vendor/clang/clang-trunk-r338150

1 files changed, 184 insertions, 0 deletions

diff --git a/lib/Analysis/ConstructionContext.cpp b/lib/Analysis/ConstructionContext.cpp
new file mode 100644
index 0000000000000..ed1e632432172
--- /dev/null
+++ b/lib/Analysis/ConstructionContext.cpp
@@ -0,0 +1,184 @@
+//===- ConstructionContext.cpp - CFG constructor information --------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// 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"
+
+using namespace clang;
+
+const ConstructionContextLayer *
+ConstructionContextLayer::create(BumpVectorContext &C, TriggerTy Trigger,
+                                 const ConstructionContextLayer *Parent) {
+  ConstructionContextLayer *CC =
+      C.getAllocator().Allocate<ConstructionContextLayer>();
+  return new (CC) ConstructionContextLayer(Trigger, Parent);
+}
+
+bool ConstructionContextLayer::isStrictlyMoreSpecificThan(
+    const ConstructionContextLayer *Other) const {
+  const ConstructionContextLayer *Self = this;
+  while (true) {
+    if (!Other)
+      return Self;
+    if (!Self || !Self->isSameLayer(Other))
+      return false;
+    Self = Self->getParent();
+    Other = Other->getParent();
+  }
+  llvm_unreachable("The above loop can only be terminated via return!");
+}
+
+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.
+  if (const Stmt *S = TopLayer->getTriggerStmt()) {
+    if (const auto *DS = dyn_cast<DeclStmt>(S)) {
+      assert(TopLayer->isLast());
+      return create<SimpleVariableConstructionContext>(C, DS);
+    }
+    if (const auto *NE = dyn_cast<CXXNewExpr>(S)) {
+      assert(TopLayer->isLast());
+      return create<NewAllocatedObjectConstructionContext>(C, NE);
+    }
+    if (const auto *BTE = dyn_cast<CXXBindTemporaryExpr>(S)) {
+      const MaterializeTemporaryExpr *MTE = nullptr;
+      assert(BTE->getType().getCanonicalType()
+                ->getAsCXXRecordDecl()->hasNonTrivialDestructor());
+      // For temporaries with destructors, there may or may not be
+      // lifetime extension on the parent layer.
+      if (const ConstructionContextLayer *ParentLayer = TopLayer->getParent()) {
+        // C++17 *requires* elision of the constructor at the return site
+        // and at variable/member initialization site, while previous standards
+        // were allowing an optional elidable constructor.
+        // This is the C++17 copy-elided construction into a ctor initializer.
+        if (const CXXCtorInitializer *I = ParentLayer->getTriggerInit()) {
+          return create<
+              CXX17ElidedCopyConstructorInitializerConstructionContext>(C,
+                                                                        I, BTE);
+        }
+        assert(ParentLayer->getTriggerStmt() &&
+               "Non-statement-based layers have been handled above!");
+        // This is the normal, non-C++17 case: a temporary object which has
+        // both destruction and materialization info attached to it in the AST.
+        if ((MTE = dyn_cast<MaterializeTemporaryExpr>(
+                 ParentLayer->getTriggerStmt()))) {
+          if (MTE->getStorageDuration() != SD_FullExpression) {
+            // If the temporary is lifetime-extended, don't save the BTE,
+            // because we don't need a temporary destructor, but an automatic
+            // destructor.
+            BTE = nullptr;
+          }
+
+          // Handle pre-C++17 copy and move elision.
+          const CXXConstructExpr *ElidedCE = nullptr;
+          const ConstructionContext *ElidedCC = nullptr;
+          if (const ConstructionContextLayer *ElidedLayer =
+                  ParentLayer->getParent()) {
+            ElidedCE = cast<CXXConstructExpr>(ElidedLayer->getTriggerStmt());
+            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, ElidedLayer->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);
+            } else {
+              return create<ElidedTemporaryObjectConstructionContext>(
+                  C, BTE, MTE, ElidedCE, ElidedCC);
+            }
+          }
+          assert(ParentLayer->isLast());
+          return create<SimpleTemporaryObjectConstructionContext>(C, BTE, MTE);
+        }
+        assert(ParentLayer->isLast());
+
+        // This is a constructor into a function argument. Not implemented yet.
+        if (isa<CallExpr>(ParentLayer->getTriggerStmt()))
+          return nullptr;
+        // This is C++17 copy-elided construction into return statement.
+        if (auto *RS = dyn_cast<ReturnStmt>(ParentLayer->getTriggerStmt())) {
+          assert(!RS->getRetValue()->getType().getCanonicalType()
+                    ->getAsCXXRecordDecl()->hasTrivialDestructor());
+          return create<CXX17ElidedCopyReturnedValueConstructionContext>(C,
+                                                                       RS, BTE);
+        }
+        // This is C++17 copy-elided construction into a simple variable.
+        if (auto *DS = dyn_cast<DeclStmt>(ParentLayer->getTriggerStmt())) {
+          assert(!cast<VarDecl>(DS->getSingleDecl())->getType()
+                      .getCanonicalType()->getAsCXXRecordDecl()
+                      ->hasTrivialDestructor());
+          return create<CXX17ElidedCopyVariableConstructionContext>(C, DS, BTE);
+        }
+        llvm_unreachable("Unexpected construction context with destructor!");
+      }
+      // 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);
+    }
+    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.
+      // FIXME: This should be an assertion.
+      if (!(MTE->getType().getCanonicalType()
+                ->getAsCXXRecordDecl()->hasTrivialDestructor() ||
+             MTE->getStorageDuration() != SD_FullExpression))
+        return nullptr;
+
+      // Handle pre-C++17 copy and move elision.
+      const CXXConstructExpr *ElidedCE = nullptr;
+      const ConstructionContext *ElidedCC = nullptr;
+      if (const ConstructionContextLayer *ElidedLayer = TopLayer->getParent()) {
+        ElidedCE = cast<CXXConstructExpr>(ElidedLayer->getTriggerStmt());
+        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, ElidedLayer->getParent());
+        if (!ElidedCC) {
+          // We may fail to create the elided construction context.
+          // In this case, skip copy elision entirely.
+          return create<SimpleTemporaryObjectConstructionContext>(C, nullptr,
+                                                                  MTE);
+        }
+        return create<ElidedTemporaryObjectConstructionContext>(
+            C, nullptr, MTE, ElidedCE, ElidedCC);
+      }
+      assert(TopLayer->isLast());
+      return create<SimpleTemporaryObjectConstructionContext>(C, nullptr, MTE);
+    }
+    if (const auto *RS = dyn_cast<ReturnStmt>(S)) {
+      assert(TopLayer->isLast());
+      return create<SimpleReturnedValueConstructionContext>(C, RS);
+    }
+    // This is a constructor into a function argument. Not implemented yet.
+    if (isa<CallExpr>(TopLayer->getTriggerStmt()))
+      return nullptr;
+    llvm_unreachable("Unexpected construction context with statement!");
+  } else if (const CXXCtorInitializer *I = TopLayer->getTriggerInit()) {
+    assert(TopLayer->isLast());
+    return create<SimpleConstructorInitializerConstructionContext>(C, I);
+  }
+  llvm_unreachable("Unexpected construction context!");
+}