CGExprConstant.cpp revision 7267f7832e5f0c7f951765e201c5a2650eb1637b 
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/ASTContext.h"
18#include "clang/AST/StmtVisitor.h"
19#include "llvm/Constants.h"
20#include "llvm/Function.h"
21#include "llvm/GlobalVariable.h"
22#include "llvm/Support/Compiler.h"
23#include "llvm/Target/TargetData.h"
24using namespace clang;
25using namespace CodeGen;
26
27namespace  {
28class VISIBILITY_HIDDEN ConstExprEmitter :
29  public StmtVisitor<ConstExprEmitter, llvm::Constant*> {
30  CodeGenModule &CGM;
31  CodeGenFunction *CGF;
32public:
33  ConstExprEmitter(CodeGenModule &cgm, CodeGenFunction *cgf)
34    : CGM(cgm), CGF(cgf) {
35  }
36
37  //===--------------------------------------------------------------------===//
38  //                            Visitor Methods
39  //===--------------------------------------------------------------------===//
40
41  llvm::Constant *VisitStmt(Stmt *S) {
42    CGM.ErrorUnsupported(S, "constant expression");
43    QualType T = cast<Expr>(S)->getType();
44    return llvm::UndefValue::get(CGM.getTypes().ConvertType(T));
45  }
46
47  llvm::Constant *VisitParenExpr(ParenExpr *PE) {
48    return Visit(PE->getSubExpr());
49  }
50
51  // Leaves
52  llvm::Constant *VisitIntegerLiteral(const IntegerLiteral *E) {
53    return llvm::ConstantInt::get(E->getValue());
54  }
55  llvm::Constant *VisitFloatingLiteral(const FloatingLiteral *E) {
56    return llvm::ConstantFP::get(E->getValue());
57  }
58  llvm::Constant *VisitCharacterLiteral(const CharacterLiteral *E) {
59    return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
60  }
61  llvm::Constant *VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr *E) {
62    return llvm::ConstantInt::get(ConvertType(E->getType()), E->getValue());
63  }
64  llvm::Constant *VisitCXXZeroInitValueExpr(const CXXZeroInitValueExpr *E) {
65    return llvm::Constant::getNullValue(ConvertType(E->getType()));
66  }
67  llvm::Constant *VisitObjCStringLiteral(const ObjCStringLiteral *E) {
68    std::string S(E->getString()->getStrData(),
69                  E->getString()->getByteLength());
70    llvm::Constant *C = CGM.getObjCRuntime().GenerateConstantString(S);
71    return llvm::ConstantExpr::getBitCast(C, ConvertType(E->getType()));
72  }
73
74  llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
75    return Visit(E->getInitializer());
76  }
77
78  llvm::Constant *VisitCastExpr(CastExpr* E) {
79    llvm::Constant *C = Visit(E->getSubExpr());
80
81    return EmitConversion(C, E->getSubExpr()->getType(), E->getType());
82  }
83
84  llvm::Constant *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
85    return Visit(DAE->getExpr());
86  }
87
88  llvm::Constant *EmitArrayInitialization(InitListExpr *ILE) {
89    std::vector<llvm::Constant*> Elts;
90    const llvm::ArrayType *AType =
91        cast<llvm::ArrayType>(ConvertType(ILE->getType()));
92    unsigned NumInitElements = ILE->getNumInits();
93    // FIXME: Check for wide strings
94    if (NumInitElements > 0 && isa<StringLiteral>(ILE->getInit(0)) &&
95        ILE->getType()->getArrayElementTypeNoTypeQual()->isCharType())
96      return Visit(ILE->getInit(0));
97    const llvm::Type *ElemTy = AType->getElementType();
98    unsigned NumElements = AType->getNumElements();
99
100    // Initialising an array requires us to automatically
101    // initialise any elements that have not been initialised explicitly
102    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
103
104    // Copy initializer elements.
105    unsigned i = 0;
106    bool RewriteType = false;
107    for (; i < NumInitableElts; ++i) {
108      llvm::Constant *C = Visit(ILE->getInit(i));
109      RewriteType |= (C->getType() != ElemTy);
110      Elts.push_back(C);
111    }
112
113    // Initialize remaining array elements.
