CGExprAgg.cpp revision 6ab3524f72a6e64aa04973fa9433b5559abb3525 
1//===--- CGExprAgg.cpp - Emit LLVM Code from Aggregate 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 Aggregate Expr nodes as LLVM code.
11//
12//===----------------------------------------------------------------------===//
13
14#include "CodeGenFunction.h"
15#include "CodeGenModule.h"
16#include "clang/AST/ASTContext.h"
17#include "clang/AST/StmtVisitor.h"
18#include "llvm/Constants.h"
19#include "llvm/Function.h"
20#include "llvm/GlobalVariable.h"
21#include "llvm/Support/Compiler.h"
22#include "llvm/Intrinsics.h"
23using namespace clang;
24using namespace CodeGen;
25
26//===----------------------------------------------------------------------===//
27//                        Aggregate Expression Emitter
28//===----------------------------------------------------------------------===//
29
30namespace  {
31class VISIBILITY_HIDDEN AggExprEmitter : public StmtVisitor<AggExprEmitter> {
32  CodeGenFunction &CGF;
33  CGBuilderTy &Builder;
34  llvm::Value *DestPtr;
35  bool VolatileDest;
36public:
37  AggExprEmitter(CodeGenFunction &cgf, llvm::Value *destPtr, bool volatileDest)
38    : CGF(cgf), Builder(CGF.Builder),
39      DestPtr(destPtr), VolatileDest(volatileDest) {
40  }
41
42  //===--------------------------------------------------------------------===//
43  //                               Utilities
44  //===--------------------------------------------------------------------===//
45
46  /// EmitAggLoadOfLValue - Given an expression with aggregate type that
47  /// represents a value lvalue, this method emits the address of the lvalue,
48  /// then loads the result into DestPtr.
49  void EmitAggLoadOfLValue(const Expr *E);
50
51  //===--------------------------------------------------------------------===//
52  //                            Visitor Methods
53  //===--------------------------------------------------------------------===//
54
55  void VisitStmt(Stmt *S) {
56    CGF.ErrorUnsupported(S, "aggregate expression");
57  }
58  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
59  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }
60
61  // l-values.
62  void VisitDeclRefExpr(DeclRefExpr *DRE) { EmitAggLoadOfLValue(DRE); }
63  void VisitMemberExpr(MemberExpr *ME) { EmitAggLoadOfLValue(ME); }
64  void VisitUnaryDeref(UnaryOperator *E) { EmitAggLoadOfLValue(E); }
65  void VisitStringLiteral(StringLiteral *E) { EmitAggLoadOfLValue(E); }
66  void VisitCompoundLiteralExpr(CompoundLiteralExpr *E)
67      { EmitAggLoadOfLValue(E); }
68
69  void VisitArraySubscriptExpr(ArraySubscriptExpr *E) {
70    EmitAggLoadOfLValue(E);
71  }
72
73  void VisitBlockDeclRefExpr(const BlockDeclRefExpr *E)
74      { EmitAggLoadOfLValue(E); }
75
76  // Operators.
77  //  case Expr::UnaryOperatorClass:
78  //  case Expr::CastExprClass:
79  void VisitCStyleCastExpr(CStyleCastExpr *E);
80  void VisitImplicitCastExpr(ImplicitCastExpr *E);
81  void VisitCallExpr(const CallExpr *E);
82  void VisitStmtExpr(const StmtExpr *E);
83  void VisitBinaryOperator(const BinaryOperator *BO);
84  void VisitBinAssign(const BinaryOperator *E);
85  void VisitBinComma(const BinaryOperator *E);
86
87  void VisitObjCMessageExpr(ObjCMessageExpr *E);
88  void VisitObjCIvarRefExpr(ObjCIvarRefExpr *E) {
89    EmitAggLoadOfLValue(E);
90  }
91  void VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E);
92  void VisitObjCKVCRefExpr(ObjCKVCRefExpr *E);
93
94  void VisitConditionalOperator(const ConditionalOperator *CO);
95  void VisitInitListExpr(InitListExpr *E);
96  void VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
97    Visit(DAE->getExpr());
98  }
99  void VisitVAArgExpr(VAArgExpr *E);
100
101  void EmitInitializationToLValue(Expr *E, LValue Address);
102  void EmitNullInitializationToLValue(LValue Address, QualType T);
103  //  case Expr::ChooseExprClass:
104
105};
106}  // end anonymous namespace.
