llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-codegen
Author: idle666 (idler66)
<details>
<summary>Changes</summary>
For example, struct base { public : base() {} template <typename T>
base(T x) {} }; struct derived : public base { public: derived() {}
derived(derived& that): base(that) {} }; int main() { derived d1; derived
d2 = d1; return 0;}
The copy constructor of base is not chosen because it is not an exact match for
the argument type derived. The templated constructor base(T x) can accept
arguments of any type T. In the line derived(const derived& that):
base(that), the that object should be copied twice — once during the
initialization of the derived class and again when passing it to the base class
constructor. The assignment d2 = d1 via base(that) would result in an infinite
recursion and eventually lead to a stack overflow.
Multiple executions of copy semantics lead to stack overflow. So, for the
templated constructor base(T x),
if T is a subclass of base, pass-by-reference should be used!
---
Full diff: https://github.com/llvm/llvm-project/pull/87321.diff
4 Files Affected:
- (modified) clang/lib/CodeGen/CGCall.cpp (+22-2)
- (modified) clang/lib/CodeGen/CodeGenFunction.h (+1-1)
- (modified) clang/unittests/CodeGen/CMakeLists.txt (+1)
- (added) llvm/TemplateInstantiationTest.cpp (+214)
``````````diff
diff --git a/clang/lib/CodeGen/CGCall.cpp b/clang/lib/CodeGen/CGCall.cpp
index 4c2577126e48b3..d265e706aa6958 100644
--- a/clang/lib/CodeGen/CGCall.cpp
+++ b/clang/lib/CodeGen/CGCall.cpp
@@ -4520,7 +4520,7 @@ void CodeGenFunction::EmitCallArgs(
(isa<ObjCMethodDecl>(AC.getDecl()) &&
isObjCMethodWithTypeParams(cast<ObjCMethodDecl>(AC.getDecl()))))
&&
"Argument and parameter types don't match");
- EmitCallArg(Args, *Arg, ArgTypes[Idx]);
+ EmitCallArg(Args, *Arg, ArgTypes[Idx], AC);
// In particular, we depend on it being the last arg in Args, and the
// objectsize bits depend on there only being one arg if !LeftToRight.
assert(InitialArgSize + 1 == Args.size() &&
@@ -4611,7 +4611,7 @@ void CallArg::copyInto(CodeGenFunction &CGF, Address
Addr) const {
}
void CodeGenFunction::EmitCallArg(CallArgList &args, const Expr *E,
- QualType type) {
+ QualType type, const AbstractCallee& AC) {
DisableDebugLocationUpdates Dis(*this, E);
if (const ObjCIndirectCopyRestoreExpr *CRE
= dyn_cast<ObjCIndirectCopyRestoreExpr>(E)) {
@@ -4627,6 +4627,26 @@ void CodeGenFunction::EmitCallArg(CallArgList &args,
const Expr *E,
return args.add(EmitReferenceBindingToExpr(E), type);
}
+ auto ShouldPassParametersByReferenceToTemplatedConstructors = [&]() {
+ if(1 != AC.getNumParams()) return false;
+ if (const CXXRecordDecl* SubRecordDecl = type->getAsCXXRecordDecl()) {
+ if (const CXXConstructorDecl* ConstructorDecl =
dyn_cast<clang::CXXConstructorDecl>(AC.getDecl())) {
+ if(const CXXRecordDecl* BaseRecordDecl =
dyn_cast<CXXRecordDecl>(ConstructorDecl->getParent())) {
+ if(SubRecordDecl->isDerivedFrom(BaseRecordDecl)) {
+ return true;
+ }
+ }
+ }
+ }
+ return false;
+ };
+ if(ShouldPassParametersByReferenceToTemplatedConstructors()) {
+ AggValueSlot Slot = args.isUsingInAlloca()
+ ? createPlaceholderSlot(*this, type) : CreateAggTemp(type, "agg.tmp");
+ RValue RV = Slot.asRValue();
+ return args.add(RV, type);
+ }
+
bool HasAggregateEvalKind = hasAggregateEvaluationKind(type);
// In the Microsoft C++ ABI, aggregate arguments are destructed by the
callee.
diff --git a/clang/lib/CodeGen/CodeGenFunction.h
b/clang/lib/CodeGen/CodeGenFunction.h
index 618e78809db408..f2305a9307396f 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -4746,7 +4746,7 @@ class CodeGenFunction : public CodeGenTypeCache {
AbstractCallee AC, unsigned ParmNum);
/// EmitCallArg - Emit a single call argument.
