CGExprConstant.cpp revision aa432560efb1ff10aec504a68fe909cd9ae7c1a2 
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
28namespace  {
29class VISIBILITY_HIDDEN ConstExprEmitter :
30  public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
31  CodeGenModule &CGM;
32  CodeGenFunction *CGF;
33public:
34  ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf)
35    : CGM(cgm), CGF(cgf) {
36  }
37
38  //===--------------------------------------------------------------------===//
39  //                            Visitor Methods
40  //===--------------------------------------------------------------------===//
41
42  llvm::Constant *VisitStmt(Stmt *S) {
43    CGM.ErrorUnsupported(S, "constant expression");
44    QualType T = cast<Expr>(S)->getType();
45    return llvm::UndefValue::get(CGM.getTypes().ConvertType(T));
46  }
47
48  llvm::Constant *VisitParenExpr(ParenExpr *PE) {
49    return Visit(PE->getSubExpr());
50  }
51
52  // Leaves
53  llvm::Constant *VisitIntegerLiteral(const IntegerLiteral *E) {
54    return llvm::ConstantInt::get(E->getValue());
55  }
56  llvm::Constant *VisitFloatingLiteral(const FloatingLiteral *E) {
57    return llvm::ConstantFP::get(E->getValue());
58  }
59  llvm::Constant *VisitCharacterLiteral(const CharacterLiteral *E) {
60    return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
61  }
62  llvm::Constant *VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr *E) {
63    return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
64  }
65  llvm::Constant *VisitCXXZeroInitValueExpr(const CXXZeroInitValueExpr *E) {
66    return llvm::Constant::getNullValue(ConvertType(E->getType()));
67  }
68  llvm::Constant *VisitObjCStringLiteral(const ObjCStringLiteral *E) {
69    std::string S(E->getString()->getStrData(),
70                  E->getString()->getByteLength());
71    llvm::Constant *C = CGM.getObjCRuntime().GenerateConstantString(S);
72    return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
73  }
74
75  llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
76    return Visit(E->getInitializer());
77  }
78
79  llvm::Constant *VisitCastExpr(CastExpr* E) {
80    llvm::Constant *C = Visit(E->getSubExpr());
81
82    return EmitConversion(C, E->getSubExpr()->getType(), E->getType());
83  }
84
85  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
86    return Visit(DAE->getExpr());
87  }
88
89  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
90    std::vector<llvm::Constant*> Elts;
91    const llvm::ArrayType *AType =
92        cast<llvm::ArrayType>(ConvertType(ILE->getType()));
93    unsigned NumInitElements = ILE->getNumInits();
94    // FIXME: Check for wide strings
95    if (NumInitElements > 0 && isa<StringLiteral>(ILE->getInit(0)) &&
96        ILE->getType()->getArrayElementTypeNoTypeQual()->isCharType())
97      return Visit(ILE->getInit(0));
98    const llvm::Type *ElemTy = AType->getElementType();
99    unsigned NumElements = AType->getNumElements();
100
101    // Initialising an array requires us to automatically
102    // initialise any elements that have not been initialised explicitly
103    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
104
105    // Copy initializer elements.
106    unsigned i = 0;
107    bool RewriteType = false;
108    for (; i < NumInitableElts; ++i) {
109      llvm::Constant *C = CGM.EmitConstantExpr(ILE->getInit(i), CGF);
110      RewriteType |= (C->getType() != ElemTy);
111      Elts.push_back(C);
112    }
113
114    // Initialize remaining array elements.
115    for (; i < NumElements; ++i)
116      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
117
118    if (RewriteType) {
119      // FIXME: Try to avoid packing the array
120      std::vector<const llvm::Type*> Types;
121      for (unsigned i = 0; i < Elts.size(); ++i)
122        Types.push_back(Elts[i]->getType());
123      const llvm::StructType *SType = llvm::StructType::get(Types, true);
124      return llvm::ConstantStruct::get(SType, Elts);
125    }
126
127    return llvm::ConstantArray::get(AType, Elts);
128  }
129
130  void InsertBitfieldIntoStruct(std::vector<llvm::Constant*>& Elts,
131                                FieldDecl* Field, Expr* E) {
132    // Calculate the value to insert
133    llvm::Constant *C = CGM.EmitConstantExpr(E, CGF);
134    llvm::ConstantInt *CI = dyn_cast<llvm::ConstantInt>(C);
135    if (!CI) {
136      CGM.ErrorUnsupported(E, "bitfield initialization");
137      return;
138    }
139    llvm::APInt V = CI->getValue();
140
141    // Calculate information about the relevant field
142    const llvm::Type* Ty = CI->getType();
143    const llvm::TargetData &TD = CGM.getTypes().getTargetData();
144    unsigned size = TD.getTypeStoreSizeInBits(Ty);
145    unsigned fieldOffset = CGM.getTypes().getLLVMFieldNo(Field) * size;
146    CodeGenTypes::BitFieldInfo bitFieldInfo =
147        CGM.getTypes().getBitFieldInfo(Field);
148    fieldOffset += bitFieldInfo.Begin;
149
150    // Find where to start the insertion
151    // FIXME: This is O(n^2) in the number of bit-fields!
