1 //===--- CGExprComplex.cpp - Emit LLVM Code for Complex Exprs -------------===//
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 Expr nodes with complex types 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/ADT/SmallString.h"
21 #include "llvm/Support/Compiler.h"
22 using namespace clang;
23 using namespace CodeGen;
24 
25 //===----------------------------------------------------------------------===//
26 //                        Complex Expression Emitter
27 //===----------------------------------------------------------------------===//
28 
29 typedef CodeGenFunction::ComplexPairTy ComplexPairTy;
30 
31 namespace  {
32 class VISIBILITY_HIDDEN ComplexExprEmitter
33   : public StmtVisitor<ComplexExprEmitter, ComplexPairTy> {
34   CodeGenFunction &CGF;
35   llvm::IRBuilder<> &Builder;
36 public:
37   ComplexExprEmitter(CodeGenFunction &cgf) : CGF(cgf), Builder(CGF.Builder) {
38   }
39 
40 
41   //===--------------------------------------------------------------------===//
42   //                               Utilities
43   //===--------------------------------------------------------------------===//
44 
45   /// EmitLoadOfLValue - Given an expression with complex type that represents a
46   /// value l-value, this method emits the address of the l-value, then loads
47   /// and returns the result.
48   ComplexPairTy EmitLoadOfLValue(const Expr *E) {
49     LValue LV = CGF.EmitLValue(E);
50     // FIXME: Volatile
51     return EmitLoadOfComplex(LV.getAddress(), false);
52   }
53 
54   /// EmitLoadOfComplex - Given a pointer to a complex value, emit code to load
55   /// the real and imaginary pieces.
56   ComplexPairTy EmitLoadOfComplex(llvm::Value *SrcPtr, bool isVolatile);
57 
58   /// EmitStoreOfComplex - Store the specified real/imag parts into the
59   /// specified value pointer.
60   void EmitStoreOfComplex(ComplexPairTy Val, llvm::Value *ResPtr, bool isVol);
61 
62   /// EmitComplexToComplexCast - Emit a cast from complex value Val to DestType.
63   ComplexPairTy EmitComplexToComplexCast(ComplexPairTy Val, QualType SrcType,
64                                          QualType DestType);
65 
66   //===--------------------------------------------------------------------===//
67   //                            Visitor Methods
68   //===--------------------------------------------------------------------===//
69 
70   ComplexPairTy VisitStmt(Stmt *S) {
71     S->dump(CGF.getContext().getSourceManager());
72     assert(0 && "Stmt can't have complex result type!");
73     return ComplexPairTy();
74   }
75   ComplexPairTy VisitExpr(Expr *S);
76   ComplexPairTy VisitParenExpr(ParenExpr *PE) { return Visit(PE->getSubExpr());}
77   ComplexPairTy VisitImaginaryLiteral(const ImaginaryLiteral *IL);
78 
79   // l-values.
80   ComplexPairTy VisitDeclRefExpr(const Expr *E) { return EmitLoadOfLValue(E); }
81   ComplexPairTy VisitArraySubscriptExpr(Expr *E) { return EmitLoadOfLValue(E); }
82   ComplexPairTy VisitMemberExpr(const Expr *E) { return EmitLoadOfLValue(E); }
83 
84   // FIXME: CompoundLiteralExpr
85 
86   ComplexPairTy EmitCast(Expr *Op, QualType DestTy);
87   ComplexPairTy VisitImplicitCastExpr(ImplicitCastExpr *E) {
88     // Unlike for scalars, we don't have to worry about function->ptr demotion
89     // here.
90     return EmitCast(E->getSubExpr(), E->getType());
91   }
92   ComplexPairTy VisitCastExpr(CastExpr *E) {
93     return EmitCast(E->getSubExpr(), E->getType());
94   }
95   ComplexPairTy VisitCallExpr(const CallExpr *E);
96   ComplexPairTy VisitStmtExpr(const StmtExpr *E);
97   ComplexPairTy VisitOverloadExpr(const OverloadExpr *OE);
98 
99   // Operators.
