1 files changed, 216 insertions, 0 deletions
diff --git a/clang/lib/Analysis/ConstructionContext.cpp b/clang/lib/Analysis/ConstructionContext.cpp
new file mode 100644
index 000000000000..6ba1e2173d2c
--- /dev/null
+++ b/clang/lib/Analysis/ConstructionContext.cpp
@@ -0,0 +1,216 @@
+//===- ConstructionContext.cpp - CFG constructor information --------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the ConstructionContext class and its sub-classes,
+// which represent various different ways of constructing C++ objects
+// with the additional information the users may want to know about
+// the constructor.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Analysis/ConstructionContext.h"
+#include "clang/AST/ExprObjC.h"
+
+using namespace clang;
+
+const ConstructionContextLayer *
+ConstructionContextLayer::create(BumpVectorContext &C,
+                                 const ConstructionContextItem &Item,
+                                 const ConstructionContextLayer *Parent) {
+  ConstructionContextLayer *CC =
+      C.getAllocator().Allocate<ConstructionContextLayer>();
+  return new (CC) ConstructionContextLayer(Item, Parent);
+}
+
+bool ConstructionContextLayer::isStrictlyMoreSpecificThan(
+    const ConstructionContextLayer *Other) const {
+  const ConstructionContextLayer *Self = this;
+  while (true) {
+    if (!Other)
+      return Self;
+    if (!Self || !(Self->Item == Other->Item))
+      return false;
+    Self = Self->getParent();
+    Other = Other->getParent();
+  }
+  llvm_unreachable("The above loop can only be terminated via return!");
+}
+
+const ConstructionContext *
+ConstructionContext::createMaterializedTemporaryFromLayers(
+    BumpVectorContext &C, const MaterializeTemporaryExpr *MTE,
+    const CXXBindTemporaryExpr *BTE,
+    const ConstructionContextLayer *ParentLayer) {
+  assert(MTE);
+
+  // If the object requires destruction and is not lifetime-extended,
+  // then it must have a BTE within its MTE, otherwise it shouldn't.
+  // FIXME: This should be an assertion.
+  if (!BTE && !(MTE->getType().getCanonicalType()->getAsCXXRecordDecl()
+                    ->hasTrivialDestructor() ||
+                MTE->getStorageDuration() != SD_FullExpression)) {
+    return nullptr;
+  }
+
+  // If the temporary is lifetime-extended, don't save the BTE,
+  // because we don't need a temporary destructor, but an automatic
+  // destructor.
+  if (MTE->getStorageDuration() != SD_FullExpression) {
+    BTE = nullptr;
+  }
+
+  // Handle pre-C++17 copy and move elision.
+  const CXXConstructExpr *ElidedCE = nullptr;
+  const ConstructionContext *ElidedCC = nullptr;
+  if (ParentLayer) {
+    const ConstructionContextItem &ElidedItem = ParentLayer->getItem();
+    assert(ElidedItem.getKind() ==
+           ConstructionContextItem::ElidableConstructorKind);
+    ElidedCE = cast<CXXConstructExpr>(ElidedItem.getStmt());
+    assert(ElidedCE->isElidable());
+    // We're creating a construction context that might have already
+    // been created elsewhere. Maybe we should unique our construction
+    // contexts. That's what we often do, but in this case it's unlikely
+    // to bring any benefits.
+    ElidedCC = createFromLayers(C, ParentLayer->getParent());
+    if (!ElidedCC) {
+      // We may fail to create the elided construction context.
+      // In this case, skip copy elision entirely.
+      return create<SimpleTemporaryObjectConstructionContext>(C, BTE, MTE);
+    }
+    return create<ElidedTemporaryObjectConstructionContext>(
+        C, BTE, MTE, ElidedCE, ElidedCC);
+  }
+
+  // This is a normal temporary.
+  assert(!ParentLayer);
+  return create<SimpleTemporaryObjectConstructionContext>(C, BTE, MTE);
+}
+
+const ConstructionContext *ConstructionContext::createBoundTemporaryFromLayers(
+    BumpVectorContext &C, const CXXBindTemporaryExpr *BTE,
+    const ConstructionContextLayer *ParentLayer) {
+  if (!ParentLayer) {
+    // A temporary object that doesn't require materialization.
+    // In particular, it shouldn't require copy elision, because
+    // copy/move constructors take a reference, which requires
+    // materialization to obtain the glvalue.
+    return create<SimpleTemporaryObjectConstructionContext>(C, BTE,
+                                                            /*MTE=*/nullptr);
+  }
+
+  const ConstructionContextItem &ParentItem = ParentLayer->getItem();
+  switch (ParentItem.getKind()) {
+  case ConstructionContextItem::VariableKind: {
+    const auto *DS = cast<DeclStmt>(ParentItem.getStmt());
+    assert(!cast<VarDecl>(DS->getSingleDecl())->getType().getCanonicalType()
+                            ->getAsCXXRecordDecl()->hasTrivialDestructor());
+    return create<CXX17ElidedCopyVariableConstructionContext>(C, DS, BTE);
+  }
+  case ConstructionContextItem::NewAllocatorKind: {
+    llvm_unreachable("This context does not accept a bound temporary!");
+  }
+  case ConstructionContextItem::ReturnKind: {
+    assert(ParentLayer->isLast());
+    const auto *RS = cast<ReturnStmt>(ParentItem.getStmt());
+    assert(!RS->getRetValue()->getType().getCanonicalType()
+              ->getAsCXXRecordDecl()->hasTrivialDestructor());
+    return create<CXX17ElidedCopyReturnedValueConstructionContext>(C, RS,
+                                                                   BTE);
+  }
+
+  case ConstructionContextItem::MaterializationKind: {
+    // No assert. We may have an elidable copy on the grandparent layer.
