm/Function.h"
19#include "llvm/GlobalVariable.h"
20#include "llvm/Support/Compiler.h"
21#include "llvm/Target/TargetData.h"
22using namespace clang;
23using namespace CodeGen;
24
25namespace  {
26class VISIBILITY_HIDDEN ConstExprEmitter :
27  public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
28  CodeGenModule &CGM;
29  CodeGenFunction *CGF;
30public:
31  ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf)
32    : CGM(cgm), CGF(cgf) {
33  }
34
35  //===--------------------------------------------------------------------===//
36  //                            Visitor Methods
37  //===--------------------------------------------------------------------===//
38
39  llvm::Constant *VisitStmt(Stmt *S) {
40    CGM.WarnUnsupported(S, "constant expression");
41    QualType T = cast<Expr>(S)->getType();
42    return llvm::UndefValue::get(CGM.getTypes().ConvertType(T));
43  }
44
45  llvm::Constant *VisitParenExpr(ParenExpr *PE) {
46    return Visit(PE->getSubExpr());
47  }
48
49  // Leaves
50  llvm::Constant *VisitIntegerLiteral(const IntegerLiteral *E) {
51    return llvm::ConstantInt::get(E->getValue());
52  }
53  llvm::Constant *VisitFloatingLiteral(const FloatingLiteral *E) {
54    return llvm::ConstantFP::get(E->getValue());
55  }
56  llvm::Constant *VisitCharacterLiteral(const CharacterLiteral *E) {
57    return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
58  }
59  llvm::Constant *VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr *E) {
60    return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
61  }
62  llvm::Constant *VisitObjCStringLiteral(const ObjCStringLiteral *E) {
63    return CGM.getObjCRuntime()->GenerateConstantString(
64        E->getString()->getStrData(), E->getString()->getByteLength());
65  }
66
67  llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
68    return Visit(E->getInitializer());
69  }
70
71  llvm::Constant *VisitCastExpr(const CastExpr* E) {
72    llvm::Constant *C = Visit(E->getSubExpr());
73
74    return EmitConversion(C, E->getSubExpr()->getType(), E->getType());
75  }
76
77  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
78    return Visit(DAE->getExpr());
79  }
80
81  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
82    std::vector<llvm::Constant*> Elts;
83    const llvm::ArrayType *AType =
84        cast<llvm::ArrayType>(ConvertType(ILE->getType()));
85    unsigned NumInitElements = ILE->getNumInits();
86    // FIXME: Check for wide strings
87    if (NumInitElements > 0 && isa<StringLiteral>(ILE->getInit(0)) &&
88        ILE->getType()->getAsArrayType()->getElementType()->isCharType())
89      return Visit(ILE->getInit(0));
90    const llvm::Type *ElemTy = AType->getElementType();
91    unsigned NumElements = AType->getNumElements();
92
93    // Initialising an array requires us to automatically
94    // initialise any elements that have not been initialised explicitly
95    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
96
97    // Copy initializer elements.
98    unsigned i = 0;
99    bool RewriteType = false;
100    for (; i < NumInitableElts; ++i) {
101      llvm::Constant *C = Visit(ILE->getInit(i));
102      RewriteType |= (C->getType() != ElemTy);
103      Elts.push_back(C);
104    }
105
106    // Initialize remaining array elements.
107    for (; i < NumElements; ++i)
108      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
109
110    if (RewriteType) {
111      // FIXME: Try to avoid packing the array
112      std::vector<const llvm::Type*> Types;
113      for (unsigned i = 0; i < Elts.size(); ++i)
114        Types.push_back(Elts[i]->getType());
115      const llvm::StructType *SType = llvm::StructType::get(Types, true);
116      return llvm::ConstantStruct::get(SType, Elts);
117    }
118
119    return llvm::ConstantArray::get(AType, Elts);
120  }
121
122  void InsertBitfieldIntoStruct(std::vector<llvm::Constant*>& Elts,
123                                FieldDecl* Field, Expr* E) {
124    // Calculate the value to insert
125    llvm::Constant *C = Visit(E);
126    llvm::ConstantInt *CI = dyn_cast<llvm::ConstantInt>(C);
127    if (!CI) {
128      CGM.WarnUnsupported(E, "bitfield initialization");
129      return;
130    }
131    llvm::APInt V = CI->getValue();
132
133    // Calculate information about the relevant field
134    const llvm::Type* Ty = CI->getType();
135    unsigned size = CGM.getTypes().getTargetData().getTypeStoreSizeInBits(Ty);
136    unsigned fieldOffset = CGM.getTypes().getLLVMFieldNo(Field) * size;
137    CodeGenTypes::BitFieldInfo bitFieldInfo =
138        CGM.getTypes().getBitFieldInfo(Field);
139    fieldOffset += bitFieldInfo.Begin;
140
141    // Find where to start the insertion
142    // FIXME: This is O(n^2) in the number of bit-fields!
