CGExprConstant.cpp revision bcf6225ad69ea388e287f952981fd076636991b2 
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 "CGObjCRuntime.h"
17#include "clang/AST/APValue.h"
18#include "clang/AST/ASTContext.h"
19#include "clang/AST/StmtVisitor.h"
20#include "llvm/Constants.h"
21#include "llvm/Function.h"
22#include "llvm/GlobalVariable.h"
23#include "llvm/Support/Compiler.h"
24#include "llvm/Target/TargetData.h"
25using namespace clang;
26using namespace CodeGen;
27
28#define USE_TRY_EVALUATE
29
30namespace  {
31class VISIBILITY_HIDDEN ConstExprEmitter :
32  public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
33  CodeGenModule &CGM;
34  CodeGenFunction *CGF;
35public:
36  ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf)
37    : CGM(cgm), CGF(cgf) {
38  }
39
40  //===--------------------------------------------------------------------===//
41  //                            Visitor Methods
42  //===--------------------------------------------------------------------===//
43
44  llvm::Constant *VisitStmt(Stmt *S) {
45    CGM.ErrorUnsupported(S, "constant expression");
46    QualType T = cast<Expr>(S)->getType();
47    return llvm::UndefValue::get(CGM.getTypes().ConvertType(T));
48  }
49
50  llvm::Constant *VisitParenExpr(ParenExpr *PE) {
51    return Visit(PE->getSubExpr());
52  }
53
54#ifndef USE_TRY_EVALUATE
55  // Leaves
56  llvm::Constant *VisitIntegerLiteral(const IntegerLiteral *E) {
57    return llvm::ConstantInt::get(E->getValue());
58  }
59  llvm::Constant *VisitFloatingLiteral(const FloatingLiteral *E) {
60    return llvm::ConstantFP::get(E->getValue());
61  }
62  llvm::Constant *VisitCharacterLiteral(const CharacterLiteral *E) {
63    return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
64  }
65  llvm::Constant *VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr *E) {
66    return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
67  }
68  llvm::Constant *VisitCXXZeroInitValueExpr(const CXXZeroInitValueExpr *E) {
69    return llvm::Constant::getNullValue(ConvertType(E->getType()));
70  }
71#endif
72  llvm::Constant *VisitObjCStringLiteral(const ObjCStringLiteral *E) {
73    std::string S(E->getString()->getStrData(),
74                  E->getString()->getByteLength());
75    llvm::Constant *C = CGM.getObjCRuntime().GenerateConstantString(S);
76    return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
77  }
78
79  llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
80    return Visit(E->getInitializer());
81  }
82
83  llvm::Constant *VisitCastExpr(CastExpr* E) {
84    llvm::Constant *C = Visit(E->getSubExpr());
85
86    return EmitConversion(C, E->getSubExpr()->getType(), E->getType());
87  }
88
89  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
90    return Visit(DAE->getExpr());
91  }
92
93  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
94    std::vector<llvm::Constant*> Elts;
95    const llvm::ArrayType *AType =
96        cast<llvm::ArrayType>(ConvertType(ILE->getType()));
97    unsigned NumInitElements = ILE->getNumInits();
98    // FIXME: Check for wide strings
99    if (NumInitElements > 0 && isa<StringLiteral>(ILE->getInit(0)) &&
100        ILE->getType()->getArrayElementTypeNoTypeQual()->isCharType())
101      return Visit(ILE->getInit(0));
102    const llvm::Type *ElemTy = AType->getElementType();
103    unsigned NumElements = AType->getNumElements();
104
105    // Initialising an array requires us to automatically
106    // initialise any elements that have not been initialised explicitly
107    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
108
109    // Copy initializer elements.
110    unsigned i = 0;
111    bool RewriteType = false;
112    for (; i < NumInitableElts; ++i) {
113      llvm::Constant *C = CGM.EmitConstantExpr(ILE->getInit(i), CGF);
114      RewriteType |= (C->getType() != ElemTy);
115      Elts.push_back(C);
116    }
117
118    // Initialize remaining array elements.
119    for (; i < NumElements; ++i)
120      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
121
122    if (RewriteType) {
123      // FIXME: Try to avoid packing the array
124      std::vector<const llvm::Type*> Types;
125      for (unsigned i = 0; i < Elts.size(); ++i)
126        Types.push_back(Elts[i]->getType());
127      const llvm::StructType *SType = llvm::StructType::get(Types, true);
128      return llvm::ConstantStruct::get(SType, Elts);
129    }
130
131    return llvm::ConstantArray::get(AType, Elts);
132  }
133
134  void InsertBitfieldIntoStruct(std::vector<llvm::Constant*>& Elts,
135                                FieldDecl* Field, Expr* E) {
136    // Calculate the value to insert
137    llvm::Constant *C = CGM.EmitConstantExpr(E, CGF);
138    llvm::ConstantInt *CI = dyn_cast<llvm::ConstantInt>(C);
139    if (!CI) {
140      CGM.ErrorUnsupported(E, "bitfield initialization");
141      return;
142    }
143    llvm::APInt V = CI->getValue();
144
145    // Calculate information about the relevant field
146    const llvm::Type* Ty = CI->getType();
147    const llvm::TargetData &TD = CGM.getTypes().getTargetData();
148    unsigned size = TD.getTypeStoreSizeInBits(Ty);
149    unsigned fieldOffset = CGM.getTypes().getLLVMFieldNo(Field) * size;
150    CodeGenTypes::BitFieldInfo bitFieldInfo =
151        CGM.getTypes().getBitFieldInfo(Field);
152    fieldOffset += bitFieldInfo.Begin;
153
154    // Find where to start the insertion
155    // FIXME: This is O(n^2) in the number of bit-fields!
