CGExprConstant.cpp revision 77e1dfcffe9ed0078b015418182784b56532998c 
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
63  llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
64    return Visit(E->getInitializer());
65  }
66
67  llvm::Constant *VisitCastExpr(const CastExpr* E) {
68    llvm::Constant *C = Visit(E->getSubExpr());
69
70    return EmitConversion(C, E->getSubExpr()->getType(), E->getType());
71  }
72
73  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
74    return Visit(DAE->getExpr());
75  }
76
77  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
78    std::vector<llvm::Constant*> Elts;
79    const llvm::ArrayType *AType =
80        cast<llvm::ArrayType>(ConvertType(ILE->getType()));
81    unsigned NumInitElements = ILE->getNumInits();
82    // FIXME: Check for wide strings
83    if (NumInitElements > 0 && isa<StringLiteral>(ILE->getInit(0)) &&
84        ILE->getType()->getAsArrayType()->getElementType()->isCharType())
85      return Visit(ILE->getInit(0));
86    const llvm::Type *ElemTy = AType->getElementType();
87    unsigned NumElements = AType->getNumElements();
88
89    // Initialising an array requires us to automatically
90    // initialise any elements that have not been initialised explicitly
91    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
92
93    // Copy initializer elements.
94    unsigned i = 0;
95    bool RewriteType = false;
96    for (; i < NumInitableElts; ++i) {
97      llvm::Constant *C = Visit(ILE->getInit(i));
98      RewriteType |= (C->getType() != ElemTy);
99      Elts.push_back(C);
100    }
101
102    // Initialize remaining array elements.
103    for (; i < NumElements; ++i)
104      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
105
106    if (RewriteType) {
107      // FIXME: Try to avoid packing the array
108      std::vector<const llvm::Type*> Types;
109      for (unsigned i = 0; i < Elts.size(); ++i)
110        Types.push_back(Elts[i]->getType());
111      const llvm::StructType *SType = llvm::StructType::get(Types, true);
112      return llvm::ConstantStruct::get(SType, Elts);
113    }
114
115    return llvm::ConstantArray::get(AType, Elts);
116  }
117
118  void InsertBitfieldIntoStruct(std::vector<llvm::Constant*>& Elts,
119                                FieldDecl* Field, Expr* E) {
120    // Calculate the value to insert
121    llvm::Constant *C = Visit(E);
122    llvm::ConstantInt *CI = dyn_cast<llvm::ConstantInt>(C);
123    if (!CI) {
124      CGM.WarnUnsupported(E, "bitfield initialization");
125      return;
126    }
127    llvm::APInt V = CI->getValue();
128
129    // Calculate information about the relevant field
130    const llvm::Type* Ty = CI->getType();
131    unsigned size = CGM.getTypes().getTargetData().getTypeStoreSizeInBits(Ty);
132    unsigned fieldOffset = CGM.getTypes().getLLVMFieldNo(Field) * size;
133    CodeGenTypes::BitFieldInfo bitFieldInfo =
134        CGM.getTypes().getBitFieldInfo(Field);
135    fieldOffset += bitFieldInfo.Begin;
136
137    // Find where to start the insertion
138    // FIXME: This is O(n^2) in the number of bit-fields!
139    // FIXME: This won't work if the struct isn't completely packed!
140    unsigned offset = 0, i = 0;
141    while (offset < (fieldOffset & -8))
142      offset += CGM.getTypes().getTargetData().getTypeStoreSizeInBits(Elts[i++]->getType());
143
144    // Insert the bits into the struct
145    // FIXME: This algorthm is only correct on X86!
146    // FIXME: THis algorthm assumes bit-fields only have byte-size elements!
147    unsigned bitsToInsert = bitFieldInfo.Size;
148    unsigned curBits = std::min(8 - (fieldOffset & 7), bitsToInsert);
149    unsigned byte = V.getLoBits(curBits).getZExtValue() << (fieldOffset & 7);
150    do {
151      llvm::Constant* byteC = llvm::ConstantInt::get(llvm::Type::Int8Ty, byte);
152      Elts[i] = llvm::ConstantExpr::getOr(Elts[i], byteC);
153      ++i;
154      V = V.lshr(curBits);
155      bitsToInsert -= curBits;
156
157      if (!bitsToInsert)
158        break;
159
160      curBits = bitsToInsert > 8 ? 8 : bitsToInsert;
161      byte = V.getLoBits(curBits).getZExtValue();
162    } while (true);
163  }
164
165  llvm::Constant *EmitStructInitialization(InitListExpr *ILE) {
166    const llvm::StructType *SType =
167        cast<llvm::StructType>(ConvertType(ILE->getType()));
168    RecordDecl *RD = ILE->getType()->getAsRecordType()->getDecl();
169    std::vector<llvm::Constant*> Elts;
170
171    // Initialize the whole structure to zero.
