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//===- 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!");
}
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