156    // FIXME: This won't work if the struct isn't completely packed!
157    unsigned offset = 0, i = 0;
158    while (offset < (fieldOffset & -8))
159      offset += TD.getTypeStoreSizeInBits(Elts[i++]->getType());
160
161    // Advance over 0 sized elements (must terminate in bounds since
162    // the bitfield must have a size).
163    while (TD.getTypeStoreSizeInBits(Elts[i]->getType()) == 0)
164      ++i;
165
166    // Promote the size of V if necessary
167    // FIXME: This should never occur, but currently it can because
168    // initializer constants are cast to bool, and because clang is
169    // not enforcing bitfield width limits.
170    if (bitFieldInfo.Size > V.getBitWidth())
171      V.zext(bitFieldInfo.Size);
172
173    // Insert the bits into the struct
174    // FIXME: This algorthm is only correct on X86!
175    // FIXME: THis algorthm assumes bit-fields only have byte-size elements!
176    unsigned bitsToInsert = bitFieldInfo.Size;
177    unsigned curBits = std::min(8 - (fieldOffset & 7), bitsToInsert);
178    unsigned byte = V.getLoBits(curBits).getZExtValue() << (fieldOffset & 7);
179    do {
180      llvm::Constant* byteC = llvm::ConstantInt::get(llvm::Type::Int8Ty, byte);
181      Elts[i] = llvm::ConstantExpr::getOr(Elts[i], byteC);
182      ++i;
183      V = V.lshr(curBits);
184      bitsToInsert -= curBits;
185
186      if (!bitsToInsert)
187        break;
188
189      curBits = bitsToInsert > 8 ? 8 : bitsToInsert;
190      byte = V.getLoBits(curBits).getZExtValue();
191    } while (true);
192  }
193
194  llvm::Constant *EmitStructInitialization(InitListExpr *ILE) {
195    const llvm::StructType *SType =
196        cast<llvm::StructType>(ConvertType(ILE->getType()));
197    RecordDecl *RD = ILE->getType()->getAsRecordType()->getDecl();
198    std::vector<llvm::Constant*> Elts;
199
200    // Initialize the whole structure to zero.
201    for (unsigned i = 0; i < SType->getNumElements(); ++i) {
202      const llvm::Type *FieldTy = SType->getElementType(i);
203      Elts.push_back(llvm::Constant::getNullValue(FieldTy));
204    }
205
206    // Copy initializer elements. Skip padding fields.
207    unsigned EltNo = 0;  // Element no in ILE
208    int FieldNo = 0; // Field no in RecordDecl
209    bool RewriteType = false;
210    while (EltNo < ILE->getNumInits() && FieldNo < RD->getNumMembers()) {
211      FieldDecl* curField = RD->getMember(FieldNo);
212      FieldNo++;
213      if (!curField->getIdentifier())
214        continue;
215
216      if (curField->isBitField()) {
217        InsertBitfieldIntoStruct(Elts, curField, ILE->getInit(EltNo));
218      } else {
219        unsigned FieldNo = CGM.getTypes().getLLVMFieldNo(curField);
220        llvm::Constant *C = CGM.EmitConstantExpr(ILE->getInit(EltNo), CGF);
221        RewriteType |= (C->getType() != Elts[FieldNo]->getType());
222        Elts[FieldNo] = C;
223      }
224      EltNo++;
225    }
226
227    if (RewriteType) {
228      // FIXME: Make this work for non-packed structs
229      assert(SType->isPacked() && "Cannot recreate unpacked structs");
230      std::vector<const llvm::Type*> Types;
231      for (unsigned i = 0; i < Elts.size(); ++i)
232        Types.push_back(Elts[i]->getType());
233      SType = llvm::StructType::get(Types, true);
234    }
235
236    return llvm::ConstantStruct::get(SType, Elts);
237  }
238
239  llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
240    RecordDecl *RD = ILE->getType()->getAsRecordType()->getDecl();
241    const llvm::Type *Ty = ConvertType(ILE->getType());
242
243    // Find the field decl we're initializing, if any
244    int FieldNo = 0; // Field no in RecordDecl
245    FieldDecl* curField = 0;
246    while (FieldNo < RD->getNumMembers()) {
247      curField = RD->getMember(FieldNo);
248      FieldNo++;
249      if (curField->getIdentifier())
250        break;
251    }
252
253    if (!curField || !curField->getIdentifier() || ILE->getNumInits() == 0)
254      return llvm::Constant::getNullValue(Ty);
255
256    if (curField->isBitField()) {
257      // Create a dummy struct for bit-field insertion
258      unsigned NumElts = CGM.getTargetData().getABITypeSize(Ty) / 8;
259      llvm::Constant* NV = llvm::Constant::getNullValue(llvm::Type::Int8Ty);
260      std::vector<llvm::Constant*> Elts(NumElts, NV);
261
262      InsertBitfieldIntoStruct(Elts, curField, ILE->getInit(0));
263      const llvm::ArrayType *RetTy =
264          llvm::ArrayType::get(NV->getType(), NumElts);
265      return llvm::ConstantArray::get(RetTy, Elts);