100   ComplexPairTy VisitPrePostIncDec(const UnaryOperator *E,
101                                    bool isInc, bool isPre);
102   ComplexPairTy VisitUnaryPostDec(const UnaryOperator *E) {
103     return VisitPrePostIncDec(E, false, false);
104   }
105   ComplexPairTy VisitUnaryPostInc(const UnaryOperator *E) {
106     return VisitPrePostIncDec(E, true, false);
107   }
108   ComplexPairTy VisitUnaryPreDec(const UnaryOperator *E) {
109     return VisitPrePostIncDec(E, false, true);
110   }
111   ComplexPairTy VisitUnaryPreInc(const UnaryOperator *E) {
112     return VisitPrePostIncDec(E, true, true);
113   }
114   ComplexPairTy VisitUnaryDeref(const Expr *E) { return EmitLoadOfLValue(E); }
115   ComplexPairTy VisitUnaryPlus     (const UnaryOperator *E) {
116     return Visit(E->getSubExpr());
117   }
118   ComplexPairTy VisitUnaryMinus    (const UnaryOperator *E);
119   ComplexPairTy VisitUnaryNot      (const UnaryOperator *E);
120   // LNot,SizeOf,AlignOf,Real,Imag never return complex.
121   ComplexPairTy VisitUnaryExtension(const UnaryOperator *E) {
122     return Visit(E->getSubExpr());
123   }
124   ComplexPairTy VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) {
125     return Visit(DAE->getExpr());
126   }
127 
128   struct BinOpInfo {
129     ComplexPairTy LHS;
130     ComplexPairTy RHS;
131     QualType Ty;  // Computation Type.
132   };
133 
134   BinOpInfo EmitBinOps(const BinaryOperator *E);
135   ComplexPairTy EmitCompoundAssign(const CompoundAssignOperator *E,
136                                    ComplexPairTy (ComplexExprEmitter::*Func)
137                                    (const BinOpInfo &));
138 
139   ComplexPairTy EmitBinAdd(const BinOpInfo &Op);
140   ComplexPairTy EmitBinSub(const BinOpInfo &Op);
141   ComplexPairTy EmitBinMul(const BinOpInfo &Op);
142   ComplexPairTy EmitBinDiv(const BinOpInfo &Op);
143 
144   ComplexPairTy VisitBinMul(const BinaryOperator *E) {
145     return EmitBinMul(EmitBinOps(E));
146   }
147   ComplexPairTy VisitBinAdd(const BinaryOperator *E) {
148     return EmitBinAdd(EmitBinOps(E));
149   }
150   ComplexPairTy VisitBinSub(const BinaryOperator *E) {
151     return EmitBinSub(EmitBinOps(E));
152   }
153   ComplexPairTy VisitBinDiv(const BinaryOperator *E) {
154     return EmitBinDiv(EmitBinOps(E));
155   }
156 
157   // Compound assignments.
158   ComplexPairTy VisitBinAddAssign(const CompoundAssignOperator *E) {
159     return EmitCompoundAssign(E, &ComplexExprEmitter::EmitBinAdd);
160   }
161   ComplexPairTy VisitBinSubAssign(const CompoundAssignOperator *E) {
162     return EmitCompoundAssign(E, &ComplexExprEmitter::EmitBinSub);
163   }
164   ComplexPairTy VisitBinMulAssign(const CompoundAssignOperator *E) {
165     return EmitCompoundAssign(E, &ComplexExprEmitter::EmitBinMul);
166   }
167   ComplexPairTy VisitBinDivAssign(const CompoundAssignOperator *E) {
168     return EmitCompoundAssign(E, &ComplexExprEmitter::EmitBinDiv);
169   }
170 
171   // GCC rejects rem/and/or/xor for integer complex.
172   // Logical and/or always return int, never complex.
173 
174   // No comparisons produce a complex result.