- void EmitCallArg(CallArgList &args, const Expr *E, QualType ArgType);
+ void EmitCallArg(CallArgList &args, const Expr *E, QualType ArgType, const
AbstractCallee& AC);
/// EmitDelegateCallArg - We are performing a delegate call; that
/// is, the current function is delegating to another one. Produce
diff --git a/clang/unittests/CodeGen/CMakeLists.txt
b/clang/unittests/CodeGen/CMakeLists.txt
index a437f441568f27..8870237c85539d 100644
--- a/clang/unittests/CodeGen/CMakeLists.txt
+++ b/clang/unittests/CodeGen/CMakeLists.txt
@@ -9,6 +9,7 @@ add_clang_unittest(ClangCodeGenTests
CodeGenExternalTest.cpp
TBAAMetadataTest.cpp
CheckTargetFeaturesTest.cpp
+ TemplateInstantiationTest.cpp
)
clang_target_link_libraries(ClangCodeGenTests
diff --git a/llvm/TemplateInstantiationTest.cpp
b/llvm/TemplateInstantiationTest.cpp
new file mode 100644
index 00000000000000..08d8f673bb1d43
--- /dev/null
+++ b/llvm/TemplateInstantiationTest.cpp
@@ -0,0 +1,214 @@
+//===- unittests/CodeGen/TemplateInstantiationTest.cpp - template
instantiation test -===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "TestCompiler.h"
+
+#include "clang/AST/ASTConsumer.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/GlobalDecl.h"
+#include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/Basic/TargetInfo.h"
+#include "clang/CodeGen/CodeGenABITypes.h"
+#include "clang/CodeGen/ModuleBuilder.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Lex/Preprocessor.h"
+#include "clang/Parse/ParseAST.h"
+#include "clang/Sema/Sema.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/TargetParser/Host.h"
+#include "llvm/TargetParser/Triple.h"
+#include "gtest/gtest.h"
+
+#include "llvm/Analysis/CallGraph.h"
+#include <unordered_set>
+
+using namespace llvm;
+using namespace clang;
+
+namespace {
+
+// forward declarations
+struct TemplateInstantiationASTConsumer;
+static void test_instantiation_fns(TemplateInstantiationASTConsumer *my);
+static bool test_instantiation_fns_ran;
+
+// This forwards the calls to the Clang CodeGenerator
+// so that we can test CodeGen functions while it is open.
+// It accumulates toplevel decls in HandleTopLevelDecl and
+// calls test_instantiation_fns() in HandleTranslationUnit
+// after forwarding that function to the CodeGenerator.
+
+struct TemplateInstantiationASTConsumer : public ASTConsumer {
+ std::unique_ptr<CodeGenerator> Builder;
+ std::vector<Decl*> toplevel_decls;
+
+ TemplateInstantiationASTConsumer(std::unique_ptr<CodeGenerator> Builder_in)
+ : ASTConsumer(), Builder(std::move(Builder_in))
+ {
+ }
+
+ ~TemplateInstantiationASTConsumer() { }
+
+ void Initialize(ASTContext &Context) override;
+ void HandleCXXStaticMemberVarInstantiation(VarDecl *VD) override;
+ bool HandleTopLevelDecl(DeclGroupRef D) override;
+ void HandleInlineFunctionDefinition(FunctionDecl *D) override;
+ void HandleInterestingDecl(DeclGroupRef D) override;
+ void HandleTranslationUnit(ASTContext &Ctx) override;
+ void HandleTagDeclDefinition(TagDecl *D) override;
+ void HandleTagDeclRequiredDefinition(const TagDecl *D) override;
+ void HandleCXXImplicitFunctionInstantiation(FunctionDecl *D) override;
+ void HandleTopLevelDeclInObjCContainer(DeclGroupRef D) override;
+ void HandleImplicitImportDecl(ImportDecl *D) override;
+ void CompleteTentativeDefinition(VarDecl *D) override;
+ void AssignInheritanceModel(CXXRecordDecl *RD) override;
+ void HandleVTable(CXXRecordDecl *RD) override;
+ ASTMutationListener *GetASTMutationListener() override;
+ ASTDeserializationListener *GetASTDeserializationListener() override;
+ void PrintStats() override;
+ bool shouldSkipFunctionBody(Decl *D) override;
+};
+
+void TemplateInstantiationASTConsumer::Initialize(ASTContext &Context) {
+ Builder->Initialize(Context);
+}
+
+bool TemplateInstantiationASTConsumer::HandleTopLevelDecl(DeclGroupRef DG) {
+
+ for (DeclGroupRef::iterator I = DG.begin(), E = DG.end(); I != E; ++I) {
+ toplevel_decls.push_back(*I);
+ }
+
+ return Builder->HandleTopLevelDecl(DG);
+}
+
+void
TemplateInstantiationASTConsumer::HandleInlineFunctionDefinition(FunctionDecl
*D) {
+ Builder->HandleInlineFunctionDefinition(D);
+}
+
+void TemplateInstantiationASTConsumer::HandleInterestingDecl(DeclGroupRef D) {
+ Builder->HandleInterestingDecl(D);