152    // FIXME: This won't work if the struct isn't completely packed!
153    unsigned offset = 0, i = 0;
154    while (offset < (fieldOffset & -8))
155      offset += TD.getTypeStoreSizeInBits(Elts[i++]->getType());
156
157    // Advance over 0 sized elements (must terminate in bounds since
158    // the bitfield must have a size).
159    while (TD.getTypeStoreSizeInBits(Elts[i]->getType()) == 0)
160      ++i;
161
162    // Promote the size of V if necessary
163    // FIXME: This should never occur, but currently it can because
164    // initializer constants are cast to bool, and because clang is
165    // not enforcing bitfield width limits.
166    if (bitFieldInfo.Size > V.getBitWidth())
167      V.zext(bitFieldInfo.Size);
168
169    // Insert the bits into the struct
170    // FIXME: This algorthm is only correct on X86!
171    // FIXME: THis algorthm assumes bit-fields only have byte-size elements!
172    unsigned bitsToInsert = bitFieldInfo.Size;
173    unsigned curBits = std::min(8 - (fieldOffset & 7), bitsToInsert);
174    unsigned byte = V.getLoBits(curBits).getZExtValue() << (fieldOffset & 7);
175    do {
176      llvm::Constant* byteC = llvm::ConstantInt::get(llvm::Type::Int8Ty, byte);
177      Elts[i] = llvm::ConstantExpr::getOr(Elts[i], byteC);
178      ++i;
179      V = V.lshr(curBits);
180      bitsToInsert -= curBits;
181
182      if (!bitsToInsert)
183        break;
184
185      curBits = bitsToInsert > 8 ? 8 : bitsToInsert;
186      byte = V.getLoBits(curBits).getZExtValue();
187    } while (true);
188  }
189
190  llvm::Constant *EmitStructInitialization(InitListExpr *ILE) {
191    const llvm::StructType *SType =
192        cast<llvm::StructType>(ConvertType(ILE->getType()));
193    RecordDecl *RD = ILE->getType()->getAsRecordType()->getDecl();
194    std::vector<llvm::Constant*> Elts;
195
196    // Initialize the whole structure to zero.
197    for (unsigned i = 0; i < SType->getNumElements(); ++i) {
198      const llvm::Type *FieldTy = SType->getElementType(i);
199      Elts.push_back(llvm::Constant::getNullValue(FieldTy));
200    }
201
202    // Copy initializer elements. Skip padding fields.
203    unsigned EltNo = 0;  // Element no in ILE
204    int FieldNo = 0; // Field no in RecordDecl
205    bool RewriteType = false;
206    while (EltNo < ILE->getNumInits() && FieldNo < RD->getNumMembers()) {
207      FieldDecl* curField = RD->getMember(FieldNo);
208      FieldNo++;
209      if (!curField->getIdentifier())
210        continue;
211
212      if (curField->isBitField()) {
213        InsertBitfieldIntoStruct(Elts, curField, ILE->getInit(EltNo));
214      } else {
215        unsigned FieldNo = CGM.getTypes().getLLVMFieldNo(curField);
216        llvm::Constant *C = CGM.EmitConstantExpr(ILE->getInit(EltNo), CGF);
217        RewriteType |= (C->getType() != Elts[FieldNo]->getType());
218        Elts[FieldNo] = C;
219      }
220      EltNo++;
221    }
222
223    if (RewriteType) {
224      // FIXME: Make this work for non-packed structs
225      assert(SType->isPacked() && "Cannot recreate unpacked structs");
226      std::vector<const llvm::Type*> Types;
227      for (unsigned i = 0; i < Elts.size(); ++i)
228        Types.push_back(Elts[i]->getType());
229      SType = llvm::StructType::get(Types, true);
230    }
231
232    return llvm::ConstantStruct::get(SType, Elts);
233  }
234
235  llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
236    RecordDecl *RD = ILE->getType()->getAsRecordType()->getDecl();
237    const llvm::Type *Ty = ConvertType(ILE->getType());
238
239    // Find the field decl we're initializing, if any
240    int FieldNo = 0; // Field no in RecordDecl
241    FieldDecl* curField = 0;
242    while (FieldNo < RD->getNumMembers()) {
243      curField = RD->getMember(FieldNo);
244      FieldNo++;
245      if (curField->getIdentifier())
246        break;
247    }
248
249    if (!curField || !curField->getIdentifier() || ILE->getNumInits() == 0)
250      return llvm::Constant::getNullValue(Ty);
251
252    if (curField->isBitField()) {
253      // Create a dummy struct for bit-field insertion
254      unsigned NumElts = CGM.getTargetData().getABITypeSize(Ty) / 8;
255      llvm::Constant* NV = llvm::Constant::getNullValue(llvm::Type::Int8Ty);
256      std::vector<llvm::Constant*> Elts(NumElts, NV);
257
258      InsertBitfieldIntoStruct(Elts, curField, ILE->getInit(0));
259      const llvm::ArrayType *RetTy =
260          llvm::ArrayType::get(NV->getType(), NumElts);
261      return llvm::ConstantArray::get(RetTy, Elts);