175   ComplexPairTy VisitBinAssign     (const BinaryOperator *E);
176   ComplexPairTy VisitBinComma      (const BinaryOperator *E);
177 
178 
179   ComplexPairTy VisitConditionalOperator(const ConditionalOperator *CO);
180   ComplexPairTy VisitChooseExpr(ChooseExpr *CE);
181 
182   ComplexPairTy VisitInitListExpr(InitListExpr *E);
183 };
184 }  // end anonymous namespace.
185 
186 //===----------------------------------------------------------------------===//
187 //                                Utilities
188 //===----------------------------------------------------------------------===//
189 
190 /// EmitLoadOfComplex - Given an RValue reference for a complex, emit code to
191 /// load the real and imaginary pieces, returning them as Real/Imag.
192 ComplexPairTy ComplexExprEmitter::EmitLoadOfComplex(llvm::Value *SrcPtr,
193                                                     bool isVolatile) {
194   llvm::SmallString<64> Name(SrcPtr->getNameStart(),
195                              SrcPtr->getNameStart()+SrcPtr->getNameLen());
196 
197   Name += ".realp";
198   llvm::Value *RealPtr = Builder.CreateStructGEP(SrcPtr, 0, Name.c_str());
199 
200   Name.pop_back();  // .realp -> .real
201   llvm::Value *Real = Builder.CreateLoad(RealPtr, isVolatile, Name.c_str());
202 
203   Name.resize(Name.size()-4); // .real -> .imagp
204   Name += "imagp";
205 
206   llvm::Value *ImagPtr = Builder.CreateStructGEP(SrcPtr, 1, Name.c_str());
207 
208   Name.pop_back();  // .imagp -> .imag
209   llvm::Value *Imag = Builder.CreateLoad(ImagPtr, isVolatile, Name.c_str());
210   return ComplexPairTy(Real, Imag);
211 }
212 
213 /// EmitStoreOfComplex - Store the specified real/imag parts into the
214 /// specified value pointer.
215 void ComplexExprEmitter::EmitStoreOfComplex(ComplexPairTy Val, llvm::Value *Ptr,
216                                             bool isVolatile) {
217   llvm::Value *RealPtr = Builder.CreateStructGEP(Ptr, 0, "real");
218   llvm::Value *ImagPtr = Builder.CreateStructGEP(Ptr, 1, "imag");
219 
220   Builder.CreateStore(Val.first, RealPtr, isVolatile);
221   Builder.CreateStore(Val.second, ImagPtr, isVolatile);
222 }
223 
224 
225 
226 //===----------------------------------------------------------------------===//
227 //                            Visitor Methods
228 //===----------------------------------------------------------------------===//
229 
230 ComplexPairTy ComplexExprEmitter::VisitExpr(Expr *E) {
231   CGF.ErrorUnsupported(E, "complex expression");
232   const llvm::Type *EltTy =
233     CGF.ConvertType(E->getType()->getAsComplexType()->getElementType());
234   llvm::Value *U = llvm::UndefValue::get(EltTy);
235   return ComplexPairTy(U, U);
236 }
237 
238 ComplexPairTy ComplexExprEmitter::
239 VisitImaginaryLiteral(const ImaginaryLiteral *IL) {
240   llvm::Value *Imag = CGF.EmitScalarExpr(IL->getSubExpr());
241   return ComplexPairTy(llvm::Constant::getNullValue(Imag->getType()), Imag);
242 }
243 
244 
245 ComplexPairTy ComplexExprEmitter::VisitCallExpr(const CallExpr *E) {
246   return CGF.EmitCallExpr(E).getComplexVal();
247 }
248 
249 ComplexPairTy ComplexExprEmitter::VisitOverloadExpr(const OverloadExpr *E) {
250   return CGF.EmitCallExpr(E->getFn(), E->arg_begin(),
251                           E->arg_end(CGF.getContext())).getComplexVal();
252 }
253 
254 ComplexPairTy ComplexExprEmitter::VisitStmtExpr(const StmtExpr *E) {
255   return CGF.EmitCompoundStmt(*E->getSubStmt(), true).getComplexVal();
256 }
257 
258 /// EmitComplexToComplexCast - Emit a cast from complex value Val to DestType.