114    for (; i < NumElements; ++i)
115      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
116
117    if (RewriteType) {
118      // FIXME: Try to avoid packing the array
119      std::vector<const llvm::Type*> Types;
120      for (unsigned i = 0; i < Elts.size(); ++i)
121        Types.push_back(Elts[i]->getType());
122      const llvm::StructType *SType = llvm::StructType::get(Types, true);
123      return llvm::ConstantStruct::get(SType, Elts);
124    }
125
126    return llvm::ConstantArray::get(AType, Elts);
127  }
128
129  void InsertBitfieldIntoStruct(std::vector<llvm::Constant*>& Elts,
130                                FieldDecl* Field, Expr* E) {
131    // Calculate the value to insert
132    llvm::Constant *C = Visit(E);
133    llvm::ConstantInt *CI = dyn_cast<llvm::ConstantInt>(C);
134    if (!CI) {
135      CGM.ErrorUnsupported(E, "bitfield initialization");
136      return;
137    }
138    llvm::APInt V = CI->getValue();
139
140    // Calculate information about the relevant field
141    const llvm::Type* Ty = CI->getType();
142    const llvm::TargetData &TD = CGM.getTypes().getTargetData();
143    unsigned size = TD.getTypeStoreSizeInBits(Ty);
144    unsigned fieldOffset = CGM.getTypes().getLLVMFieldNo(Field) * size;
145    CodeGenTypes::BitFieldInfo bitFieldInfo =
146        CGM.getTypes().getBitFieldInfo(Field);
147    fieldOffset += bitFieldInfo.Begin;
148
149    // Find where to start the insertion
150    // FIXME: This is O(n^2) in the number of bit-fields!
151    // FIXME: This won't work if the struct isn't completely packed!
152    unsigned offset = 0, i = 0;
153    while (offset < (fieldOffset & -8))
154      offset += TD.getTypeStoreSizeInBits(Elts[i++]->getType());
155
156    // Advance over 0 sized elements (must terminate in bounds since
157    // the bitfield must have a size).
158    while (TD.getTypeStoreSizeInBits(Elts[i]->getType()) == 0)
159      ++i;
160
161    // Promote the size of V if necessary
162    // FIXME: This should never occur, but currently it can because
163    // initializer constants are cast to bool, and because clang is
164    // not enforcing bitfield width limits.
165    if (bitFieldInfo.Size > V.getBitWidth())
166      V.zext(bitFieldInfo.Size);
167
168    // Insert the bits into the struct
169    // FIXME: This algorthm is only correct on X86!
170    // FIXME: THis algorthm assumes bit-fields only have byte-size elements!
171    unsigned bitsToInsert = bitFieldInfo.Size;
172    unsigned curBits = std::min(8 - (fieldOffset & 7), bitsToInsert);
173    unsigned byte = V.getLoBits(curBits).getZExtValue() << (fieldOffset & 7);
174    do {
175      llvm::Constant* byteC = llvm::ConstantInt::get(llvm::Type::Int8Ty, byte);
176      Elts[i] = llvm::ConstantExpr::getOr(Elts[i], byteC);
177      ++i;
178      V = V.lshr(curBits);
179      bitsToInsert -= curBits;
180
181      if (!bitsToInsert)
182        break;
183
184      curBits = bitsToInsert > 8 ? 8 : bitsToInsert;
185      byte = V.getLoBits(curBits).getZExtValue();
186    } while (true);
187  }
188
189  llvm::Constant *EmitStructInitialization(InitListExpr *ILE) {
190    const llvm::StructType *SType =
191        cast<llvm::StructType>(ConvertType(ILE->getType()));
192    RecordDecl *RD = ILE->getType()->getAsRecordType()->getDecl();
193    std::vector<llvm::Constant*> Elts;
194
195    // Initialize the whole structure to zero.
196    for (unsigned i = 0; i < SType->getNumElements(); ++i) {
197      const llvm::Type *FieldTy = SType->getElementType(i);
198      Elts.push_back(llvm::Constant::getNullValue(FieldTy));
199    }
200
201    // Copy initializer elements. Skip padding fields.