143    // FIXME: This won't work if the struct isn't completely packed!
144    unsigned offset = 0, i = 0;
145    while (offset < (fieldOffset & -8))
146      offset += CGM.getTypes().getTargetData().getTypeStoreSizeInBits(Elts[i++]->getType());
147
148    // Promote the size of V if necessary
149    // FIXME: This should never occur, but currently it can because
150    // initializer constants are cast to bool, and because clang is
151    // not enforcing bitfield width limits.
152    if (bitFieldInfo.Size > V.getBitWidth())
153      V.zext(bitFieldInfo.Size);
154
155    // Insert the bits into the struct
156    // FIXME: This algorthm is only correct on X86!
157    // FIXME: THis algorthm assumes bit-fields only have byte-size elements!
158    unsigned bitsToInsert = bitFieldInfo.Size;
159    unsigned curBits = std::min(8 - (fieldOffset & 7), bitsToInsert);
160    unsigned byte = V.getLoBits(curBits).getZExtValue() << (fieldOffset & 7);
161    do {
162      llvm::Constant* byteC = llvm::ConstantInt::get(llvm::Type::Int8Ty, byte);
163      Elts[i] = llvm::ConstantExpr::getOr(Elts[i], byteC);
164      ++i;
165      V = V.lshr(curBits);
166      bitsToInsert -= curBits;
167
168      if (!bitsToInsert)
169        break;
170
171      curBits = bitsToInsert > 8 ? 8 : bitsToInsert;
172      byte = V.getLoBits(curBits).getZExtValue();
173    } while (true);
174  }
175
176  llvm::Constant *EmitStructInitialization(InitListExpr *ILE) {
177    const llvm::StructType *SType =
178        cast<llvm::StructType>(ConvertType(ILE->getType()));
179    RecordDecl *RD = ILE->getType()->getAsRecordType()->getDecl();
180    std::vector<llvm::Constant*> Elts;
181
182    // Initialize the whole structure to zero.
183    for (unsigned i = 0; i < SType->getNumElements(); ++i) {
184      const llvm::Type *FieldTy = SType->getElementType(i);
185      Elts.push_back(llvm::Constant::getNullValue(FieldTy));
186    }
187
188    // Copy initializer elements. Skip padding fields.
189    unsigned EltNo = 0;  // Element no in ILE
190    int FieldNo = 0; // Field no in RecordDecl
191    bool RewriteType = false;
192    while (EltNo < ILE->getNumInits() && FieldNo < RD->getNumMembers()) {
193      FieldDecl* curField = RD->getMember(FieldNo);
194      FieldNo++;
195      if (!curField->getIdentifier())
196        continue;
197
198      if (curField->isBitField()) {
199        InsertBitfieldIntoStruct(Elts, curField, ILE->getInit(EltNo));
200      } else {
201        unsigned FieldNo = CGM.getTypes().getLLVMFieldNo(curField);
202        llvm::Constant* C = Visit(ILE->getInit(EltNo));
203        RewriteType |= (C->getType() != Elts[FieldNo]->getType());
204        Elts[FieldNo] = C;
205      }
206      EltNo++;
207    }
208
209    if (RewriteType) {
210      // FIXME: Make this work for non-packed structs
211      assert(SType->isPacked() && "Cannot recreate unpacked structs");
212      std::vector<const llvm::Type*> Types;
213      for (unsigned i = 0; i < Elts.size(); ++i)
214        Types.push_back(Elts[i]->getType());
215      SType = llvm::StructType::get(Types, true);
216    }
217
218    return llvm::ConstantStruct::get(SType, Elts);
219  }
220
221  llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
222    RecordDecl *RD = ILE->getType()->getAsRecordType()->getDecl();
223    const llvm::Type *Ty = ConvertType(ILE->getType());
224
225    // Find the field decl we're initializing, if any
226    int FieldNo = 0; // Field no in RecordDecl
227    FieldDecl* curField = 0;
228    while (FieldNo < RD->getNumMembers()) {
229      curField = RD->getMember(FieldNo);
230      FieldNo++;
231      if (curField->getIdentifier())
232        break;
233    }
234
235    if (!curField || !curField->getIdentifier() || ILE->getNumInits() == 0)
236      return llvm::Constant::getNullValue(Ty);
237
238    if (curField->isBitField()) {
239      // Create a dummy struct for bit-field insertion
240      unsigned NumElts = CGM.getTargetData().getABITypeSize(Ty) / 8;
241      llvm::Constant* NV = llvm::Constant::getNullValue(llvm::Type::Int8Ty);
242      std::vector<llvm::Constant*> Elts(NumElts, NV);
243
244      InsertBitfieldIntoStruct(Elts, curField, ILE->getInit(0));
245      const llvm::ArrayType *RetTy =
246          llvm::ArrayType::get(NV->getType(), NumElts);
247      return llvm::ConstantArray::get(RetTy, Elts);
248    }
249
