Re-commit r289252 and r289285, and fix PR31374

llvm-svn: 289787

18 files changed, 765 insertions, 67 deletions

diff --git a/clang/include/clang/AST/APValue.h b/clang/include/clang/AST/APValue.h
index e58c21923f5..7c431f3be8c 100644
--- a/clang/include/clang/AST/APValue.h
+++ b/clang/include/clang/AST/APValue.h
@@ -135,14 +135,15 @@ public:
   }
   APValue(const APValue &RHS);
   APValue(APValue &&RHS) : Kind(Uninitialized) { swap(RHS); }
-  APValue(LValueBase B, const CharUnits &O, NoLValuePath N, unsigned CallIndex)
+  APValue(LValueBase B, const CharUnits &O, NoLValuePath N, unsigned CallIndex,
+          bool IsNullPtr = false)
       : Kind(Uninitialized) {
-    MakeLValue(); setLValue(B, O, N, CallIndex);
+    MakeLValue(); setLValue(B, O, N, CallIndex, IsNullPtr);
   }
   APValue(LValueBase B, const CharUnits &O, ArrayRef<LValuePathEntry> Path,
-          bool OnePastTheEnd, unsigned CallIndex)
+          bool OnePastTheEnd, unsigned CallIndex, bool IsNullPtr = false)
       : Kind(Uninitialized) {
-    MakeLValue(); setLValue(B, O, Path, OnePastTheEnd, CallIndex);
+    MakeLValue(); setLValue(B, O, Path, OnePastTheEnd, CallIndex, IsNullPtr);
   }
   APValue(UninitArray, unsigned InitElts, unsigned Size) : Kind(Uninitialized) {
     MakeArray(InitElts, Size);
@@ -254,6 +255,7 @@ public:
   bool hasLValuePath() const;
   ArrayRef<LValuePathEntry> getLValuePath() const;
   unsigned getLValueCallIndex() const;
+  bool isNullPointer() const;
 
   APValue &getVectorElt(unsigned I) {
     assert(isVector() && "Invalid accessor");
@@ -374,10 +376,10 @@ public:
     ((ComplexAPFloat *)(char *)Data.buffer)->Imag = std::move(I);
   }
   void setLValue(LValueBase B, const CharUnits &O, NoLValuePath,
-                 unsigned CallIndex);
+                 unsigned CallIndex, bool IsNullPtr);
   void setLValue(LValueBase B, const CharUnits &O,
                  ArrayRef<LValuePathEntry> Path, bool OnePastTheEnd,
-                 unsigned CallIndex);
+                 unsigned CallIndex, bool IsNullPtr);
   void setUnion(const FieldDecl *Field, const APValue &Value) {
     assert(isUnion() && "Invalid accessor");
     ((UnionData*)(char*)Data.buffer)->Field = Field;
diff --git a/clang/include/clang/AST/ASTContext.h b/clang/include/clang/AST/ASTContext.h
index 47d29bc2092..a07f4126826 100644
--- a/clang/include/clang/AST/ASTContext.h
+++ b/clang/include/clang/AST/ASTContext.h
@@ -2299,6 +2299,10 @@ public:
       return (*AddrSpaceMap)[AS - LangAS::Offset];
   }
 
+  /// Get target-dependent integer value for null pointer which is used for
+  /// constant folding.
+  uint64_t getTargetNullPointerValue(QualType QT) const;
+
   bool addressSpaceMapManglingFor(unsigned AS) const {
     return AddrSpaceMapMangling || 
            AS < LangAS::Offset || 
diff --git a/clang/include/clang/Basic/TargetInfo.h b/clang/include/clang/Basic/TargetInfo.h
index b6b9aea690d..ec566f06426 100644
--- a/clang/include/clang/Basic/TargetInfo.h
+++ b/clang/include/clang/Basic/TargetInfo.h
@@ -42,6 +42,7 @@ class DiagnosticsEngine;
 class LangOptions;
 class CodeGenOptions;
 class MacroBuilder;
+class QualType;
 class SourceLocation;
 class SourceManager;
 
@@ -300,6 +301,12 @@ public:
     return PointerWidth;
   }
 
+  /// \brief Get integer value for null pointer.
+  /// \param AddrSpace address space of pointee in source language.
+  virtual uint64_t getNullPointerValue(unsigned AddrSpace) const {
+    return 0;
+  }
+
   /// \brief Return the size of '_Bool' and C++ 'bool' for this target, in bits.
   unsigned getBoolWidth() const { return BoolWidth; }
 
diff --git a/clang/lib/AST/APValue.cpp b/clang/lib/AST/APValue.cpp
index 89231599727..488ad3373ca 100644
--- a/clang/lib/AST/APValue.cpp
+++ b/clang/lib/AST/APValue.cpp
@@ -27,6 +27,7 @@ namespace {
     CharUnits Offset;
     unsigned PathLength;
     unsigned CallIndex;
+    bool IsNullPtr;
   };
 }
 
@@ -149,10 +150,11 @@ APValue::APValue(const APValue &RHS) : Kind(Uninitialized) {
     MakeLValue();
     if (RHS.hasLValuePath())
       setLValue(RHS.getLValueBase(), RHS.getLValueOffset(), RHS.getLValuePath(),
-                RHS.isLValueOnePastTheEnd(), RHS.getLValueCallIndex());
+                RHS.isLValueOnePastTheEnd(), RHS.getLValueCallIndex(),
+                RHS.isNullPointer());
     else
       setLValue(RHS.getLValueBase(), RHS.getLValueOffset(), NoLValuePath(),
-                RHS.getLValueCallIndex());
+                RHS.getLValueCallIndex(), RHS.isNullPointer());
     break;
   case Array:
     MakeArray(RHS.getArrayInitializedElts(), RHS.getArraySize());
@@ -579,8 +581,13 @@ unsigned APValue::getLValueCallIndex() const {
   return ((const LV*)(const char*)Data.buffer)->CallIndex;
 }
 
+bool APValue::isNullPointer() const {
+  assert(isLValue() && "Invalid usage");
+  return ((const LV*)(const char*)Data.buffer)->IsNullPtr;
+}
+
 void APValue::setLValue(LValueBase B, const CharUnits &O, NoLValuePath,
-                        unsigned CallIndex) {
+                        unsigned CallIndex, bool IsNullPtr) {
   assert(isLValue() && "Invalid accessor");
   LV &LVal = *((LV*)(char*)Data.buffer);
   LVal.BaseAndIsOnePastTheEnd.setPointer(B);
@@ -588,11 +595,12 @@ void APValue::setLValue(LValueBase B, const CharUnits &O, NoLValuePath,
   LVal.Offset = O;
   LVal.CallIndex = CallIndex;
   LVal.resizePath((unsigned)-1);
+  LVal.IsNullPtr = IsNullPtr;
 }
 
 void APValue::setLValue(LValueBase B, const CharUnits &O,
                         ArrayRef<LValuePathEntry> Path, bool IsOnePastTheEnd,
-                        unsigned CallIndex) {
+                        unsigned CallIndex, bool IsNullPtr) {
   assert(isLValue() && "Invalid accessor");
   LV &LVal = *((LV*)(char*)Data.buffer);
   LVal.BaseAndIsOnePastTheEnd.setPointer(B);
@@ -601,6 +609,7 @@ void APValue::setLValue(LValueBase B, const CharUnits &O,
   LVal.CallIndex = CallIndex;
   LVal.resizePath(Path.size());
   memcpy(LVal.getPath(), Path.data(), Path.size() * sizeof(LValuePathEntry));
+  LVal.IsNullPtr = IsNullPtr;
 }
 
 const ValueDecl *APValue::getMemberPointerDecl() const {
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index 73ea66e98e8..7a98ac4c6e9 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -9434,6 +9434,16 @@ ASTContext::ObjCMethodsAreEqual(const ObjCMethodDecl *MethodDecl,
   