202    unsigned EltNo = 0;  // Element no in ILE
203    int FieldNo = 0; // Field no in RecordDecl
204    bool RewriteType = false;
205    while (EltNo < ILE->getNumInits() && FieldNo < RD->getNumMembers()) {
206      FieldDecl* curField = RD->getMember(FieldNo);
207      FieldNo++;
208      if (!curField->getIdentifier())
209        continue;
210
211      if (curField->isBitField()) {
212        InsertBitfieldIntoStruct(Elts, curField, ILE->getInit(EltNo));
213      } else {
214        unsigned FieldNo = CGM.getTypes().getLLVMFieldNo(curField);
215        llvm::Constant* C = Visit(ILE->getInit(EltNo));
216        RewriteType |= (C->getType() != Elts[FieldNo]->getType());
217        Elts[FieldNo] = C;
218      }
219      EltNo++;
220    }
221
222    if (RewriteType) {
223      // FIXME: Make this work for non-packed structs
224      assert(SType->isPacked() && "Cannot recreate unpacked structs");
225      std::vector<const llvm::Type*> Types;
226      for (unsigned i = 0; i < Elts.size(); ++i)
227        Types.push_back(Elts[i]->getType());
228      SType = llvm::StructType::get(Types, true);
229    }
230
231    return llvm::ConstantStruct::get(SType, Elts);
232  }
233
234  llvm::Constant *EmitUnionInitialization(InitListExpr *ILE) {
235    RecordDecl *RD = ILE->getType()->getAsRecordType()->getDecl();
236    const llvm::Type *Ty = ConvertType(ILE->getType());
237
238    // Find the field decl we're initializing, if any
239    int FieldNo = 0; // Field no in RecordDecl
240    FieldDecl* curField = 0;
241    while (FieldNo < RD->getNumMembers()) {
242      curField = RD->getMember(FieldNo);
243      FieldNo++;
244      if (curField->getIdentifier())
245        break;
246    }
247
248    if (!curField || !curField->getIdentifier() || ILE->getNumInits() == 0)
249      return llvm::Constant::getNullValue(Ty);
250
251    if (curField->isBitField()) {
252      // Create a dummy struct for bit-field insertion
253      unsigned NumElts = CGM.getTargetData().getABITypeSize(Ty) / 8;
254      llvm::Constant* NV = llvm::Constant::getNullValue(llvm::Type::Int8Ty);
255      std::vector<llvm::Constant*> Elts(NumElts, NV);
256
257      InsertBitfieldIntoStruct(Elts, curField, ILE->getInit(0));
258      const llvm::ArrayType *RetTy =
259          llvm::ArrayType::get(NV->getType(), NumElts);
260      return llvm::ConstantArray::get(RetTy, Elts);
261    }
262
263    llvm::Constant *C = Visit(ILE->getInit(0));
264
265    // Build a struct with the union sub-element as the first member,
266    // and padded to the appropriate size
267    std::vector<llvm::Constant*> Elts;
268    std::vector<const llvm::Type*> Types;
269    Elts.push_back(C);
270    Types.push_back(C->getType());
271    unsigned CurSize = CGM.getTargetData().getTypeStoreSize(C->getType());
272    unsigned TotalSize = CGM.getTargetData().getTypeStoreSize(Ty);
273    while (CurSize < TotalSize) {
274      Elts.push_back(llvm::Constant::getNullValue(llvm::Type::Int8Ty));
275      Types.push_back(llvm::Type::Int8Ty);
276      CurSize++;
277    }
278
279    // This always generates a packed struct
280    // FIXME: Try to generate an unpacked struct when we can
281    llvm::StructType* STy = llvm::StructType::get(Types, true);
282    return llvm::ConstantStruct::get(STy, Elts);
283  }
284
285  llvm::Constant *EmitVectorInitialization(InitListExpr *ILE) {
286    const llvm::VectorType *VType =
287        cast<llvm::VectorType>(ConvertType(ILE->getType()));
288    const llvm::Type *ElemTy = VType->getElementType();
289    std::vector<llvm::Constant*> Elts;
290    unsigned NumElements = VType->getNumElements();
291    unsigned NumInitElements = ILE->getNumInits();
292
293    unsigned NumInitableElts = std::min(NumInitElements, NumElements);
294
295    // Copy initializer elements.
296    unsigned i = 0;
297    for (; i < NumInitableElts; ++i) {
298      llvm::Constant *C = Visit(ILE->getInit(i));
299      Elts.push_back(C);
300    }
301
302    for (; i < NumElements; ++i)
303      Elts.push_back(llvm::Constant::getNullValue(ElemTy));
304
305    return llvm::ConstantVector::get(VType, Elts);
306  }
307
308  llvm::Constant *VisitInitListExpr(InitListExpr *ILE) {
309    if (ILE->getType()->isScalarType()) {
310      // We have a scalar in braces. Just use the first element.
311      if (ILE->getNumInits() > 0)
312        return Visit(ILE->getInit(0));
313
314      const llvm::Type* RetTy = CGM.getTypes().ConvertType(ILE->getType());
315      return llvm::Constant::getNullValue(RetTy);
316    }
317
318    if (ILE->getType()->isArrayType())
319      return EmitArrayInitialization(ILE);
320
321    if (ILE->getType()->isStructureType())
322      return EmitStructInitialization(ILE);
323
324    if (ILE->getType()->isUnionType())
325      return EmitUnionInitialization(ILE);
326
327    if (ILE->getType()->isVectorType())
328      return EmitVectorInitialization(ILE);
329
330    assert(0 && "Unable to handle InitListExpr");
331    // Get rid of control reaches end of void function warning.
332    // Not reached.
