Revert r332847; it caused us to miscompile certain forms of reference initialization.

llvm-svn: 332886

2 files changed, 19 insertions, 33 deletions

diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 3efd8dc6a60..0e1fb98bf77 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -10312,6 +10312,12 @@ bool Expr::EvaluateAsBooleanCondition(bool &Result,
          HandleConversionToBool(Scratch.Val, Result);
 }
 
+static bool hasUnacceptableSideEffect(Expr::EvalStatus &Result,
+                                      Expr::SideEffectsKind SEK) {
+  return (SEK < Expr::SE_AllowSideEffects && Result.HasSideEffects) ||
+         (SEK < Expr::SE_AllowUndefinedBehavior && Result.HasUndefinedBehavior);
+}
+
 bool Expr::EvaluateAsInt(APSInt &Result, const ASTContext &Ctx,
                          SideEffectsKind AllowSideEffects) const {
   if (!getType()->isIntegralOrEnumerationType())
@@ -10319,7 +10325,7 @@ bool Expr::EvaluateAsInt(APSInt &Result, const ASTContext &Ctx,
 
   EvalResult ExprResult;
   if (!EvaluateAsRValue(ExprResult, Ctx) || !ExprResult.Val.isInt() ||
-      ExprResult.hasUnacceptableSideEffect(AllowSideEffects))
+      hasUnacceptableSideEffect(ExprResult, AllowSideEffects))
     return false;
 
   Result = ExprResult.Val.getInt();
@@ -10333,7 +10339,7 @@ bool Expr::EvaluateAsFloat(APFloat &Result, const ASTContext &Ctx,
 
   EvalResult ExprResult;
   if (!EvaluateAsRValue(ExprResult, Ctx) || !ExprResult.Val.isFloat() ||
-      ExprResult.hasUnacceptableSideEffect(AllowSideEffects))
+      hasUnacceptableSideEffect(ExprResult, AllowSideEffects))
     return false;
 
   Result = ExprResult.Val.getFloat();
@@ -10411,7 +10417,7 @@ bool Expr::EvaluateAsInitializer(APValue &Value, const ASTContext &Ctx,
 bool Expr::isEvaluatable(const ASTContext &Ctx, SideEffectsKind SEK) const {
   EvalResult Result;
   return EvaluateAsRValue(Result, Ctx) &&
-         !Result.hasUnacceptableSideEffect(SEK);
+         !hasUnacceptableSideEffect(Result, SEK);
 }
 
 APSInt Expr::EvaluateKnownConstInt(const ASTContext &Ctx,
diff --git a/clang/lib/CodeGen/CGExprConstant.cpp b/clang/lib/CodeGen/CGExprConstant.cpp
index ae05df1be58..7b076ea3e65 100644
--- a/clang/lib/CodeGen/CGExprConstant.cpp
+++ b/clang/lib/CodeGen/CGExprConstant.cpp
@@ -1392,40 +1392,20 @@ static QualType getNonMemoryType(CodeGenModule &CGM, QualType type) {
   return type;
 }
 
-/// Checks if the specified initializer is equivalent to zero initialization.
-static bool isZeroInitializer(ConstantEmitter &CE, const Expr *Init) {
-  if (auto *E = dyn_cast_or_null<CXXConstructExpr>(Init)) {
-    CXXConstructorDecl *CD = E->getConstructor();
-    return CD->isDefaultConstructor() && CD->isTrivial();
-  }
-
-  if (auto *IL = dyn_cast_or_null<InitListExpr>(Init)) {
-    for (auto I : IL->inits())
-      if (!isZeroInitializer(CE, I))
-        return false;
-    if (const Expr *Filler = IL->getArrayFiller())
-      return isZeroInitializer(CE, Filler);
-    return true;
-  }
-
-  QualType InitTy = Init->getType();
-  if (InitTy->isIntegralOrEnumerationType() || InitTy->isPointerType()) {
-    Expr::EvalResult Result;
-    if (Init->EvaluateAsRValue(Result, CE.CGM.getContext()) &&
-        !Result.hasUnacceptableSideEffect(Expr::SE_NoSideEffects))
-      return (Result.Val.isInt() && Result.Val.getInt().isNullValue()) ||
-             (Result.Val.isLValue() && Result.Val.isNullPointer());
-  }
-
-  return false;
-}
-
 llvm::Constant *ConstantEmitter::tryEmitPrivateForVarInit(const VarDecl &D) {
   // Make a quick check if variable can be default NULL initialized
   // and avoid going through rest of code which may do, for c++11,
   // initialization of memory to all NULLs.
-  if (!D.hasLocalStorage() && isZeroInitializer(*this, D.getInit()))
-    return CGM.EmitNullConstant(D.getType());
+  if (!D.hasLocalStorage()) {
+    QualType Ty = CGM.getContext().getBaseElementType(D.getType());
+    if (Ty->isRecordType())
+      if (const CXXConstructExpr *E =
+          dyn_cast_or_null<CXXConstructExpr>(D.getInit())) {
+        const CXXConstructorDecl *CD = E->getConstructor();
+        if (CD->isTrivial() && CD->isDefaultConstructor())
+          return CGM.EmitNullConstant(D.getType());
+      }
+  }
 
   QualType destType = D.getType();