 }
 
+uint64_t ASTContext::getTargetNullPointerValue(QualType QT) const {
+  unsigned AS;
+  if (QT->getUnqualifiedDesugaredType()->isNullPtrType())
+    AS = 0;
+  else
+    AS = QT->getPointeeType().getAddressSpace();
+
+  return getTargetInfo().getNullPointerValue(AS);
+}
+
 // Explicitly instantiate this in case a Redeclarable<T> is used from a TU that
 // doesn't include ASTContext.h
 template
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 36f5e6aae55..0abdaa879ec 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -1088,6 +1088,7 @@ namespace {
     unsigned InvalidBase : 1;
     unsigned CallIndex : 31;
     SubobjectDesignator Designator;
+    bool IsNullPtr;
 
     const APValue::LValueBase getLValueBase() const { return Base; }
     CharUnits &getLValueOffset() { return Offset; }
@@ -1095,13 +1096,15 @@ namespace {
     unsigned getLValueCallIndex() const { return CallIndex; }
     SubobjectDesignator &getLValueDesignator() { return Designator; }
     const SubobjectDesignator &getLValueDesignator() const { return Designator;}
+    bool isNullPointer() const { return IsNullPtr;}
 
     void moveInto(APValue &V) const {
       if (Designator.Invalid)
-        V = APValue(Base, Offset, APValue::NoLValuePath(), CallIndex);
+        V = APValue(Base, Offset, APValue::NoLValuePath(), CallIndex,
+                    IsNullPtr);
       else
         V = APValue(Base, Offset, Designator.Entries,
-                    Designator.IsOnePastTheEnd, CallIndex);
+                    Designator.IsOnePastTheEnd, CallIndex, IsNullPtr);
     }
     void setFrom(ASTContext &Ctx, const APValue &V) {
       assert(V.isLValue());
@@ -1110,14 +1113,17 @@ namespace {
       InvalidBase = false;
       CallIndex = V.getLValueCallIndex();
       Designator = SubobjectDesignator(Ctx, V);
+      IsNullPtr = V.isNullPointer();
     }
 
-    void set(APValue::LValueBase B, unsigned I = 0, bool BInvalid = false) {
+    void set(APValue::LValueBase B, unsigned I = 0, bool BInvalid = false,
+             bool IsNullPtr_ = false, uint64_t Offset_ = 0) {
       Base = B;
-      Offset = CharUnits::Zero();
+      Offset = CharUnits::fromQuantity(Offset_);
       InvalidBase = BInvalid;
       CallIndex = I;
       Designator = SubobjectDesignator(getType(B));
+      IsNullPtr = IsNullPtr_;
     }
 
     void setInvalid(APValue::LValueBase B, unsigned I = 0) {
@@ -1130,7 +1136,7 @@ namespace {
                           CheckSubobjectKind CSK) {
       if (Designator.Invalid)
         return false;
-      if (!Base) {
+      if (IsNullPtr) {
         Info.CCEDiag(E, diag::note_constexpr_null_subobject)
           << CSK;
         Designator.setInvalid();
@@ -1159,9 +1165,22 @@ namespace {
       if (checkSubobject(Info, E, Imag ? CSK_Imag : CSK_Real))
         Designator.addComplexUnchecked(EltTy, Imag);
     }
-    void adjustIndex(EvalInfo &Info, const Expr *E, uint64_t N) {
-      if (N && checkNullPointer(Info, E, CSK_ArrayIndex))
-        Designator.adjustIndex(Info, E, N);
+    void clearIsNullPointer() {
+      IsNullPtr = false;
+    }
+    void adjustOffsetAndIndex(EvalInfo &Info, const Expr *E, uint64_t Index,
+                              CharUnits ElementSize) {
+      // Compute the new offset in the appropriate width.
+      Offset += Index * ElementSize;
+      if (Index && checkNullPointer(Info, E, CSK_ArrayIndex))
+        Designator.adjustIndex(Info, E, Index);
+      if (Index)
+        clearIsNullPointer();
+    }
+    void adjustOffset(CharUnits N) {
+      Offset += N;
+      if (N.getQuantity())
+        clearIsNullPointer();
     }
   };
 
@@ -2036,7 +2055,7 @@ static bool HandleLValueMember(EvalInfo &Info, const Expr *E, LValue &LVal,
   }
 
   unsigned I = FD->getFieldIndex();
-  LVal.Offset += Info.Ctx.toCharUnitsFromBits(RL->getFieldOffset(I));
+  LVal.adjustOffset(Info.Ctx.toCharUnitsFromBits(RL->getFieldOffset(I)));
   LVal.addDecl(Info, E, FD);
   return true;
 }
@@ -2090,9 +2109,7 @@ static bool HandleLValueArrayAdjustment(EvalInfo &Info, const Expr *E,
   if (!HandleSizeof(Info, E->getExprLoc(), EltTy, SizeOfPointee))
     return false;
 
-  // Compute the new offset in the appropriate width.
-  LVal.Offset += Adjustment * SizeOfPointee;
-  LVal.adjustIndex(Info, E, Adjustment);
+  LVal.adjustOffsetAndIndex(Info, E, Adjustment, SizeOfPointee);
   return true;
 }
 
@@ -5081,7 +5098,9 @@ public:
     return true;
   }
   bool ZeroInitialization(const Expr *E) {
-    return Success((Expr*)nullptr);
+    auto Offset = Info.Ctx.getTargetNullPointerValue(E->getType());
+    Result.set((Expr*)nullptr, 0, false, true, Offset);
+    return true;
   }
 
   bool VisitBinaryOperator(const BinaryOperator *E);
@@ -5180,6 +5199,8 @@ bool PointerExprEvaluator::VisitCastExpr(const CastExpr* E) {
       else
         CCEDiag(E, diag::note_constexpr_invalid_cast) << 2;
     }
+    if (E->getCastKind() == CK_AddressSpaceConversion && Result.IsNullPtr)
+      ZeroInitialization(E);
     return true;
 
   case CK_DerivedToBase:
@@ -5221,6 +5242,7 @@ bool PointerExprEvaluator::VisitCastExpr(const CastExpr* E) {
       Result.Offset = CharUnits::fromQuantity(N);
       Result.CallIndex = 0;
       Result.Designator.setInvalid();
+      Result.IsNullPtr = false;
       return true;
     } else {
       // Cast is of an lvalue, no need to change value.
@@ -8395,8 +8417,13 @@ bool IntExprEvaluator::VisitCastExpr(const CastExpr *E) {
       return true;
     }
 
-    APSInt AsInt = Info.Ctx.MakeIntValue(LV.getLValueOffset().getQuantity(), 
-                                         SrcType);
+    uint64_t V;
+    if (LV.isNullPointer())
+      V = Info.Ctx.getTargetNullPointerValue(SrcType);
+    else
+      V = LV.getLValueOffset().getQuantity();
+
+    APSInt AsInt = Info.Ctx.MakeIntValue(V, SrcType);
     return Success(HandleIntToIntCast(Info, E, DestType, SrcType, AsInt), E);
   }
 
diff --git a/clang/lib/Basic/Targets.cpp b/clang/lib/Basic/Targets.cpp
index 91eabb36bd3..ee84089835b 100644
--- a/clang/lib/Basic/Targets.cpp
+++ b/clang/lib/Basic/Targets.cpp
@@ -2245,6 +2245,13 @@ public:
         return CCCR_OK;
     }
   }
+
+  // In amdgcn target the null pointer in global, constant, and generic
+  // address space has value 0 but in private and local address space has
+  // value ~0.
+  uint64_t getNullPointerValue(unsigned AS) const override {
+    return AS != LangAS::opencl_local && AS != 0 ? 0 : ~0;
+  }
 };
 
 const Builtin::Info AMDGPUTargetInfo::BuiltinInfo[] = {
diff --git a/clang/lib/CodeGen/CGDecl.cpp b/clang/lib/CodeGen/CGDecl.cpp
index 695e92ea1d0..46573477580 100644
--- a/clang/lib/CodeGen/CGDecl.cpp
+++ b/clang/lib/CodeGen/CGDecl.cpp
@@ -708,7 +708,7 @@ void CodeGenFunction::EmitScalarInit(const Expr *init, const ValueDecl *D,
     }
 
     auto ty = cast<llvm::PointerType>(tempLV.getAddress().getElementType());
-    llvm::Value *zero = llvm::ConstantPointerNull::get(ty);
+    llvm::Value *zero = CGM.getNullPointer(ty, tempLV.getType());
 