262    }
263
264    llvm::Constant *C = CGM.EmitConstantExpr(ILE->getInit(0), CGF);
265
266    // Build a struct with the union sub-element as the first member,
267    // and padded to the appropriate size
268    std::vector<llvm::Constant*> Elts;
269    std::vector<const llvm::Type*> Types;
270    Elts.push_back(C);
271    Types.push_back(C->getType());
272    unsigned CurSize = CGM.getTargetData().getTypeStoreSize(C->getType());
273    unsigned TotalSize = CGM.getTargetData().getTypeStoreSize(Ty);
274    while (CurSize < TotalSize) {
275      Elts.push_back(llvm::Constant::getNullValue(llvm::Type::Int8Ty));
276      Types.push_back(llvm::Type::Int8Ty);
277      CurSize++;
278    }
279
280    // This always generates a packed struct
281    // FIXME: Try to generate an unpacked struct when we can
282    llvm::StructType* STy = llvm::StructType::get(Types, true);
283    return llvm::ConstantStruct::get(STy, Elts);
284  }
285
286  llvm::Constant *EmitVectorInitialization(InitListExpr *ILE) {
287    const llvm::VectorType *VType =
288        cast<llvm::VectorType>(ConvertType(ILE->getType()));
289    const llvm::Type *ElemTy = VType->getElementType();
290    std::vector<llvm::Constant*> Elts;
291    unsigned NumElements = VType->getNumElements();
292    unsigned NumInitElements = ILE->getNumInits();
293
294    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
295
296    // Copy initializer elements.
297    unsigned i = 0;
298    for (; i < NumInitableElts; ++i) {
299      llvm::Constant *C = CGM.EmitConstantExpr(ILE->getInit(i), CGF);
300      Elts.push_back(C);
301    }
302
303    for (; i < NumElements; ++i)
304      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
305
306    return llvm::ConstantVector::get(VType, Elts);
307  }
308
309  llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
310    if (ILE->getType()->isScalarType()) {
311      // We have a scalar in braces. Just use the first element.
312      if (ILE->getNumInits() > 0)
313        return CGM.EmitConstantExpr(ILE->getInit(0), CGF);
314
315      const llvm::Type* RetTy = CGM.getTypes().ConvertType(ILE->getType());
316      return llvm::Constant::getNullValue(RetTy);
317    }
318
319    // FIXME: We don't codegen or sema designators yet.
320    if (ILE->hadDesignators()) {
321      CGM.ErrorUnsupported(ILE, "initializer list with designators");
322      return llvm::UndefValue::get(ConvertType(ILE->getType()));
323    }
324
325    if (ILE->getType()->isArrayType())
326      return EmitArrayInitialization(ILE);
327
328    if (ILE->getType()->isStructureType())
329      return EmitStructInitialization(ILE);
330
331    if (ILE->getType()->isUnionType())
332      return EmitUnionInitialization(ILE);
333
334    if (ILE->getType()->isVectorType())
335      return EmitVectorInitialization(ILE);
336
337    assert(0 && "Unable to handle InitListExpr");
338    // Get rid of control reaches end of void function warning.
339    // Not reached.
340    return 0;
341  }
342
343  llvm::Constant *VisitImplicitCastExpr(ImplicitCastExpr *ICExpr) {
344    Expr* SExpr = ICExpr->getSubExpr();
345    QualType SType = SExpr->getType();
346    llvm::Constant *C; // the intermediate expression
347    QualType T;        // the type of the intermediate expression
348    if (SType->isArrayType()) {
349      // Arrays decay to a pointer to the first element
350      // VLAs would require special handling, but they can't occur here
351      C = EmitLValue(SExpr);
352      llvm::Constant *Idx0 = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
353      llvm::Constant *Ops[] = {Idx0, Idx0};
354      C = llvm::ConstantExpr::getGetElementPtr(C, Ops, 2);
355      T = CGM.getContext().getArrayDecayedType(SType);
356    } else if (SType->isFunctionType()) {
357      // Function types decay to a pointer to the function
358      C = EmitLValue(SExpr);
359      T = CGM.getContext().getPointerType(SType);
360    } else {
361      C = Visit(SExpr);
362      T = SType;
363    }
364
365    // Perform the conversion; note that an implicit cast can both promote
366    // and convert an array/function
367    return EmitConversion(C, T, ICExpr->getType());
368  }
369
370  llvm::Constant *VisitStringLiteral(StringLiteral *E) {
371    assert(!E->getType()->isPointerType() && "Strings are always arrays");
372
373    // Otherwise this must be a string initializing an array in a static
374    // initializer.  Don't emit it as the address of the string, emit the string
375    // data itself as an inline array.