333    return 0;
334  }
335
336  llvm::Constant *VisitImplicitCastExpr(ImplicitCastExpr *ICExpr) {
337    Expr* SExpr = ICExpr->getSubExpr();
338    QualType SType = SExpr->getType();
339    llvm::Constant *C; // the intermediate expression
340    QualType T;        // the type of the intermediate expression
341    if (SType->isArrayType()) {
342      // Arrays decay to a pointer to the first element
343      // VLAs would require special handling, but they can't occur here
344      C = EmitLValue(SExpr);
345      llvm::Constant *Idx0 = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
346      llvm::Constant *Ops[] = {Idx0, Idx0};
347      C = llvm::ConstantExpr::getGetElementPtr(C, Ops, 2);
348      T = CGM.getContext().getArrayDecayedType(SType);
349    } else if (SType->isFunctionType()) {
350      // Function types decay to a pointer to the function
351      C = EmitLValue(SExpr);
352      T = CGM.getContext().getPointerType(SType);
353    } else {
354      C = Visit(SExpr);
355      T = SType;
356    }
357
358    // Perform the conversion; note that an implicit cast can both promote
359    // and convert an array/function
360    return EmitConversion(C, T, ICExpr->getType());
361  }
362
363  llvm::Constant *VisitStringLiteral(StringLiteral *E) {
364    assert(!E->getType()->isPointerType() && "Strings are always arrays");
365
366    // Otherwise this must be a string initializing an array in a static
367    // initializer.  Don't emit it as the address of the string, emit the string
368    // data itself as an inline array.
369    return llvm::ConstantArray::get(CGM.GetStringForStringLiteral(E), false);
370  }
371
372  llvm::Constant *VisitDeclRefExpr(DeclRefExpr *E) {
373    const ValueDecl *Decl = E->getDecl();
374    if (const EnumConstantDecl *EC = dyn_cast<EnumConstantDecl>(Decl))
375      return llvm::ConstantInt::get(EC->getInitVal());
376    assert(0 && "Unsupported decl ref type!");
377    return 0;
378  }
379
380  llvm::Constant *VisitSizeOfAlignOfTypeExpr(const SizeOfAlignOfTypeExpr *E) {
381    return EmitSizeAlignOf(E->getArgumentType(), E->getType(), E->isSizeOf());
382  }
383
384  llvm::Constant *VisitAddrLabelExpr(const AddrLabelExpr *E) {
385    assert(CGF && "Invalid address of label expression outside function.");
386    llvm::Constant *C =
387      llvm::ConstantInt::get(llvm::Type::Int32Ty,
388                             CGF->GetIDForAddrOfLabel(E->getLabel()));
389    return llvm::ConstantExpr::getIntToPtr(C, ConvertType(E->getType()));
390  }
391
392  // Unary operators
393  llvm::Constant *VisitUnaryPlus(const UnaryOperator *E) {
394    return Visit(E->getSubExpr());
395  }
396  llvm::Constant *VisitUnaryMinus(const UnaryOperator *E) {
397    return llvm::ConstantExpr::getNeg(Visit(E->getSubExpr()));
398  }
399  llvm::Constant *VisitUnaryNot(const UnaryOperator *E) {
400    return llvm::ConstantExpr::getNot(Visit(E->getSubExpr()));
401  }
402  llvm::Constant *VisitUnaryLNot(const UnaryOperator *E) {
403    llvm::Constant *SubExpr = Visit(E->getSubExpr());
404
405    if (E->getSubExpr()->getType()->isRealFloatingType()) {
406      // Compare against 0.0 for fp scalars.
407      llvm::Constant *Zero = llvm::Constant::getNullValue(SubExpr->getType());
408      SubExpr = llvm::ConstantExpr::getFCmp(llvm::FCmpInst::FCMP_UEQ, SubExpr,
409                                            Zero);
410    } else {
411      assert((E->getSubExpr()->getType()->isIntegerType() ||
412              E->getSubExpr()->getType()->isPointerType()) &&
413             "Unknown scalar type to convert");
414      // Compare against an integer or pointer null.