259 ComplexPairTy ComplexExprEmitter::EmitComplexToComplexCast(ComplexPairTy Val,
260                                                            QualType SrcType,
261                                                            QualType DestType) {
262   // Get the src/dest element type.
263   SrcType = SrcType->getAsComplexType()->getElementType();
264   DestType = DestType->getAsComplexType()->getElementType();
265 
266   // C99 6.3.1.6: When a value of complextype is converted to another
267   // complex type, both the real and imaginary parts followthe conversion
268   // rules for the corresponding real types.
269   Val.first = CGF.EmitScalarConversion(Val.first, SrcType, DestType);
270   Val.second = CGF.EmitScalarConversion(Val.second, SrcType, DestType);
271   return Val;
272 }
273 
274 ComplexPairTy ComplexExprEmitter::EmitCast(Expr *Op, QualType DestTy) {
275   // Two cases here: cast from (complex to complex) and (scalar to complex).
276   if (Op->getType()->isAnyComplexType())
277     return EmitComplexToComplexCast(Visit(Op), Op->getType(), DestTy);
278 
279   // C99 6.3.1.7: When a value of real type is converted to a complex type, the
280   // real part of the complex  result value is determined by the rules of
281   // conversion to the corresponding real type and the imaginary part of the
282   // complex result value is a positive zero or an unsigned zero.
283   llvm::Value *Elt = CGF.EmitScalarExpr(Op);
284 
285   // Convert the input element to the element type of the complex.
286   DestTy = DestTy->getAsComplexType()->getElementType();
287   Elt = CGF.EmitScalarConversion(Elt, Op->getType(), DestTy);
288 
289   // Return (realval, 0).
290   return ComplexPairTy(Elt, llvm::Constant::getNullValue(Elt->getType()));
291 }
292 
293 ComplexPairTy ComplexExprEmitter::VisitPrePostIncDec(const UnaryOperator *E,
294                                                      bool isInc, bool isPre) {
295   LValue LV = CGF.EmitLValue(E->getSubExpr());
296   // FIXME: Handle volatile!
297   ComplexPairTy InVal = EmitLoadOfComplex(LV.getAddress(), false);
298 
299   uint64_t AmountVal = isInc ? 1 : -1;
300 
301   llvm::Value *NextVal;
302   if (isa<llvm::IntegerType>(InVal.first->getType()))
303     NextVal = llvm::ConstantInt::get(InVal.first->getType(), AmountVal);
304   else if (InVal.first->getType() == llvm::Type::FloatTy)
305     // FIXME: Handle long double.
306     NextVal =
307       llvm::ConstantFP::get(llvm::APFloat(static_cast<float>(AmountVal)));
308   else {
309     // FIXME: Handle long double.
310     assert(InVal.first->getType() == llvm::Type::DoubleTy);
311     NextVal =
312       llvm::ConstantFP::get(llvm::APFloat(static_cast<double>(AmountVal)));
313   }
314 
315   // Add the inc/dec to the real part.
316   NextVal = Builder.CreateAdd(InVal.first, NextVal, isInc ? "inc" : "dec");
317 
318   ComplexPairTy IncVal(NextVal, InVal.second);
319 
320   // Store the updated result through the lvalue.
321   EmitStoreOfComplex(IncVal, LV.getAddress(), false);  /* FIXME: Volatile */
322 
323   // If this is a postinc, return the value read from memory, otherwise use the
324   // updated value.
