Set and use Elidable in elimination of copy ctors.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@78331 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CGCXX.cpp

@@ -258,16 +258,10 @@ CodeGenFunction::EmitCXXConstructExpr(llvm::Value *Dest,
 
   // Code gen optimization to eliminate copy constructor and return 
   // its first argument instead.
-  const CXXConstructorDecl *CDecl = E->getConstructor();
-  if (E->getNumArgs() == 1 &&
-      CDecl->isCopyConstructor(getContext())) {
+  if (E->isElidable()) {
     CXXConstructExpr::const_arg_iterator i = E->arg_begin();
-    const Expr *SubExpr = (*i);
-    // FIXME. Any other cases can be optimized away?
-    if (isa<CallExpr>(SubExpr) || isa<CXXTemporaryObjectExpr>(SubExpr)) {
-      EmitAggExpr(SubExpr, Dest, false);
-      return;
-    }
+    EmitAggExpr((*i), Dest, false);
+    return;
   }
   // Call the constructor.
   EmitCXXConstructorCall(E->getConstructor(), Ctor_Complete, Dest, 

lib/Sema/SemaExprCXX.cpp

@@ -911,8 +911,10 @@ Sema::PerformImplicitConversion(Expr *&From, QualType ToType,
     assert(!ToType->isReferenceType());
     
     // FIXME: Keep track of whether the copy constructor is elidable or not.
-    From = BuildCXXConstructExpr(Context,
-                                 ToType, SCS.CopyConstructor, false, &From, 1);
+    bool Elidable = (isa<CallExpr>(From) || 
+                     isa<CXXTemporaryObjectExpr>(From));
+    From = BuildCXXConstructExpr(Context, ToType, 
+                                 SCS.CopyConstructor, Elidable, &From, 1);
     return false;
   }
 

lib/Sema/SemaInit.cpp

@@ -176,9 +176,10 @@ bool Sema::CheckInitializerTypes(Expr *&Init, QualType &DeclType,
                                              DirectInit? IK_Direct : IK_Copy);
         if (!Constructor)
           return true;
-        
+        bool Elidable = (isa<CallExpr>(Init) || 
+                         isa<CXXTemporaryObjectExpr>(Init));
         Init = BuildCXXConstructExpr(Context,
-                                     DeclType, Constructor, false, &Init, 1);
+                                     DeclType, Constructor, Elidable, &Init, 1);
         Init = MaybeCreateCXXExprWithTemporaries(Init, /*DestroyTemps=*/true);
         return false;
       }