Introduce a new expression node, ImplicitValueInitExpr, that

represents an implicit value-initialization of a subobject of a
particular type. This replaces the (ab)use of CXXZeroValueInitExpr
within initializer lists for the "holes" that occur due to the use of
C99 designated initializers.

The new test case is currently XFAIL'd, because CodeGen's
ConstExprEmitter (in lib/CodeGen/CGExprConstant.cpp) needs to be
taught to value-initialize when it sees ImplicitValueInitExprs.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@63317 91177308-0d34-0410-b5e6-96231b3b80d8

8 files changed, 53 insertions, 22 deletions

diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index c1c8084cd5..8a04198293 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -735,6 +735,8 @@ bool Expr::isConstantInitializer(ASTContext &Ctx) const {
     }
     return true;
   }
+  case ImplicitValueInitExprClass:
+    return true;
   case ParenExprClass: {
     return cast<ParenExpr>(this)->getSubExpr()->isConstantInitializer(Ctx);
   }
@@ -1672,7 +1674,7 @@ Stmt::child_iterator InitListExpr::child_end() {
   return InitExprs.size() ? &InitExprs[0] + InitExprs.size() : 0;
 }
 
-/// DesignatedInitExpr
+// DesignatedInitExpr
 Stmt::child_iterator DesignatedInitExpr::child_begin() {
   char* Ptr = static_cast<char*>(static_cast<void *>(this));
   Ptr += sizeof(DesignatedInitExpr);
@@ -1683,6 +1685,15 @@ Stmt::child_iterator DesignatedInitExpr::child_end() {
   return child_iterator(&*child_begin() + NumSubExprs);
 }
 
+// ImplicitValueInitExpr
+Stmt::child_iterator ImplicitValueInitExpr::child_begin() { 
+  return child_iterator(); 
+}
+
+Stmt::child_iterator ImplicitValueInitExpr::child_end() { 
+  return child_iterator(); 
+}
+
 // ObjCStringLiteral
 Stmt::child_iterator ObjCStringLiteral::child_begin() { 
   return child_iterator();
diff --git a/lib/AST/StmtPrinter.cpp b/lib/AST/StmtPrinter.cpp
index 7a558ab8dd..27bab206a4 100644
--- a/lib/AST/StmtPrinter.cpp
+++ b/lib/AST/StmtPrinter.cpp
@@ -906,6 +906,10 @@ void StmtPrinter::VisitDesignatedInitExpr(DesignatedInitExpr *Node) {
   PrintExpr(Node->getInit());
 }
 
+void StmtPrinter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *Node) {
+  OS << "/*implicit*/" << Node->getType().getAsString() << "()";
+}
+
 void StmtPrinter::VisitVAArgExpr(VAArgExpr *Node) {
   OS << "va_arg(";
   PrintExpr(Node->getSubExpr());
diff --git a/lib/CodeGen/CGExprAgg.cpp b/lib/CodeGen/CGExprAgg.cpp
index b487bacc71..f985763b5c 100644
--- a/lib/CodeGen/CGExprAgg.cpp
+++ b/lib/CodeGen/CGExprAgg.cpp
@@ -339,10 +339,10 @@ void AggExprEmitter::EmitNonConstInit(InitListExpr *E) {
 
 void AggExprEmitter::EmitInitializationToLValue(Expr* E, LValue LV) {
   // FIXME: Are initializers affected by volatile?
-  if (E->getType()->isComplexType()) {
-    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
-  } else if (isa<CXXZeroInitValueExpr>(E)) {
+  if (isa<ImplicitValueInitExpr>(E)) {
     EmitNullInitializationToLValue(LV, E->getType());
+  } else if (E->getType()->isComplexType()) {
+    CGF.EmitComplexExprIntoAddr(E, LV.getAddress(), false);
   } else if (CGF.hasAggregateLLVMType(E->getType())) {
     CGF.EmitAnyExpr(E, LV.getAddress(), false);
   } else {
diff --git a/lib/CodeGen/CGExprComplex.cpp b/lib/CodeGen/CGExprComplex.cpp
index 73fceedee5..387635cb06 100644
--- a/lib/CodeGen/CGExprComplex.cpp
+++ b/lib/CodeGen/CGExprComplex.cpp
@@ -130,6 +130,12 @@ public:
     llvm::Constant *Null = llvm::Constant::getNullValue(CGF.ConvertType(Elem));
     return ComplexPairTy(Null, Null);
   }
+  ComplexPairTy VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
+    assert(E->getType()->isAnyComplexType() && "Expected complex type!");
+    QualType Elem = E->getType()->getAsComplexType()->getElementType();
+    llvm::Constant *Null = llvm::Constant::getNullValue(CGF.ConvertType(Elem));
+    return ComplexPairTy(Null, Null);
+  }
   
   struct BinOpInfo {
     ComplexPairTy LHS;
diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index e523ab3acf..3aedf9bc7f 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -248,11 +248,6 @@ public:
 