172    for (unsigned i = 0; i < SType->getNumElements(); ++i) {
173      const llvm::Type *FieldTy = SType->getElementType(i);
174      Elts.push_back(llvm::Constant::getNullValue(FieldTy));
175    }
176
177    // Copy initializer elements. Skip padding fields.
178    unsigned EltNo = 0;  // Element no in ILE
179    int FieldNo = 0; // Field no in RecordDecl
180    bool RewriteType = false;
181    while (EltNo < ILE->getNumInits() && FieldNo < RD->getNumMembers()) {
182      FieldDecl* curField = RD->getMember(FieldNo);
183      FieldNo++;
184      if (!curField->getIdentifier())
185        continue;
186
187      if (curField->isBitField()) {
188        InsertBitfieldIntoStruct(Elts, curField, ILE->getInit(EltNo));
189      } else {
190        unsigned FieldNo = CGM.getTypes().getLLVMFieldNo(curField);
191        llvm::Constant* C = Visit(ILE->getInit(EltNo));
192        RewriteType |= (C->getType() != Elts[FieldNo]->getType());
193        Elts[FieldNo] = C;
194      }
195      EltNo++;
196    }
197
198    if (RewriteType) {
199      // FIXME: Make this work for non-packed structs
200      assert(SType->isPacked() && "Cannot recreate unpacked structs");
201      std::vector<const llvm::Type*> Types;
202      for (unsigned i = 0; i < Elts.size(); ++i)
203        Types.push_back(Elts[i]->getType());
204      SType = llvm::StructType::get(Types, true);
205    }
206
207    return llvm::ConstantStruct::get(SType, Elts);
208  }
209
210  llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
211    RecordDecl *RD = ILE->getType()->getAsRecordType()->getDecl();
212    const llvm::Type *Ty = ConvertType(ILE->getType());
213
214    // Find the field decl we're initializing, if any
215    int FieldNo = 0; // Field no in RecordDecl
216    FieldDecl* curField;
217    do {
218      curField = RD->getMember(FieldNo);
219      FieldNo++;
220    } while (!curField->getIdentifier() && FieldNo < RD->getNumMembers());
221
222    if (ILE->getNumInits() == 0 || !curField->getIdentifier())
223      return llvm::Constant::getNullValue(Ty);
224
225    if (curField->isBitField()) {
226      // Create a dummy struct for bit-field insertion
227      unsigned NumElts = CGM.getTargetData().getABITypeSize(Ty) / 8;
228      llvm::Constant* NV = llvm::Constant::getNullValue(llvm::Type::Int8Ty);
229      std::vector<llvm::Constant*> Elts(NumElts, NV);
230
231      InsertBitfieldIntoStruct(Elts, curField, ILE->getInit(0));
232      const llvm::ArrayType *RetTy =
233          llvm::ArrayType::get(NV->getType(), NumElts);
234      return llvm::ConstantArray::get(RetTy, Elts);
235    }
236
237    llvm::Constant *C = Visit(ILE->getInit(0));
238
239    // Build a struct with the union sub-element as the first member,
240    // and padded to the appropriate size
241    std::vector<llvm::Constant*> Elts;
242    std::vector<const llvm::Type*> Types;
243    Elts.push_back(C);
244    Types.push_back(C->getType());
245    unsigned CurSize = CGM.getTargetData().getTypeStoreSize(C->getType());
246    unsigned TotalSize = CGM.getTargetData().getTypeStoreSize(Ty);
247    while (CurSize < TotalSize) {
248      Elts.push_back(llvm::Constant::getNullValue(llvm::Type::Int8Ty));
249      Types.push_back(llvm::Type::Int8Ty);
250      CurSize++;
251    }
252
253    // This always generates a packed struct
254    // FIXME: Try to generate an unpacked struct when we can
255    llvm::StructType* STy = llvm::StructType::get(Types, true);
256    return llvm::ConstantStruct::get(STy, Elts);
257  }
258
259  llvm::Constant *EmitVectorInitialization(InitListExpr *ILE) {
260    const llvm::VectorType *VType =
261        cast<llvm::VectorType>(ConvertType(ILE->getType()));
262    const llvm::Type *ElemTy = VType->getElementType();
263    std::vector<llvm::Constant*> Elts;
264    unsigned NumElements = VType->getNumElements();
265    unsigned NumInitElements = ILE->getNumInits();
266
267    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
268
269    // Copy initializer elements.
