[Temporary] Add an ExprWithCleanups for each C++ MaterializeTemporary…

…Expr.

These ExprWithCleanups are added for holding a RunCleanupsScope not
for destructor calls; rather, they are for lifetime marks. This requires
ExprWithCleanups to keep a bit to indicate whether it have cleanups with
side effects (e.g. dtor calls).

Differential Revision: http://reviews.llvm.org/D20498

llvm-svn: 272296

clang/include/clang/AST/ExprCXX.h

@@ -2877,7 +2877,8 @@ class ExprWithCleanups final
   Stmt *SubExpr;
 
   ExprWithCleanups(EmptyShell, unsigned NumObjects);
-  ExprWithCleanups(Expr *SubExpr, ArrayRef<CleanupObject> Objects);
+  ExprWithCleanups(Expr *SubExpr, bool CleanupsHaveSideEffects,
+                   ArrayRef<CleanupObject> Objects);
 
   friend TrailingObjects;
   friend class ASTStmtReader;
@@ -2887,6 +2888,7 @@ class ExprWithCleanups final
                                   unsigned numObjects);
 
   static ExprWithCleanups *Create(const ASTContext &C, Expr *subexpr,
+                                  bool CleanupsHaveSideEffects,
                                   ArrayRef<CleanupObject> objects);
 
   ArrayRef<CleanupObject> getObjects() const {
@@ -2903,6 +2905,9 @@ class ExprWithCleanups final
 
   Expr *getSubExpr() { return cast<Expr>(SubExpr); }
   const Expr *getSubExpr() const { return cast<Expr>(SubExpr); }
+  bool cleanupsHaveSideEffects() const {
+    return ExprWithCleanupsBits.CleanupsHaveSideEffects;
+  }
 
   /// As with any mutator of the AST, be very careful
   /// when modifying an existing AST to preserve its invariants.

clang/include/clang/AST/Stmt.h

@@ -192,7 +192,10 @@ class LLVM_ALIGNAS(LLVM_PTR_SIZE) Stmt {
 
     unsigned : NumExprBits;
 
-    unsigned NumObjects : 32 - NumExprBits;
+    // When false, it must not have side effects.
+    bool CleanupsHaveSideEffects : 1;
+
+    unsigned NumObjects : 32 - 1 - NumExprBits;
   };
 
   class PseudoObjectExprBitfields {

clang/include/clang/Sema/CleanupInfo.h

@@ -0,0 +1,47 @@
+//===--- CleanupInfo.cpp - Cleanup Control in Sema ------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements a set of operations on whether generating an
+//  ExprWithCleanups in a full expression.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_SEMA_CLEANUP_INFO_H
+#define LLVM_CLANG_SEMA_CLEANUP_INFO_H
+
+namespace clang {
+
+class CleanupInfo {
+  bool ExprNeedsCleanups = false;
+  bool CleanupsHaveSideEffects = false;
+
+public:
+  bool exprNeedsCleanups() const { return ExprNeedsCleanups; }
+
+  bool cleanupsHaveSideEffects() const { return CleanupsHaveSideEffects; }
+
+  void setExprNeedsCleanups(bool SideEffects) {
+    ExprNeedsCleanups = true;
+    CleanupsHaveSideEffects |= SideEffects;
+  }
+
+  void reset() {
+    ExprNeedsCleanups = false;
+    CleanupsHaveSideEffects = false;
+  }
+
+  void mergeFrom(CleanupInfo Rhs) {
+    ExprNeedsCleanups |= Rhs.ExprNeedsCleanups;
+    CleanupsHaveSideEffects |= Rhs.CleanupsHaveSideEffects;
+  }
+};
+
+} // end namespace clang
+
+#endif

clang/include/clang/Sema/ScopeInfo.h

@@ -19,6 +19,7 @@
 #include "clang/AST/Type.h"
 #include "clang/Basic/CapturedStmt.h"
 #include "clang/Basic/PartialDiagnostic.h"
+#include "clang/Sema/CleanupInfo.h"
 #include "clang/Sema/Ownership.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/SmallSet.h"
@@ -682,7 +683,7 @@ class LambdaScopeInfo final : public CapturingScopeInfo {
   bool ExplicitParams;
 