415      llvm::Constant *Zero = llvm::Constant::getNullValue(SubExpr->getType());
416      SubExpr = llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_EQ, SubExpr,
417                                            Zero);
418    }
419
420    return llvm::ConstantExpr::getZExt(SubExpr, ConvertType(E->getType()));
421  }
422  llvm::Constant *VisitUnarySizeOf(const UnaryOperator *E) {
423    return EmitSizeAlignOf(E->getSubExpr()->getType(), E->getType(), true);
424  }
425  llvm::Constant *VisitUnaryAlignOf(const UnaryOperator *E) {
426    return EmitSizeAlignOf(E->getSubExpr()->getType(), E->getType(), false);
427  }
428  llvm::Constant *VisitUnaryAddrOf(const UnaryOperator *E) {
429    return EmitLValue(E->getSubExpr());
430  }
431  llvm::Constant *VisitUnaryOffsetOf(const UnaryOperator *E) {
432    int64_t Val = E->evaluateOffsetOf(CGM.getContext());
433
434    assert(E->getType()->isIntegerType() && "Result type must be an integer!");
435
436    uint32_t ResultWidth =
437      static_cast<uint32_t>(CGM.getContext().getTypeSize(E->getType()));
438    return llvm::ConstantInt::get(llvm::APInt(ResultWidth, Val));
439  }
440
441  llvm::Constant *VisitUnaryExtension(const UnaryOperator *E) {
442    return Visit(E->getSubExpr());
443  }
444
445  // Binary operators
446  llvm::Constant *VisitBinOr(const BinaryOperator *E) {
447    llvm::Constant *LHS = Visit(E->getLHS());
448    llvm::Constant *RHS = Visit(E->getRHS());
449
450    return llvm::ConstantExpr::getOr(LHS, RHS);
451  }
452  llvm::Constant *VisitBinSub(const BinaryOperator *E) {
453    llvm::Constant *LHS = Visit(E->getLHS());
454    llvm::Constant *RHS = Visit(E->getRHS());
455
456    if (!isa<llvm::PointerType>(RHS->getType())) {
457      // pointer - int
458      if (isa<llvm::PointerType>(LHS->getType())) {
459        llvm::Constant *Idx = llvm::ConstantExpr::getNeg(RHS);
460
461        return llvm::ConstantExpr::getGetElementPtr(LHS, &Idx, 1);
462      }
463
464      // int - int
465      return llvm::ConstantExpr::getSub(LHS, RHS);
466    }
467
468    assert(isa<llvm::PointerType>(LHS->getType()));
469
470    const llvm::Type *ResultType = ConvertType(E->getType());
471    const QualType Type = E->getLHS()->getType();
472    const QualType ElementType = Type->getAsPointerType()->getPointeeType();
473
474    LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType);
475    RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType);
476
477    llvm::Constant *sub = llvm::ConstantExpr::getSub(LHS, RHS);
478    llvm::Constant *size = EmitSizeAlignOf(ElementType, E->getType(), true);
479    return llvm::ConstantExpr::getSDiv(sub, size);
480  }
481
482  llvm::Constant *VisitBinShl(const BinaryOperator *E) {
483    llvm::Constant *LHS = Visit(E->getLHS());
484    llvm::Constant *RHS = Visit(E->getRHS());
485
486    // LLVM requires the LHS and RHS to be the same type: promote or truncate the
487    // RHS to the same size as the LHS.
488    if (LHS->getType() != RHS->getType())
489      RHS = llvm::ConstantExpr::getIntegerCast(RHS, LHS->getType(), false);
490
491    return llvm::ConstantExpr::getShl(LHS, RHS);
492  }
493
494  llvm::Constant *VisitBinMul(const BinaryOperator *E) {
495    llvm::Constant *LHS = Visit(E->getLHS());
496    llvm::Constant *RHS = Visit(E->getRHS());
497
498    return llvm::ConstantExpr::getMul(LHS, RHS);
499  }
500
501  llvm::Constant *VisitBinDiv(const BinaryOperator *E) {
502    llvm::Constant *LHS = Visit(E->getLHS());
503    llvm::Constant *RHS = Visit(E->getRHS());
504
505    if (LHS->getType()->isFPOrFPVector())
506      return llvm::ConstantExpr::getFDiv(LHS, RHS);
507    else if (E->getType()->isUnsignedIntegerType())
508      return llvm::ConstantExpr::getUDiv(LHS, RHS);
509    else
510      return llvm::ConstantExpr::getSDiv(LHS, RHS);
511  }
512
513  llvm::Constant *VisitBinAdd(const BinaryOperator *E) {
514    llvm::Constant *LHS = Visit(E->getLHS());
515    llvm::Constant *RHS = Visit(E->getRHS());
516
517    if (!E->getType()->isPointerType())
518      return llvm::ConstantExpr::getAdd(LHS, RHS);
519
520    llvm::Constant *Ptr, *Idx;