+    const auto *MTE = cast<MaterializeTemporaryExpr>(ParentItem.getStmt());
+    return createMaterializedTemporaryFromLayers(C, MTE, BTE,
+                                                 ParentLayer->getParent());
+  }
+  case ConstructionContextItem::TemporaryDestructorKind: {
+    llvm_unreachable("Duplicate CXXBindTemporaryExpr in the AST!");
+  }
+  case ConstructionContextItem::ElidedDestructorKind: {
+    llvm_unreachable("Elided destructor items are not produced by the CFG!");
+  }
+  case ConstructionContextItem::ElidableConstructorKind: {
+    llvm_unreachable("Materialization is necessary to put temporary into a "
+                     "copy or move constructor!");
+  }
+  case ConstructionContextItem::ArgumentKind: {
+    assert(ParentLayer->isLast());
+    const auto *E = cast<Expr>(ParentItem.getStmt());
+    assert(isa<CallExpr>(E) || isa<CXXConstructExpr>(E) ||
+           isa<ObjCMessageExpr>(E));
+    return create<ArgumentConstructionContext>(C, E, ParentItem.getIndex(),
+                                               BTE);
+  }
+  case ConstructionContextItem::InitializerKind: {
+    assert(ParentLayer->isLast());
+    const auto *I = ParentItem.getCXXCtorInitializer();
+    assert(!I->getAnyMember()->getType().getCanonicalType()
+             ->getAsCXXRecordDecl()->hasTrivialDestructor());
+    return create<CXX17ElidedCopyConstructorInitializerConstructionContext>(
+        C, I, BTE);
+  }
+  } // switch (ParentItem.getKind())
+
+  llvm_unreachable("Unexpected construction context with destructor!");
+}
+
+const ConstructionContext *ConstructionContext::createFromLayers(
+    BumpVectorContext &C, const ConstructionContextLayer *TopLayer) {
+  // Before this point all we've had was a stockpile of arbitrary layers.
+  // Now validate that it is shaped as one of the finite amount of expected
+  // patterns.
+  const ConstructionContextItem &TopItem = TopLayer->getItem();
+  switch (TopItem.getKind()) {
+  case ConstructionContextItem::VariableKind: {
+    assert(TopLayer->isLast());
+    const auto *DS = cast<DeclStmt>(TopItem.getStmt());
+    return create<SimpleVariableConstructionContext>(C, DS);
+  }
+  case ConstructionContextItem::NewAllocatorKind: {
+    assert(TopLayer->isLast());
+    const auto *NE = cast<CXXNewExpr>(TopItem.getStmt());
+    return create<NewAllocatedObjectConstructionContext>(C, NE);
+  }
+  case ConstructionContextItem::ReturnKind: {
+    assert(TopLayer->isLast());
+    const auto *RS = cast<ReturnStmt>(TopItem.getStmt());
+    return create<SimpleReturnedValueConstructionContext>(C, RS);
+  }
+  case ConstructionContextItem::MaterializationKind: {
+    const auto *MTE = cast<MaterializeTemporaryExpr>(TopItem.getStmt());
+    return createMaterializedTemporaryFromLayers(C, MTE, /*BTE=*/nullptr,
+                                                 TopLayer->getParent());
+  }
+  case ConstructionContextItem::TemporaryDestructorKind: {
+    const auto *BTE = cast<CXXBindTemporaryExpr>(TopItem.getStmt());
+    assert(BTE->getType().getCanonicalType()->getAsCXXRecordDecl()
+              ->hasNonTrivialDestructor());
+    return createBoundTemporaryFromLayers(C, BTE, TopLayer->getParent());
+  }
+  case ConstructionContextItem::ElidedDestructorKind: {
+    llvm_unreachable("Elided destructor items are not produced by the CFG!");
+  }
+  case ConstructionContextItem::ElidableConstructorKind: {
+    llvm_unreachable("The argument needs to be materialized first!");
+  }
+  case ConstructionContextItem::InitializerKind: {
+    assert(TopLayer->isLast());
+    const CXXCtorInitializer *I = TopItem.getCXXCtorInitializer();
+    return create<SimpleConstructorInitializerConstructionContext>(C, I);
+  }
+  case ConstructionContextItem::ArgumentKind: {
+    assert(TopLayer->isLast());
+    const auto *E = cast<Expr>(TopItem.getStmt());
+    return create<ArgumentConstructionContext>(C, E, TopItem.getIndex(),
+                                               /*BTE=*/nullptr);
+  }
+  } // switch (TopItem.getKind())
+  llvm_unreachable("Unexpected construction context!");
+}