   /// \brief Whether any of the capture expressions requires cleanups.
-  bool ExprNeedsCleanups;
+  CleanupInfo Cleanup;
 
   /// \brief Whether the lambda contains an unexpanded parameter pack.
   bool ContainsUnexpandedParameterPack;
@@ -730,7 +731,7 @@ class LambdaScopeInfo final : public CapturingScopeInfo {
   LambdaScopeInfo(DiagnosticsEngine &Diag)
     : CapturingScopeInfo(Diag, ImpCap_None), Lambda(nullptr),
       CallOperator(nullptr), NumExplicitCaptures(0), Mutable(false),
-      ExplicitParams(false), ExprNeedsCleanups(false),
+      ExplicitParams(false), Cleanup{},
       ContainsUnexpandedParameterPack(false), AutoTemplateParameterDepth(0),
       GLTemplateParameterList(nullptr) {
     Kind = SK_Lambda;

clang/include/clang/Sema/Sema.h

@@ -34,6 +34,7 @@
 #include "clang/Basic/TemplateKinds.h"
 #include "clang/Basic/TypeTraits.h"
 #include "clang/Sema/AnalysisBasedWarnings.h"
+#include "clang/Sema/CleanupInfo.h"
 #include "clang/Sema/DeclSpec.h"
 #include "clang/Sema/ExternalSemaSource.h"
 #include "clang/Sema/IdentifierResolver.h"
@@ -440,9 +441,8 @@ class Sema {
   /// if Sema is already doing so, which would cause infinite recursions.
   bool IsBuildingRecoveryCallExpr;
 
-  /// ExprNeedsCleanups - True if the current evaluation context
-  /// requires cleanups to be run at its conclusion.
-  bool ExprNeedsCleanups;
+  /// Used to control the generation of ExprWithCleanups.
+  CleanupInfo Cleanup;
 
   /// ExprCleanupObjects - This is the stack of objects requiring
   /// cleanup that are created by the current full expression.  The
@@ -830,7 +830,7 @@ class Sema {
     ExpressionEvaluationContext Context;
 
     /// \brief Whether the enclosing context needed a cleanup.
-    bool ParentNeedsCleanups;
+    CleanupInfo ParentCleanup;
 
     /// \brief Whether we are in a decltype expression.
     bool IsDecltype;
@@ -871,10 +871,10 @@ class Sema {
 
     ExpressionEvaluationContextRecord(ExpressionEvaluationContext Context,
                                       unsigned NumCleanupObjects,
-                                      bool ParentNeedsCleanups,
+                                      CleanupInfo ParentCleanup,
                                       Decl *ManglingContextDecl,
                                       bool IsDecltype)
-      : Context(Context), ParentNeedsCleanups(ParentNeedsCleanups),
+      : Context(Context), ParentCleanup(ParentCleanup),
         IsDecltype(IsDecltype), NumCleanupObjects(NumCleanupObjects),
         NumTypos(0),
         ManglingContextDecl(ManglingContextDecl), MangleNumbering() { }
@@ -4872,6 +4872,10 @@ class Sema {
   Stmt *MaybeCreateStmtWithCleanups(Stmt *SubStmt);
   ExprResult MaybeCreateExprWithCleanups(ExprResult SubExpr);
 
+  MaterializeTemporaryExpr *
+  CreateMaterializeTemporaryExpr(QualType T, Expr *Temporary,
+                                 bool BoundToLvalueReference);
+
   ExprResult ActOnFinishFullExpr(Expr *Expr) {
     return ActOnFinishFullExpr(Expr, Expr ? Expr->getExprLoc()
                                           : SourceLocation());

clang/lib/AST/Expr.cpp

@@ -2890,7 +2890,6 @@ bool Expr::HasSideEffects(const ASTContext &Ctx,
   case CXXThrowExprClass:
   case CXXNewExprClass:
   case CXXDeleteExprClass:
-  case ExprWithCleanupsClass:
   case CoawaitExprClass:
   case CoyieldExprClass:
     // These always have a side-effect.
@@ -2903,6 +2902,12 @@ bool Expr::HasSideEffects(const ASTContext &Ctx,
     return Finder.hasSideEffects();
   }
 