376    return llvm::ConstantArray::get(CGM.GetStringForStringLiteral(E), false);
377  }
378
379  llvm::Constant *VisitDeclRefExpr(DeclRefExpr *E) {
380    const NamedDecl *Decl = E->getDecl();
381    if (const EnumConstantDecl *EC = dyn_cast<EnumConstantDecl>(Decl))
382      return llvm::ConstantInt::get(EC->getInitVal());
383    assert(0 && "Unsupported decl ref type!");
384    return 0;
385  }
386
387  llvm::Constant *VisitSizeOfAlignOfExpr(const SizeOfAlignOfExpr *E) {
388    return EmitSizeAlignOf(E->getTypeOfArgument(), E->getType(), E->isSizeOf());
389  }
390
391  llvm::Constant *VisitAddrLabelExpr(const AddrLabelExpr *E) {
392    assert(CGF && "Invalid address of label expression outside function.");
393    llvm::Constant *C =
394      llvm::ConstantInt::get(llvm::Type::Int32Ty,
395                             CGF->GetIDForAddrOfLabel(E->getLabel()));
396    return llvm::ConstantExpr::getIntToPtr(C, ConvertType(E->getType()));
397  }
398
399  // Unary operators
400  llvm::Constant *VisitUnaryPlus(const UnaryOperator *E) {
401    return Visit(E->getSubExpr());
402  }
403  llvm::Constant *VisitUnaryMinus(const UnaryOperator *E) {
404    return llvm::ConstantExpr::getNeg(Visit(E->getSubExpr()));
405  }
406  llvm::Constant *VisitUnaryNot(const UnaryOperator *E) {
407    return llvm::ConstantExpr::getNot(Visit(E->getSubExpr()));
408  }
409  llvm::Constant *VisitUnaryLNot(const UnaryOperator *E) {
410    llvm::Constant *SubExpr = Visit(E->getSubExpr());
411
412    if (E->getSubExpr()->getType()->isRealFloatingType()) {
413      // Compare against 0.0 for fp scalars.
414      llvm::Constant *Zero = llvm::Constant::getNullValue(SubExpr->getType());
415      SubExpr = llvm::ConstantExpr::getFCmp(llvm::FCmpInst::FCMP_UEQ, SubExpr,
416                                            Zero);
417    } else {
418      assert((E->getSubExpr()->getType()->isIntegerType() ||
419              E->getSubExpr()->getType()->isPointerType()) &&
420             "Unknown scalar type to convert");
421      // Compare against an integer or pointer null.
422      llvm::Constant *Zero = llvm::Constant::getNullValue(SubExpr->getType());
423      SubExpr = llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_EQ, SubExpr,
424                                            Zero);
425    }
426
427    return llvm::ConstantExpr::getZExt(SubExpr, ConvertType(E->getType()));
428  }
429  llvm::Constant *VisitUnaryAddrOf(const UnaryOperator *E) {
430    return EmitLValue(E->getSubExpr());
431  }
432  llvm::Constant *VisitUnaryOffsetOf(const UnaryOperator *E) {
433    int64_t Val = E->evaluateOffsetOf(CGM.getContext());
434
435    assert(E->getType()->isIntegerType() && "Result type must be an integer!");
436
437    uint32_t ResultWidth =
438      static_cast<uint32_t>(CGM.getContext().getTypeSize(E->getType()));
439    return llvm::ConstantInt::get(llvm::APInt(ResultWidth, Val));
440  }
441
442  llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) {
443    return Visit(E->getSubExpr());
444  }
445
446  // Binary operators
447  llvm::Constant *VisitBinOr(const BinaryOperator *E) {
448    llvm::Constant *LHS = Visit(E->getLHS());
449    llvm::Constant *RHS = Visit(E->getRHS());
450
451    return llvm::ConstantExpr::getOr(LHS, RHS);
452  }
453  llvm::Constant *VisitBinSub(const BinaryOperator *E) {
454    llvm::Constant *LHS = Visit(E->getLHS());
455    llvm::Constant *RHS = Visit(E->getRHS());
456
457    if (!isa<llvm::PointerType>(RHS->getType())) {
458      // pointer - int
459      if (isa<llvm::PointerType>(LHS->getType())) {
460        llvm::Constant *Idx = llvm::ConstantExpr::getNeg(RHS);
461
462        return llvm::ConstantExpr::getGetElementPtr(LHS, &Idx, 1);
463      }
464
465      // int - int
466      return llvm::ConstantExpr::getSub(LHS, RHS);
467    }
468
469    assert(isa<llvm::PointerType>(LHS->getType()));
470
471    const llvm::Type *ResultType = ConvertType(E->getType());
472    const QualType Type = E->getLHS()->getType();
473    const QualType ElementType = Type->getAsPointerType()->getPointeeType();
474
475    LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType);
476    RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType);
477
478    llvm::Constant *sub = llvm::ConstantExpr::getSub(LHS, RHS);
479    llvm::Constant *size = EmitSizeAlignOf(ElementType, E->getType(), true);
480    return llvm::ConstantExpr::getSDiv(sub, size);
481  }
482
483  llvm::Constant *VisitBinShl(const BinaryOperator *E) {
484    llvm::Constant *LHS = Visit(E->getLHS());
485    llvm::Constant *RHS = Visit(E->getRHS());
486
487    // LLVM requires the LHS and RHS to be the same type: promote or truncate the
488    // RHS to the same size as the LHS.