521    if (isa<llvm::PointerType>(LHS->getType())) { // pointer + int
522      Ptr = LHS;
523      Idx = RHS;
524    } else { // int + pointer
525      Ptr = RHS;
526      Idx = LHS;
527    }
528
529    return llvm::ConstantExpr::getGetElementPtr(Ptr, &Idx, 1);
530  }
531
532  llvm::Constant *VisitBinAnd(const BinaryOperator *E) {
533    llvm::Constant *LHS = Visit(E->getLHS());
534    llvm::Constant *RHS = Visit(E->getRHS());
535
536    return llvm::ConstantExpr::getAnd(LHS, RHS);
537  }
538
539  llvm::Constant *EmitCmp(const BinaryOperator *E,
540                          llvm::CmpInst::Predicate SignedPred,
541                          llvm::CmpInst::Predicate UnsignedPred,
542                          llvm::CmpInst::Predicate FloatPred) {
543    llvm::Constant *LHS = Visit(E->getLHS());
544    llvm::Constant *RHS = Visit(E->getRHS());
545    llvm::Constant *Result;
546    if (LHS->getType()->isInteger() ||
547        isa<llvm::PointerType>(LHS->getType())) {
548      if (E->getLHS()->getType()->isSignedIntegerType())
549        Result = llvm::ConstantExpr::getICmp(SignedPred, LHS, RHS);
550      else
551        Result = llvm::ConstantExpr::getICmp(UnsignedPred, LHS, RHS);
552    } else if (LHS->getType()->isFloatingPoint()) {
553      Result = llvm::ConstantExpr::getFCmp(FloatPred, LHS, RHS);
554    } else {
555      CGM.ErrorUnsupported(E, "constant expression");
556      Result = llvm::ConstantInt::getFalse();
557    }
558
559    const llvm::Type* ResultType = ConvertType(E->getType());
560    return llvm::ConstantExpr::getZExtOrBitCast(Result, ResultType);
561  }
562
563  llvm::Constant *VisitBinNE(const BinaryOperator *E) {
564    return EmitCmp(E, llvm::CmpInst::ICMP_NE, llvm::CmpInst::ICMP_NE,
565                   llvm::CmpInst::FCMP_ONE);
566  }
567
568  llvm::Constant *VisitBinEQ(const BinaryOperator *E) {
569    return EmitCmp(E, llvm::CmpInst::ICMP_EQ, llvm::CmpInst::ICMP_EQ,
570                   llvm::CmpInst::FCMP_OEQ);
571  }
572
573  llvm::Constant *VisitBinLT(const BinaryOperator *E) {
574    return EmitCmp(E, llvm::CmpInst::ICMP_SLT, llvm::CmpInst::ICMP_ULT,
575                   llvm::CmpInst::FCMP_OLT);
576  }
577
578  llvm::Constant *VisitBinLE(const BinaryOperator *E) {
579    return EmitCmp(E, llvm::CmpInst::ICMP_SLE, llvm::CmpInst::ICMP_ULE,
580                   llvm::CmpInst::FCMP_OLE);
581  }
582
583  llvm::Constant *VisitBinGT(const BinaryOperator *E) {
584    return EmitCmp(E, llvm::CmpInst::ICMP_SGT, llvm::CmpInst::ICMP_UGT,
585                   llvm::CmpInst::FCMP_OGT);
586  }
587
588  llvm::Constant *VisitBinGE(const BinaryOperator *E) {
589    return EmitCmp(E, llvm::CmpInst::ICMP_SGE, llvm::CmpInst::ICMP_SGE,
590                   llvm::CmpInst::FCMP_OGE);
591  }
592
593  llvm::Constant *VisitConditionalOperator(const ConditionalOperator *E) {
594    llvm::Constant *Cond = Visit(E->getCond());
595    llvm::Constant *CondVal = EmitConversionToBool(Cond, E->getType());
596    llvm::ConstantInt *CondValInt = dyn_cast<llvm::ConstantInt>(CondVal);
597    if (!CondValInt) {
598      CGM.ErrorUnsupported(E, "constant expression");
599      return llvm::Constant::getNullValue(ConvertType(E->getType()));
600    }
601    if (CondValInt->isOne()) {
602      if (E->getLHS())
603        return Visit(E->getLHS());
604      return Cond;
605    }
606
607    return Visit(E->getRHS());
608  }
609
610  // Utility methods
611  const llvm::Type *ConvertType(QualType T) {
612    return CGM.getTypes().ConvertType(T);
613  }
614
615  llvm::Constant *EmitConversionToBool(llvm::Constant *Src, QualType SrcType) {
616    assert(SrcType->isCanonical() && "EmitConversion strips typedefs");
617
618    if (SrcType->isRealFloatingType()) {
619      // Compare against 0.0 for fp scalars.
620      llvm::Constant *Zero = llvm::Constant::getNullValue(Src->getType());
621      return llvm::ConstantExpr::getFCmp(llvm::FCmpInst::FCMP_UNE, Src, Zero);
622    }
623
624    assert((SrcType->isIntegerType() || SrcType->isPointerType()) &&
625           "Unknown scalar type to convert");
626
627    // Compare against an integer or pointer null.