+  case ExprWithCleanupsClass:
+    if (IncludePossibleEffects)
+      if (cast<ExprWithCleanups>(this)->cleanupsHaveSideEffects())
+        return true;
+    break;
+
   case ParenExprClass:
   case ArraySubscriptExprClass:
   case OMPArraySectionExprClass:

clang/lib/AST/ExprCXX.cpp

@@ -1039,23 +1039,27 @@ bool LambdaExpr::isMutable() const {
 }
 
 ExprWithCleanups::ExprWithCleanups(Expr *subexpr,
+                                   bool CleanupsHaveSideEffects,
                                    ArrayRef<CleanupObject> objects)
   : Expr(ExprWithCleanupsClass, subexpr->getType(),
          subexpr->getValueKind(), subexpr->getObjectKind(),
          subexpr->isTypeDependent(), subexpr->isValueDependent(),
          subexpr->isInstantiationDependent(),
          subexpr->containsUnexpandedParameterPack()),
     SubExpr(subexpr) {
+  ExprWithCleanupsBits.CleanupsHaveSideEffects = CleanupsHaveSideEffects;
   ExprWithCleanupsBits.NumObjects = objects.size();
   for (unsigned i = 0, e = objects.size(); i != e; ++i)
     getTrailingObjects<CleanupObject>()[i] = objects[i];
 }
 
 ExprWithCleanups *ExprWithCleanups::Create(const ASTContext &C, Expr *subexpr,
+                                           bool CleanupsHaveSideEffects,
                                            ArrayRef<CleanupObject> objects) {
   void *buffer = C.Allocate(totalSizeToAlloc<CleanupObject>(objects.size()),
                             llvm::alignOf<ExprWithCleanups>());
-  return new (buffer) ExprWithCleanups(subexpr, objects);
+  return new (buffer)
+      ExprWithCleanups(subexpr, CleanupsHaveSideEffects, objects);
 }
 
 ExprWithCleanups::ExprWithCleanups(EmptyShell empty, unsigned numObjects)

clang/lib/Analysis/Consumed.cpp

@@ -466,9 +466,15 @@ class ConsumedStmtVisitor : public ConstStmtVisitor<ConsumedStmtVisitor> {
   MapType PropagationMap;
 
   InfoEntry findInfo(const Expr *E) {
+    if (auto Cleanups = dyn_cast<ExprWithCleanups>(E))
+      if (!Cleanups->cleanupsHaveSideEffects())
+        E = Cleanups->getSubExpr();
     return PropagationMap.find(E->IgnoreParens());
   }
   ConstInfoEntry findInfo(const Expr *E) const {
+    if (auto Cleanups = dyn_cast<ExprWithCleanups>(E))
+      if (!Cleanups->cleanupsHaveSideEffects())
+        E = Cleanups->getSubExpr();
     return PropagationMap.find(E->IgnoreParens());
   }
   void insertInfo(const Expr *E, const PropagationInfo &PI) {

clang/lib/CodeGen/CGExprConstant.cpp

@@ -764,6 +764,12 @@ class ConstExprEmitter :
     return Visit(DIE->getExpr());
   }
 
+  llvm::Constant *VisitExprWithCleanups(ExprWithCleanups *E) {
+    if (!E->cleanupsHaveSideEffects())
+      return Visit(E->getSubExpr());
+    return nullptr;
+  }
+
   llvm::Constant *VisitMaterializeTemporaryExpr(MaterializeTemporaryExpr *E) {
     return Visit(E->GetTemporaryExpr());
   }

clang/lib/Sema/Sema.cpp

@@ -88,7 +88,7 @@ Sema::Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
     ConstSegStack(nullptr), CodeSegStack(nullptr), CurInitSeg(nullptr),
     VisContext(nullptr),
     IsBuildingRecoveryCallExpr(false),
-    ExprNeedsCleanups(false), LateTemplateParser(nullptr),
+    Cleanup{}, LateTemplateParser(nullptr),
     LateTemplateParserCleanup(nullptr),
     OpaqueParser(nullptr), IdResolver(pp), StdInitializerList(nullptr),
     CXXTypeInfoDecl(nullptr), MSVCGuidDecl(nullptr),
@@ -124,7 +124,8 @@ Sema::Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
   // Tell diagnostics how to render things from the AST library.
   Diags.SetArgToStringFn(&FormatASTNodeDiagnosticArgument, &Context);
 