     // If __weak, we want to use a barrier under certain conditions.
     if (lifetime == Qualifiers::OCL_Weak)
diff --git a/clang/lib/CodeGen/CGExprAgg.cpp b/clang/lib/CodeGen/CGExprAgg.cpp
index e24a0853c80..35148bea001 100644
--- a/clang/lib/CodeGen/CGExprAgg.cpp
+++ b/clang/lib/CodeGen/CGExprAgg.cpp
@@ -1052,7 +1052,8 @@ static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
     return true;
   // (int*)0 - Null pointer expressions.
   if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
-    return ICE->getCastKind() == CK_NullToPointer;
+    return ICE->getCastKind() == CK_NullToPointer &&
+        CGF.getTypes().isPointerZeroInitializable(E->getType());
   // '\0'
   if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
     return CL->getValue() == 0;
diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index 345e0a9216a..752f419f64e 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -16,6 +16,7 @@
 #include "CGObjCRuntime.h"
 #include "CGRecordLayout.h"
 #include "CodeGenModule.h"
+#include "TargetInfo.h"
 #include "clang/AST/APValue.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/RecordLayout.h"
@@ -1262,6 +1263,10 @@ llvm::Constant *CodeGenModule::EmitConstantExpr(const Expr *E,
   return C;
 }
 
+llvm::Constant *CodeGenModule::getNullPointer(llvm::PointerType *T, QualType QT) {
+  return getTargetCodeGenInfo().getNullPointer(*this, T, QT);
+}
+
 llvm::Constant *CodeGenModule::EmitConstantValue(const APValue &Value,
                                                  QualType DestType,
                                                  CodeGenFunction *CGF) {
@@ -1293,6 +1298,7 @@ llvm::Constant *CodeGenModule::EmitConstantValue(const APValue &Value,
       llvm::ConstantInt::get(Int64Ty, Value.getLValueOffset().getQuantity());
 
     llvm::Constant *C = nullptr;
+
     if (APValue::LValueBase LVBase = Value.getLValueBase()) {
       // An array can be represented as an lvalue referring to the base.
       if (isa<llvm::ArrayType>(DestTy)) {
@@ -1323,7 +1329,9 @@ llvm::Constant *CodeGenModule::EmitConstantValue(const APValue &Value,
 
       // Convert to the appropriate type; this could be an lvalue for
       // an integer.
-      if (isa<llvm::PointerType>(DestTy)) {
+      if (auto PT = dyn_cast<llvm::PointerType>(DestTy)) {
+        if (Value.isNullPointer())
+          return getNullPointer(PT, DestType);
         // Convert the integer to a pointer-sized integer before converting it
         // to a pointer.
         C = llvm::ConstantExpr::getIntegerCast(
@@ -1510,7 +1518,7 @@ static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
                                                const CXXRecordDecl *base);
 
 static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
-                                        const CXXRecordDecl *record,
+                                        const RecordDecl *record,
                                         bool asCompleteObject) {
   const CGRecordLayout &layout = CGM.getTypes().getCGRecordLayout(record);
   llvm::StructType *structure =
@@ -1520,25 +1528,29 @@ static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
   unsigned numElements = structure->getNumElements();
   std::vector<llvm::Constant *> elements(numElements);
 
+  auto CXXR = dyn_cast<CXXRecordDecl>(record);
   // Fill in all the bases.
-  for (const auto &I : record->bases()) {
-    if (I.isVirtual()) {
-      // Ignore virtual bases; if we're laying out for a complete
-      // object, we'll lay these out later.
-      continue;
-    }
+  if (CXXR) {
+    for (const auto &I : CXXR->bases()) {
+      if (I.isVirtual()) {
+        // Ignore virtual bases; if we're laying out for a complete
+        // object, we'll lay these out later.
+        continue;
+      }
 
-    const CXXRecordDecl *base = 
-      cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl());
+      const CXXRecordDecl *base =
+        cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl());
 
-    // Ignore empty bases.
-    if (base->isEmpty() ||
-        CGM.getContext().getASTRecordLayout(base).getNonVirtualSize().isZero())
-      continue;
-    
-    unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base);
-    llvm::Type *baseType = structure->getElementType(fieldIndex);
-    elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
+      // Ignore empty bases.
+      if (base->isEmpty() ||
+          CGM.getContext().getASTRecordLayout(base).getNonVirtualSize()
+              .isZero())
+        continue;
+
+      unsigned fieldIndex = layout.getNonVirtualBaseLLVMFieldNo(base);
+      llvm::Type *baseType = structure->getElementType(fieldIndex);
+      elements[fieldIndex] = EmitNullConstantForBase(CGM, baseType, base);
+    }
   }
 
   // Fill in all the fields.
@@ -1562,8 +1574,8 @@ static llvm::Constant *EmitNullConstant(CodeGenModule &CGM,
   }
 
   // Fill in the virtual bases, if we're working with the complete object.
-  if (asCompleteObject) {
-    for (const auto &I : record->vbases()) {
+  if (CXXR && asCompleteObject) {
+    for (const auto &I : CXXR->vbases()) {
       const CXXRecordDecl *base = 
         cast<CXXRecordDecl>(I.getType()->castAs<RecordType>()->getDecl());
 
@@ -1605,6 +1617,10 @@ static llvm::Constant *EmitNullConstantForBase(CodeGenModule &CGM,
 }
 
 llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
+  if (T->getAs<PointerType>())
+    return getNullPointer(
+        cast<llvm::PointerType>(getTypes().ConvertTypeForMem(T)), T);
+
   if (getTypes().isZeroInitializable(T))
     return llvm::Constant::getNullValue(getTypes().ConvertTypeForMem(T));
     
@@ -1620,10 +1636,8 @@ llvm::Constant *CodeGenModule::EmitNullConstant(QualType T) {
     return llvm::ConstantArray::get(ATy, Array);
   }
 
-  if (const RecordType *RT = T->getAs<RecordType>()) {
-    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
-    return ::EmitNullConstant(*this, RD, /*complete object*/ true);
-  }
+  if (const RecordType *RT = T->getAs<RecordType>())
+    return ::EmitNullConstant(*this, RT->getDecl(), /*complete object*/ true);
 
   assert(T->isMemberDataPointerType() &&
          "Should only see pointers to data members here!");
diff --git a/clang/lib/CodeGen/CGExprScalar.cpp b/clang/lib/CodeGen/CGExprScalar.cpp
index e763e6ab020..e9bdbda34aa 100644
--- a/clang/lib/CodeGen/CGExprScalar.cpp
+++ b/clang/lib/CodeGen/CGExprScalar.cpp
@@ -19,6 +19,7 @@
 #include "TargetInfo.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclObjC.h"
+#include "clang/AST/Expr.h"
 #include "clang/AST/RecordLayout.h"
 #include "clang/AST/StmtVisitor.h"
 #include "clang/Basic/TargetInfo.h"
@@ -171,9 +172,9 @@ public:
   }
 
