From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Wed, 22 Feb 2017 22:09:50 +0000 (+0000)
Subject: PR32034: Evaluate _Atomic(T) in-place when T is a class or array type.
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=73bb0d7edc912d9f944c9272df93be141331d567;p=clang

PR32034: Evaluate _Atomic(T) in-place when T is a class or array type.

This is necessary in order for the evaluation of an _Atomic initializer for
those types to have an associated object, which an initializer for class or
array type needs.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@295886 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 1bb252d2d1..ddc48de2c6 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -1437,7 +1437,8 @@ static bool EvaluateIntegerOrLValue(const Expr *E, APValue &Result,
                                     EvalInfo &Info);
 static bool EvaluateFloat(const Expr *E, APFloat &Result, EvalInfo &Info);
 static bool EvaluateComplex(const Expr *E, ComplexValue &Res, EvalInfo &Info);
-static bool EvaluateAtomic(const Expr *E, APValue &Result, EvalInfo &Info);
+static bool EvaluateAtomic(const Expr *E, const LValue *This, APValue &Result,
+                           EvalInfo &Info);
 static bool EvaluateAsRValue(EvalInfo &Info, const Expr *E, APValue &Result);
 
 //===----------------------------------------------------------------------===//
@@ -4743,7 +4744,10 @@ public:
 
     case CK_AtomicToNonAtomic: {
       APValue AtomicVal;
-      if (!EvaluateAtomic(E->getSubExpr(), AtomicVal, Info))
+      // This does not need to be done in place even for class/array types:
+      // atomic-to-non-atomic conversion implies copying the object
+      // representation.
+      if (!Evaluate(AtomicVal, Info, E->getSubExpr()))
         return false;
       return DerivedSuccess(AtomicVal, E);
     }
@@ -9689,10 +9693,11 @@ bool ComplexExprEvaluator::VisitInitListExpr(const InitListExpr *E) {
 namespace {
 class AtomicExprEvaluator :
     public ExprEvaluatorBase<AtomicExprEvaluator> {
+  const LValue *This;
   APValue &Result;
 public:
-  AtomicExprEvaluator(EvalInfo &Info, APValue &Result)
-      : ExprEvaluatorBaseTy(Info), Result(Result) {}
+  AtomicExprEvaluator(EvalInfo &Info, const LValue *This, APValue &Result)
+      : ExprEvaluatorBaseTy(Info), This(This), Result(Result) {}
 
   bool Success(const APValue &V, const Expr *E) {
     Result = V;
@@ -9702,7 +9707,10 @@ public:
   bool ZeroInitialization(const Expr *E) {
     ImplicitValueInitExpr VIE(
         E->getType()->castAs<AtomicType>()->getValueType());
-    return Evaluate(Result, Info, &VIE);
+    // For atomic-qualified class (and array) types in C++, initialize the
+    // _Atomic-wrapped subobject directly, in-place.
+    return This ? EvaluateInPlace(Result, Info, *This, &VIE)
+                : Evaluate(Result, Info, &VIE);
   }
 
   bool VisitCastExpr(const CastExpr *E) {
@@ -9710,15 +9718,17 @@ public:
     default:
       return ExprEvaluatorBaseTy::VisitCastExpr(E);
     case CK_NonAtomicToAtomic:
-      return Evaluate(Result, Info, E->getSubExpr());
+      return This ? EvaluateInPlace(Result, Info, *This, E->getSubExpr())
+                  : Evaluate(Result, Info, E->getSubExpr());
     }
   }
 };
 } // end anonymous namespace
 
-static bool EvaluateAtomic(const Expr *E, APValue &Result, EvalInfo &Info) {
+static bool EvaluateAtomic(const Expr *E, const LValue *This, APValue &Result,
+                           EvalInfo &Info) {
   assert(E->isRValue() && E->getType()->isAtomicType());
-  return AtomicExprEvaluator(Info, Result).Visit(E);
+  return AtomicExprEvaluator(Info, This, Result).Visit(E);
 }
 
 //===----------------------------------------------------------------------===//
@@ -9823,8 +9833,17 @@ static bool Evaluate(APValue &Result, EvalInfo &Info, const Expr *E) {
     if (!EvaluateVoid(E, Info))
       return false;
   } else if (T->isAtomicType()) {
-    if (!EvaluateAtomic(E, Result, Info))
-      return false;
+    QualType Unqual = T.getAtomicUnqualifiedType();
+    if (Unqual->isArrayType() || Unqual->isRecordType()) {
+      LValue LV;
+      LV.set(E, Info.CurrentCall->Index);
+      APValue &Value = Info.CurrentCall->createTemporary(E, false);
+      if (!EvaluateAtomic(E, &LV, Value, Info))
+        return false;
+    } else {
+      if (!EvaluateAtomic(E, nullptr, Result, Info))
+        return false;
+    }
   } else if (Info.getLangOpts().CPlusPlus11) {
     Info.FFDiag(E, diag::note_constexpr_nonliteral) << E->getType();
     return false;
@@ -9849,10 +9868,16 @@ static bool EvaluateInPlace(APValue &Result, EvalInfo &Info, const LValue &This,
   if (E->isRValue()) {
     // Evaluate arrays and record types in-place, so that later initializers can
     // refer to earlier-initialized members of the object.
-    if (E->getType()->isArrayType())
+    QualType T = E->getType();
+    if (T->isArrayType())
       return EvaluateArray(E, This, Result, Info);
-    else if (E->getType()->isRecordType())
+    else if (T->isRecordType())
       return EvaluateRecord(E, This, Result, Info);
+    else if (T->isAtomicType()) {
+      QualType Unqual = T.getAtomicUnqualifiedType();
+      if (Unqual->isArrayType() || Unqual->isRecordType())
+        return EvaluateAtomic(E, &This, Result, Info);
+    }
   }
 
   // For any other type, in-place evaluation is unimportant.
diff --git a/test/SemaCXX/constant-expression-cxx11.cpp b/test/SemaCXX/constant-expression-cxx11.cpp
index b7ee9ad346..4abbc8e928 100644
--- a/test/SemaCXX/constant-expression-cxx11.cpp
+++ b/test/SemaCXX/constant-expression-cxx11.cpp
@@ -1280,6 +1280,15 @@ namespace Atomic {
     constexpr TestVar testVar{-1};
     static_assert(testVar.value == -1, "");
   }
+
+  namespace PR32034 {
+    struct A {};
+    struct B { _Atomic(A) a; };
+    constexpr int n = (B(), B(), 0);
+
+    struct C { constexpr C() {} void *self = this; };
+    constexpr _Atomic(C) c = C();
+  }
 }
 
 namespace InstantiateCaseStmt {