2 files changed, 55 insertions, 12 deletions

diff --git a/clang/lib/Analysis/CFG.cpp b/clang/lib/Analysis/CFG.cpp
index 0672b3d9256..77eb1d37a40 100644
--- a/clang/lib/Analysis/CFG.cpp
+++ b/clang/lib/Analysis/CFG.cpp
@@ -760,9 +760,7 @@ private:
           const ConstructionContext *CC =
               ConstructionContext::createFromLayers(cfg->getBumpVectorContext(),
                                                     Layer);
-          B->appendCXXRecordTypedCall(
-              CE, cast<TemporaryObjectConstructionContext>(CC),
-              cfg->getBumpVectorContext());
+          B->appendCXXRecordTypedCall(CE, CC, cfg->getBumpVectorContext());
           cleanupConstructionContext(CE);
           return;
         }
@@ -1284,7 +1282,7 @@ void CFGBuilder::findConstructionContexts(
   }
   case Stmt::ImplicitCastExprClass: {
     auto *Cast = cast<ImplicitCastExpr>(Child);
-    // TODO: We need to support CK_ConstructorConversion, maybe other kinds?
+    // Should we support other implicit cast kinds?
     switch (Cast->getCastKind()) {
     case CK_NoOp:
     case CK_ConstructorConversion:
@@ -4920,8 +4918,14 @@ static void print_construction_context(raw_ostream &OS,
     break;
   }
   case ConstructionContext::SimpleVariableKind: {
-    const auto *DSCC = cast<SimpleVariableConstructionContext>(CC);
-    S1 = DSCC->getDeclStmt();
+    const auto *SDSCC = cast<SimpleVariableConstructionContext>(CC);
+    S1 = SDSCC->getDeclStmt();
+    break;
+  }
+  case ConstructionContext::CXX17ElidedCopyVariableKind: {
+    const auto *CDSCC = cast<CXX17ElidedCopyVariableConstructionContext>(CC);
+    S1 = CDSCC->getDeclStmt();
+    S2 = CDSCC->getCXXBindTemporaryExpr();
     break;
   }
   case ConstructionContext::NewAllocatedObjectKind: {
@@ -4929,9 +4933,16 @@ static void print_construction_context(raw_ostream &OS,
     S1 = NECC->getCXXNewExpr();
     break;
   }
-  case ConstructionContext::ReturnedValueKind: {
-    const auto *RSCC = cast<ReturnedValueConstructionContext>(CC);
+  case ConstructionContext::SimpleReturnedValueKind: {
+    const auto *RSCC = cast<SimpleReturnedValueConstructionContext>(CC);
+    S1 = RSCC->getReturnStmt();
+    break;
+  }
+  case ConstructionContext::CXX17ElidedCopyReturnedValueKind: {
+    const auto *RSCC =
+        cast<CXX17ElidedCopyReturnedValueConstructionContext>(CC);
     S1 = RSCC->getReturnStmt();
+    S2 = RSCC->getCXXBindTemporaryExpr();
     break;
   }
   case ConstructionContext::TemporaryObjectKind: {
diff --git a/clang/lib/Analysis/ConstructionContext.cpp b/clang/lib/Analysis/ConstructionContext.cpp
index 1a1bc7db8fb..68e1cc04746 100644
--- a/clang/lib/Analysis/ConstructionContext.cpp
+++ b/clang/lib/Analysis/ConstructionContext.cpp
@@ -64,11 +64,43 @@ const ConstructionContext *ConstructionContext::createFromLayers(
       // lifetime extension on the parent layer.
       if (const ConstructionContextLayer *ParentLayer = TopLayer->getParent()) {
         assert(ParentLayer->isLast());
-        MTE = cast<MaterializeTemporaryExpr>(ParentLayer->getTriggerStmt());
+        if ((MTE = dyn_cast<MaterializeTemporaryExpr>(
+                 ParentLayer->getTriggerStmt()))) {
+          // A temporary object which has both destruction and
+          // materialization info.
+          auto *CC =
+              C.getAllocator().Allocate<TemporaryObjectConstructionContext>();
+          return new (CC) TemporaryObjectConstructionContext(BTE, MTE);
+        }
+        // C++17 *requires* elision of the constructor at the return site
+        // and at variable initialization site, while previous standards
+        // were allowing an optional elidable constructor.
+        if (auto *RS = dyn_cast<ReturnStmt>(ParentLayer->getTriggerStmt())) {
+          assert(!RS->getRetValue()->getType().getCanonicalType()
+                    ->getAsCXXRecordDecl()->hasTrivialDestructor());
+          auto *CC =
+              C.getAllocator()
+                  .Allocate<
+                      CXX17ElidedCopyReturnedValueConstructionContext>();
+          return new (CC)
+              CXX17ElidedCopyReturnedValueConstructionContext(RS, BTE);
+        }
+        if (auto *DS = dyn_cast<DeclStmt>(ParentLayer->getTriggerStmt())) {
+          assert(!cast<VarDecl>(DS->getSingleDecl())->getType()
+                      .getCanonicalType()->getAsCXXRecordDecl()
+                      ->hasTrivialDestructor());
+          auto *CC =
+              C.getAllocator()
+                  .Allocate<CXX17ElidedCopyVariableConstructionContext>();
+          return new (CC) CXX17ElidedCopyVariableConstructionContext(DS, BTE);
+        }
+        llvm_unreachable("Unexpected construction context with destructor!");
       }
+      // A temporary object that doesn't require materialization.
       auto *CC =
           C.getAllocator().Allocate<TemporaryObjectConstructionContext>();
-      return new (CC) TemporaryObjectConstructionContext(BTE, MTE);
+      return new (CC)
+          TemporaryObjectConstructionContext(BTE, /*MTE=*/nullptr);
     } else if (const auto *MTE = dyn_cast<MaterializeTemporaryExpr>(S)) {
       // If the object requires destruction and is not lifetime-extended,
       // then it must have a BTE within its MTE.
@@ -82,8 +114,8 @@ const ConstructionContext *ConstructionContext::createFromLayers(
     } else if (const auto *RS = dyn_cast<ReturnStmt>(S)) {
       assert(TopLayer->isLast());
       auto *CC =
-          C.getAllocator().Allocate<ReturnedValueConstructionContext>();
-      return new (CC) ReturnedValueConstructionContext(RS);
+          C.getAllocator().Allocate<SimpleReturnedValueConstructionContext>();
+      return new (CC) SimpleReturnedValueConstructionContext(RS);
     }
   } else if (const CXXCtorInitializer *I = TopLayer->getTriggerInit()) {
     assert(TopLayer->isLast());