266    }
267
268    llvm::Constant *C = CGM.EmitConstantExpr(ILE->getInit(0), CGF);
269
270    // Build a struct with the union sub-element as the first member,
271    // and padded to the appropriate size
272    std::vector<llvm::Constant*> Elts;
273    std::vector<const llvm::Type*> Types;
274    Elts.push_back(C);
275    Types.push_back(C->getType());
276    unsigned CurSize = CGM.getTargetData().getTypeStoreSize(C->getType());
277    unsigned TotalSize = CGM.getTargetData().getTypeStoreSize(Ty);
278    while (CurSize < TotalSize) {
279      Elts.push_back(llvm::Constant::getNullValue(llvm::Type::Int8Ty));
280      Types.push_back(llvm::Type::Int8Ty);
281      CurSize++;
282    }
283
284    // This always generates a packed struct
285    // FIXME: Try to generate an unpacked struct when we can
286    llvm::StructType* STy = llvm::StructType::get(Types, true);
287    return llvm::ConstantStruct::get(STy, Elts);
288  }
289
290  llvm::Constant *EmitVectorInitialization(InitListExpr *ILE) {
291    const llvm::VectorType *VType =
292        cast<llvm::VectorType>(ConvertType(ILE->getType()));
293    const llvm::Type *ElemTy = VType->getElementType();
294    std::vector<llvm::Constant*> Elts;
295    unsigned NumElements = VType->getNumElements();
296    unsigned NumInitElements = ILE->getNumInits();
297
298    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
299
300    // Copy initializer elements.
301    unsigned i = 0;
302    for (; i < NumInitableElts; ++i) {
303      llvm::Constant *C = CGM.EmitConstantExpr(ILE->getInit(i), CGF);
304      Elts.push_back(C);
305    }
306
307    for (; i < NumElements; ++i)
308      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
309
310    return llvm::ConstantVector::get(VType, Elts);
311  }
312
313  llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
314    if (ILE->getType()->isScalarType()) {
315      // We have a scalar in braces. Just use the first element.
316      if (ILE->getNumInits() > 0)
317        return CGM.EmitConstantExpr(ILE->getInit(0), CGF);
318
319      const llvm::Type* RetTy = CGM.getTypes().ConvertType(ILE->getType());
320      return llvm::Constant::getNullValue(RetTy);
321    }
322
323    // FIXME: We don't codegen or sema designators yet.
324    if (ILE->hadDesignators()) {
325      CGM.ErrorUnsupported(ILE, "initializer list with designators");
326      return llvm::UndefValue::get(ConvertType(ILE->getType()));
327    }
328
329    if (ILE->getType()->isArrayType())
330      return EmitArrayInitialization(ILE);
331
332    if (ILE->getType()->isStructureType())
333      return EmitStructInitialization(ILE);
334
335    if (ILE->getType()->isUnionType())
336      return EmitUnionInitialization(ILE);
337
338    if (ILE->getType()->isVectorType())
339      return EmitVectorInitialization(ILE);
340
341    assert(0 && "Unable to handle InitListExpr");
342    // Get rid of control reaches end of void function warning.
343    // Not reached.
344    return 0;
345  }
346
347  llvm::Constant *VisitImplicitCastExpr(ImplicitCastExpr *ICExpr) {
348    Expr* SExpr = ICExpr->getSubExpr();
349    QualType SType = SExpr->getType();
350    llvm::Constant *C; // the intermediate expression
351    QualType T;        // the type of the intermediate expression
352    if (SType->isArrayType()) {
353      // Arrays decay to a pointer to the first element
354      // VLAs would require special handling, but they can't occur here
355      C = EmitLValue(SExpr);
356      llvm::Constant *Idx0 = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
357      llvm::Constant *Ops[] = {Idx0, Idx0};
358      C = llvm::ConstantExpr::getGetElementPtr(C, Ops, 2);
359      T = CGM.getContext().getArrayDecayedType(SType);
360    } else if (SType->isFunctionType()) {
361      // Function types decay to a pointer to the function
362      C = EmitLValue(SExpr);
363      T = CGM.getContext().getPointerType(SType);
364    } else {
365      C = Visit(SExpr);
366      T = SType;
367    }
368
369    // Perform the conversion; note that an implicit cast can both promote
370    // and convert an array/function
371    return EmitConversion(C, T, ICExpr->getType());
372  }
373
374  llvm::Constant *VisitStringLiteral(StringLiteral *E) {
375    assert(!E->getType()->isPointerType() && "Strings are always arrays");
376
377    // Otherwise this must be a string initializing an array in a static
378    // initializer.  Don't emit it as the address of the string, emit the string
379    // data itself as an inline array.