250    llvm::Constant *C = Visit(ILE->getInit(0));
251
252    // Build a struct with the union sub-element as the first member,
253    // and padded to the appropriate size
254    std::vector<llvm::Constant*> Elts;
255    std::vector<const llvm::Type*> Types;
256    Elts.push_back(C);
257    Types.push_back(C->getType());
258    unsigned CurSize = CGM.getTargetData().getTypeStoreSize(C->getType());
259    unsigned TotalSize = CGM.getTargetData().getTypeStoreSize(Ty);
260    while (CurSize < TotalSize) {
261      Elts.push_back(llvm::Constant::getNullValue(llvm::Type::Int8Ty));
262      Types.push_back(llvm::Type::Int8Ty);
263      CurSize++;
264    }
265
266    // This always generates a packed struct
267    // FIXME: Try to generate an unpacked struct when we can
268    llvm::StructType* STy = llvm::StructType::get(Types, true);
269    return llvm::ConstantStruct::get(STy, Elts);
270  }
271
272  llvm::Constant *EmitVectorInitialization(InitListExpr *ILE) {
273    const llvm::VectorType *VType =
274        cast<llvm::VectorType>(ConvertType(ILE->getType()));
275    const llvm::Type *ElemTy = VType->getElementType();
276    std::vector<llvm::Constant*> Elts;
277    unsigned NumElements = VType->getNumElements();
278    unsigned NumInitElements = ILE->getNumInits();
279
280    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
281
282    // Copy initializer elements.
283    unsigned i = 0;
284    for (; i < NumInitableElts; ++i) {
285      llvm::Constant *C = Visit(ILE->getInit(i));
286      Elts.push_back(C);
287    }
288
289    for (; i < NumElements; ++i)
290      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
291
292    return llvm::ConstantVector::get(VType, Elts);
293  }
294
295  llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
296    if (ILE->getType()->isScalarType()) {
297      // We have a scalar in braces. Just use the first element.
298      if (ILE->getNumInits() > 0)
299        return Visit(ILE->getInit(0));
300
301      const llvm::Type* RetTy = CGM.getTypes().ConvertType(ILE->getType());
302      return llvm::Constant::getNullValue(RetTy);
303    }
304
305    if (ILE->getType()->isArrayType())
306      return EmitArrayInitialization(ILE);
307
308    if (ILE->getType()->isStructureType())
309      return EmitStructInitialization(ILE);
310
311    if (ILE->getType()->isUnionType())
312      return EmitUnionInitialization(ILE);
313
314    if (ILE->getType()->isVectorType())
315      return EmitVectorInitialization(ILE);
316
317    assert(0 && "Unable to handle InitListExpr");
318    // Get rid of control reaches end of void function warning.
319    // Not reached.
320    return 0;
321  }
322
323  llvm::Constant *VisitImplicitCastExpr(ImplicitCastExpr *ICExpr) {
324    Expr* SExpr = ICExpr->getSubExpr();
325    QualType SType = SExpr->getType();
326    llvm::Constant *C; // the intermediate expression
327    QualType T;        // the type of the intermediate expression
328    if (SType->isArrayType()) {
329      // Arrays decay to a pointer to the first element
330      // VLAs would require special handling, but they can't occur here
331      C = EmitLValue(SExpr);
332      llvm::Constant *Idx0 = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
333      llvm::Constant *Ops[] = {Idx0, Idx0};
334      C = llvm::ConstantExpr::getGetElementPtr(C, Ops, 2);
335
336      QualType ElemType = SType->getAsArrayType()->getElementType();
337      T = CGM.getContext().getPointerType(ElemType);
338    } else if (SType->isFunctionType()) {
339      // Function types decay to a pointer to the function
340      C = EmitLValue(SExpr);
341      T = CGM.getContext().getPointerType(SType);
342    } else {
343      C = Visit(SExpr);
344      T = SType;
345    }
346
347    // Perform the conversion; note that an implicit cast can both promote
348    // and convert an array/function
349    return EmitConversion(C, T, ICExpr->getType());
350  }
351
352  llvm::Constant *VisitStringLiteral(StringLiteral *E) {
353    const char *StrData = E->getStrData();
354    unsigned Len = E->getByteLength();
355    assert(!E->getType()->isPointerType() && "Strings are always arrays");
356
357    // Otherwise this must be a string initializing an array in a static
358    // initializer.  Don't emit it as the address of the string, emit the string
359    // data itself as an inline array.