-  ExprEvalContexts.emplace_back(PotentiallyEvaluated, 0, false, nullptr, false);
+  ExprEvalContexts.emplace_back(PotentiallyEvaluated, 0, CleanupInfo{}, nullptr,
+                                false);
 
   FunctionScopes.push_back(new FunctionScopeInfo(Diags));
 

clang/lib/Sema/SemaCast.cpp

@@ -641,8 +641,8 @@ void CastOperation::CheckDynamicCast() {
     // If we're dynamic_casting from a prvalue to an rvalue reference, we need
     // to materialize the prvalue before we bind the reference to it.
     if (SrcExpr.get()->isRValue())
-      SrcExpr = new (Self.Context) MaterializeTemporaryExpr(
-          SrcType, SrcExpr.get(), /*IsLValueReference*/false);
+      SrcExpr = Self.CreateMaterializeTemporaryExpr(
+          SrcType, SrcExpr.get(), /*IsLValueReference*/ false);
     SrcPointee = SrcType;
   }
 
@@ -1649,8 +1649,8 @@ static TryCastResult TryConstCast(Sema &Self, ExprResult &SrcExpr,
   if (NeedToMaterializeTemporary)
     // This is a const_cast from a class prvalue to an rvalue reference type.
     // Materialize a temporary to store the result of the conversion.
-    SrcExpr = new (Self.Context) MaterializeTemporaryExpr(
-        SrcType, SrcExpr.get(), /*IsLValueReference*/ false);
+    SrcExpr = Self.CreateMaterializeTemporaryExpr(SrcType, SrcExpr.get(),
+                                                  /*IsLValueReference*/ false);
 
   return TC_Success;
 }

clang/lib/Sema/SemaCoroutine.cpp

@@ -244,7 +244,7 @@ ExprResult Sema::BuildCoawaitExpr(SourceLocation Loc, Expr *E) {
   // If the expression is a temporary, materialize it as an lvalue so that we
   // can use it multiple times.
   if (E->getValueKind() == VK_RValue)
-    E = new (Context) MaterializeTemporaryExpr(E->getType(), E, true);
+    E = CreateMaterializeTemporaryExpr(E->getType(), E, true);
 
   // Build the await_ready, await_suspend, await_resume calls.
   ReadySuspendResumeResult RSS = buildCoawaitCalls(*this, Loc, E);
@@ -311,7 +311,7 @@ ExprResult Sema::BuildCoyieldExpr(SourceLocation Loc, Expr *E) {
   // If the expression is a temporary, materialize it as an lvalue so that we
   // can use it multiple times.
   if (E->getValueKind() == VK_RValue)
-    E = new (Context) MaterializeTemporaryExpr(E->getType(), E, true);
+    E = CreateMaterializeTemporaryExpr(E->getType(), E, true);
 
   // Build the await_ready, await_suspend, await_resume calls.
   ReadySuspendResumeResult RSS = buildCoawaitCalls(*this, Loc, E);

clang/lib/Sema/SemaDecl.cpp

@@ -11648,7 +11648,7 @@ Decl *Sema::ActOnFinishFunctionBody(Decl *dcl, Stmt *Body,
     assert(ExprCleanupObjects.size() ==
                ExprEvalContexts.back().NumCleanupObjects &&
            "Leftover temporaries in function");
-    assert(!ExprNeedsCleanups && "Unaccounted cleanups in function");
+    assert(!Cleanup.exprNeedsCleanups() && "Unaccounted cleanups in function");
     assert(MaybeODRUseExprs.empty() &&
            "Leftover expressions for odr-use checking");
   }