   /// EmitPointerToBoolConversion - Perform a pointer to boolean conversion.
-  Value *EmitPointerToBoolConversion(Value *V) {
-    Value *Zero = llvm::ConstantPointerNull::get(
-                                      cast<llvm::PointerType>(V->getType()));
+  Value *EmitPointerToBoolConversion(Value *V, QualType QT) {
+    Value *Zero = CGF.CGM.getNullPointer(cast<llvm::PointerType>(V->getType()), QT);
+
     return Builder.CreateICmpNE(V, Zero, "tobool");
   }
 
@@ -597,7 +598,7 @@ Value *ScalarExprEmitter::EmitConversionToBool(Value *Src, QualType SrcType) {
     return EmitIntToBoolConversion(Src);
 
   assert(isa<llvm::PointerType>(Src->getType()));
-  return EmitPointerToBoolConversion(Src);
+  return EmitPointerToBoolConversion(Src, SrcType);
 }
 
 void ScalarExprEmitter::EmitFloatConversionCheck(
@@ -1400,11 +1401,23 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
     return Builder.CreateBitCast(Src, DstTy);
   }
   case CK_AddressSpaceConversion: {
-    Value *Src = Visit(const_cast<Expr*>(E));
+    Expr::EvalResult Result;
+    if (E->EvaluateAsRValue(Result, CGF.getContext()) &&
+        Result.Val.isNullPointer()) {
+      // If E has side effect, it is emitted even if its final result is a
+      // null pointer. In that case, a DCE pass should be able to
+      // eliminate the useless instructions emitted during translating E.
+      if (Result.HasSideEffects)
+        Visit(E);
+      return CGF.CGM.getNullPointer(cast<llvm::PointerType>(
+          ConvertType(DestTy)), DestTy);
+    }
     // Since target may map different address spaces in AST to the same address
     // space, an address space conversion may end up as a bitcast.
-    return Builder.CreatePointerBitCastOrAddrSpaceCast(Src,
-                                                       ConvertType(DestTy));
+    auto *Src = Visit(E);
+    return CGF.CGM.getTargetCodeGenInfo().performAddrSpaceCast(CGF, Src,
+                                                               E->getType(),
+                                                               DestTy);
   }
   case CK_AtomicToNonAtomic:
   case CK_NonAtomicToAtomic:
@@ -1459,8 +1472,8 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
     if (MustVisitNullValue(E))
       (void) Visit(E);
 
-    return llvm::ConstantPointerNull::get(
-                               cast<llvm::PointerType>(ConvertType(DestTy)));
+    return CGF.CGM.getNullPointer(cast<llvm::PointerType>(ConvertType(DestTy)),
+                              DestTy);
 
   case CK_NullToMemberPointer: {
     if (MustVisitNullValue(E))
@@ -1553,7 +1566,7 @@ Value *ScalarExprEmitter::VisitCastExpr(CastExpr *CE) {
   case CK_IntegralToBoolean:
     return EmitIntToBoolConversion(Visit(E));
   case CK_PointerToBoolean:
-    return EmitPointerToBoolConversion(Visit(E));
+    return EmitPointerToBoolConversion(Visit(E), E->getType());
   case CK_FloatingToBoolean:
     return EmitFloatToBoolConversion(Visit(E));
   case CK_MemberPointerToBoolean: {
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 404cbae1d83..64c2bd673cc 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -2663,9 +2663,16 @@ void CodeGenModule::EmitGlobalVarDefinition(const VarDecl *D,
   else
     GV->setDLLStorageClass(llvm::GlobalVariable::DefaultStorageClass);
 
-  if (Linkage == llvm::GlobalVariable::CommonLinkage)
+  if (Linkage == llvm::GlobalVariable::CommonLinkage) {
     // common vars aren't constant even if declared const.
     GV->setConstant(false);
+    // Tentative definition of global variables may be initialized with
+    // non-zero null pointers. In this case they should have weak linkage
+    // since common linkage must have zero initializer and must not have
+    // explicit section therefore cannot have non-zero initial value.
+    if (!GV->getInitializer()->isNullValue())
+      GV->setLinkage(llvm::GlobalVariable::WeakAnyLinkage);
+  }
 
   setNonAliasAttributes(D, GV);
 
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index d4c096ed67b..f26c92d5670 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -1156,6 +1156,11 @@ public:
   llvm::Value *
   createOpenCLIntToSamplerConversion(const Expr *E, CodeGenFunction &CGF);
 
+  /// Get target specific null pointer.
+  /// \param T is the LLVM type of the null pointer.
+  /// \param QT is the clang QualType of the null pointer.
+  llvm::Constant *getNullPointer(llvm::PointerType *T, QualType QT);
+
 private:
   llvm::Constant *
   GetOrCreateLLVMFunction(StringRef MangledName, llvm::Type *Ty, GlobalDecl D,
diff --git a/clang/lib/CodeGen/CodeGenTypes.cpp b/clang/lib/CodeGen/CodeGenTypes.cpp
index c92095bbbe6..b95b4fff573 100644
--- a/clang/lib/CodeGen/CodeGenTypes.cpp
+++ b/clang/lib/CodeGen/CodeGenTypes.cpp
@@ -736,10 +736,14 @@ CodeGenTypes::getCGRecordLayout(const RecordDecl *RD) {
   return *Layout;
 }
 
+bool CodeGenTypes::isPointerZeroInitializable(QualType T) {
+  assert (T->isAnyPointerType() && "Invalid type");
+  return isZeroInitializable(T);
+}
+
 bool CodeGenTypes::isZeroInitializable(QualType T) {
-  // No need to check for member pointers when not compiling C++.
-  if (!Context.getLangOpts().CPlusPlus)
-    return true;
+  if (T->getAs<PointerType>())
+    return Context.getTargetNullPointerValue(T) == 0;
 
   if (const auto *AT = Context.getAsArrayType(T)) {
     if (isa<IncompleteArrayType>(AT))
@@ -753,7 +757,7 @@ bool CodeGenTypes::isZeroInitializable(QualType T) {
   // Records are non-zero-initializable if they contain any
   // non-zero-initializable subobjects.
   if (const RecordType *RT = T->getAs<RecordType>()) {
-    const CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
+    auto RD = cast<RecordDecl>(RT->getDecl());
     return isZeroInitializable(RD);
   }
 
diff --git a/clang/lib/CodeGen/CodeGenTypes.h b/clang/lib/CodeGen/CodeGenTypes.h
index 00df10dd138..2ce6591e4eb 100644
--- a/clang/lib/CodeGen/CodeGenTypes.h
+++ b/clang/lib/CodeGen/CodeGenTypes.h
@@ -352,6 +352,10 @@ public:  // These are internal details of CGT that shouldn't be used externally.
   /// zero-initialized (in the C++ sense) with an LLVM zeroinitializer.
   bool isZeroInitializable(QualType T);
 
+  /// Check if the pointer type can be zero-initialized (in the C++ sense)
+  /// with an LLVM zeroinitializer.
+  bool isPointerZeroInitializable(QualType T);
+
   /// IsZeroInitializable - Return whether a record type can be
   /// zero-initialized (in the C++ sense) with an LLVM zeroinitializer.
   bool isZeroInitializable(const RecordDecl *RD);
diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 38b164b113a..391eb53d250 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -401,6 +401,20 @@ unsigned TargetCodeGenInfo::getOpenCLKernelCallingConv() const {
   return llvm::CallingConv::C;
 }
 
+llvm::Constant *TargetCodeGenInfo::getNullPointer(const CodeGen::CodeGenModule &CGM,
+    llvm::PointerType *T, QualType QT) const {
+  return llvm::ConstantPointerNull::get(T);
+}
+
+llvm::Value *TargetCodeGenInfo::performAddrSpaceCast(
+    CodeGen::CodeGenFunction &CGF, llvm::Value *Src, QualType SrcTy,
+    QualType DestTy) const {
+  // Since target may map different address spaces in AST to the same address
+  // space, an address space conversion may end up as a bitcast.
+  return CGF.Builder.CreatePointerBitCastOrAddrSpaceCast(Src,
+             CGF.ConvertType(DestTy));
+}
+
 static bool isEmptyRecord(ASTContext &Context, QualType T, bool AllowArrays);
 