360    const ConstantArrayType *CAT = E->getType()->getAsConstantArrayType();
361    assert(CAT && "String isn't pointer or array!");
362
363    std::string Str(StrData, StrData + Len);
364    // Null terminate the string before potentially truncating it.
365    // FIXME: What about wchar_t strings?
366    Str.push_back(0);
367
368    uint64_t RealLen = CAT->getSize().getZExtValue();
369    // String or grow the initializer to the required size.
370    if (RealLen != Str.size())
371      Str.resize(RealLen);
372
373    return llvm::ConstantArray::get(Str, false);
374  }
375
376  llvm::Constant *VisitDeclRefExpr(DeclRefExpr *E) {
377    const ValueDecl *Decl = E->getDecl();
378    if (const EnumConstantDecl *EC = dyn_cast<EnumConstantDecl>(Decl))
379      return llvm::ConstantInt::get(EC->getInitVal());
380    assert(0 && "Unsupported decl ref type!");
381    return 0;
382  }
383
384  llvm::Constant *VisitSizeOfAlignOfTypeExpr(const SizeOfAlignOfTypeExpr *E) {
385    return EmitSizeAlignOf(E->getArgumentType(), E->getType(), E->isSizeOf());
386  }
387
388  // Unary operators
389  llvm::Constant *VisitUnaryPlus(const UnaryOperator *E) {
390    return Visit(E->getSubExpr());
391  }
392  llvm::Constant *VisitUnaryMinus(const UnaryOperator *E) {
393    return llvm::ConstantExpr::getNeg(Visit(E->getSubExpr()));
394  }
395  llvm::Constant *VisitUnaryNot(const UnaryOperator *E) {
396    return llvm::ConstantExpr::getNot(Visit(E->getSubExpr()));
397  }
398  llvm::Constant *VisitUnaryLNot(const UnaryOperator *E) {
399    llvm::Constant *SubExpr = Visit(E->getSubExpr());
400
401    if (E->getSubExpr()->getType()->isRealFloatingType()) {
402      // Compare against 0.0 for fp scalars.
403      llvm::Constant *Zero = llvm::Constant::getNullValue(SubExpr->getType());
404      SubExpr = llvm::ConstantExpr::getFCmp(llvm::FCmpInst::FCMP_UEQ, SubExpr,
405                                            Zero);
406    } else {
407      assert((E->getSubExpr()->getType()->isIntegerType() ||
408              E->getSubExpr()->getType()->isPointerType()) &&
409             "Unknown scalar type to convert");
410      // Compare against an integer or pointer null.