+}
+
+void TemplateInstantiationASTConsumer::HandleTranslationUnit(ASTContext
&Context) {
+ // HandleTranslationUnit can close the module
+ Builder->HandleTranslationUnit(Context);
+ test_instantiation_fns(this);
+}
+
+void TemplateInstantiationASTConsumer::HandleTagDeclDefinition(TagDecl *D) {
+ Builder->HandleTagDeclDefinition(D);
+}
+
+void TemplateInstantiationASTConsumer::HandleTagDeclRequiredDefinition(const
TagDecl *D) {
+ Builder->HandleTagDeclRequiredDefinition(D);
+}
+
+void
TemplateInstantiationASTConsumer::HandleCXXImplicitFunctionInstantiation(FunctionDecl
*D) {
+ Builder->HandleCXXImplicitFunctionInstantiation(D);
+}
+
+void
TemplateInstantiationASTConsumer::HandleTopLevelDeclInObjCContainer(DeclGroupRef
D) {
+ Builder->HandleTopLevelDeclInObjCContainer(D);
+}
+
+void TemplateInstantiationASTConsumer::HandleImplicitImportDecl(ImportDecl *D)
{
+ Builder->HandleImplicitImportDecl(D);
+}
+
+void TemplateInstantiationASTConsumer::CompleteTentativeDefinition(VarDecl *D)
{
+ Builder->CompleteTentativeDefinition(D);
+}
+
+void TemplateInstantiationASTConsumer::AssignInheritanceModel(CXXRecordDecl
*RD) {
+ Builder->AssignInheritanceModel(RD);
+}
+
+void
TemplateInstantiationASTConsumer::HandleCXXStaticMemberVarInstantiation(VarDecl
*VD) {
+ Builder->HandleCXXStaticMemberVarInstantiation(VD);
+}
+
+void TemplateInstantiationASTConsumer::HandleVTable(CXXRecordDecl *RD) {
+ Builder->HandleVTable(RD);
+ }
+
+ASTMutationListener
*TemplateInstantiationASTConsumer::GetASTMutationListener() {
+ return Builder->GetASTMutationListener();
+}
+
+ASTDeserializationListener
*TemplateInstantiationASTConsumer::GetASTDeserializationListener() {
+ return Builder->GetASTDeserializationListener();
+}
+
+void TemplateInstantiationASTConsumer::PrintStats() {
+ Builder->PrintStats();
+}
+
+bool TemplateInstantiationASTConsumer::shouldSkipFunctionBody(Decl *D) {
+ return Builder->shouldSkipFunctionBody(D);
+}
+
+const char TestProgram[] = "struct base { public : base() {} template
<typename T> base(T x) {} }; struct derived : public base { public: derived()
{} derived(derived& that): base(that) {} }; int main() { derived d1; derived d2
= d1; return 0;}";
+
+bool hasCycles(const Function *CurrentFunction,
+ std::unordered_set<const Function *> &VisitedFunctions,
+ std::unordered_set<const Function *> &RecursionStack,
+ const CallGraphNode* CurrentNode) {
+ VisitedFunctions.insert(CurrentFunction);
+ RecursionStack.insert(CurrentFunction);
+ for (CallGraphNode::const_iterator IT = CurrentNode->begin(), END =
CurrentNode->end(); IT != END; ++IT) {
+ if (const Function *CalleeFunction = IT->second->getFunction()) {
+ if (RecursionStack.count(CalleeFunction)) {
+ return true;
+ }
+ if (VisitedFunctions.count(CalleeFunction) == 0 &&
hasCycles(CalleeFunction, VisitedFunctions, RecursionStack, IT->second)) {
+ return true;
+ }
+ }
+ }
+ RecursionStack.erase(CurrentFunction);
+ return false;
+}
+
+static void test_instantiation_fns(TemplateInstantiationASTConsumer
*InstantiationASTConsumer) {
+ test_instantiation_fns_ran = true;
+ llvm::Module* Mdl = InstantiationASTConsumer->Builder->GetModule();
+ CallGraph Graph(*Mdl);
+ std::unordered_set<const Function *> VisitedFunctions;
+ std::unordered_set<const Function *> RecursionStack;
+ for (llvm::CallGraph::const_iterator IT = Graph.begin(), END = Graph.end();
+ IT != END; ++IT) {
+ const Function* Fnc = IT->first;
+ const CallGraphNode* GraphNode = IT->second.get();
+ if (Fnc && VisitedFunctions.count(Fnc) == 0){
+ if(hasCycles(Fnc, VisitedFunctions, RecursionStack, GraphNode)) {
+ test_instantiation_fns_ran = false;
+ break;
+ }
+ }
+ }
+}
+
+TEST(TemplatedConstructorTemplateInstantiationTest,
TemplatedConstructorTemplateInstantiationTest) {
+ clang::LangOptions LO;
+ LO.CPlusPlus = 1;
+ TestCompiler Compiler(LO);
+ auto CustomASTConsumer
+ =
std::make_unique<TemplateInstantiationASTConsumer>(std::move(Compiler.CG));
+
+ Compiler.init(TestProgram, std::move(CustomASTConsumer));
+ ParseAST(Compiler.compiler.getSema(), false, false);
+
+ ASSERT_TRUE(test_instantiation_fns_ran);
+}
+
+} // end anonymous namespace
+
``````````
</details>
https://github.com/llvm/llvm-project/pull/87321
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