489    if (LHS->getType() != RHS->getType())
490      RHS = llvm::ConstantExpr::getIntegerCast(RHS, LHS->getType(), false);
491
492    return llvm::ConstantExpr::getShl(LHS, RHS);
493  }
494
495  llvm::Constant *VisitBinMul(const BinaryOperator *E) {
496    llvm::Constant *LHS = Visit(E->getLHS());
497    llvm::Constant *RHS = Visit(E->getRHS());
498
499    return llvm::ConstantExpr::getMul(LHS, RHS);
500  }
501
502  llvm::Constant *VisitBinDiv(const BinaryOperator *E) {
503    llvm::Constant *LHS = Visit(E->getLHS());
504    llvm::Constant *RHS = Visit(E->getRHS());
505
506    if (LHS->getType()->isFPOrFPVector())
507      return llvm::ConstantExpr::getFDiv(LHS, RHS);
508    else if (E->getType()->isUnsignedIntegerType())
509      return llvm::ConstantExpr::getUDiv(LHS, RHS);
510    else
511      return llvm::ConstantExpr::getSDiv(LHS, RHS);
512  }
513
514  llvm::Constant *VisitBinAdd(const BinaryOperator *E) {
515    llvm::Constant *LHS = Visit(E->getLHS());
516    llvm::Constant *RHS = Visit(E->getRHS());
517
518    if (!E->getType()->isPointerType())
519      return llvm::ConstantExpr::getAdd(LHS, RHS);
520
521    llvm::Constant *Ptr, *Idx;
522    if (isa<llvm::PointerType>(LHS->getType())) { // pointer + int
523      Ptr = LHS;
524      Idx = RHS;
525    } else { // int + pointer
526      Ptr = RHS;
527      Idx = LHS;
528    }
529
530    return llvm::ConstantExpr::getGetElementPtr(Ptr, &Idx, 1);
531  }
532
533  llvm::Constant *VisitBinAnd(const BinaryOperator *E) {
534    llvm::Constant *LHS = Visit(E->getLHS());
535    llvm::Constant *RHS = Visit(E->getRHS());
536
537    return llvm::ConstantExpr::getAnd(LHS, RHS);
538  }
539
540  llvm::Constant *EmitCmp(const BinaryOperator *E,
541                          llvm::CmpInst::Predicate SignedPred,
542                          llvm::CmpInst::Predicate UnsignedPred,
543                          llvm::CmpInst::Predicate FloatPred) {
544    llvm::Constant *LHS = Visit(E->getLHS());
545    llvm::Constant *RHS = Visit(E->getRHS());
546    llvm::Constant *Result;
547    if (LHS->getType()->isInteger() ||
548        isa<llvm::PointerType>(LHS->getType())) {
549      if (E->getLHS()->getType()->isSignedIntegerType())
550        Result = llvm::ConstantExpr::getICmp(SignedPred, LHS, RHS);
551      else
552        Result = llvm::ConstantExpr::getICmp(UnsignedPred, LHS, RHS);
553    } else if (LHS->getType()->isFloatingPoint()) {
554      Result = llvm::ConstantExpr::getFCmp(FloatPred, LHS, RHS);
555    } else {
556      CGM.ErrorUnsupported(E, "constant expression");
557      Result = llvm::ConstantInt::getFalse();
558    }
559
560    const llvm::Type* ResultType = ConvertType(E->getType());
561    return llvm::ConstantExpr::getZExtOrBitCast(Result, ResultType);
562  }
563
564  llvm::Constant *VisitBinNE(const BinaryOperator *E) {
565    return EmitCmp(E, llvm::CmpInst::ICMP_NE, llvm::CmpInst::ICMP_NE,
566                   llvm::CmpInst::FCMP_ONE);
567  }
568
569  llvm::Constant *VisitBinEQ(const BinaryOperator *E) {
570    return EmitCmp(E, llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_EQ,
571                   llvm::CmpInst::FCMP_OEQ);
572  }
573
574  llvm::Constant *VisitBinLT(const BinaryOperator *E) {
575    return EmitCmp(E, llvm::CmpInst::ICMP_SLT, llvm::CmpInst::ICMP_ULT,
576                   llvm::CmpInst::FCMP_OLT);
577  }
578
579  llvm::Constant *VisitBinLE(const BinaryOperator *E) {
580    return EmitCmp(E, llvm::CmpInst::ICMP_SLE, llvm::CmpInst::ICMP_ULE,
581                   llvm::CmpInst::FCMP_OLE);
582  }
583
584  llvm::Constant *VisitBinGT(const BinaryOperator *E) {
585    return EmitCmp(E, llvm::CmpInst::ICMP_SGT, llvm::CmpInst::ICMP_UGT,
586                   llvm::CmpInst::FCMP_OGT);
587  }
588
589  llvm::Constant *VisitBinGE(const BinaryOperator *E) {