 /// isEmptyField - Return true iff a the field is "empty", that is it
@@ -7075,8 +7089,10 @@ public:
   void setTargetAttributes(const Decl *D, llvm::GlobalValue *GV,
                            CodeGen::CodeGenModule &M) const override;
   unsigned getOpenCLKernelCallingConv() const override;
-};
 
+  llvm::Constant *getNullPointer(const CodeGen::CodeGenModule &CGM,
+      llvm::PointerType *T, QualType QT) const override;
+};
 }
 
 static void appendOpenCLVersionMD (CodeGen::CodeGenModule &CGM);
@@ -7140,6 +7156,24 @@ unsigned AMDGPUTargetCodeGenInfo::getOpenCLKernelCallingConv() const {
   return llvm::CallingConv::AMDGPU_KERNEL;
 }
 
+// Currently LLVM assumes null pointers always have value 0,
+// which results in incorrectly transformed IR. Therefore, instead of
+// emitting null pointers in private and local address spaces, a null
+// pointer in generic address space is emitted which is casted to a
+// pointer in local or private address space.
+llvm::Constant *AMDGPUTargetCodeGenInfo::getNullPointer(
+    const CodeGen::CodeGenModule &CGM, llvm::PointerType *PT,
+    QualType QT) const {
+  if (CGM.getContext().getTargetNullPointerValue(QT) == 0)
+    return llvm::ConstantPointerNull::get(PT);
+
+  auto &Ctx = CGM.getContext();
+  auto NPT = llvm::PointerType::get(PT->getElementType(),
+      Ctx.getTargetAddressSpace(LangAS::opencl_generic));
+  return llvm::ConstantExpr::getAddrSpaceCast(
+      llvm::ConstantPointerNull::get(NPT), PT);
+}
+
 //===----------------------------------------------------------------------===//
 // SPARC v8 ABI Implementation.
 // Based on the SPARC Compliance Definition version 2.4.1.
diff --git a/clang/lib/CodeGen/TargetInfo.h b/clang/lib/CodeGen/TargetInfo.h
index e46382596af..223d6d047af 100644
--- a/clang/lib/CodeGen/TargetInfo.h
+++ b/clang/lib/CodeGen/TargetInfo.h
@@ -220,6 +220,22 @@ public:
 
   /// Get LLVM calling convention for OpenCL kernel.
   virtual unsigned getOpenCLKernelCallingConv() const;
+
+  /// Get target specific null pointer.
+  /// \param T is the LLVM type of the null pointer.
+  /// \param QT is the clang QualType of the null pointer.
+  /// \return ConstantPointerNull with the given type \p T.
+  /// Each target can override it to return its own desired constant value.
+  virtual llvm::Constant *getNullPointer(const CodeGen::CodeGenModule &CGM,
+      llvm::PointerType *T, QualType QT) const;
+
+  /// Perform address space cast of an expression of pointer type.
+  /// \param V is the LLVM value to be casted to another address space.
+  /// \param SrcTy is the QualType of \p V.
+  /// \param DestTy is the destination QualType.
+  virtual llvm::Value *performAddrSpaceCast(CodeGen::CodeGenFunction &CGF,
+      llvm::Value *V, QualType SrcTy, QualType DestTy) const;
+
 };
 