380    return llvm::ConstantArray::get(CGM.GetStringForStringLiteral(E), false);
381  }
382
383#ifndef USE_TRY_EVALUATE
384  llvm::Constant *VisitDeclRefExpr(DeclRefExpr *E) {
385    const NamedDecl *Decl = E->getDecl();
386    if (const EnumConstantDecl *EC = dyn_cast<EnumConstantDecl>(Decl))
387      return llvm::ConstantInt::get(EC->getInitVal());
388    assert(0 && "Unsupported decl ref type!");
389    return 0;
390  }
391
392  llvm::Constant *VisitSizeOfAlignOfExpr(const SizeOfAlignOfExpr *E) {
393    return EmitSizeAlignOf(E->getTypeOfArgument(), E->getType(), E->isSizeOf());
394  }
395#endif
396
397  llvm::Constant *VisitAddrLabelExpr(const AddrLabelExpr *E) {
398    assert(CGF && "Invalid address of label expression outside function.");
399    llvm::Constant *C =
400      llvm::ConstantInt::get(llvm::Type::Int32Ty,
401                             CGF->GetIDForAddrOfLabel(E->getLabel()));
402    return llvm::ConstantExpr::getIntToPtr(C, ConvertType(E->getType()));
403  }
404
405#ifndef USE_TRY_EVALUATE
406  // Unary operators
407  llvm::Constant *VisitUnaryPlus(const UnaryOperator *E) {
408    return Visit(E->getSubExpr());
409  }
410  llvm::Constant *VisitUnaryMinus(const UnaryOperator *E) {
411    return llvm::ConstantExpr::getNeg(Visit(E->getSubExpr()));
412  }
413  llvm::Constant *VisitUnaryNot(const UnaryOperator *E) {
414    return llvm::ConstantExpr::getNot(Visit(E->getSubExpr()));
415  }
416  llvm::Constant *VisitUnaryLNot(const UnaryOperator *E) {
417    llvm::Constant *SubExpr = Visit(E->getSubExpr());
418
419    if (E->getSubExpr()->getType()->isRealFloatingType()) {
420      // Compare against 0.0 for fp scalars.
421      llvm::Constant *Zero = llvm::Constant::getNullValue(SubExpr->getType());
422      SubExpr = llvm::ConstantExpr::getFCmp(llvm::FCmpInst::FCMP_UEQ, SubExpr,
423                                            Zero);
424    } else {
425      assert((E->getSubExpr()->getType()->isIntegerType() ||
426              E->getSubExpr()->getType()->isPointerType()) &&
427             "Unknown scalar type to convert");
428      // Compare against an integer or pointer null.
429      llvm::Constant *Zero = llvm::Constant::getNullValue(SubExpr->getType());
430      SubExpr = llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_EQ, SubExpr,
431                                            Zero);
432    }
433
434    return llvm::ConstantExpr::getZExt(SubExpr, ConvertType(E->getType()));
435  }
436#endif
437
438  llvm::Constant *VisitUnaryAddrOf(const UnaryOperator *E) {
439    return EmitLValue(E->getSubExpr());
440  }
441  llvm::Constant *VisitUnaryOffsetOf(const UnaryOperator *E) {
442    int64_t Val = E->evaluateOffsetOf(CGM.getContext());
443
444    assert(E->getType()->isIntegerType() && "Result type must be an integer!");
445
446    uint32_t ResultWidth =
447      static_cast<uint32_t>(CGM.getContext().getTypeSize(E->getType()));
448    return llvm::ConstantInt::get(llvm::APInt(ResultWidth, Val));
449  }
450
451  llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) {
452    return Visit(E->getSubExpr());
453  }
454
455  // Binary operators
456#ifndef USE_TRY_EVALUATE
457  llvm::Constant *VisitBinOr(const BinaryOperator *E) {
458    llvm::Constant *LHS = Visit(E->getLHS());
459    llvm::Constant *RHS = Visit(E->getRHS());
460
461    return llvm::ConstantExpr::getOr(LHS, RHS);
462  }
463  llvm::Constant *VisitBinSub(const BinaryOperator *E) {
464    llvm::Constant *LHS = Visit(E->getLHS());
465    llvm::Constant *RHS = Visit(E->getRHS());
466
467    if (!isa<llvm::PointerType>(RHS->getType())) {
468      // pointer - int
469      if (isa<llvm::PointerType>(LHS->getType())) {
470        llvm::Constant *Idx = llvm::ConstantExpr::getNeg(RHS);
471
472        return llvm::ConstantExpr::getGetElementPtr(LHS, &Idx, 1);
473      }
474
475      // int - int
476      return llvm::ConstantExpr::getSub(LHS, RHS);
477    }
478
479    assert(isa<llvm::PointerType>(LHS->getType()));
480
481    const llvm::Type *ResultType = ConvertType(E->getType());
482    const QualType Type = E->getLHS()->getType();
483    const QualType ElementType = Type->getAsPointerType()->getPointeeType();
484
485    LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType);
486    RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType);
487
488    llvm::Constant *sub = llvm::ConstantExpr::getSub(LHS, RHS);
489    llvm::Constant *size = EmitSizeAlignOf(ElementType, E->getType(), true);
490    return llvm::ConstantExpr::getSDiv(sub, size);
491  }
492
493  llvm::Constant *VisitBinShl(const BinaryOperator *E) {
494    llvm::Constant *LHS = Visit(E->getLHS());
495    llvm::Constant *RHS = Visit(E->getRHS());
496
497    // LLVM requires the LHS and RHS to be the same type: promote or truncate the
498    // RHS to the same size as the LHS.