590    return EmitCmp(E, llvm::CmpInst::ICMP_SGE, llvm::CmpInst::ICMP_SGE,
591                   llvm::CmpInst::FCMP_OGE);
592  }
593
594  llvm::Constant *VisitConditionalOperator(const ConditionalOperator *E) {
595    llvm::Constant *Cond = Visit(E->getCond());
596    llvm::Constant *CondVal = EmitConversionToBool(Cond, E->getType());
597    llvm::ConstantInt *CondValInt = dyn_cast<llvm::ConstantInt>(CondVal);
598    if (!CondValInt) {
599      CGM.ErrorUnsupported(E, "constant expression");
600      return llvm::Constant::getNullValue(ConvertType(E->getType()));
601    }
602    if (CondValInt->isOne()) {
603      if (E->getLHS())
604        return Visit(E->getLHS());
605      return Cond;
606    }
607
608    return Visit(E->getRHS());
609  }
610
611  llvm::Constant *VisitCallExpr(const CallExpr *E) {
612    APValue Result;
613    if (E->Evaluate(Result, CGM.getContext())) {
614      if (Result.isInt())
615        return llvm::ConstantInt::get(Result.getInt());
616      if (Result.isFloat())
617        return llvm::ConstantFP::get(Result.getFloat());
618    }
619
620    // Handle __builtin___CFStringMakeConstantString.
621    if (E->isBuiltinCall() ==Builtin::BI__builtin___CFStringMakeConstantString){
622      const Expr *Arg = E->getArg(0)->IgnoreParenCasts();
623
624      const StringLiteral *Literal = cast<StringLiteral>(Arg);
625      std::string S(Literal->getStrData(), Literal->getByteLength());
626      return CGM.GetAddrOfConstantCFString(S);
627    }
628
629    CGM.ErrorUnsupported(E, "constant call expression");
630    return llvm::Constant::getNullValue(ConvertType(E->getType()));
631  }
632
633  // Utility methods
634  const llvm::Type *ConvertType(QualType T) {
635    return CGM.getTypes().ConvertType(T);
636  }
637
638  llvm::Constant *EmitConversionToBool(llvm::Constant *Src, QualType SrcType) {
639    assert(SrcType->isCanonical() && "EmitConversion strips typedefs");
640
641    if (SrcType->isRealFloatingType()) {
642      // Compare against 0.0 for fp scalars.
643      llvm::Constant *Zero = llvm::Constant::getNullValue(Src->getType());
644      return llvm::ConstantExpr::getFCmp(llvm::FCmpInst::FCMP_UNE, Src, Zero);
645    }
646
647    assert((SrcType->isIntegerType() || SrcType->isPointerType()) &&
648           "Unknown scalar type to convert");
649
650    // Compare against an integer or pointer null.
651    llvm::Constant *Zero = llvm::Constant::getNullValue(Src->getType());
652    return llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_NE, Src, Zero);
653  }
654
655  llvm::Constant *EmitConversion(llvm::Constant *Src, QualType SrcType,
656                                 QualType DstType) {
657    SrcType = CGM.getContext().getCanonicalType(SrcType);
658    DstType = CGM.getContext().getCanonicalType(DstType);
659    if (SrcType == DstType) return Src;
660
661    // Handle conversions to bool first, they are special: comparisons against 0.
662    if (DstType->isBooleanType())
663      return EmitConversionToBool(Src, SrcType);
664
665    const llvm::Type *DstTy = ConvertType(DstType);
666
667    // Ignore conversions like int -> uint.
668    if (Src->getType() == DstTy)
669      return Src;
670
671    // Handle pointer conversions next: pointers can only be converted to/from
672    // other pointers and integers.
673    if (isa<llvm::PointerType>(DstTy)) {
674      // The source value may be an integer, or a pointer.
675      if (isa<llvm::PointerType>(Src->getType()))
676        return llvm::ConstantExpr::getBitCast(Src, DstTy);
677      assert(SrcType->isIntegerType() &&"Not ptr->ptr or int->ptr conversion?");
678      return llvm::ConstantExpr::getIntToPtr(Src, DstTy);
679    }
680
681    if (isa<llvm::PointerType>(Src->getType())) {
682      // Must be an ptr to int cast.