411      llvm::Constant *Zero = llvm::Constant::getNullValue(SubExpr->getType());
412      SubExpr = llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_EQ, SubExpr,
413                                            Zero);
414    }
415
416    return llvm::ConstantExpr::getZExt(SubExpr, ConvertType(E->getType()));
417  }
418  llvm::Constant *VisitUnarySizeOf(const UnaryOperator *E) {
419    return EmitSizeAlignOf(E->getSubExpr()->getType(), E->getType(), true);
420  }
421  llvm::Constant *VisitUnaryAlignOf(const UnaryOperator *E) {
422    return EmitSizeAlignOf(E->getSubExpr()->getType(), E->getType(), false);
423  }
424  llvm::Constant *VisitUnaryAddrOf(const UnaryOperator *E) {
425    return EmitLValue(E->getSubExpr());
426  }
427  llvm::Constant *VisitUnaryOffsetOf(const UnaryOperator *E) {
428    int64_t Val = E->evaluateOffsetOf(CGM.getContext());
429
430    assert(E->getType()->isIntegerType() && "Result type must be an integer!");
431
432    uint32_t ResultWidth =
433      static_cast<uint32_t>(CGM.getContext().getTypeSize(E->getType()));
434    return llvm::ConstantInt::get(llvm::APInt(ResultWidth, Val));
435  }
436
437  llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) {
438    return Visit(E->getSubExpr());
439  }
440
441  // Binary operators
442  llvm::Constant *VisitBinOr(const BinaryOperator *E) {
443    llvm::Constant *LHS = Visit(E->getLHS());
444    llvm::Constant *RHS = Visit(E->getRHS());
445
446    return llvm::ConstantExpr::getOr(LHS, RHS);
447  }
448  llvm::Constant *VisitBinSub(const BinaryOperator *E) {
449    llvm::Constant *LHS = Visit(E->getLHS());
450    llvm::Constant *RHS = Visit(E->getRHS());
451
452    if (!isa<llvm::PointerType>(RHS->getType())) {
453      // pointer - int
454      if (isa<llvm::PointerType>(LHS->getType())) {
455        llvm::Constant *Idx = llvm::ConstantExpr::getNeg(RHS);
456
457        return llvm::ConstantExpr::getGetElementPtr(LHS, &Idx, 1);
458      }
459
460      // int - int
461      return llvm::ConstantExpr::getSub(LHS, RHS);
462    }
463
464    assert(isa<llvm::PointerType>(LHS->getType()));
465
466    const llvm::Type *ResultType = ConvertType(E->getType());
467    const QualType Type = E->getLHS()->getType();
468    const QualType ElementType = Type->getAsPointerType()->getPointeeType();
469
470    LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType);
471    RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType);
472
473    llvm::Constant *sub = llvm::ConstantExpr::getSub(LHS, RHS);
474    llvm::Constant *size = EmitSizeAlignOf(ElementType, E->getType(), true);
475    return llvm::ConstantExpr::getSDiv(sub, size);
476  }
477
478  llvm::Constant *VisitBinShl(const BinaryOperator *E) {
479    llvm::Constant *LHS = Visit(E->getLHS());
480    llvm::Constant *RHS = Visit(E->getRHS());
481
482    // LLVM requires the LHS and RHS to be the same type: promote or truncate the
483    // RHS to the same size as the LHS.
484    if (LHS->getType() != RHS->getType())
485      RHS = llvm::ConstantExpr::getIntegerCast(RHS, LHS->getType(), false);
486
487    return llvm::ConstantExpr::getShl(LHS, RHS);
488  }
489
490  llvm::Constant *VisitBinMul(const BinaryOperator *E) {
491    llvm::Constant *LHS = Visit(E->getLHS());
492    llvm::Constant *RHS = Visit(E->getRHS());
493
494    return llvm::ConstantExpr::getMul(LHS, RHS);
495  }
496
497  llvm::Constant *VisitBinDiv(const BinaryOperator *E) {
498    llvm::Constant *LHS = Visit(E->getLHS());
499    llvm::Constant *RHS = Visit(E->getRHS());
500
501    if (LHS->getType()->isFPOrFPVector())
502      return llvm::ConstantExpr::getFDiv(LHS, RHS);
503    else if (E->getType()->isUnsignedIntegerType())
504      return llvm::ConstantExpr::getUDiv(LHS, RHS);
505    else
506      return llvm::ConstantExpr::getSDiv(LHS, RHS);
507  }
508
509  llvm::Constant *VisitBinAdd(const BinaryOperator *E) {
510    llvm::Constant *LHS = Visit(E->getLHS());
511    llvm::Constant *RHS = Visit(E->getRHS());
512
513    if (!E->getType()->isPointerType())
514      return llvm::ConstantExpr::getAdd(LHS, RHS);
515
516    llvm::Constant *Ptr, *Idx;
517    if (isa<llvm::PointerType>(LHS->getType())) { // pointer + int
518      Ptr = LHS;
519      Idx = RHS;
520    } else { // int + pointer
521      Ptr = RHS;
522      Idx = LHS;
523    }
524
525    return llvm::ConstantExpr::getGetElementPtr(Ptr, &Idx, 1);
526  }
527