 } // namespace CodeGen
diff --git a/clang/test/CodeGenOpenCL/amdgpu-nullptr.cl b/clang/test/CodeGenOpenCL/amdgpu-nullptr.cl
new file mode 100644
index 00000000000..2d36fa90a6a
--- /dev/null
+++ b/clang/test/CodeGenOpenCL/amdgpu-nullptr.cl
@@ -0,0 +1,534 @@
+// RUN: %clang_cc1 %s -cl-std=CL2.0 -include opencl-c.h -triple amdgcn -emit-llvm -o - | FileCheck %s
+// RUN: %clang_cc1 %s -O0 -cl-std=CL2.0 -include opencl-c.h -triple amdgcn -emit-llvm -o - | FileCheck --check-prefix=NOOPT %s
+
+typedef struct {
+  private char *p1;
+  local char *p2;
+  constant char *p3;
+  global char *p4;
+  generic char *p5;
+} StructTy1;
+
+typedef struct {
+  constant char *p3;
+  global char *p4;
+  generic char *p5;
+} StructTy2;
+
+// LLVM requests global variable with common linkage to be initialized with zeroinitializer, therefore use -fno-common
+// to suppress common linkage for tentative definition.
+
+// Test 0 as initializer.
+
+// CHECK: @private_p = local_unnamed_addr addrspace(1) global i8* addrspacecast (i8 addrspace(4)* null to i8*), align 4
+private char *private_p = 0;
+
+// CHECK: @local_p = local_unnamed_addr addrspace(1) global i8 addrspace(3)* addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*), align 4
+local char *local_p = 0;
+
+// CHECK: @global_p = local_unnamed_addr addrspace(1) global i8 addrspace(1)* null, align 4
+global char *global_p = 0;
+
+// CHECK: @constant_p = local_unnamed_addr addrspace(1) global i8 addrspace(2)* null, align 4
+constant char *constant_p = 0;
+
+// CHECK: @generic_p = local_unnamed_addr addrspace(1) global i8 addrspace(4)* null, align 4
+generic char *generic_p = 0;
+
+// Test NULL as initializer.
+
+// CHECK: @private_p_NULL = local_unnamed_addr addrspace(1) global i8* addrspacecast (i8 addrspace(4)* null to i8*), align 4
+private char *private_p_NULL = NULL;
+
+// CHECK: @local_p_NULL = local_unnamed_addr addrspace(1) global i8 addrspace(3)* addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*), align 4
+local char *local_p_NULL = NULL;
+
+// CHECK: @global_p_NULL = local_unnamed_addr addrspace(1) global i8 addrspace(1)* null, align 4
+global char *global_p_NULL = NULL;
+
+// CHECK: @constant_p_NULL = local_unnamed_addr addrspace(1) global i8 addrspace(2)* null, align 4
+constant char *constant_p_NULL = NULL;
+
+// CHECK: @generic_p_NULL = local_unnamed_addr addrspace(1) global i8 addrspace(4)* null, align 4
+generic char *generic_p_NULL = NULL;
+
+// Test constant folding of null pointer.
+// A null pointer should be folded to a null pointer in the target address space.
+
+// CHECK: @fold_generic = local_unnamed_addr addrspace(1) global i32 addrspace(4)* null, align 4
+generic int *fold_generic = (global int*)(generic float*)(private char*)0;
+
+// CHECK: @fold_priv = local_unnamed_addr addrspace(1) global i16* addrspacecast (i16 addrspace(4)* null to i16*), align 4
+private short *fold_priv = (private short*)(generic int*)(global void*)0;
+
+// CHECK: @fold_priv_arith = local_unnamed_addr addrspace(1) global i8* inttoptr (i32 9 to i8*), align 4
+private char *fold_priv_arith = (private char*)0 + 10;
+
+// CHECK: @fold_int = local_unnamed_addr addrspace(1) global i32 13, align 4
+int fold_int = (int)(private void*)(generic char*)(global int*)0 + 14;
+
+// CHECK: @fold_int2 = local_unnamed_addr addrspace(1) global i32 12, align 4
+int fold_int2 = (int) ((private void*)0 + 13);
+
+// CHECK: @fold_int3 = local_unnamed_addr addrspace(1) global i32 -1, align 4
+int fold_int3 = (int) ((private int*)0);
+
+// CHECK: @fold_int4 = local_unnamed_addr addrspace(1) global i32 7, align 4
+int fold_int4 = (int) &((private int*)0)[2];
+
+// CHECK: @fold_int5 = local_unnamed_addr addrspace(1) global i32 3, align 4
+int fold_int5 = (int) &((private StructTy1*)0)->p2;
+
+// Test static variable initialization.
+
+// NOOPT: @test_static_var.sp1 = internal addrspace(1) global i8* addrspacecast (i8 addrspace(4)* null to i8*), align 4
+// NOOPT: @test_static_var.sp2 = internal addrspace(1) global i8* addrspacecast (i8 addrspace(4)* null to i8*), align 4
+// NOOPT: @test_static_var.sp3 = internal addrspace(1) global i8* addrspacecast (i8 addrspace(4)* null to i8*), align 4
+// NOOPT: @test_static_var.sp4 = internal addrspace(1) global i8* null, align 4
+// NOOPT: @test_static_var.sp5 = internal addrspace(1) global i8* null, align 4
+// NOOPT: @test_static_var.SS1 = internal addrspace(1) global %struct.StructTy1 { i8* addrspacecast (i8 addrspace(4)* null to i8*), i8 addrspace(3)* addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*), i8 addrspace(2)* null, i8 addrspace(1)* null, i8 addrspace(4)* null }, align 4
+// NOOPT: @test_static_var.SS2 = internal addrspace(1) global %struct.StructTy2 zeroinitializer, align 4
+
+void test_static_var(void) {
+  static private char *sp1 = 0;
+  static private char *sp2 = NULL;
+  static private char *sp3;
+  static private char *sp4 = (private char*)((void)0, 0);
+  const int x = 0;
+  static private char *sp5 = (private char*)x;
+  static StructTy1 SS1;
+  static StructTy2 SS2;
+}
+
+// Test function-scope variable initialization.
+// NOOPT-LABEL: test_func_scope_var
+// NOOPT: store i8* addrspacecast (i8 addrspace(4)* null to i8*), i8** %sp1, align 4
+// NOOPT: store i8* addrspacecast (i8 addrspace(4)* null to i8*), i8** %sp2, align 4
+// NOOPT: store i8* null, i8** %sp3, align 4
+// NOOPT: store i8* null, i8** %sp4, align 4
+// NOOPT: %[[SS1:.*]] = bitcast %struct.StructTy1* %SS1 to i8*
+// NOOPT: call void @llvm.memcpy.p0i8.p2i8.i64(i8* %[[SS1]], i8 addrspace(2)* bitcast (%struct.StructTy1 addrspace(2)* @test_func_scope_var.SS1 to i8 addrspace(2)*), i64 32, i32 4, i1 false)
+// NOOPT: %[[SS2:.*]] = bitcast %struct.StructTy2* %SS2 to i8*
+// NOOPT: call void @llvm.memset.p0i8.i64(i8* %[[SS2]], i8 0, i64 24, i32 4, i1 false)
+
+void test_func_scope_var(void) {
+  private char *sp1 = 0;
+  private char *sp2 = NULL;
+  private char *sp3 = (private char*)((void)0, 0);
+  const int x = 0;
+  private char *sp4 = (private char*)x;
+  StructTy1 SS1 = {0, 0, 0, 0, 0};
+  StructTy2 SS2 = {0, 0, 0};
+}
+
+// Test default initialization of pointers.
+
+// Tentative definition of global variables with non-zero initializer
+// cannot have common linkage since common linkage requires zero initialization
+// and does not have explicit section.
+
+// CHECK: @p1 = weak local_unnamed_addr addrspace(1) global i8* addrspacecast (i8 addrspace(4)* null to i8*), align 4
+private char *p1;
+
+// CHECK: @p2 = weak local_unnamed_addr addrspace(1) global i8 addrspace(3)* addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*), align 4
+local char *p2;
+
+// CHECK: @p3 = common local_unnamed_addr addrspace(1) global i8 addrspace(2)* null, align 4
+constant char *p3;
+
+// CHECK: @p4 = common local_unnamed_addr addrspace(1) global i8 addrspace(1)* null, align 4
+global char *p4;
+
+// CHECK: @p5 = common local_unnamed_addr addrspace(1) global i8 addrspace(4)* null, align 4
+generic char *p5;
+
+// Test default initialization of sturcture.
+
+// CHECK: @S1 = weak local_unnamed_addr addrspace(1) global %struct.StructTy1 { i8* addrspacecast (i8 addrspace(4)* null to i8*), i8 addrspace(3)* addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*), i8 addrspace(2)* null, i8 addrspace(1)* null, i8 addrspace(4)* null }, align 4
+StructTy1 S1;
+
+// CHECK: @S2 = common local_unnamed_addr addrspace(1) global %struct.StructTy2 zeroinitializer, align 4