683      assert(isa<llvm::IntegerType>(DstTy) && "not ptr->int?");
684      return llvm::ConstantExpr::getPtrToInt(Src, DstTy);
685    }
686
687    // A scalar source can be splatted to a vector of the same element type
688    if (isa<llvm::VectorType>(DstTy) && !isa<VectorType>(SrcType)) {
689      assert((cast<llvm::VectorType>(DstTy)->getElementType()
690              == Src->getType()) &&
691             "Vector element type must match scalar type to splat.");
692      unsigned NumElements = DstType->getAsVectorType()->getNumElements();
693      llvm::SmallVector<llvm::Constant*, 16> Elements;
694      for (unsigned i = 0; i < NumElements; i++)
695        Elements.push_back(Src);
696
697      return llvm::ConstantVector::get(&Elements[0], NumElements);
698    }
699
700    if (isa<llvm::VectorType>(Src->getType()) ||
701        isa<llvm::VectorType>(DstTy)) {
702      return llvm::ConstantExpr::getBitCast(Src, DstTy);
703    }
704
705    // Finally, we have the arithmetic types: real int/float.
706    if (isa<llvm::IntegerType>(Src->getType())) {
707      bool InputSigned = SrcType->isSignedIntegerType();
708      if (isa<llvm::IntegerType>(DstTy))
709        return llvm::ConstantExpr::getIntegerCast(Src, DstTy, InputSigned);
710      else if (InputSigned)
711        return llvm::ConstantExpr::getSIToFP(Src, DstTy);
712      else
713        return llvm::ConstantExpr::getUIToFP(Src, DstTy);
714    }
715
716    assert(Src->getType()->isFloatingPoint() && "Unknown real conversion");
717    if (isa<llvm::IntegerType>(DstTy)) {
718      if (DstType->isSignedIntegerType())
719        return llvm::ConstantExpr::getFPToSI(Src, DstTy);
720      else
721        return llvm::ConstantExpr::getFPToUI(Src, DstTy);
722    }
723
724    assert(DstTy->isFloatingPoint() && "Unknown real conversion");
725    if (DstTy->getTypeID() < Src->getType()->getTypeID())
726      return llvm::ConstantExpr::getFPTrunc(Src, DstTy);
727    else
728      return llvm::ConstantExpr::getFPExtend(Src, DstTy);
729  }
730
731  llvm::Constant *EmitSizeAlignOf(QualType TypeToSize,
732                                  QualType RetType, bool isSizeOf) {
733    std::pair<uint64_t, unsigned> Info =
734      CGM.getContext().getTypeInfo(TypeToSize);
735
736    uint64_t Val = isSizeOf ? Info.first : Info.second;
737    Val /= 8;  // Return size in bytes, not bits.
738
739    assert(RetType->isIntegerType() && "Result type must be an integer!");
740
741    uint32_t ResultWidth =
742      static_cast<uint32_t>(CGM.getContext().getTypeSize(RetType));
743    return llvm::ConstantInt::get(llvm::APInt(ResultWidth, Val));
744  }
745
746public:
747  llvm::Constant *EmitLValue(Expr *E) {
748    switch (E->getStmtClass()) {
749    default: break;
750    case Expr::ParenExprClass:
751      // Elide parenthesis
752      return EmitLValue(cast<ParenExpr>(E)->getSubExpr());
753    case Expr::CompoundLiteralExprClass: {
754      // Note that due to the nature of compound literals, this is guaranteed
755      // to be the only use of the variable, so we just generate it here.
756      CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
757      llvm::Constant* C = Visit(CLE->getInitializer());
758      C = new llvm::GlobalVariable(C->getType(),E->getType().isConstQualified(),
759                                   llvm::GlobalValue::InternalLinkage,
760                                   C, ".compoundliteral", &CGM.getModule());
761      return C;
762    }
763    case Expr::DeclRefExprClass: {
764      NamedDecl *Decl = cast<DeclRefExpr>(E)->getDecl();
765      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
766        return CGM.GetAddrOfFunction(FD);
767      if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
768        if (VD->isFileVarDecl())
769          return CGM.GetAddrOfGlobalVar(VD);
770        else if (VD->isBlockVarDecl()) {
771          assert(CGF && "Can't access static local vars without CGF");
772          return CGF->GetAddrOfStaticLocalVar(VD);
773        }
774      }
775      break;
776    }
777    case Expr::MemberExprClass: {
778      MemberExpr* ME = cast<MemberExpr>(E);
779      llvm::Constant *Base;
780      if (ME->isArrow())
781        Base = Visit(ME->getBase());
782      else
783        Base = EmitLValue(ME->getBase());
784
785      unsigned FieldNumber = CGM.getTypes().getLLVMFieldNo(ME->getMemberDecl());
786      llvm::Constant *Zero = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
787      llvm::Constant *Idx = llvm::ConstantInt::get(llvm::Type::Int32Ty,
788                                                   FieldNumber);
789      llvm::Value *Ops[] = {Zero, Idx};
790      return llvm::ConstantExpr::getGetElementPtr(Base, Ops, 2);
791    }
792    case Expr::ArraySubscriptExprClass: {
793      ArraySubscriptExpr* ASExpr = cast<ArraySubscriptExpr>(E);