499    if (LHS->getType() != RHS->getType())
500      RHS = llvm::ConstantExpr::getIntegerCast(RHS, LHS->getType(), false);
501
502    return llvm::ConstantExpr::getShl(LHS, RHS);
503  }
504
505  llvm::Constant *VisitBinMul(const BinaryOperator *E) {
506    llvm::Constant *LHS = Visit(E->getLHS());
507    llvm::Constant *RHS = Visit(E->getRHS());
508
509    return llvm::ConstantExpr::getMul(LHS, RHS);
510  }
511
512  llvm::Constant *VisitBinDiv(const BinaryOperator *E) {
513    llvm::Constant *LHS = Visit(E->getLHS());
514    llvm::Constant *RHS = Visit(E->getRHS());
515
516    if (LHS->getType()->isFPOrFPVector())
517      return llvm::ConstantExpr::getFDiv(LHS, RHS);
518    else if (E->getType()->isUnsignedIntegerType())
519      return llvm::ConstantExpr::getUDiv(LHS, RHS);
520    else
521      return llvm::ConstantExpr::getSDiv(LHS, RHS);
522  }
523
524  llvm::Constant *VisitBinAdd(const BinaryOperator *E) {
525    llvm::Constant *LHS = Visit(E->getLHS());
526    llvm::Constant *RHS = Visit(E->getRHS());
527
528    if (!E->getType()->isPointerType())
529      return llvm::ConstantExpr::getAdd(LHS, RHS);
530
531    llvm::Constant *Ptr, *Idx;
532    if (isa<llvm::PointerType>(LHS->getType())) { // pointer + int
533      Ptr = LHS;
534      Idx = RHS;
535    } else { // int + pointer
536      Ptr = RHS;
537      Idx = LHS;
538    }
539
540    return llvm::ConstantExpr::getGetElementPtr(Ptr, &Idx, 1);
541  }
542
543  llvm::Constant *VisitBinAnd(const BinaryOperator *E) {
544    llvm::Constant *LHS = Visit(E->getLHS());
545    llvm::Constant *RHS = Visit(E->getRHS());
546
547    return llvm::ConstantExpr::getAnd(LHS, RHS);
548  }
549
550  llvm::Constant *EmitCmp(const BinaryOperator *E,
551                          llvm::CmpInst::Predicate SignedPred,
552                          llvm::CmpInst::Predicate UnsignedPred,
553                          llvm::CmpInst::Predicate FloatPred) {
554    llvm::Constant *LHS = Visit(E->getLHS());
555    llvm::Constant *RHS = Visit(E->getRHS());
556    llvm::Constant *Result;
557    if (LHS->getType()->isInteger() ||
558        isa<llvm::PointerType>(LHS->getType())) {
559      if (E->getLHS()->getType()->isSignedIntegerType())
560        Result = llvm::ConstantExpr::getICmp(SignedPred, LHS, RHS);
561      else
562        Result = llvm::ConstantExpr::getICmp(UnsignedPred, LHS, RHS);
563    } else if (LHS->getType()->isFloatingPoint()) {
564      Result = llvm::ConstantExpr::getFCmp(FloatPred, LHS, RHS);
565    } else {
566      CGM.ErrorUnsupported(E, "constant expression");
567      Result = llvm::ConstantInt::getFalse();
568    }
569
570    const llvm::Type* ResultType = ConvertType(E->getType());
571    return llvm::ConstantExpr::getZExtOrBitCast(Result, ResultType);
572  }
573
574  llvm::Constant *VisitBinNE(const BinaryOperator *E) {
575    return EmitCmp(E, llvm::CmpInst::ICMP_NE, llvm::CmpInst::ICMP_NE,
576                   llvm::CmpInst::FCMP_ONE);
577  }
578
579  llvm::Constant *VisitBinEQ(const BinaryOperator *E) {
580    return EmitCmp(E, llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_EQ,
581                   llvm::CmpInst::FCMP_OEQ);
582  }
583
584  llvm::Constant *VisitBinLT(const BinaryOperator *E) {
585    return EmitCmp(E, llvm::CmpInst::ICMP_SLT, llvm::CmpInst::ICMP_ULT,
586                   llvm::CmpInst::FCMP_OLT);
587  }
588
589  llvm::Constant *VisitBinLE(const BinaryOperator *E) {
590    return EmitCmp(E, llvm::CmpInst::ICMP_SLE, llvm::CmpInst::ICMP_ULE,
591                   llvm::CmpInst::FCMP_OLE);
592  }
593
594  llvm::Constant *VisitBinGT(const BinaryOperator *E) {
595    return EmitCmp(E, llvm::CmpInst::ICMP_SGT, llvm::CmpInst::ICMP_UGT,
596                   llvm::CmpInst::FCMP_OGT);
597  }
598
599  llvm::Constant *VisitBinGE(const BinaryOperator *E) {