+StructTy2 S2;
+
+// Test default initialization of array.
+// CHECK: @A1 = weak local_unnamed_addr addrspace(1) global [2 x %struct.StructTy1] [%struct.StructTy1 { i8* addrspacecast (i8 addrspace(4)* null to i8*), i8 addrspace(3)* addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*), i8 addrspace(2)* null, i8 addrspace(1)* null, i8 addrspace(4)* null }, %struct.StructTy1 { i8* addrspacecast (i8 addrspace(4)* null to i8*), i8 addrspace(3)* addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*), i8 addrspace(2)* null, i8 addrspace(1)* null, i8 addrspace(4)* null }], align 4
+StructTy1 A1[2];
+
+// CHECK: @A2 = common local_unnamed_addr addrspace(1) global [2 x %struct.StructTy2] zeroinitializer, align 4
+StructTy2 A2[2];
+
+// Test comparison with 0.
+
+// CHECK-LABEL: cmp_private
+// CHECK: icmp eq i8* %p, addrspacecast (i8 addrspace(4)* null to i8*)
+void cmp_private(private char* p) {
+  if (p != 0)
+    *p = 0;
+}
+
+// CHECK-LABEL: cmp_local
+// CHECK: icmp eq i8 addrspace(3)* %p, addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*)
+void cmp_local(local char* p) {
+  if (p != 0)
+    *p = 0;
+}
+
+// CHECK-LABEL: cmp_global
+// CHECK: icmp eq i8 addrspace(1)* %p, null
+void cmp_global(global char* p) {
+  if (p != 0)
+    *p = 0;
+}
+
+// CHECK-LABEL: cmp_constant
+// CHECK: icmp eq i8 addrspace(2)* %p, null
+char cmp_constant(constant char* p) {
+  if (p != 0)
+    return *p;
+  else
+    return 0;
+}
+
+// CHECK-LABEL: cmp_generic
+// CHECK: icmp eq i8 addrspace(4)* %p, null
+void cmp_generic(generic char* p) {
+  if (p != 0)
+    *p = 0;
+}
+
+// Test comparison with NULL.
+
+// CHECK-LABEL: cmp_NULL_private
+// CHECK: icmp eq i8* %p, addrspacecast (i8 addrspace(4)* null to i8*)
+void cmp_NULL_private(private char* p) {
+  if (p != NULL)
+    *p = 0;
+}
+
+// CHECK-LABEL: cmp_NULL_local
+// CHECK: icmp eq i8 addrspace(3)* %p, addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*)
+void cmp_NULL_local(local char* p) {
+  if (p != NULL)
+    *p = 0;
+}
+
+// CHECK-LABEL: cmp_NULL_global
+// CHECK: icmp eq i8 addrspace(1)* %p, null
+void cmp_NULL_global(global char* p) {
+  if (p != NULL)
+    *p = 0;
+}
+
+// CHECK-LABEL: cmp_NULL_constant
+// CHECK: icmp eq i8 addrspace(2)* %p, null
+char cmp_NULL_constant(constant char* p) {
+  if (p != NULL)
+    return *p;
+  else
+    return 0;
+}
+
+// CHECK-LABEL: cmp_NULL_generic
+// CHECK: icmp eq i8 addrspace(4)* %p, null
+void cmp_NULL_generic(generic char* p) {
+  if (p != NULL)
+    *p = 0;
+}
+
+// Test storage 0 as null pointer.
+// CHECK-LABEL: test_storage_null_pointer
+// CHECK: store i8* addrspacecast (i8 addrspace(4)* null to i8*), i8* addrspace(4)* %arg_private
+// CHECK: store i8 addrspace(3)* addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*), i8 addrspace(3)* addrspace(4)* %arg_local
+// CHECK: store i8 addrspace(1)* null, i8 addrspace(1)* addrspace(4)* %arg_global
+// CHECK: store i8 addrspace(2)* null, i8 addrspace(2)* addrspace(4)* %arg_constant
+// CHECK: store i8 addrspace(4)* null, i8 addrspace(4)* addrspace(4)* %arg_generic
+void test_storage_null_pointer(private char** arg_private,
+                               local char** arg_local,
+                               global char** arg_global,
+                               constant char** arg_constant,
+                               generic char** arg_generic) {
+   *arg_private = 0;
+   *arg_local = 0;
+   *arg_global = 0;
+   *arg_constant = 0;
+   *arg_generic = 0;
+}
+
+// Test storage NULL as null pointer.
+// CHECK-LABEL: test_storage_null_pointer_NULL
+// CHECK: store i8* addrspacecast (i8 addrspace(4)* null to i8*), i8* addrspace(4)* %arg_private
+// CHECK: store i8 addrspace(3)* addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*), i8 addrspace(3)* addrspace(4)* %arg_local
+// CHECK: store i8 addrspace(1)* null, i8 addrspace(1)* addrspace(4)* %arg_global
+// CHECK: store i8 addrspace(2)* null, i8 addrspace(2)* addrspace(4)* %arg_constant
+// CHECK: store i8 addrspace(4)* null, i8 addrspace(4)* addrspace(4)* %arg_generic
+void test_storage_null_pointer_NULL(private char** arg_private,
+                                    local char** arg_local,
+                                    global char** arg_global,
+                                    constant char** arg_constant,
+                                    generic char** arg_generic) {
+   *arg_private = NULL;
+   *arg_local = NULL;
+   *arg_global = NULL;
+   *arg_constant = NULL;
+   *arg_generic = NULL;
+}
+
+// Test pass null pointer to function as argument.
+void test_pass_null_pointer_arg_calee(private char* arg_private,
+                                      local char* arg_local,
+                                      global char* arg_global,
+                                      constant char* arg_constant,
+                                      generic char* arg_generic);
+
+// CHECK-LABEL: test_pass_null_pointer_arg
+// CHECK: call void @test_pass_null_pointer_arg_calee(i8* addrspacecast (i8 addrspace(4)* null to i8*), i8 addrspace(3)* addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*), i8 addrspace(1)* null, i8 addrspace(2)* null, i8 addrspace(4)* null)
+// CHECK: call void @test_pass_null_pointer_arg_calee(i8* addrspacecast (i8 addrspace(4)* null to i8*), i8 addrspace(3)* addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*), i8 addrspace(1)* null, i8 addrspace(2)* null, i8 addrspace(4)* null)
+void test_pass_null_pointer_arg(void) {
+  test_pass_null_pointer_arg_calee(0, 0, 0, 0, 0);
+  test_pass_null_pointer_arg_calee(NULL, NULL, NULL, NULL, NULL);
+}
+
+// Test cast null pointer to size_t.
+void test_cast_null_pointer_to_sizet_calee(size_t arg_private,
+                                           size_t arg_local,
+                                           size_t arg_global,
+                                           size_t arg_constant,
+                                           size_t arg_generic);
+
+// CHECK-LABEL: test_cast_null_pointer_to_sizet
+// CHECK: call void @test_cast_null_pointer_to_sizet_calee(i64 ptrtoint (i8* addrspacecast (i8 addrspace(4)* null to i8*) to i64), i64 ptrtoint (i8 addrspace(3)* addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*) to i64), i64 0, i64 0, i64 0)
+// CHECK: call void @test_cast_null_pointer_to_sizet_calee(i64 ptrtoint (i8* addrspacecast (i8 addrspace(4)* null to i8*) to i64), i64 ptrtoint (i8 addrspace(3)* addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*) to i64), i64 0, i64 0, i64 0)
+void test_cast_null_pointer_to_sizet(void) {
+  test_cast_null_pointer_to_sizet_calee((size_t)((private char*)0),
+                                        (size_t)((local char*)0),
+                                        (size_t)((global char*)0),
+                                        (size_t)((constant char*)0),
+                                        (size_t)((generic char*)0));
+  test_cast_null_pointer_to_sizet_calee((size_t)((private char*)NULL),
+                                        (size_t)((local char*)NULL),
+                                        (size_t)((global char*)NULL),
+                                        (size_t)((constant char*)0), // NULL cannot be casted to constant pointer since it is defined as a generic pointer
+                                        (size_t)((generic char*)NULL));
+}
+
+// Test comparision between null pointers.