270    unsigned i = 0;
271    for (; i < NumInitableElts; ++i) {
272      llvm::Constant *C = Visit(ILE->getInit(i));
273      Elts.push_back(C);
274    }
275
276    for (; i < NumElements; ++i)
277      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
278
279    return llvm::ConstantVector::get(VType, Elts);
280  }
281
282  llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
283    if (ILE->getType()->isScalarType()) {
284      // We have a scalar in braces. Just use the first element.
285      if (ILE->getNumInits() > 0)
286        return Visit(ILE->getInit(0));
287
288      const llvm::Type* RetTy = CGM.getTypes().ConvertType(ILE->getType());
289      return llvm::Constant::getNullValue(RetTy);
290    }
291
292    if (ILE->getType()->isArrayType())
293      return EmitArrayInitialization(ILE);
294
295    if (ILE->getType()->isStructureType())
296      return EmitStructInitialization(ILE);
297
298    if (ILE->getType()->isUnionType())
299      return EmitUnionInitialization(ILE);
300
301    if (ILE->getType()->isVectorType())
302      return EmitVectorInitialization(ILE);
303
304    assert(0 && "Unable to handle InitListExpr");
305    // Get rid of control reaches end of void function warning.
306    // Not reached.
307    return 0;
308  }
309
310  llvm::Constant *VisitImplicitCastExpr(ImplicitCastExpr *ICExpr) {
311    Expr* SExpr = ICExpr->getSubExpr();
312    QualType SType = SExpr->getType();
313    llvm::Constant *C; // the intermediate expression
314    QualType T;        // the type of the intermediate expression
315    if (SType->isArrayType()) {
316      // Arrays decay to a pointer to the first element
317      // VLAs would require special handling, but they can't occur here
318      C = EmitLValue(SExpr);
319      llvm::Constant *Idx0 = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
320      llvm::Constant *Ops[] = {Idx0, Idx0};
321      C = llvm::ConstantExpr::getGetElementPtr(C, Ops, 2);
322
323      QualType ElemType = SType->getAsArrayType()->getElementType();
324      T = CGM.getContext().getPointerType(ElemType);
325    } else if (SType->isFunctionType()) {
326      // Function types decay to a pointer to the function
327      C = EmitLValue(SExpr);
328      T = CGM.getContext().getPointerType(SType);
329    } else {
330      C = Visit(SExpr);
331      T = SType;
332    }
333
334    // Perform the conversion; note that an implicit cast can both promote
335    // and convert an array/function
336    return EmitConversion(C, T, ICExpr->getType());
337  }
338
339  llvm::Constant *VisitStringLiteral(StringLiteral *E) {
340    const char *StrData = E->getStrData();
341    unsigned Len = E->getByteLength();
342    assert(!E->getType()->isPointerType() && "Strings are always arrays");
343
344    // Otherwise this must be a string initializing an array in a static
345    // initializer.  Don't emit it as the address of the string, emit the string
346    // data itself as an inline array.
347    const ConstantArrayType *CAT = E->getType()->getAsConstantArrayType();
348    assert(CAT && "String isn't pointer or array!");
349
350    std::string Str(StrData, StrData + Len);
351    // Null terminate the string before potentially truncating it.
352    // FIXME: What about wchar_t strings?
353    Str.push_back(0);
354
355    uint64_t RealLen = CAT->getSize().getZExtValue();
356    // String or grow the initializer to the required size.