600    return EmitCmp(E, llvm::CmpInst::ICMP_SGE, llvm::CmpInst::ICMP_SGE,
601                   llvm::CmpInst::FCMP_OGE);
602  }
603
604  llvm::Constant *VisitConditionalOperator(const ConditionalOperator *E) {
605    llvm::Constant *Cond = Visit(E->getCond());
606    llvm::Constant *CondVal = EmitConversionToBool(Cond, E->getType());
607    llvm::ConstantInt *CondValInt = dyn_cast<llvm::ConstantInt>(CondVal);
608    if (!CondValInt) {
609      CGM.ErrorUnsupported(E, "constant expression");
610      return llvm::Constant::getNullValue(ConvertType(E->getType()));
611    }
612    if (CondValInt->isOne()) {
613      if (E->getLHS())
614        return Visit(E->getLHS());
615      return Cond;
616    }
617
618    return Visit(E->getRHS());
619  }
620#endif
621
622  llvm::Constant *VisitCallExpr(const CallExpr *E) {
623    APValue Result;
624    if (E->Evaluate(Result, CGM.getContext())) {
625      if (Result.isInt())
626        return llvm::ConstantInt::get(Result.getInt());
627      if (Result.isFloat())
628        return llvm::ConstantFP::get(Result.getFloat());
629    }
630
631    // Handle __builtin___CFStringMakeConstantString.
632    if (E->isBuiltinCall() ==Builtin::BI__builtin___CFStringMakeConstantString){
633      const Expr *Arg = E->getArg(0)->IgnoreParenCasts();
634
635      const StringLiteral *Literal = cast<StringLiteral>(Arg);
636      std::string S(Literal->getStrData(), Literal->getByteLength());
637      return CGM.GetAddrOfConstantCFString(S);
638    }
639
640    CGM.ErrorUnsupported(E, "constant call expression");
641    return llvm::Constant::getNullValue(ConvertType(E->getType()));
642  }
643
644  // Utility methods
645  const llvm::Type *ConvertType(QualType T) {
646    return CGM.getTypes().ConvertType(T);
647  }
648
649  llvm::Constant *EmitConversionToBool(llvm::Constant *Src, QualType SrcType) {
650    assert(SrcType->isCanonical() && "EmitConversion strips typedefs");
651
652    if (SrcType->isRealFloatingType()) {
653      // Compare against 0.0 for fp scalars.
654      llvm::Constant *Zero = llvm::Constant::getNullValue(Src->getType());
655      return llvm::ConstantExpr::getFCmp(llvm::FCmpInst::FCMP_UNE, Src, Zero);
656    }
657
658    assert((SrcType->isIntegerType() || SrcType->isPointerType()) &&
659           "Unknown scalar type to convert");
660
661    // Compare against an integer or pointer null.
662    llvm::Constant *Zero = llvm::Constant::getNullValue(Src->getType());
663    return llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_NE, Src, Zero);
664  }
665
666  llvm::Constant *EmitConversion(llvm::Constant *Src, QualType SrcType,
667                                 QualType DstType) {
668    SrcType = CGM.getContext().getCanonicalType(SrcType);
669    DstType = CGM.getContext().getCanonicalType(DstType);
670    if (SrcType == DstType) return Src;
671
672    // Handle conversions to bool first, they are special: comparisons against 0.
673    if (DstType->isBooleanType())
674      return EmitConversionToBool(Src, SrcType);
675
676    const llvm::Type *DstTy = ConvertType(DstType);
677
678    // Ignore conversions like int -> uint.
679    if (Src->getType() == DstTy)
680      return Src;
681
682    // Handle pointer conversions next: pointers can only be converted to/from
683    // other pointers and integers.
684    if (isa<llvm::PointerType>(DstTy)) {
685      // The source value may be an integer, or a pointer.
686      if (isa<llvm::PointerType>(Src->getType()))
687        return llvm::ConstantExpr::getBitCast(Src, DstTy);
688      assert(SrcType->isIntegerType() &&"Not ptr->ptr or int->ptr conversion?");
689      return llvm::ConstantExpr::getIntToPtr(Src, DstTy);
690    }
691
692    if (isa<llvm::PointerType>(Src->getType())) {
693      // Must be an ptr to int cast.