107
108//===----------------------------------------------------------------------===//
109//                                Utilities
110//===----------------------------------------------------------------------===//
111
112/// EmitAggLoadOfLValue - Given an expression with aggregate type that
113/// represents a value lvalue, this method emits the address of the lvalue,
114/// then loads the result into DestPtr.
115void AggExprEmitter::EmitAggLoadOfLValue(const Expr *E) {
116  LValue LV = CGF.EmitLValue(E);
117  assert(LV.isSimple() && "Can't have aggregate bitfield, vector, etc");
118  llvm::Value *SrcPtr = LV.getAddress();
119
120  // If the result is ignored, don't copy from the value.
121  if (DestPtr == 0)
122    // FIXME: If the source is volatile, we must read from it.
123    return;
124
125  CGF.EmitAggregateCopy(DestPtr, SrcPtr, E->getType());
126}
127
128//===----------------------------------------------------------------------===//
129//                            Visitor Methods
130//===----------------------------------------------------------------------===//
131
132void AggExprEmitter::VisitCStyleCastExpr(CStyleCastExpr *E) {
133  // GCC union extension
134  if (E->getType()->isUnionType()) {
135    RecordDecl *SD = E->getType()->getAsRecordType()->getDecl();
136    LValue FieldLoc = CGF.EmitLValueForField(DestPtr,
137                                             *SD->field_begin(CGF.getContext()),
138                                             true, 0);
139    EmitInitializationToLValue(E->getSubExpr(), FieldLoc);
140    return;
141  }
142
143  Visit(E->getSubExpr());
144}
145
146void AggExprEmitter::VisitImplicitCastExpr(ImplicitCastExpr *E) {
147  assert(CGF.getContext().typesAreCompatible(
148                          E->getSubExpr()->getType().getUnqualifiedType(),
149                          E->getType().getUnqualifiedType()) &&
150         "Implicit cast types must be compatible");
151  Visit(E->getSubExpr());
152}
153
154void AggExprEmitter::VisitCallExpr(const CallExpr *E) {
155  RValue RV = CGF.EmitCallExpr(E);
156  assert(RV.isAggregate() && "Return value must be aggregate value!");
157
158  // If the result is ignored, don't copy from the value.
159  if (DestPtr == 0)
160    // FIXME: If the source is volatile, we must read from it.
161    return;
162
163  CGF.EmitAggregateCopy(DestPtr, RV.getAggregateAddr(), E->getType());
164}
165
166void AggExprEmitter::VisitObjCMessageExpr(ObjCMessageExpr *E) {
167  RValue RV = CGF.EmitObjCMessageExpr(E);
168  assert(RV.isAggregate() && "Return value must be aggregate value!");
169
170  // If the result is ignored, don't copy from the value.
171  if (DestPtr == 0)
172    // FIXME: If the source is volatile, we must read from it.
173    return;
174
175  CGF.EmitAggregateCopy(DestPtr, RV.getAggregateAddr(), E->getType());
176}
177
178void AggExprEmitter::VisitObjCPropertyRefExpr(ObjCPropertyRefExpr *E) {
179  RValue RV = CGF.EmitObjCPropertyGet(E);
180  assert(RV.isAggregate() && "Return value must be aggregate value!");
181
182  // If the result is ignored, don't copy from the value.
183  if (DestPtr == 0)
184    // FIXME: If the source is volatile, we must read from it.
185    return;
186
187  CGF.EmitAggregateCopy(DestPtr, RV.getAggregateAddr(), E->getType());
188}
189
190void AggExprEmitter::VisitObjCKVCRefExpr(ObjCKVCRefExpr *E) {
191  RValue RV = CGF.EmitObjCPropertyGet(E);
192  assert(RV.isAggregate() && "Return value must be aggregate value!");
193
194  // If the result is ignored, don't copy from the value.
195  if (DestPtr == 0)
196    // FIXME: If the source is volatile, we must read from it.
197    return;
198
199  CGF.EmitAggregateCopy(DestPtr, RV.getAggregateAddr(), E->getType());
200}
201
202void AggExprEmitter::VisitBinComma(const BinaryOperator *E) {
203  CGF.EmitAnyExpr(E->getLHS());
204  CGF.EmitAggExpr(E->getRHS(), DestPtr, false);
205}
206
207void AggExprEmitter::VisitStmtExpr(const StmtExpr *E) {
208  CGF.EmitCompoundStmt(*E->getSubStmt(), true, DestPtr, VolatileDest);
209}
210
211void AggExprEmitter::VisitBinaryOperator(const BinaryOperator *E) {
212  CGF.ErrorUnsupported(E, "aggregate binary expression");
213}
214
215void AggExprEmitter::VisitBinAssign(const BinaryOperator *E) {
216  // For an assignment to work, the value on the right has
217  // to be compatible with the value on the left.