357    if (RealLen != Str.size())
358      Str.resize(RealLen);
359
360    return llvm::ConstantArray::get(Str, false);
361  }
362
363  llvm::Constant *VisitDeclRefExpr(DeclRefExpr *E) {
364    const ValueDecl *Decl = E->getDecl();
365    if (const EnumConstantDecl *EC = dyn_cast<EnumConstantDecl>(Decl))
366      return llvm::ConstantInt::get(EC->getInitVal());
367    assert(0 && "Unsupported decl ref type!");
368    return 0;
369  }
370
371  llvm::Constant *VisitSizeOfAlignOfTypeExpr(const SizeOfAlignOfTypeExpr *E) {
372    return EmitSizeAlignOf(E->getArgumentType(), E->getType(), E->isSizeOf());
373  }
374
375  // Unary operators
376  llvm::Constant *VisitUnaryPlus(const UnaryOperator *E) {
377    return Visit(E->getSubExpr());
378  }
379  llvm::Constant *VisitUnaryMinus(const UnaryOperator *E) {
380    return llvm::ConstantExpr::getNeg(Visit(E->getSubExpr()));
381  }
382  llvm::Constant *VisitUnaryNot(const UnaryOperator *E) {
383    return llvm::ConstantExpr::getNot(Visit(E->getSubExpr()));
384  }
385  llvm::Constant *VisitUnaryLNot(const UnaryOperator *E) {
386    llvm::Constant *SubExpr = Visit(E->getSubExpr());
387
388    if (E->getSubExpr()->getType()->isRealFloatingType()) {
389      // Compare against 0.0 for fp scalars.
390      llvm::Constant *Zero = llvm::Constant::getNullValue(SubExpr->getType());
391      SubExpr = llvm::ConstantExpr::getFCmp(llvm::FCmpInst::FCMP_UEQ, SubExpr,
392                                            Zero);
393    } else {
394      assert((E->getSubExpr()->getType()->isIntegerType() ||
395              E->getSubExpr()->getType()->isPointerType()) &&
396             "Unknown scalar type to convert");
397      // Compare against an integer or pointer null.
398      llvm::Constant *Zero = llvm::Constant::getNullValue(SubExpr->getType());
399      SubExpr = llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_EQ, SubExpr,
400                                            Zero);
401    }
402
403    return llvm::ConstantExpr::getZExt(SubExpr, ConvertType(E->getType()));
404  }
405  llvm::Constant *VisitUnarySizeOf(const UnaryOperator *E) {
406    return EmitSizeAlignOf(E->getSubExpr()->getType(), E->getType(), true);
407  }
408  llvm::Constant *VisitUnaryAlignOf(const UnaryOperator *E) {
409    return EmitSizeAlignOf(E->getSubExpr()->getType(), E->getType(), false);
410  }
411  llvm::Constant *VisitUnaryAddrOf(const UnaryOperator *E) {
412    return EmitLValue(E->getSubExpr());
413  }
414  llvm::Constant *VisitUnaryOffsetOf(const UnaryOperator *E) {
415    int64_t Val = E->evaluateOffsetOf(CGM.getContext());
416
417    assert(E->getType()->isIntegerType() && "Result type must be an integer!");
418
419    uint32_t ResultWidth =
420      static_cast<uint32_t>(CGM.getContext().getTypeSize(E->getType()));
421    return llvm::ConstantInt::get(llvm::APInt(ResultWidth, Val));
422  }
423
424  llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) {
425    return Visit(E->getSubExpr());
426  }
427
428  // Binary operators
429  llvm::Constant *VisitBinOr(const BinaryOperator *E) {
430    llvm::Constant *LHS = Visit(E->getLHS());
431    llvm::Constant *RHS = Visit(E->getRHS());
432
433    return llvm::ConstantExpr::getOr(LHS, RHS);
434  }
435  llvm::Constant *VisitBinSub(const BinaryOperator *E) {
436    llvm::Constant *LHS = Visit(E->getLHS());
437    llvm::Constant *RHS = Visit(E->getRHS());
438
439    if (!isa<llvm::PointerType>(RHS->getType())) {
440      // pointer - int
441      if (isa<llvm::PointerType>(LHS->getType())) {
442        llvm::Constant *Idx = llvm::ConstantExpr::getNeg(RHS);
443
444        return llvm::ConstantExpr::getGetElementPtr(LHS, &Idx, 1);
445      }
446
447      // int - int
448      return llvm::ConstantExpr::getSub(LHS, RHS);
449    }
450
451    assert(isa<llvm::PointerType>(LHS->getType()));
452
453    const llvm::Type *ResultType = ConvertType(E->getType());
454    const QualType Type = E->getLHS()->getType();
455    const QualType ElementType = Type->getAsPointerType()->getPointeeType();
456
457    LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType);
458    RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType);
459
460    llvm::Constant *sub = llvm::ConstantExpr::getSub(LHS, RHS);
461    llvm::Constant *size = EmitSizeAlignOf(ElementType, E->getType(), true);
462    return llvm::ConstantExpr::getSDiv(sub, size);
463  }
464
465  llvm::Constant *VisitBinShl(const BinaryOperator *E) {
466    llvm::Constant *LHS = Visit(E->getLHS());
467    llvm::Constant *RHS = Visit(E->getRHS());
468
469    // LLVM requires the LHS and RHS to be the same type: promote or truncate the
470    // RHS to the same size as the LHS.