694      assert(isa<llvm::IntegerType>(DstTy) && "not ptr->int?");
695      return llvm::ConstantExpr::getPtrToInt(Src, DstTy);
696    }
697
698    // A scalar source can be splatted to a vector of the same element type
699    if (isa<llvm::VectorType>(DstTy) && !isa<VectorType>(SrcType)) {
700      assert((cast<llvm::VectorType>(DstTy)->getElementType()
701              == Src->getType()) &&
702             "Vector element type must match scalar type to splat.");
703      unsigned NumElements = DstType->getAsVectorType()->getNumElements();
704      llvm::SmallVector<llvm::Constant*, 16> Elements;
705      for (unsigned i = 0; i < NumElements; i++)
706        Elements.push_back(Src);
707
708      return llvm::ConstantVector::get(&Elements[0], NumElements);
709    }
710
711    if (isa<llvm::VectorType>(Src->getType()) ||
712        isa<llvm::VectorType>(DstTy)) {
713      return llvm::ConstantExpr::getBitCast(Src, DstTy);
714    }
715
716    // Finally, we have the arithmetic types: real int/float.
717    if (isa<llvm::IntegerType>(Src->getType())) {
718      bool InputSigned = SrcType->isSignedIntegerType();
719      if (isa<llvm::IntegerType>(DstTy))
720        return llvm::ConstantExpr::getIntegerCast(Src, DstTy, InputSigned);
721      else if (InputSigned)
722        return llvm::ConstantExpr::getSIToFP(Src, DstTy);
723      else
724        return llvm::ConstantExpr::getUIToFP(Src, DstTy);
725    }
726
727    assert(Src->getType()->isFloatingPoint() && "Unknown real conversion");
728    if (isa<llvm::IntegerType>(DstTy)) {
729      if (DstType->isSignedIntegerType())
730        return llvm::ConstantExpr::getFPToSI(Src, DstTy);
731      else
732        return llvm::ConstantExpr::getFPToUI(Src, DstTy);
733    }
734
735    assert(DstTy->isFloatingPoint() && "Unknown real conversion");
736    if (DstTy->getTypeID() < Src->getType()->getTypeID())
737      return llvm::ConstantExpr::getFPTrunc(Src, DstTy);
738    else
739      return llvm::ConstantExpr::getFPExtend(Src, DstTy);
740  }
741
742  llvm::Constant *EmitSizeAlignOf(QualType TypeToSize,
743                                  QualType RetType, bool isSizeOf) {
744    std::pair<uint64_t, unsigned> Info =
745      CGM.getContext().getTypeInfo(TypeToSize);
746
747    uint64_t Val = isSizeOf ? Info.first : Info.second;
748    Val /= 8;  // Return size in bytes, not bits.
749
750    assert(RetType->isIntegerType() && "Result type must be an integer!");
751
752    uint32_t ResultWidth =
753      static_cast<uint32_t>(CGM.getContext().getTypeSize(RetType));
754    return llvm::ConstantInt::get(llvm::APInt(ResultWidth, Val));
755  }
756
757public:
758  llvm::Constant *EmitLValue(Expr *E) {
759    switch (E->getStmtClass()) {
760    default: break;
761    case Expr::ParenExprClass:
762      // Elide parenthesis
763      return EmitLValue(cast<ParenExpr>(E)->getSubExpr());
764    case Expr::CompoundLiteralExprClass: {
765      // Note that due to the nature of compound literals, this is guaranteed
766      // to be the only use of the variable, so we just generate it here.