628    llvm::Constant *Zero = llvm::Constant::getNullValue(Src->getType());
629    return llvm::ConstantExpr::getICmp(llvm::ICmpInst::ICMP_NE, Src, Zero);
630  }
631
632  llvm::Constant *EmitConversion(llvm::Constant *Src, QualType SrcType,
633                                 QualType DstType) {
634    SrcType = CGM.getContext().getCanonicalType(SrcType);
635    DstType = CGM.getContext().getCanonicalType(DstType);
636    if (SrcType == DstType) return Src;
637
638    // Handle conversions to bool first, they are special: comparisons against 0.
639    if (DstType->isBooleanType())
640      return EmitConversionToBool(Src, SrcType);
641
642    const llvm::Type *DstTy = ConvertType(DstType);
643
644    // Ignore conversions like int -> uint.
645    if (Src->getType() == DstTy)
646      return Src;
647
648    // Handle pointer conversions next: pointers can only be converted to/from
649    // other pointers and integers.
650    if (isa<llvm::PointerType>(DstTy)) {
651      // The source value may be an integer, or a pointer.
652      if (isa<llvm::PointerType>(Src->getType()))
653        return llvm::ConstantExpr::getBitCast(Src, DstTy);
654      assert(SrcType->isIntegerType() &&"Not ptr->ptr or int->ptr conversion?");
655      return llvm::ConstantExpr::getIntToPtr(Src, DstTy);
656    }
657
658    if (isa<llvm::PointerType>(Src->getType())) {
659      // Must be an ptr to int cast.
660      assert(isa<llvm::IntegerType>(DstTy) && "not ptr->int?");
661      return llvm::ConstantExpr::getPtrToInt(Src, DstTy);
662    }
663
664    // A scalar source can be splatted to a vector of the same element type
665    if (isa<llvm::VectorType>(DstTy) && !isa<VectorType>(SrcType)) {
666      const llvm::VectorType *VT = cast<llvm::VectorType>(DstTy);
667      assert((VT->getElementType() == Src->getType()) &&
668             "Vector element type must match scalar type to splat.");
669      unsigned NumElements = DstType->getAsVectorType()->getNumElements();
670      llvm::SmallVector<llvm::Constant*, 16> Elements;
671      for (unsigned i = 0; i < NumElements; i++)
672        Elements.push_back(Src);
673
674      return llvm::ConstantVector::get(&Elements[0], NumElements);
675    }
676
677    if (isa<llvm::VectorType>(Src->getType()) ||
678        isa<llvm::VectorType>(DstTy)) {
679      return llvm::ConstantExpr::getBitCast(Src, DstTy);
680    }
681
682    // Finally, we have the arithmetic types: real int/float.
683    if (isa<llvm::IntegerType>(Src->getType())) {
684      bool InputSigned = SrcType->isSignedIntegerType();
685      if (isa<llvm::IntegerType>(DstTy))
686        return llvm::ConstantExpr::getIntegerCast(Src, DstTy, InputSigned);
687      else if (InputSigned)
688        return llvm::ConstantExpr::getSIToFP(Src, DstTy);
689      else
690        return llvm::ConstantExpr::getUIToFP(Src, DstTy);
691    }
692
693    assert(Src->getType()->isFloatingPoint() && "Unknown real conversion");
694    if (isa<llvm::IntegerType>(DstTy)) {
695      if (DstType->isSignedIntegerType())
696        return llvm::ConstantExpr::getFPToSI(Src, DstTy);
697      else
698        return llvm::ConstantExpr::getFPToUI(Src, DstTy);
699    }
700
701    assert(DstTy->isFloatingPoint() && "Unknown real conversion");
702    if (DstTy->getTypeID() < Src->getType()->getTypeID())
703      return llvm::ConstantExpr::getFPTrunc(Src, DstTy);
704    else
705      return llvm::ConstantExpr::getFPExtend(Src, DstTy);
706  }
707
708  llvm::Constant *EmitSizeAlignOf(QualType TypeToSize,
709                                  QualType RetType, bool isSizeOf) {
710    std::pair<uint64_t, unsigned> Info =
711      CGM.getContext().getTypeInfo(TypeToSize);
712
713    uint64_t Val = isSizeOf ? Info.first : Info.second;
714    Val /= 8;  // Return size in bytes, not bits.
715
716    assert(RetType->isIntegerType() && "Result type must be an integer!");
717
718    uint32_t ResultWidth =
719      static_cast<uint32_t>(CGM.getContext().getTypeSize(RetType));
720    return llvm::ConstantInt::get(llvm::APInt(ResultWidth, Val));
721  }
722
723  llvm::Constant *EmitLValue(Expr *E) {
724    switch (E->getStmtClass()) {
725    default: break;
726    case Expr::ParenExprClass:
727      // Elide parenthesis
728      return EmitLValue(cast<ParenExpr>(E)->getSubExpr());
729    case Expr::CompoundLiteralExprClass: {
730      // Note that due to the nature of compound literals, this is guaranteed
731      // to be the only use of the variable, so we just generate it here.