471    if (LHS->getType() != RHS->getType())
472      RHS = llvm::ConstantExpr::getIntegerCast(RHS, LHS->getType(), false);
473
474    return llvm::ConstantExpr::getShl(LHS, RHS);
475  }
476
477  llvm::Constant *VisitBinMul(const BinaryOperator *E) {
478    llvm::Constant *LHS = Visit(E->getLHS());
479    llvm::Constant *RHS = Visit(E->getRHS());
480
481    return llvm::ConstantExpr::getMul(LHS, RHS);
482  }
483
484  llvm::Constant *VisitBinDiv(const BinaryOperator *E) {
485    llvm::Constant *LHS = Visit(E->getLHS());
486    llvm::Constant *RHS = Visit(E->getRHS());
487
488    if (LHS->getType()->isFPOrFPVector())
489      return llvm::ConstantExpr::getFDiv(LHS, RHS);
490    else if (E->getType()->isUnsignedIntegerType())
491      return llvm::ConstantExpr::getUDiv(LHS, RHS);
492    else
493      return llvm::ConstantExpr::getSDiv(LHS, RHS);
494  }
495
496  llvm::Constant *VisitBinAdd(const BinaryOperator *E) {
497    llvm::Constant *LHS = Visit(E->getLHS());
498    llvm::Constant *RHS = Visit(E->getRHS());
499
500    if (!E->getType()->isPointerType())
501      return llvm::ConstantExpr::getAdd(LHS, RHS);
502
503    llvm::Constant *Ptr, *Idx;
504    if (isa<llvm::PointerType>(LHS->getType())) { // pointer + int
505      Ptr = LHS;
506      Idx = RHS;
507    } else { // int + pointer
508      Ptr = RHS;
509      Idx = LHS;
510    }
511
512    return llvm::ConstantExpr::getGetElementPtr(Ptr, &Idx, 1);
513  }
514
515  llvm::Constant *VisitBinAnd(const BinaryOperator *E) {
516    llvm::Constant *LHS = Visit(E->getLHS());
517    llvm::Constant *RHS = Visit(E->getRHS());
518
519    return llvm::ConstantExpr::getAnd(LHS, RHS);
520  }
521
522  llvm::Constant *EmitCmp(const BinaryOperator *E,
523                          llvm::CmpInst::Predicate SignedPred,
524                          llvm::CmpInst::Predicate UnsignedPred,
525                          llvm::CmpInst::Predicate FloatPred) {
526    llvm::Constant *LHS = Visit(E->getLHS());
527    llvm::Constant *RHS = Visit(E->getRHS());
528    llvm::Constant *Result;
529    if (LHS->getType()->isInteger() ||
530        isa<llvm::PointerType>(LHS->getType())) {
531      if (E->getLHS()->getType()->isSignedIntegerType())
532        Result = llvm::ConstantExpr::getICmp(SignedPred, LHS, RHS);
533      else
534        Result = llvm::ConstantExpr::getICmp(UnsignedPred, LHS, RHS);
535    } else if (LHS->getType()->isFloatingPoint()) {
536      Result = llvm::ConstantExpr::getFCmp(FloatPred, LHS, RHS);
537    } else {
538      CGM.WarnUnsupported(E, "constant expression");
539      Result = llvm::ConstantInt::getFalse();
540    }
541
542    const llvm::Type* ResultType = ConvertType(E->getType());
543    return llvm::ConstantExpr::getZExtOrBitCast(Result, ResultType);
544  }
545
546  llvm::Constant *VisitBinNE(const BinaryOperator *E) {
547    return EmitCmp(E, llvm::CmpInst::ICMP_NE, llvm::CmpInst::ICMP_NE,
548                   llvm::CmpInst::FCMP_ONE);
549  }
550
551  llvm::Constant *VisitBinEQ(const BinaryOperator *E) {
552    return EmitCmp(E, llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_EQ,