218  assert(CGF.getContext().typesAreCompatible(
219             E->getLHS()->getType().getUnqualifiedType(),
220             E->getRHS()->getType().getUnqualifiedType())
221         && "Invalid assignment");
222  LValue LHS = CGF.EmitLValue(E->getLHS());
223
224  // We have to special case property setters, otherwise we must have
225  // a simple lvalue (no aggregates inside vectors, bitfields).
226  if (LHS.isPropertyRef()) {
227    // FIXME: Volatility?
228    llvm::Value *AggLoc = DestPtr;
229    if (!AggLoc)
230      AggLoc = CGF.CreateTempAlloca(CGF.ConvertType(E->getRHS()->getType()));
231    CGF.EmitAggExpr(E->getRHS(), AggLoc, false);
232    CGF.EmitObjCPropertySet(LHS.getPropertyRefExpr(),
233                            RValue::getAggregate(AggLoc));
234  }
235  else if (LHS.isKVCRef()) {
236    // FIXME: Volatility?
237    llvm::Value *AggLoc = DestPtr;
238    if (!AggLoc)
239      AggLoc = CGF.CreateTempAlloca(CGF.ConvertType(E->getRHS()->getType()));
240    CGF.EmitAggExpr(E->getRHS(), AggLoc, false);
241    CGF.EmitObjCPropertySet(LHS.getKVCRefExpr(),
242                            RValue::getAggregate(AggLoc));
243  } else {
244    // Codegen the RHS so that it stores directly into the LHS.
245    CGF.EmitAggExpr(E->getRHS(), LHS.getAddress(), false /*FIXME: VOLATILE LHS*/);
246
247    if (DestPtr == 0)
248      return;
249
250    // If the result of the assignment is used, copy the RHS there also.
251    CGF.EmitAggregateCopy(DestPtr, LHS.getAddress(), E->getType());
252  }
253}
254
255void AggExprEmitter::VisitConditionalOperator(const ConditionalOperator *E) {
256  llvm::BasicBlock *LHSBlock = CGF.createBasicBlock("cond.true");
257  llvm::BasicBlock *RHSBlock = CGF.createBasicBlock("cond.false");
258  llvm::BasicBlock *ContBlock = CGF.createBasicBlock("cond.end");
259
260  llvm::Value *Cond = CGF.EvaluateExprAsBool(E->getCond());
261  Builder.CreateCondBr(Cond, LHSBlock, RHSBlock);
262
263  CGF.EmitBlock(LHSBlock);
264
265  // Handle the GNU extension for missing LHS.
266  assert(E->getLHS() && "Must have LHS for aggregate value");
267
268  Visit(E->getLHS());
269  CGF.EmitBranch(ContBlock);
270
271  CGF.EmitBlock(RHSBlock);
272
273  Visit(E->getRHS());
274  CGF.EmitBranch(ContBlock);
275
276  CGF.EmitBlock(ContBlock);
277}
278
279void AggExprEmitter::VisitVAArgExpr(VAArgExpr *VE) {
280  llvm::Value *ArgValue = CGF.EmitVAListRef(VE->getSubExpr());
281  llvm::Value *ArgPtr = CGF.EmitVAArg(ArgValue, VE->getType());
282
283  if (!ArgPtr) {
284    CGF.ErrorUnsupported(VE, "aggregate va_arg expression");
285    return;
286  }
287
288  if (DestPtr)
289    // FIXME: volatility
290    CGF.EmitAggregateCopy(DestPtr, ArgPtr, VE->getType());
291}
292
293void AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
294  // FIXME: Are initializers affected by volatile?