732      CompoundLiteralExpr *CLE = cast<CompoundLiteralExpr>(E);
733      llvm::Constant* C = Visit(CLE->getInitializer());
734      C = new llvm::GlobalVariable(C->getType(),E->getType().isConstQualified(),
735                                   llvm::GlobalValue::InternalLinkage,
736                                   C, ".compoundliteral", &CGM.getModule());
737      return C;
738    }
739    case Expr::DeclRefExprClass: {
740      ValueDecl *Decl = cast<DeclRefExpr>(E)->getDecl();
741      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(Decl))
742        return CGM.GetAddrOfFunction(FD);
743      if (const VarDecl* VD = dyn_cast<VarDecl>(Decl)) {
744        if (VD->isFileVarDecl())
745          return CGM.GetAddrOfGlobalVar(VD);
746        else if (VD->isBlockVarDecl()) {
747          assert(CGF && "Can't access static local vars without CGF");
748          return CGF->GetAddrOfStaticLocalVar(VD);
749        }
750      }
751      break;
752    }
753    case Expr::MemberExprClass: {
754      MemberExpr* ME = cast<MemberExpr>(E);
755      llvm::Constant *Base;
756      if (ME->isArrow())
757        Base = Visit(ME->getBase());
758      else
759        Base = EmitLValue(ME->getBase());
760
761      unsigned FieldNumber = CGM.getTypes().getLLVMFieldNo(ME->getMemberDecl());
762      llvm::Constant *Zero = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
763      llvm::Constant *Idx = llvm::ConstantInt::get(llvm::Type::Int32Ty,
764                                                   FieldNumber);
765      llvm::Value *Ops[] = {Zero, Idx};
766      return llvm::ConstantExpr::getGetElementPtr(Base, Ops, 2);
767    }
768    case Expr::ArraySubscriptExprClass: {
769      ArraySubscriptExpr* ASExpr = cast<ArraySubscriptExpr>(E);
770      llvm::Constant *Base = Visit(ASExpr->getBase());
771      llvm::Constant *Index = Visit(ASExpr->getIdx());
772      assert(!ASExpr->getBase()->getType()->isVectorType() &&
773             "Taking the address of a vector component is illegal!");
774      return llvm::ConstantExpr::getGetElementPtr(Base, &Index, 1);
775    }
776    case Expr::StringLiteralClass:
777      return CGM.GetAddrOfConstantStringFromLiteral(cast<StringLiteral>(E));
778    case Expr::UnaryOperatorClass: {
779      UnaryOperator *Exp = cast<UnaryOperator>(E);
780      switch (Exp->getOpcode()) {
781      default: break;
782      case UnaryOperator::Extension:
783        // Extension is just a wrapper for expressions
784        return EmitLValue(Exp->getSubExpr());
785      case UnaryOperator::Real:
786      case UnaryOperator::Imag: {
787        // The address of __real or __imag is just a GEP off the address
788        // of the internal expression
789        llvm::Constant* C = EmitLValue(Exp->getSubExpr());
790        llvm::Constant *Zero = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
791        llvm::Constant *Idx  = llvm::ConstantInt::get(llvm::Type::Int32Ty,
792                                       Exp->getOpcode() == UnaryOperator::Imag);
793        llvm::Value *Ops[] = {Zero, Idx};
794        return llvm::ConstantExpr::getGetElementPtr(C, Ops, 2);
795      }
796      case UnaryOperator::Deref:
797        // The address of a deref is just the value of the expression
798        return Visit(Exp->getSubExpr());
799      }
800      break;
801    }
802    }
803    CGM.ErrorUnsupported(E, "constant l-value expression");
804    llvm::Type *Ty = llvm::PointerType::getUnqual(ConvertType(E->getType()));
805    return llvm::UndefValue::get(Ty);
806  }
807
808};
809
810}  // end anonymous namespace.
811
812
813llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
814                                                CodeGenFunction *CGF) {
815  QualType type = Context.getCanonicalType(E->getType());
816
817  if (type->isIntegerType()) {
818    llvm::APSInt Value(static_cast<uint32_t>(Context.getTypeSize(type)));
819    if (E->isIntegerConstantExpr(Value, Context)) {
820      return llvm::ConstantInt::get(Value);
821    }
822  }
823
824  llvm::Constant* C = ConstExprEmitter(*this, CGF).Visit(const_cast<Expr*>(E));
825  if (C->getType() == llvm::Type::Int1Ty) {
826    const llvm::Type *BoolTy = getTypes().ConvertTypeForMem(E->getType());
827    C = llvm::ConstantExpr::getZExt(C, BoolTy);
828  }
829  return C;
830}
831