528  llvm::Constant *VisitBinAnd(const BinaryOperator *E) {
529    llvm::Constant *LHS = Visit(E->getLHS());
530    llvm::Constant *RHS = Visit(E->getRHS());
531
532    return llvm::ConstantExpr::getAnd(LHS, RHS);
533  }
534
535  llvm::Constant *EmitCmp(const BinaryOperator *E,
536                          llvm::CmpInst::Predicate SignedPred,
537                          llvm::CmpInst::Predicate UnsignedPred,
538                          llvm::CmpInst::Predicate FloatPred) {
539    llvm::Constant *LHS = Visit(E->getLHS());
540    llvm::Constant *RHS = Visit(E->getRHS());
541    llvm::Constant *Result;
542    if (LHS->getType()->isInteger() ||
543        isa<llvm::PointerType>(LHS->getType())) {
544      if (E->getLHS()->getType()->isSignedIntegerType())
545        Result = llvm::ConstantExpr::getICmp(SignedPred, LHS, RHS);
546      else
547        Result = llvm::ConstantExpr::getICmp(UnsignedPred, LHS, RHS);
548    } else if (LHS->getType()->isFloatingPoint()) {
549      Result = llvm::ConstantExpr::getFCmp(FloatPred, LHS, RHS);
550    } else {
551      CGM.WarnUnsupported(E, "constant expression");
552      Result = llvm::ConstantInt::getFalse();
553    }
554
555    const llvm::Type* ResultType = ConvertType(E->getType());
556    return llvm::ConstantExpr::getZExtOrBitCast(Result, ResultType);
557  }
558
559  llvm::Constant *VisitBinNE(const BinaryOperator *E) {
560    return EmitCmp(E, llvm::CmpInst::ICMP_NE, llvm::CmpInst::ICMP_NE,
561                   llvm::CmpInst::FCMP_ONE);
562  }
563
564  llvm::Constant *VisitBinEQ(const BinaryOperator *E) {
565    return EmitCmp(E, llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_EQ,
566                   llvm::CmpInst::FCMP_OEQ);
567  }
568
569  llvm::Constant *VisitBinLT(const BinaryOperator *E) {
570    return EmitCmp(E, llvm::CmpInst::ICMP_SLT, llvm::CmpInst::ICMP_ULT,
571                   llvm::CmpInst::FCMP_OLT);
572  }
573
574  llvm::Constant *VisitBinLE(const BinaryOperator *E) {
575    return EmitCmp(E, llvm::CmpInst::ICMP_SLE, llvm::CmpInst::ICMP_ULE,
576                   llvm::CmpInst::FCMP_OLE);
577  }
578
579  llvm::Constant *VisitBinGT(const BinaryOperator *E) {
580    return EmitCmp(E, llvm::CmpInst::ICMP_SGT, llvm::CmpInst::ICMP_UGT,
581                   llvm::CmpInst::FCMP_OGT);
582  }
583
584  llvm::Constant *VisitBinGE(const BinaryOperator *E) {
585    return EmitCmp(E, llvm::CmpInst::ICMP_SGE, llvm::CmpInst::ICMP_SGE,
586                   llvm::CmpInst::FCMP_OGE);
587  }
588
589  llvm::Constant *VisitConditionalOperator(const ConditionalOperator *E) {
590    llvm::Constant *Cond = Visit(E->getCond());
591    llvm::Constant *CondVal = EmitConversionToBool(Cond, E->getType());
592    llvm::ConstantInt *CondValInt = dyn_cast<llvm::ConstantInt>(CondVal);
593    if (!CondValInt) {
594      CGM.WarnUnsupported(E, "constant expression");
595      return llvm::Constant::getNullValue(ConvertType(E->getType()));
596    }
597    if (CondValInt->isOne()) {
598      if (E->getLHS())
599        return Visit(E->getLHS());
600      return Cond;
601    }
602
603    return Visit(E->getRHS());
604  }
605
606  // Utility methods
607  const llvm::Type *ConvertType(QualType T) {
608    return CGM.getTypes().ConvertType(T);
609  }
610
611  llvm::Constant *EmitConversionToBool(llvm::Constant *Src, QualType SrcType) {
612    assert(SrcType->isCanonical() && "EmitConversion strips typedefs");
613
614    if (SrcType->isRealFloatingType()) {
615      // Compare against 0.0 for fp scalars.
616      llvm::Constant *Zero = llvm::Constant::getNullValue(Src->getType());
617      return llvm::ConstantExpr::getFCmp(llvm::FCmpInst::FCMP_UNE, Src, Zero);
618    }
619
620    assert((SrcType->isIntegerType() || SrcType->isPointerType()) &&
621           "Unknown scalar type to convert");
622
623    // Compare against an integer or pointer null.
624    llvm::Constant *Zero = llvm::Constant::getNullValue(Src->getType());
625    return llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_NE, Src, Zero);
626  }
627
628  llvm::Constant *EmitConversion(llvm::Constant *Src, QualType SrcType,
629                                 QualType DstType) {
630    SrcType = CGM.getContext().getCanonicalType(SrcType);
631    DstType = CGM.getContext().getCanonicalType(DstType);
632    if (SrcType == DstType) return Src;
633
634    // Handle conversions to bool first, they are special: comparisons against 0.