295  if (isa<ImplicitValueInitExpr>(E)) {
296    EmitNullInitializationToLValue(LV, E->getType());
297  } else if (E->getType()->isComplexType()) {
298    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
299  } else if (CGF.hasAggregateLLVMType(E->getType())) {
300    CGF.EmitAnyExpr(E, LV.getAddress(), false);
301  } else {
302    CGF.EmitStoreThroughLValue(CGF.EmitAnyExpr(E), LV, E->getType());
303  }
304}
305
306void AggExprEmitter::EmitNullInitializationToLValue(LValue LV, QualType T) {
307  if (!CGF.hasAggregateLLVMType(T)) {
308    // For non-aggregates, we can store zero
309    llvm::Value *Null = llvm::Constant::getNullValue(CGF.ConvertType(T));
310    CGF.EmitStoreThroughLValue(RValue::get(Null), LV, T);
311  } else {
312    // Otherwise, just memset the whole thing to zero.  This is legal
313    // because in LLVM, all default initializers are guaranteed to have a
314    // bit pattern of all zeros.
315    // There's a potential optimization opportunity in combining
316    // memsets; that would be easy for arrays, but relatively
317    // difficult for structures with the current code.
318    CGF.EmitMemSetToZero(LV.getAddress(), T);
319  }
320}
321
322void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
323#if 0
324  // FIXME: Disabled while we figure out what to do about
325  // test/CodeGen/bitfield.c
326  //
327  // If we can, prefer a copy from a global; this is a lot less
328  // code for long globals, and it's easier for the current optimizers
329  // to analyze.
330  // FIXME: Should we really be doing this? Should we try to avoid
331  // cases where we emit a global with a lot of zeros?  Should
332  // we try to avoid short globals?
333  if (E->isConstantInitializer(CGF.getContext(), 0)) {
334    llvm::Constant* C = CGF.CGM.EmitConstantExpr(E, &CGF);
335    llvm::GlobalVariable* GV =
336    new llvm::GlobalVariable(C->getType(), true,
337                             llvm::GlobalValue::InternalLinkage,
338                             C, "", &CGF.CGM.getModule(), 0);
339    CGF.EmitAggregateCopy(DestPtr, GV, E->getType());
340    return;
341  }
342#endif
343  if (E->hadArrayRangeDesignator()) {
344    CGF.ErrorUnsupported(E, "GNU array range designator extension");
345  }
346
347  // Handle initialization of an array.
348  if (E->getType()->isArrayType()) {
349    const llvm::PointerType *APType =
350      cast<llvm::PointerType>(DestPtr->getType());
351    const llvm::ArrayType *AType =
352      cast<llvm::ArrayType>(APType->getElementType());
353
354    uint64_t NumInitElements = E->getNumInits();
355
356    if (E->getNumInits() > 0) {
357      QualType T1 = E->getType();
358      QualType T2 = E->getInit(0)->getType();
359      if (CGF.getContext().getCanonicalType(T1).getUnqualifiedType() ==
360          CGF.getContext().getCanonicalType(T2).getUnqualifiedType()) {
361        EmitAggLoadOfLValue(E->getInit(0));
362        return;
363      }
364    }
365
366    uint64_t NumArrayElements = AType->getNumElements();
367    QualType ElementType = CGF.getContext().getCanonicalType(E->getType());
368    ElementType = CGF.getContext().getAsArrayType(ElementType)->getElementType();
369
370    unsigned CVRqualifier = ElementType.getCVRQualifiers();
371
372    for (uint64_t i = 0; i != NumArrayElements; ++i) {
373      llvm::Value *NextVal = Builder.CreateStructGEP(DestPtr, i, ".array");
374      if (i < NumInitElements)
375        EmitInitializationToLValue(E->getInit(i),
376                                   LValue::MakeAddr(NextVal, CVRqualifier));
377      else
378        EmitNullInitializationToLValue(LValue::MakeAddr(NextVal, CVRqualifier),
379                                       ElementType);
380    }
381    return;
382  }
383
384  assert(E->getType()->isRecordType() && "Only support structs/unions here!");
385
386  // Do struct initialization; this code just sets each individual member
387  // to the approprate value.  This makes bitfield support automatic;
388  // the disadvantage is that the generated code is more difficult for
389  // the optimizer, especially with bitfields.
390  unsigned NumInitElements = E->getNumInits();
391  RecordDecl *SD = E->getType()->getAsRecordType()->getDecl();
392  unsigned CurInitVal = 0;
393
394  if (E->getType()->isUnionType()) {
395    // Only initialize one field of a union. The field itself is
396    // specified by the initializer list.
397    if (!E->getInitializedFieldInUnion()) {
398      // Empty union; we have nothing to do.