325   return isPre ? IncVal : InVal;
326 }
327 
328 ComplexPairTy ComplexExprEmitter::VisitUnaryMinus(const UnaryOperator *E) {
329   ComplexPairTy Op = Visit(E->getSubExpr());
330   llvm::Value *ResR = Builder.CreateNeg(Op.first,  "neg.r");
331   llvm::Value *ResI = Builder.CreateNeg(Op.second, "neg.i");
332   return ComplexPairTy(ResR, ResI);
333 }
334 
335 ComplexPairTy ComplexExprEmitter::VisitUnaryNot(const UnaryOperator *E) {
336   // ~(a+ib) = a + i*-b
337   ComplexPairTy Op = Visit(E->getSubExpr());
338   llvm::Value *ResI = Builder.CreateNeg(Op.second, "conj.i");
339   return ComplexPairTy(Op.first, ResI);
340 }
341 
342 ComplexPairTy ComplexExprEmitter::EmitBinAdd(const BinOpInfo &Op) {
343   llvm::Value *ResR = Builder.CreateAdd(Op.LHS.first,  Op.RHS.first,  "add.r");
344   llvm::Value *ResI = Builder.CreateAdd(Op.LHS.second, Op.RHS.second, "add.i");
345   return ComplexPairTy(ResR, ResI);
346 }
347 
348 ComplexPairTy ComplexExprEmitter::EmitBinSub(const BinOpInfo &Op) {
349   llvm::Value *ResR = Builder.CreateSub(Op.LHS.first,  Op.RHS.first,  "sub.r");
350   llvm::Value *ResI = Builder.CreateSub(Op.LHS.second, Op.RHS.second, "sub.i");
351   return ComplexPairTy(ResR, ResI);
352 }
353 
354 
355 ComplexPairTy ComplexExprEmitter::EmitBinMul(const BinOpInfo &Op) {
356   llvm::Value *ResRl = Builder.CreateMul(Op.LHS.first, Op.RHS.first, "mul.rl");
357   llvm::Value *ResRr = Builder.CreateMul(Op.LHS.second, Op.RHS.second,"mul.rr");
358   llvm::Value *ResR  = Builder.CreateSub(ResRl, ResRr, "mul.r");
359 
360   llvm::Value *ResIl = Builder.CreateMul(Op.LHS.second, Op.RHS.first, "mul.il");
361   llvm::Value *ResIr = Builder.CreateMul(Op.LHS.first, Op.RHS.second, "mul.ir");
362   llvm::Value *ResI  = Builder.CreateAdd(ResIl, ResIr, "mul.i");
363   return ComplexPairTy(ResR, ResI);
364 }
365 
366 ComplexPairTy ComplexExprEmitter::EmitBinDiv(const BinOpInfo &Op) {
367   llvm::Value *LHSr = Op.LHS.first, *LHSi = Op.LHS.second;
368   llvm::Value *RHSr = Op.RHS.first, *RHSi = Op.RHS.second;
369 
370   // (a+ib) / (c+id) = ((ac+bd)/(cc+dd)) + i((bc-ad)/(cc+dd))
371   llvm::Value *Tmp1 = Builder.CreateMul(LHSr, RHSr, "tmp"); // a*c
372   llvm::Value *Tmp2 = Builder.CreateMul(LHSi, RHSi, "tmp"); // b*d
373   llvm::Value *Tmp3 = Builder.CreateAdd(Tmp1, Tmp2, "tmp"); // ac+bd
374 
375   llvm::Value *Tmp4 = Builder.CreateMul(RHSr, RHSr, "tmp"); // c*c
376   llvm::Value *Tmp5 = Builder.CreateMul(RHSi, RHSi, "tmp"); // d*d
377   llvm::Value *Tmp6 = Builder.CreateAdd(Tmp4, Tmp5, "tmp"); // cc+dd
378 
379   llvm::Value *Tmp7 = Builder.CreateMul(LHSi, RHSr, "tmp"); // b*c
380   llvm::Value *Tmp8 = Builder.CreateMul(LHSr, RHSi, "tmp"); // a*d
381   llvm::Value *Tmp9 = Builder.CreateSub(Tmp7, Tmp8, "tmp"); // bc-ad
382 
383   llvm::Value *DSTr, *DSTi;
384   if (Tmp3->getType()->isFloatingPoint()) {
385     DSTr = Builder.CreateFDiv(Tmp3, Tmp6, "tmp");
386     DSTi = Builder.CreateFDiv(Tmp9, Tmp6, "tmp");
387   } else {
388     if (Op.Ty->getAsComplexType()->getElementType()->isUnsignedIntegerType()) {
389       DSTr = Builder.CreateUDiv(Tmp3, Tmp6, "tmp");
390       DSTi = Builder.CreateUDiv(Tmp9, Tmp6, "tmp");
391     } else {
392       DSTr = Builder.CreateSDiv(Tmp3, Tmp6, "tmp");
393       DSTi = Builder.CreateSDiv(Tmp9, Tmp6, "tmp");
394     }
395   }
396 
397   return ComplexPairTy(DSTr, DSTi);
398 }
399 
400 ComplexExprEmitter::BinOpInfo
401 ComplexExprEmitter::EmitBinOps(const BinaryOperator *E) {
402   BinOpInfo Ops;
403   Ops.LHS = Visit(E->getLHS());
404   Ops.RHS = Visit(E->getRHS());
405   Ops.Ty = E->getType();
406   return Ops;
407 }
408 
409 
410 // Compound assignments.