635    if (DstType->isBooleanType())
636      return EmitConversionToBool(Src, SrcType);
637
638    const llvm::Type *DstTy = ConvertType(DstType);
639
640    // Ignore conversions like int -> uint.
641    if (Src->getType() == DstTy)
642      return Src;
643
644    // Handle pointer conversions next: pointers can only be converted to/from
645    // other pointers and integers.
646    if (isa<llvm::PointerType>(DstTy)) {
647      // The source value may be an integer, or a pointer.
648      if (isa<llvm::PointerType>(Src->getType()))
649        return llvm::ConstantExpr::getBitCast(Src, DstTy);
650      assert(SrcType->isIntegerType() &&"Not ptr->ptr or int->ptr conversion?");
651      return llvm::ConstantExpr::getIntToPtr(Src, DstTy);
652    }
653
654    if (isa<llvm::PointerType>(Src->getType())) {
655      // Must be an ptr to int cast.
656      assert(isa<llvm::IntegerType>(DstTy) && "not ptr->int?");
657      return llvm::ConstantExpr::getPtrToInt(Src, DstTy);
658    }
659
660    // A scalar source can be splatted to a vector of the same element type
661    if (isa<llvm::VectorType>(DstTy) && !isa<VectorType>(SrcType)) {
662      const llvm::VectorType *VT = cast<llvm::VectorType>(DstTy);
663      assert((VT->getElementType() == Src->getType()) &&
664             "Vector element type must match scalar type to splat.");
665      unsigned NumElements = DstType->getAsVectorType()->getNumElements();
666      llvm::SmallVector<llvm::Constant*, 16> Elements;
667      for (unsigned i = 0; i < NumElements; i++)
668        Elements.push_back(Src);
669
670      return llvm::ConstantVector::get(&Elements[0], NumElements);
671    }
672
673    if (isa<llvm::VectorType>(Src->getType()) ||
674        isa<llvm::VectorType>(DstTy)) {
675      return llvm::ConstantExpr::getBitCast(Src, DstTy);
676    }
677
678    // Finally, we have the arithmetic types: real int/float.
679    if (isa<llvm::IntegerType>(Src->getType())) {
680      bool InputSigned = SrcType->isSignedIntegerType();
681      if (isa<llvm::IntegerType>(DstTy))
682        return llvm::ConstantExpr::getIntegerCast(Src, DstTy, InputSigned);
683      else if (InputSigned)
684        return llvm::ConstantExpr::getSIToFP(Src, DstTy);
685      else
686        return llvm::ConstantExpr::getUIToFP(Src, DstTy);
687    }
688
689    assert(Src->getType()->isFloatingPoint() && "Unknown real conversion");
690    if (isa<llvm::IntegerType>(DstTy)) {
691      if (DstType->isSignedIntegerType())
692        return llvm::ConstantExpr::getFPToSI(Src, DstTy);
693      else
694        return llvm::ConstantExpr::getFPToUI(Src, DstTy);
695    }
696
697    assert(DstTy->isFloatingPoint() && "Unknown real conversion");
698    if (DstTy->getTypeID() < Src->getType()->getTypeID())
699      return llvm::ConstantExpr::getFPTrunc(Src, DstTy);
700    else
701      return llvm::ConstantExpr::getFPExtend(Src, DstTy);
702  }
703
704  llvm::Constant *EmitSizeAlignOf(QualType TypeToSize,
705                                  QualType RetType, bool isSizeOf) {
706    std::pair<uint64_t, unsigned> Info =
707      CGM.getContext().getTypeInfo(TypeToSize);
708
709    uint64_t Val = isSizeOf ? Info.first : Info.second;
710    Val /= 8;  // Return size in bytes, not bits.
711
712    assert(RetType->isIntegerType() && "Result type must be an integer!");
713
714    uint32_t ResultWidth =
715      static_cast<uint32_t>(CGM.getContext().getTypeSize(RetType));
716    return llvm::ConstantInt::get(llvm::APInt(ResultWidth, Val));
717  }
718
719  llvm::Constant *EmitLValue(Expr *E) {
720    switch (E->getStmtClass()) {
721    default: break;
722    case Expr::ParenExprClass:
723      // Elide parenthesis
724      return EmitLValue(cast<ParenExpr>(E)->getSubExpr());
725    case Expr::CompoundLiteralExprClass: {
726      // Note that due to the nature of compound literals, this is guaranteed
727      // to be the only use of the variable, so we just generate it here.