794      llvm::Constant *Base = Visit(ASExpr->getBase());
795      llvm::Constant *Index = Visit(ASExpr->getIdx());
796      assert(!ASExpr->getBase()->getType()->isVectorType() &&
797             "Taking the address of a vector component is illegal!");
798      return llvm::ConstantExpr::getGetElementPtr(Base, &Index, 1);
799    }
800    case Expr::StringLiteralClass:
801      return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E));
802    case Expr::ObjCStringLiteralClass: {
803      ObjCStringLiteral* SL = cast<ObjCStringLiteral>(E);
804      std::string S(SL->getString()->getStrData(),
805                    SL->getString()->getByteLength());
806      llvm::Constant *C = CGM.getObjCRuntime().GenerateConstantString(S);
807      return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
808    }
809    case Expr::UnaryOperatorClass: {
810      UnaryOperator *Exp = cast<UnaryOperator>(E);
811      switch (Exp->getOpcode()) {
812      default: break;
813      case UnaryOperator::Extension:
814        // Extension is just a wrapper for expressions
815        return EmitLValue(Exp->getSubExpr());
816      case UnaryOperator::Real:
817      case UnaryOperator::Imag: {
818        // The address of __real or __imag is just a GEP off the address
819        // of the internal expression
820        llvm::Constant* C = EmitLValue(Exp->getSubExpr());
821        llvm::Constant *Zero = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
822        llvm::Constant *Idx  = llvm::ConstantInt::get(llvm::Type::Int32Ty,
823                                       Exp->getOpcode() == UnaryOperator::Imag);
824        llvm::Value *Ops[] = {Zero, Idx};
825        return llvm::ConstantExpr::getGetElementPtr(C, Ops, 2);
826      }
827      case UnaryOperator::Deref:
828        // The address of a deref is just the value of the expression
829        return Visit(Exp->getSubExpr());
830      }
831      break;
832    }
833    }
834    CGM.ErrorUnsupported(E, "constant l-value expression");
835    llvm::Type *Ty = llvm::PointerType::getUnqual(ConvertType(E->getType()));
836    return llvm::UndefValue::get(Ty);
837  }
838};
839
840}  // end anonymous namespace.
841
842llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
843                                                CodeGenFunction *CGF) {
844  QualType type = Context.getCanonicalType(E->getType());
845
846#ifdef USE_TRY_EVALUATE
847  APValue V;
848  if (E->Evaluate(V, Context)) {
849    // FIXME: Assert that the value doesn't have any side effects.
850    switch (V.getKind()) {
851    default: assert(0 && "unhandled value kind!");
852    case APValue::LValue: {
853      llvm::Constant *Offset = llvm::ConstantInt::get(llvm::Type::Int64Ty,
854                                                      V.getLValueOffset());
855
856      if (const Expr *LVBase = V.getLValueBase()) {
857        llvm::Constant *C =
858          ConstExprEmitter(*this, CGF).EmitLValue(const_cast<Expr*>(LVBase));
859
860        const llvm::Type *Type =
861          llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
862        const llvm::Type *DestType = C->getType();
863
864        // FIXME: It's a little ugly that we need to cast to a pointer,
865        // apply the GEP and then cast back.
866        C = llvm::ConstantExpr::getBitCast(C, Type);
867        C = llvm::ConstantExpr::getGetElementPtr(C, &Offset, 1);
868
869        return llvm::ConstantExpr::getBitCast(C, DestType);
870      }
871
872      return llvm::ConstantExpr::getIntToPtr(Offset,
873                                             getTypes().ConvertType(type));
874    }
875    case APValue::Int:
876      llvm::Constant *C = llvm::ConstantInt::get(V.getInt());
877
878      if (C->getType() == llvm::Type::Int1Ty) {
879        const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
880        C = llvm::ConstantExpr::getZExt(C, BoolTy);
881      }
882      return C;
883    case APValue::Float:
884      return llvm::ConstantFP::get(V.getFloat());
885    case APValue::ComplexFloat: {
886      llvm::Constant *Complex[2];
887
888      Complex[0] = llvm::ConstantFP::get(V.getComplexFloatReal());
889      Complex[1] = llvm::ConstantFP::get(V.getComplexFloatImag());
890
891      return llvm::ConstantStruct::get(Complex, 2);
892    }
893    }
894  }
895#else
896  if (type->isIntegerType()) {
897    llvm::APSInt Value(static_cast<uint32_t>(Context.getTypeSize(type)));
898    if (E->isIntegerConstantExpr(Value, Context)) {
899      return llvm::ConstantInt::get(Value);
900    }
901  }
902#endif
903
904  llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
905  if (C->getType() == llvm::Type::Int1Ty) {
906    const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
907    C = llvm::ConstantExpr::getZExt(C, BoolTy);
908  }
909  return C;
910}
911