411 ComplexPairTy ComplexExprEmitter::
412 EmitCompoundAssign(const CompoundAssignOperator *E,
413                    ComplexPairTy (ComplexExprEmitter::*Func)(const BinOpInfo&)){
414   QualType LHSTy = E->getLHS()->getType(), RHSTy = E->getRHS()->getType();
415 
416   // Load the LHS and RHS operands.
417   LValue LHSLV = CGF.EmitLValue(E->getLHS());
418 
419   BinOpInfo OpInfo;
420   OpInfo.Ty = E->getComputationType();
421 
422   // We know the LHS is a complex lvalue.
423   OpInfo.LHS = EmitLoadOfComplex(LHSLV.getAddress(), false);// FIXME: Volatile.
424   OpInfo.LHS = EmitComplexToComplexCast(OpInfo.LHS, LHSTy, OpInfo.Ty);
425 
426   // It is possible for the RHS to be complex or scalar.
427   OpInfo.RHS = EmitCast(E->getRHS(), OpInfo.Ty);
428 
429   // Expand the binary operator.
430   ComplexPairTy Result = (this->*Func)(OpInfo);
431 
432   // Truncate the result back to the LHS type.
433   Result = EmitComplexToComplexCast(Result, OpInfo.Ty, LHSTy);
434 
435   // Store the result value into the LHS lvalue.
436   EmitStoreOfComplex(Result, LHSLV.getAddress(), false); // FIXME: VOLATILE
437   return Result;
438 }
439 
440 ComplexPairTy ComplexExprEmitter::VisitBinAssign(const BinaryOperator *E) {
441   assert(CGF.getContext().getCanonicalType(E->getLHS()->getType()) ==
442          CGF.getContext().getCanonicalType(E->getRHS()->getType()) &&
443          "Invalid assignment");
444   // Emit the RHS.
445   ComplexPairTy Val = Visit(E->getRHS());
446 
447   // Compute the address to store into.
448   LValue LHS = CGF.EmitLValue(E->getLHS());
449 
450   // Store into it.
451   // FIXME: Volatility!
452   EmitStoreOfComplex(Val, LHS.getAddress(), false);
453   return Val;
454 }
455 
456 ComplexPairTy ComplexExprEmitter::VisitBinComma(const BinaryOperator *E) {
457   CGF.EmitStmt(E->getLHS());
458   return Visit(E->getRHS());
459 }
460 
461 ComplexPairTy ComplexExprEmitter::
462 VisitConditionalOperator(const ConditionalOperator *E) {
463   llvm::BasicBlock *LHSBlock = llvm::BasicBlock::Create("cond.?");
464   llvm::BasicBlock *RHSBlock = llvm::BasicBlock::Create("cond.:");
465   llvm::BasicBlock *ContBlock = llvm::BasicBlock::Create("cond.cont");
466 
467   llvm::Value *Cond = CGF.EvaluateExprAsBool(E->getCond());
468   Builder.CreateCondBr(Cond, LHSBlock, RHSBlock);
469 
470   CGF.EmitBlock(LHSBlock);
471 
472   // Handle the GNU extension for missing LHS.