728      CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
729      llvm::Constant* C = Visit(CLE->getInitializer());
730      C = new llvm::GlobalVariable(C->getType(),E->getType().isConstQualified(),
731                                   llvm::GlobalValue::InternalLinkage,
732                                   C, ".compoundliteral", &CGM.getModule());
733      return C;
734    }
735    case Expr::DeclRefExprClass: {
736      ValueDecl *Decl = cast<DeclRefExpr>(E)->getDecl();
737      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
738        return CGM.GetAddrOfFunction(FD);
739      if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
740        if (VD->isFileVarDecl())
741          return CGM.GetAddrOfGlobalVar(VD);
742        else if (VD->isBlockVarDecl()) {
743          assert(CGF && "Can't access static local vars without CGF");
744          return CGF->GetAddrOfStaticLocalVar(VD);
745        }
746      }
747      break;
748    }
749    case Expr::MemberExprClass: {
750      MemberExpr* ME = cast<MemberExpr>(E);
751      llvm::Constant *Base;
752      if (ME->isArrow())
753        Base = Visit(ME->getBase());
754      else
755        Base = EmitLValue(ME->getBase());
756
757      unsigned FieldNumber = CGM.getTypes().getLLVMFieldNo(ME->getMemberDecl());
758      llvm::Constant *Zero = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
759      llvm::Constant *Idx = llvm::ConstantInt::get(llvm::Type::Int32Ty,
760                                                   FieldNumber);
761      llvm::Value *Ops[] = {Zero, Idx};
762      return llvm::ConstantExpr::getGetElementPtr(Base, Ops, 2);
763    }
764    case Expr::ArraySubscriptExprClass: {
765      ArraySubscriptExpr* ASExpr = cast<ArraySubscriptExpr>(E);
766      llvm::Constant *Base = Visit(ASExpr->getBase());
767      llvm::Constant *Index = Visit(ASExpr->getIdx());
768      assert(!ASExpr->getBase()->getType()->isVectorType() &&
769             "Taking the address of a vector component is illegal!");
770      return llvm::ConstantExpr::getGetElementPtr(Base, &Index, 1);
771    }
772    case Expr::StringLiteralClass: {
773      StringLiteral *String = cast<StringLiteral>(E);
774      assert(!String->isWide() && "Cannot codegen wide strings yet");
775      const char *StrData = String->getStrData();
776      unsigned Len = String->getByteLength();
777
778      return CGM.GetAddrOfConstantString(std::string(StrData, StrData + Len));
779    }
780    case Expr::UnaryOperatorClass: {
781      UnaryOperator *Exp = cast<UnaryOperator>(E);
782      switch (Exp->getOpcode()) {
783      default: break;
784      case UnaryOperator::Extension:
785        // Extension is just a wrapper for expressions
786        return EmitLValue(Exp->getSubExpr());
787      case UnaryOperator::Real:
788      case UnaryOperator::Imag: {
789        // The address of __real or __imag is just a GEP off the address
790        // of the internal expression
791        llvm::Constant* C = EmitLValue(Exp->getSubExpr());
792        llvm::Constant *Zero = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
793        llvm::Constant *Idx  = llvm::ConstantInt::get(llvm::Type::Int32Ty,
794                                       Exp->getOpcode() == UnaryOperator::Imag);
795        llvm::Value *Ops[] = {Zero, Idx};
796        return llvm::ConstantExpr::getGetElementPtr(C, Ops, 2);
797      }
798      case UnaryOperator::Deref:
799        // The address of a deref is just the value of the expression
800        return Visit(Exp->getSubExpr());
801      }
802      break;
803    }
804    }
805    CGM.WarnUnsupported(E, "constant l-value expression");
806    llvm::Type *Ty = llvm::PointerType::getUnqual(ConvertType(E->getType()));
807    return llvm::UndefValue::get(Ty);
808  }
809
810};
811
812}  // end anonymous namespace.
813
814
815llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
816                                                CodeGenFunction *CGF) {
817  QualType type = Context.getCanonicalType(E->getType());
818
819  if (type->isIntegerType()) {
820    llvm::APSInt Value(static_cast<uint32_t>(Context.getTypeSize(type)));
821    if (E->isIntegerConstantExpr(Value, Context)) {
822      return llvm::ConstantInt::get(Value);
823    }
824  }
825
826  llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
827  if (C->getType() == llvm::Type::Int1Ty) {
828    const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
829    C = llvm::ConstantExpr::getZExt(C, BoolTy);
830  }
831  return C;
832}
833