     FieldDecl* curField = ILE->getInitializedFieldInUnion();
     if (!curField) {
-#ifndef NDEBUG
-#endif
-    }
-
-    if (!curField) {
       // There's no field to initialize, so value-initialize the union.
 #ifndef NDEBUG
       // Make sure that it's really an empty and not a failure of
diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp
index dd8b30041e..f855e23ba0 100644
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@@ -200,6 +200,9 @@ public:
     return V;
   }
   
+  Value *VisitImplicitValueInitExpr(const ImplicitValueInitExpr *E) {
+    return llvm::Constant::getNullValue(ConvertType(E->getType()));
+  }
   Value *VisitImplicitCastExpr(const ImplicitCastExpr *E);
   Value *VisitCastExpr(const CastExpr *E) { 
     return EmitCastExpr(E->getSubExpr(), E->getType());
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 7572560be1..1559213fcb 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -2220,17 +2220,17 @@ bool Sema::CheckForConstantInitializer(Expr *Init, QualType DclT) {
   if (CompoundLiteralExpr *e = dyn_cast<CompoundLiteralExpr>(Init))
     return CheckForConstantInitializer(e->getInitializer(), DclT);
 
+  if (isa<ImplicitValueInitExpr>(Init)) {
+    // FIXME: In C++, check for non-POD types.
+    return false;
+  }
+
   if (InitListExpr *Exp = dyn_cast<InitListExpr>(Init)) {
     unsigned numInits = Exp->getNumInits();
     for (unsigned i = 0; i < numInits; i++) {
       // FIXME: Need to get the type of the declaration for C++,
       // because it could be a reference?
 
-      // Implicitly-generated value initializations are okay.
-      if (isa<CXXZeroInitValueExpr>(Exp->getInit(i)) &&
-          cast<CXXZeroInitValueExpr>(Exp->getInit(i))->isImplicit()) 
-        continue;
-
       if (CheckForConstantInitializer(Exp->getInit(i),
                                       Exp->getInit(i)->getType()))
         return true;
diff --git a/lib/Sema/SemaInit.cpp b/lib/Sema/SemaInit.cpp
index 527f965dc3..5d7f705edb 100644
--- a/lib/Sema/SemaInit.cpp
+++ b/lib/Sema/SemaInit.cpp
@@ -17,7 +17,6 @@
 #include "clang/Parse/Designator.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/Expr.h"
-#include "clang/AST/ExprCXX.h"
 #include <map>
 using namespace clang;
 
@@ -137,10 +136,9 @@ static void fillInValueInitializations(ASTContext &Context, InitListExpr *ILE) {
       // FIXME: Check for fields with reference type in C++?
       if (!ILE->getInit(Init))
         ILE->setInit(Init, 
-                     new (Context) CXXZeroInitValueExpr(Field->getType(), 
-                                                        SourceLocation(),
-                                                        SourceLocation()));
-      else if (InitListExpr *InnerILE = dyn_cast<InitListExpr>(ILE->getInit(Init)))
+                     new (Context) ImplicitValueInitExpr(Field->getType()));
+      else if (InitListExpr *InnerILE 
+                 = dyn_cast<InitListExpr>(ILE->getInit(Init)))
         fillInValueInitializations(Context, InnerILE);
       ++Init;
     }
@@ -160,9 +158,7 @@ static void fillInValueInitializations(ASTContext &Context, InitListExpr *ILE) {
   for (unsigned Init = 0, NumInits = ILE->getNumInits(); Init != NumInits; 
        ++Init) {
     if (!ILE->getInit(Init))
-      ILE->setInit(Init, new (Context) CXXZeroInitValueExpr(ElementType, 
-                                                            SourceLocation(),
-                                                            SourceLocation()));
+      ILE->setInit(Init, new (Context) ImplicitValueInitExpr(ElementType));
     else if (InitListExpr *InnerILE =dyn_cast<InitListExpr>(ILE->getInit(Init)))
       fillInValueInitializations(Context, InnerILE);
   }
@@ -550,6 +546,22 @@ void InitListChecker::CheckStructUnionTypes(InitListExpr *IList,
     hadError = true;
     return;
   }    
+
+  if (DeclType->isUnionType() && IList->getNumInits() == 0) {
+    // Value-initialize the first named member of the union.
+    RecordDecl *RD = DeclType->getAsRecordType()->getDecl();
+    for (RecordDecl::field_iterator FieldEnd = RD->field_end();
+         Field != FieldEnd; ++Field) {
+      if (Field->getDeclName()) {
+        StructuredList->setInitializedFieldInUnion(*Field);
+        break;
+      }
+    }
+    return;
+  }
+
+
+
   // If structDecl is a forward declaration, this loop won't do
   // anything except look at designated initializers; That's okay,
   // because an error should get printed out elsewhere. It might be