473   assert(E->getLHS() && "Must have LHS for complex value");
474 
475   ComplexPairTy LHS = Visit(E->getLHS());
476   Builder.CreateBr(ContBlock);
477   LHSBlock = Builder.GetInsertBlock();
478 
479   CGF.EmitBlock(RHSBlock);
480 
481   ComplexPairTy RHS = Visit(E->getRHS());
482   Builder.CreateBr(ContBlock);
483   RHSBlock = Builder.GetInsertBlock();
484 
485   CGF.EmitBlock(ContBlock);
486 
487   // Create a PHI node for the real part.
488   llvm::PHINode *RealPN = Builder.CreatePHI(LHS.first->getType(), "cond.r");
489   RealPN->reserveOperandSpace(2);
490   RealPN->addIncoming(LHS.first, LHSBlock);
491   RealPN->addIncoming(RHS.first, RHSBlock);
492 
493   // Create a PHI node for the imaginary part.
494   llvm::PHINode *ImagPN = Builder.CreatePHI(LHS.first->getType(), "cond.i");
495   ImagPN->reserveOperandSpace(2);
496   ImagPN->addIncoming(LHS.second, LHSBlock);
497   ImagPN->addIncoming(RHS.second, RHSBlock);
498 
499   return ComplexPairTy(RealPN, ImagPN);
500 }
501 
502 ComplexPairTy ComplexExprEmitter::VisitChooseExpr(ChooseExpr *E) {
503   // Emit the LHS or RHS as appropriate.
504   return Visit(E->isConditionTrue(CGF.getContext()) ? E->getLHS() :E->getRHS());
505 }
506 
507 ComplexPairTy ComplexExprEmitter::VisitInitListExpr(InitListExpr *E) {
508   if (E->getNumInits())
509     return Visit(E->getInit(0));
510 
511   // Empty init list intializes to null
512   QualType Ty = E->getType()->getAsComplexType()->getElementType();
513   const llvm::Type* LTy = CGF.ConvertType(Ty);
514   llvm::Value* zeroConstant = llvm::Constant::getNullValue(LTy);
515   return ComplexPairTy(zeroConstant, zeroConstant);
516 }
517 
518 //===----------------------------------------------------------------------===//
519 //                         Entry Point into this File
520 //===----------------------------------------------------------------------===//
521 
522 /// EmitComplexExpr - Emit the computation of the specified expression of
523 /// complex type, ignoring the result.
524 ComplexPairTy CodeGenFunction::EmitComplexExpr(const Expr *E) {
525   assert(E && E->getType()->isAnyComplexType() &&
526          "Invalid complex expression to emit");
527 
528   return ComplexExprEmitter(*this).Visit(const_cast<Expr*>(E));
529 }
530 
531 /// EmitComplexExprIntoAddr - Emit the computation of the specified expression
532 /// of complex type, storing into the specified Value*.
533 void CodeGenFunction::EmitComplexExprIntoAddr(const Expr *E,
534                                               llvm::Value *DestAddr,
535                                               bool DestIsVolatile) {
536   assert(E && E->getType()->isAnyComplexType() &&
537          "Invalid complex expression to emit");
538   ComplexExprEmitter Emitter(*this);
539   ComplexPairTy Val = Emitter.Visit(const_cast<Expr*>(E));
540   Emitter.EmitStoreOfComplex(Val, DestAddr, DestIsVolatile);
541 }
542 
543 /// LoadComplexFromAddr - Load a complex number from the specified address.
544 ComplexPairTy CodeGenFunction::LoadComplexFromAddr(llvm::Value *SrcAddr,
545                                                    bool SrcIsVolatile) {
546   return ComplexExprEmitter(*this).EmitLoadOfComplex(SrcAddr, SrcIsVolatile);
547 }
548