553                   llvm::CmpInst::FCMP_OEQ);
554  }
555
556  llvm::Constant *VisitBinLT(const BinaryOperator *E) {
557    return EmitCmp(E, llvm::CmpInst::ICMP_SLT, llvm::CmpInst::ICMP_ULT,
558                   llvm::CmpInst::FCMP_OLT);
559  }
560
561  llvm::Constant *VisitBinLE(const BinaryOperator *E) {
562    return EmitCmp(E, llvm::CmpInst::ICMP_SLE, llvm::CmpInst::ICMP_ULE,
563                   llvm::CmpInst::FCMP_OLE);
564  }
565
566  llvm::Constant *VisitBinGT(const BinaryOperator *E) {
567    return EmitCmp(E, llvm::CmpInst::ICMP_SGT, llvm::CmpInst::ICMP_UGT,
568                   llvm::CmpInst::FCMP_OGT);
569  }
570
571  llvm::Constant *VisitBinGE(const BinaryOperator *E) {
572    return EmitCmp(E, llvm::CmpInst::ICMP_SGE, llvm::CmpInst::ICMP_SGE,
573                   llvm::CmpInst::FCMP_OGE);
574  }
575
576  llvm::Constant *VisitConditionalOperator(const ConditionalOperator *E) {
577    llvm::Constant *Cond = Visit(E->getCond());
578    llvm::Constant *CondVal = EmitConversionToBool(Cond, E->getType());
579    llvm::ConstantInt *CondValInt = dyn_cast<llvm::ConstantInt>(CondVal);
580    if (!CondValInt) {
581      CGM.WarnUnsupported(E, "constant expression");
582      return llvm::Constant::getNullValue(ConvertType(E->getType()));
583    }
584    if (CondValInt->isOne()) {
585      if (E->getLHS())
586        return Visit(E->getLHS());
587      return Cond;
588    }
589
590    return Visit(E->getRHS());
591  }
592
593  // Utility methods
594  const llvm::Type *ConvertType(QualType T) {
595    return CGM.getTypes().ConvertType(T);
596  }
597
598  llvm::Constant *EmitConversionToBool(llvm::Constant *Src, QualType SrcType) {
599    assert(SrcType->isCanonical() && "EmitConversion strips typedefs");
600
601    if (SrcType->isRealFloatingType()) {
602      // Compare against 0.0 for fp scalars.
603      llvm::Constant *Zero = llvm::Constant::getNullValue(Src->getType());
604      return llvm::ConstantExpr::getFCmp(llvm::FCmpInst::FCMP_UNE, Src, Zero);
605    }
606
607    assert((SrcType->isIntegerType() || SrcType->isPointerType()) &&
608           "Unknown scalar type to convert");
609
610    // Compare against an integer or pointer null.
611    llvm::Constant *Zero = llvm::Constant::getNullValue(Src->getType());
612    return llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_NE, Src, Zero);
613  }
614
615  llvm::Constant *EmitConversion(llvm::Constant *Src, QualType SrcType,
616                                 QualType DstType) {
617    SrcType = SrcType.getCanonicalType();
618    DstType = DstType.getCanonicalType();
619    if (SrcType == DstType) return Src;
620
621    // Handle conversions to bool first, they are special: comparisons against 0.
622    if (DstType->isBooleanType())
623      return EmitConversionToBool(Src, SrcType);
624
625    const llvm::Type *DstTy = ConvertType(DstType);
626
627    // Ignore conversions like int -> uint.
628    if (Src->getType() == DstTy)
629      return Src;
630
631    // Handle pointer conversions next: pointers can only be converted to/from
632    // other pointers and integers.