399
400#ifndef NDEBUG
401      // Make sure that it's really an empty and not a failure of
402      // semantic analysis.
403      for (RecordDecl::field_iterator Field = SD->field_begin(CGF.getContext()),
404                                   FieldEnd = SD->field_end(CGF.getContext());
405           Field != FieldEnd; ++Field)
406        assert(Field->isUnnamedBitfield() && "Only unnamed bitfields allowed");
407#endif
408      return;
409    }
410
411    // FIXME: volatility
412    FieldDecl *Field = E->getInitializedFieldInUnion();
413    LValue FieldLoc = CGF.EmitLValueForField(DestPtr, Field, true, 0);
414
415    if (NumInitElements) {
416      // Store the initializer into the field
417      EmitInitializationToLValue(E->getInit(0), FieldLoc);
418    } else {
419      // Default-initialize to null
420      EmitNullInitializationToLValue(FieldLoc, Field->getType());
421    }
422
423    return;
424  }
425
426  // Here we iterate over the fields; this makes it simpler to both
427  // default-initialize fields and skip over unnamed fields.
428  for (RecordDecl::field_iterator Field = SD->field_begin(CGF.getContext()),
429                               FieldEnd = SD->field_end(CGF.getContext());
430       Field != FieldEnd; ++Field) {
431    // We're done once we hit the flexible array member
432    if (Field->getType()->isIncompleteArrayType())
433      break;
434
435    if (Field->isUnnamedBitfield())
436      continue;
437
438    // FIXME: volatility
439    LValue FieldLoc = CGF.EmitLValueForField(DestPtr, *Field, false, 0);
440    if (CurInitVal < NumInitElements) {
441      // Store the initializer into the field
442      EmitInitializationToLValue(E->getInit(CurInitVal++), FieldLoc);
443    } else {
444      // We're out of initalizers; default-initialize to null
445      EmitNullInitializationToLValue(FieldLoc, Field->getType());
446    }
447  }
448}
449
450//===----------------------------------------------------------------------===//
451//                        Entry Points into this File
452//===----------------------------------------------------------------------===//
453
454/// EmitAggExpr - Emit the computation of the specified expression of
455/// aggregate type.  The result is computed into DestPtr.  Note that if
456/// DestPtr is null, the value of the aggregate expression is not needed.
457void CodeGenFunction::EmitAggExpr(const Expr *E, llvm::Value *DestPtr,
458                                  bool VolatileDest) {
459  assert(E && hasAggregateLLVMType(E->getType()) &&
460         "Invalid aggregate expression to emit");
461
462  AggExprEmitter(*this, DestPtr, VolatileDest).Visit(const_cast<Expr*>(E));
463}
464
465void CodeGenFunction::EmitAggregateClear(llvm::Value *DestPtr, QualType Ty) {
466  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
467
468  EmitMemSetToZero(DestPtr, Ty);
469}
470
471void CodeGenFunction::EmitAggregateCopy(llvm::Value *DestPtr,
472                                        llvm::Value *SrcPtr, QualType Ty) {
473  assert(!Ty->isAnyComplexType() && "Shouldn't happen for complex");
474
475  // Aggregate assignment turns into llvm.memcpy.  This is almost valid per
476  // C99 6.5.16.1p3, which states "If the value being stored in an object is
477  // read from another object that overlaps in anyway the storage of the first
478  // object, then the overlap shall be exact and the two objects shall have
479  // qualified or unqualified versions of a compatible type."
480  //
481  // memcpy is not defined if the source and destination pointers are exactly
482  // equal, but other compilers do this optimization, and almost every memcpy
483  // implementation handles this case safely.  If there is a libc that does not
484  // safely handle this, we can add a target hook.
485  const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
486  if (DestPtr->getType() != BP)
487    DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
488  if (SrcPtr->getType() != BP)
489    SrcPtr = Builder.CreateBitCast(SrcPtr, BP, "tmp");
490
491  // Get size and alignment info for this aggregate.
492  std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
493
494  // FIXME: Handle variable sized types.
495  const llvm::Type *IntPtr = llvm::IntegerType::get(LLVMPointerWidth);
496
497  Builder.CreateCall4(CGM.getMemCpyFn(),
498                      DestPtr, SrcPtr,
499                      // TypeInfo.first describes size in bits.
500                      llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
501                      llvm::ConstantInt::get(llvm::Type::Int32Ty,
502                                             TypeInfo.second/8));
503}
504