767      CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
768      llvm::Constant* C = Visit(CLE->getInitializer());
769      C = new llvm::GlobalVariable(C->getType(),E->getType().isConstQualified(),
770                                   llvm::GlobalValue::InternalLinkage,
771                                   C, ".compoundliteral", &CGM.getModule());
772      return C;
773    }
774    case Expr::DeclRefExprClass: {
775      NamedDecl *Decl = cast<DeclRefExpr>(E)->getDecl();
776      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
777        return CGM.GetAddrOfFunction(FD);
778      if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
779        if (VD->isFileVarDecl())
780          return CGM.GetAddrOfGlobalVar(VD);
781        else if (VD->isBlockVarDecl()) {
782          assert(CGF && "Can't access static local vars without CGF");
783          return CGF->GetAddrOfStaticLocalVar(VD);
784        }
785      }
786      break;
787    }
788    case Expr::MemberExprClass: {
789      MemberExpr* ME = cast<MemberExpr>(E);
790      llvm::Constant *Base;
791      if (ME->isArrow())
792        Base = Visit(ME->getBase());
793      else
794        Base = EmitLValue(ME->getBase());
795
796      unsigned FieldNumber = CGM.getTypes().getLLVMFieldNo(ME->getMemberDecl());
797      llvm::Constant *Zero = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
798      llvm::Constant *Idx = llvm::ConstantInt::get(llvm::Type::Int32Ty,
799                                                   FieldNumber);
800      llvm::Value *Ops[] = {Zero, Idx};
801      return llvm::ConstantExpr::getGetElementPtr(Base, Ops, 2);
802    }
803    case Expr::ArraySubscriptExprClass: {
804      ArraySubscriptExpr* ASExpr = cast<ArraySubscriptExpr>(E);
805      llvm::Constant *Base = Visit(ASExpr->getBase());
806      llvm::Constant *Index = Visit(ASExpr->getIdx());
807      assert(!ASExpr->getBase()->getType()->isVectorType() &&
808             "Taking the address of a vector component is illegal!");
809      return llvm::ConstantExpr::getGetElementPtr(Base, &Index, 1);
810    }
811    case Expr::StringLiteralClass:
812      return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E));
813    case Expr::ObjCStringLiteralClass: {
814      ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E);
815      std::string S(SL->getString()->getStrData(),
816                    SL->getString()->getByteLength());
817      llvm::Constant *C = CGM.getObjCRuntime().GenerateConstantString(S);
818      return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
819    }
820    case Expr::UnaryOperatorClass: {
821      UnaryOperator *Exp = cast<UnaryOperator>(E);
822      switch (Exp->getOpcode()) {
823      default: break;
824      case UnaryOperator::Extension:
825        // Extension is just a wrapper for expressions
826        return EmitLValue(Exp->getSubExpr());
827      case UnaryOperator::Real:
828      case UnaryOperator::Imag: {
829        // The address of __real or __imag is just a GEP off the address
830        // of the internal expression
831        llvm::Constant* C = EmitLValue(Exp->getSubExpr());
832        llvm::Constant *Zero = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
833        llvm::Constant *Idx  = llvm::ConstantInt::get(llvm::Type::Int32Ty,
834                                       Exp->getOpcode() == UnaryOperator::Imag);
835        llvm::Value *Ops[] = {Zero, Idx};
836        return llvm::ConstantExpr::getGetElementPtr(C, Ops, 2);
837      }
838      case UnaryOperator::Deref:
839        // The address of a deref is just the value of the expression
840        return Visit(Exp->getSubExpr());
841      }
842      break;
843    }
844    }
845    CGM.ErrorUnsupported(E, "constant l-value expression");
846    llvm::Type *Ty = llvm::PointerType::getUnqual(ConvertType(E->getType()));
847    return llvm::UndefValue::get(Ty);
848  }
849};
850
851}  // end anonymous namespace.
852
853llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
854                                                CodeGenFunction *CGF) {
855  QualType type = Context.getCanonicalType(E->getType());
856
857#ifdef USE_TRY_EVALUATE
858  APValue V;
859  if (E->Evaluate(V, Context)) {
860    // FIXME: Assert that the value doesn't have any side effects.
861    switch (V.getKind()) {
862    default: assert(0 && "unhandled value kind!");
863    case APValue::LValue: {
864      llvm::Constant *Offset = llvm::ConstantInt::get(llvm::Type::Int64Ty,
865                                                      V.getLValueOffset());
866
867      if (const Expr *LVBase = V.getLValueBase()) {
868        llvm::Constant *C =
869          ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase));
870
871        const llvm::Type *Type =
872          llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
873        const llvm::Type *DestType = getTypes().ConvertTypeForMem(E->getType());
874
875        // FIXME: It's a little ugly that we need to cast to a pointer,
876        // apply the GEP and then cast back.
877        C = llvm::ConstantExpr::getBitCast(C, Type);
878        C = llvm::ConstantExpr::getGetElementPtr(C, &Offset, 1);
879
880        return llvm::ConstantExpr::getBitCast(C, DestType);
881      }
882
883      return llvm::ConstantExpr::getIntToPtr(Offset,
884                                             getTypes().ConvertType(type));
885    }
886    case APValue::Int: {
887      llvm::Constant *C = llvm::ConstantInt::get(V.getInt());
888
889      if (C->getType() == llvm::Type::Int1Ty) {
890        const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
891        C = llvm::ConstantExpr::getZExt(C, BoolTy);
892      }
893      return C;
894    }
895    case APValue::Float:
896      return llvm::ConstantFP::get(V.getFloat());
897    case APValue::ComplexFloat: {
898      llvm::Constant *Complex[2];
899
900      Complex[0] = llvm::ConstantFP::get(V.getComplexFloatReal());
901      Complex[1] = llvm::ConstantFP::get(V.getComplexFloatImag());
902
903      return llvm::ConstantStruct::get(Complex, 2);
904    }
905    }
906  }
907#else
908  if (type->isIntegerType()) {
909    llvm::APSInt Value(static_cast<uint32_t>(Context.getTypeSize(type)));
910    if (E->isIntegerConstantExpr(Value, Context)) {
911      return llvm::ConstantInt::get(Value);
912    }
913  }
914#endif
915
916  llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
917  if (C->getType() == llvm::Type::Int1Ty) {
918    const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
919    C = llvm::ConstantExpr::getZExt(C, BoolTy);
920  }
921  return C;
922}
923