633    if (isa<PointerType>(DstType)) {
634      // The source value may be an integer, or a pointer.
635      if (isa<llvm::PointerType>(Src->getType()))
636        return llvm::ConstantExpr::getBitCast(Src, DstTy);
637      assert(SrcType->isIntegerType() &&"Not ptr->ptr or int->ptr conversion?");
638      return llvm::ConstantExpr::getIntToPtr(Src, DstTy);
639    }
640
641    if (isa<PointerType>(SrcType)) {
642      // Must be an ptr to int cast.
643      assert(isa<llvm::IntegerType>(DstTy) && "not ptr->int?");
644      return llvm::ConstantExpr::getPtrToInt(Src, DstTy);
645    }
646
647    // A scalar source can be splatted to a vector of the same element type
648    if (isa<llvm::VectorType>(DstTy) && !isa<VectorType>(SrcType)) {
649      const llvm::VectorType *VT = cast<llvm::VectorType>(DstTy);
650      assert((VT->getElementType() == Src->getType()) &&
651             "Vector element type must match scalar type to splat.");
652      unsigned NumElements = DstType->getAsVectorType()->getNumElements();
653      llvm::SmallVector<llvm::Constant*, 16> Elements;
654      for (unsigned i = 0; i < NumElements; i++)
655        Elements.push_back(Src);
656
657      return llvm::ConstantVector::get(&Elements[0], NumElements);
658    }
659
660    if (isa<llvm::VectorType>(Src->getType()) ||
661        isa<llvm::VectorType>(DstTy)) {
662      return llvm::ConstantExpr::getBitCast(Src, DstTy);
663    }
664
665    // Finally, we have the arithmetic types: real int/float.
666    if (isa<llvm::IntegerType>(Src->getType())) {
667      bool InputSigned = SrcType->isSignedIntegerType();
668      if (isa<llvm::IntegerType>(DstTy))
669        return llvm::ConstantExpr::getIntegerCast(Src, DstTy, InputSigned);
670      else if (InputSigned)
671        return llvm::ConstantExpr::getSIToFP(Src, DstTy);
672      else
673        return llvm::ConstantExpr::getUIToFP(Src, DstTy);
674    }
675
676    assert(Src->getType()->isFloatingPoint() && "Unknown real conversion");
677    if (isa<llvm::IntegerType>(DstTy)) {
678      if (DstType->isSignedIntegerType())
679        return llvm::ConstantExpr::getFPToSI(Src, DstTy);
680      else
681        return llvm::ConstantExpr::getFPToUI(Src, DstTy);
682    }
683
684    assert(DstTy->isFloatingPoint() && "Unknown real conversion");
685    if (DstTy->getTypeID() < Src->getType()->getTypeID())
686      return llvm::ConstantExpr::getFPTrunc(Src, DstTy);
687    else
688      return llvm::ConstantExpr::getFPExtend(Src, DstTy);
689  }
690
691  llvm::Constant *EmitSizeAlignOf(QualType TypeToSize,
692                                  QualType RetType, bool isSizeOf) {
693    std::pair<uint64_t, unsigned> Info =
694      CGM.getContext().getTypeInfo(TypeToSize);
695
696    uint64_t Val = isSizeOf ? Info.first : Info.second;
697    Val /= 8;  // Return size in bytes, not bits.
698
699    assert(RetType->isIntegerType() && "Result type must be an integer!");
700
701    uint32_t ResultWidth =
702      static_cast<uint32_t>(CGM.getContext().getTypeSize(RetType));
703    return llvm::ConstantInt::get(llvm::APInt(ResultWidth, Val));
704  }
705
706  llvm::Constant *EmitLValue(Expr *E) {
707    switch (E->getStmtClass()) {
708    default: break;
709    case Expr::ParenExprClass:
710      // Elide parenthesis
711      return EmitLValue(cast<ParenExpr>(E)->getSubExpr());
712    case Expr::CompoundLiteralExprClass: {
713      // Note that due to the nature of compound literals, this is guaranteed
714      // to be the only use of the variable, so we just generate it here.