+#define TEST_EQ00(addr1, addr2) int test_eq00_##addr1##_##addr2(void) { return (addr1 char*)0 == (addr2 char*)0; }
+#define TEST_EQ0N(addr1, addr2) int test_eq0N_##addr1##_##addr2(void) { return (addr1 char*)0 == (addr2 char*)NULL; }
+#define TEST_EQN0(addr1, addr2) int test_eqN0_##addr1##_##addr2(void) { return (addr1 char*)NULL == (addr2 char*)0; }
+#define TEST_EQNN(addr1, addr2) int test_eqNN_##addr1##_##addr2(void) { return (addr1 char*)0 == (addr2 char*)NULL; }
+#define TEST_NE00(addr1, addr2) int test_ne00_##addr1##_##addr2(void) { return (addr1 char*)0 != (addr2 char*)0; }
+#define TEST_NE0N(addr1, addr2) int test_ne0N_##addr1##_##addr2(void) { return (addr1 char*)0 != (addr2 char*)NULL; }
+#define TEST_NEN0(addr1, addr2) int test_neN0_##addr1##_##addr2(void) { return (addr1 char*)NULL != (addr2 char*)0; }
+#define TEST_NENN(addr1, addr2) int test_neNN_##addr1##_##addr2(void) { return (addr1 char*)0 != (addr2 char*)NULL; }
+#define TEST(addr1, addr2) \
+        TEST_EQ00(addr1, addr2) \
+        TEST_EQ0N(addr1, addr2) \
+        TEST_EQN0(addr1, addr2) \
+        TEST_EQNN(addr1, addr2) \
+        TEST_NE00(addr1, addr2) \
+        TEST_NE0N(addr1, addr2) \
+        TEST_NEN0(addr1, addr2) \
+        TEST_NENN(addr1, addr2)
+
+// CHECK-LABEL: test_eq00_generic_private
+// CHECK: ret i32 1
+// CHECK-LABEL: test_eq0N_generic_private
+// CHECK: ret i32 1
+// CHECK-LABEL: test_eqN0_generic_private
+// CHECK: ret i32 1
+// CHECK-LABEL: test_eqNN_generic_private
+// CHECK: ret i32 1
+// CHECK-LABEL: test_ne00_generic_private
+// CHECK: ret i32 0
+// CHECK-LABEL: test_ne0N_generic_private
+// CHECK: ret i32 0
+// CHECK-LABEL: test_neN0_generic_private
+// CHECK: ret i32 0
+// CHECK-LABEL: test_neNN_generic_private
+// CHECK: ret i32 0
+TEST(generic, private)
+
+// CHECK-LABEL: test_eq00_generic_local
+// CHECK: ret i32 1
+// CHECK-LABEL: test_eq0N_generic_local
+// CHECK: ret i32 1
+// CHECK-LABEL: test_eqN0_generic_local
+// CHECK: ret i32 1
+// CHECK-LABEL: test_eqNN_generic_local
+// CHECK: ret i32 1
+// CHECK-LABEL: test_ne00_generic_local
+// CHECK: ret i32 0
+// CHECK-LABEL: test_ne0N_generic_local
+// CHECK: ret i32 0
+// CHECK-LABEL: test_neN0_generic_local
+// CHECK: ret i32 0
+// CHECK-LABEL: test_neNN_generic_local
+// CHECK: ret i32 0
+TEST(generic, local)
+
+// CHECK-LABEL: test_eq00_generic_global
+// CHECK: ret i32 1
+// CHECK-LABEL: test_eq0N_generic_global
+// CHECK: ret i32 1
+// CHECK-LABEL: test_eqN0_generic_global
+// CHECK: ret i32 1
+// CHECK-LABEL: test_eqNN_generic_global
+// CHECK: ret i32 1
+// CHECK-LABEL: test_ne00_generic_global
+// CHECK: ret i32 0
+// CHECK-LABEL: test_ne0N_generic_global
+// CHECK: ret i32 0
+// CHECK-LABEL: test_neN0_generic_global
+// CHECK: ret i32 0
+// CHECK-LABEL: test_neNN_generic_global
+// CHECK: ret i32 0
+TEST(generic, global)
+
+// CHECK-LABEL: test_eq00_generic_generic
+// CHECK: ret i32 1
+// CHECK-LABEL: test_eq0N_generic_generic
+// CHECK: ret i32 1
+// CHECK-LABEL: test_eqN0_generic_generic
+// CHECK: ret i32 1
+// CHECK-LABEL: test_eqNN_generic_generic
+// CHECK: ret i32 1
+// CHECK-LABEL: test_ne00_generic_generic
+// CHECK: ret i32 0
+// CHECK-LABEL: test_ne0N_generic_generic
+// CHECK: ret i32 0
+// CHECK-LABEL: test_neN0_generic_generic
+// CHECK: ret i32 0
+// CHECK-LABEL: test_neNN_generic_generic
+// CHECK: ret i32 0
+TEST(generic, generic)
+
+// CHECK-LABEL: test_eq00_constant_constant
+// CHECK: ret i32 1
+TEST_EQ00(constant, constant)
+
+// Test cast to bool.
+
+// CHECK-LABEL: cast_bool_private
+// CHECK: icmp eq i8* %p, addrspacecast (i8 addrspace(4)* null to i8*)
+void cast_bool_private(private char* p) {
+  if (p)
+    *p = 0;
+}
+
+// CHECK-LABEL: cast_bool_local
+// CHECK: icmp eq i8 addrspace(3)* %p, addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*)
+void cast_bool_local(local char* p) {
+  if (p)
+    *p = 0;
+}
+
+// CHECK-LABEL: cast_bool_global
+// CHECK: icmp eq i8 addrspace(1)* %p, null
+void cast_bool_global(global char* p) {
+  if (p)
+    *p = 0;
+}
+
+// CHECK-LABEL: cast_bool_constant
+// CHECK: icmp eq i8 addrspace(2)* %p, null
+char cast_bool_constant(constant char* p) {
+  if (p)
+    return *p;
+  else
+    return 0;
+}
+
+// CHECK-LABEL: cast_bool_generic
+// CHECK: icmp eq i8 addrspace(4)* %p, null
+void cast_bool_generic(generic char* p) {
+  if (p)
+    *p = 0;
+}
+
+// Test initialize a struct using memset.
+// For large structures which is mostly zero, clang generats llvm.memset for
+// the zero part and store for non-zero members.
+typedef struct {
+  long a, b, c, d;
+  private char *p;
+} StructTy3;
+
+// CHECK-LABEL: test_memset
+// CHECK: call void @llvm.memset.p0i8.i64(i8* {{.*}}, i8 0, i64 32, i32 8, i1 false)
+// CHECK: store i8* addrspacecast (i8 addrspace(4)* null to i8*), i8** {{.*}}
+StructTy3 test_memset(void) {
+  StructTy3 S3 = {0, 0, 0, 0, 0};
+  return S3;
+}
+
+// Test casting literal 0 to pointer.
+// A 0 literal casted to pointer should become a null pointer.
+
+// CHECK-LABEL: test_cast_0_to_ptr
+// CHECK: ret i32* addrspacecast (i32 addrspace(4)* null to i32*)
+private int* test_cast_0_to_ptr(void) {
+  return (private int*)0;
+}
+
+// Test casting non-literal integer with 0 value to pointer.
+// A non-literal integer expression with 0 value is casted to a pointer with
+// zero value. 
+
+// CHECK-LABEL: test_cast_int_to_ptr1
+// CHECK: ret i32* null
+private int* test_cast_int_to_ptr1(void) {
+  return (private int*)((void)0, 0);
+}
+
+// CHECK-LABEL: test_cast_int_to_ptr2
+// CHECK: ret i32* null
+private int* test_cast_int_to_ptr2(void) {
+  int x = 0;
+  return (private int*)x;
+}
+
+// Test logical operations.
+// CHECK-LABEL: test_not_nullptr
+// CHECK: ret i32 1
+int test_not_nullptr(void) {
+  return !(private char*)NULL;
+}
+
+// CHECK-LABEL: test_and_nullptr
+// CHECK: ret i32 0
+int test_and_nullptr(int a) {
+  return a && ((private char*)NULL);
+}
+
+// CHECK-LABEL: test_not_ptr
+// CHECK: %[[lnot:.*]] = icmp eq i8* %p, addrspacecast (i8 addrspace(4)* null to i8*)
+// CHECK: %[[lnot_ext:.*]] = zext i1 %[[lnot]] to i32
+// CHECK: ret i32 %[[lnot_ext]]
+int test_not_ptr(private char* p) {
+  return !p;
+}
+// CHECK-LABEL: test_and_ptr
+// CHECK: %[[tobool:.*]] = icmp ne i8* %p1, addrspacecast (i8 addrspace(4)* null to i8*)
+// CHECK: %[[tobool1:.*]] = icmp ne i8 addrspace(3)* %p2, addrspacecast (i8 addrspace(4)* null to i8 addrspace(3)*)
+// CHECK: %[[res:.*]] = and i1 %[[tobool]], %[[tobool1]]
+// CHECK: %[[land_ext:.*]] = zext i1 %[[res]] to i32
+// CHECK: ret i32 %[[land_ext]]
+int test_and_ptr(private char* p1, local char* p2) {
+  return p1 && p2;
+}
+
+// Test folding of null pointer in function scope.
+// NOOPT-LABEL: test_fold
+// NOOPT: call void @test_fold_callee
+// NOOPT: store i32 addrspace(1)* null, i32 addrspace(1)** %glob, align 4
+// NOOPT: %{{.*}} = sub i64 %{{.*}}, 0
+// NOOPT: call void @test_fold_callee
+// NOOPT: %{{.*}} = add nsw i64 %{{.*}}, sext (i32 ptrtoint (i32* addrspacecast (i32 addrspace(4)* null to i32*) to i32) to i64)
+// NOOPT: %{{.*}} = sub nsw i64 %{{.*}}, 1
+void test_fold_callee(void);
+void test_fold(void) {
+  global int* glob = (test_fold_callee(), (global int*)(generic char*)0);
+  long x = glob - (global int*)(generic char*)0;
+  x = x + (int)(test_fold_callee(), (private int*)(generic char*)(global short*)0);
+  x = x - (int)((private int*)0 == (private int*)(generic char*)0);
+}