715      CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
716      llvm::Constant* C = Visit(CLE->getInitializer());
717      C = new llvm::GlobalVariable(C->getType(),E->getType().isConstQualified(),
718                                   llvm::GlobalValue::InternalLinkage,
719                                   C, ".compoundliteral", &CGM.getModule());
720      return C;
721    }
722    case Expr::DeclRefExprClass: {
723      ValueDecl *Decl = cast<DeclRefExpr>(E)->getDecl();
724      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
725        return CGM.GetAddrOfFunctionDecl(FD, false);
726      if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
727        if (VD->isFileVarDecl())
728          return CGM.GetAddrOfGlobalVar(VD, false);
729        else if (VD->isBlockVarDecl()) {
730          assert(CGF && "Can't access static local vars without CGF");
731          return CGF->GetAddrOfStaticLocalVar(VD);
732        }
733      }
734      break;
735    }
736    case Expr::MemberExprClass: {
737      MemberExpr* ME = cast<MemberExpr>(E);
738      llvm::Constant *Base;
739      if (ME->isArrow())
740        Base = Visit(ME->getBase());
741      else
742        Base = EmitLValue(ME->getBase());
743
744      unsigned FieldNumber = CGM.getTypes().getLLVMFieldNo(ME->getMemberDecl());
745      llvm::Constant *Zero = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
746      llvm::Constant *Idx = llvm::ConstantInt::get(llvm::Type::Int32Ty,
747                                                   FieldNumber);
748      llvm::Value *Ops[] = {Zero, Idx};
749      return llvm::ConstantExpr::getGetElementPtr(Base, Ops, 2);
750    }
751    case Expr::ArraySubscriptExprClass: {
752      ArraySubscriptExpr* ASExpr = cast<ArraySubscriptExpr>(E);
753      llvm::Constant *Base = Visit(ASExpr->getBase());
754      llvm::Constant *Index = Visit(ASExpr->getIdx());
755      assert(!ASExpr->getBase()->getType()->isVectorType() &&
756             "Taking the address of a vector component is illegal!");
757      return llvm::ConstantExpr::getGetElementPtr(Base, &Index, 1);
758    }
759    case Expr::StringLiteralClass: {
760      StringLiteral *String = cast<StringLiteral>(E);
761      assert(!String->isWide() && "Cannot codegen wide strings yet");
762      const char *StrData = String->getStrData();
763      unsigned Len = String->getByteLength();
764
765      return CGM.GetAddrOfConstantString(std::string(StrData, StrData + Len));
766    }
767    case Expr::UnaryOperatorClass: {
768      UnaryOperator *Exp = cast<UnaryOperator>(E);
769      switch (Exp->getOpcode()) {
770      default: break;
771      case UnaryOperator::Extension:
772        // Extension is just a wrapper for expressions
773        return EmitLValue(Exp->getSubExpr());
774      case UnaryOperator::Real:
775      case UnaryOperator::Imag: {
776        // The address of __real or __imag is just a GEP off the address
777        // of the internal expression
778        llvm::Constant* C = EmitLValue(Exp->getSubExpr());
779        llvm::Constant *Zero = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
780        llvm::Constant *Idx  = llvm::ConstantInt::get(llvm::Type::Int32Ty,
781                                       Exp->getOpcode() == UnaryOperator::Imag);
782        llvm::Value *Ops[] = {Zero, Idx};
783        return llvm::ConstantExpr::getGetElementPtr(C, Ops, 2);
784      }
785      case UnaryOperator::Deref:
786        // The address of a deref is just the value of the expression
787        return Visit(Exp->getSubExpr());
788      }
789      break;
790    }
791    }
792    CGM.WarnUnsupported(E, "constant l-value expression");
793    llvm::Type *Ty = llvm::PointerType::getUnqual(ConvertType(E->getType()));
794    return llvm::UndefValue::get(Ty);
795  }
796
797};
798
799}  // end anonymous namespace.
800
801
802llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
803                                                CodeGenFunction *CGF)
804{
805  QualType type = E->getType().getCanonicalType();
806
807  if (type->isIntegerType()) {
808    llvm::APSInt Value(static_cast<uint32_t>(Context.getTypeSize(type)));
809    if (E->isIntegerConstantExpr(Value, Context)) {
810      return llvm::ConstantInt::get(Value);
811    }
812  }
813
814  llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
815  if (C->getType() == llvm::Type::Int1Ty) {
816    const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
817    C = llvm::ConstantExpr::getZExt(C, BoolTy);
818  }
819  return C;
820}
821