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-rw-r--r--clang/lib/CodeGen/CodeGenModule.cpp46
-rw-r--r--clang/lib/CodeGen/CodeGenModule.h12
-rw-r--r--clang/test/CodeGenCXX/dllexport.cpp15
-rw-r--r--clang/test/CodeGenCXX/explicit-instantiation.cpp13
4 files changed, 69 insertions, 17 deletions
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 25aaa30855b..a863591aa04 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -1102,14 +1102,18 @@ void CodeGenModule::EmitDeferred() {
llvm::GlobalValue *GV = G.GV;
DeferredDeclsToEmit.pop_back();
- assert(GV == GetGlobalValue(getMangledName(D)));
+ assert(!GV || GV == GetGlobalValue(getMangledName(D)));
+ if (!GV)
+ GV = GetGlobalValue(getMangledName(D));
+
+
// Check to see if we've already emitted this. This is necessary
// for a couple of reasons: first, decls can end up in the
// deferred-decls queue multiple times, and second, decls can end
// up with definitions in unusual ways (e.g. by an extern inline
// function acquiring a strong function redefinition). Just
// ignore these cases.
- if(!GV->isDeclaration())
+ if (GV && !GV->isDeclaration())
continue;
// Otherwise, emit the definition and move on to the next one.
@@ -1234,12 +1238,22 @@ bool CodeGenModule::isInSanitizerBlacklist(llvm::GlobalVariable *GV,
return false;
}
-bool CodeGenModule::MayDeferGeneration(const ValueDecl *Global) {
+bool CodeGenModule::MustBeEmitted(const ValueDecl *Global) {
// Never defer when EmitAllDecls is specified.
if (LangOpts.EmitAllDecls)
- return false;
+ return true;
+
+ return getContext().DeclMustBeEmitted(Global);
+}
- return !getContext().DeclMustBeEmitted(Global);
+bool CodeGenModule::MayBeEmittedEagerly(const ValueDecl *Global) {
+ if (const auto *FD = dyn_cast<FunctionDecl>(Global))
+ if (FD->getTemplateSpecializationKind() == TSK_ImplicitInstantiation)
+ // Implicit template instantiations may change linkage if they are later
+ // explicitly instantiated, so they should not be emitted eagerly.
+ return false;
+
+ return true;
}
llvm::Constant *CodeGenModule::GetAddrOfUuidDescriptor(
@@ -1348,9 +1362,10 @@ void CodeGenModule::EmitGlobal(GlobalDecl GD) {
return;
}
- // Defer code generation when possible if this is a static definition, inline
- // function etc. These we only want to emit if they are used.
- if (!MayDeferGeneration(Global)) {
+ // Defer code generation to first use when possible, e.g. if this is an inline
+ // function. If the global must always be emitted, do it eagerly if possible
+ // to benefit from cache locality.
+ if (MustBeEmitted(Global) && MayBeEmittedEagerly(Global)) {
// Emit the definition if it can't be deferred.
EmitGlobalDefinition(GD);
return;
@@ -1363,13 +1378,16 @@ void CodeGenModule::EmitGlobal(GlobalDecl GD) {
DelayedCXXInitPosition[Global] = CXXGlobalInits.size();
CXXGlobalInits.push_back(nullptr);
}
-
- // If the value has already been used, add it directly to the
- // DeferredDeclsToEmit list.
+
StringRef MangledName = getMangledName(GD);
- if (llvm::GlobalValue *GV = GetGlobalValue(MangledName))
+ if (llvm::GlobalValue *GV = GetGlobalValue(MangledName)) {
+ // The value has already been used and should therefore be emitted.
addDeferredDeclToEmit(GV, GD);
- else {
+ } else if (MustBeEmitted(Global)) {
+ // The value must be emitted, but cannot be emitted eagerly.
+ assert(!MayBeEmittedEagerly(Global));
+ addDeferredDeclToEmit(/*GV=*/nullptr, GD);
+ } else {
// Otherwise, remember that we saw a deferred decl with this name. The
// first use of the mangled name will cause it to move into
// DeferredDeclsToEmit.
@@ -1843,7 +1861,7 @@ CodeGenModule::CreateRuntimeVariable(llvm::Type *Ty,
void CodeGenModule::EmitTentativeDefinition(const VarDecl *D) {
assert(!D->getInit() && "Cannot emit definite definitions here!");
- if (MayDeferGeneration(D)) {
+ if (!MustBeEmitted(D)) {
// If we have not seen a reference to this variable yet, place it
// into the deferred declarations table to be emitted if needed
// later.
diff --git a/clang/lib/CodeGen/CodeGenModule.h b/clang/lib/CodeGen/CodeGenModule.h
index 619356a70a4..54f3a82feb2 100644
--- a/clang/lib/CodeGen/CodeGenModule.h
+++ b/clang/lib/CodeGen/CodeGenModule.h
@@ -1200,9 +1200,15 @@ private:
/// Emits the initializer for a uuidof string.
llvm::Constant *EmitUuidofInitializer(StringRef uuidstr);
- /// Determine if the given decl can be emitted lazily; this is only relevant
- /// for definitions. The given decl must be either a function or var decl.
- bool MayDeferGeneration(const ValueDecl *D);
+ /// Determine whether the definition must be emitted; if this returns \c
+ /// false, the definition can be emitted lazily if it's used.
+ bool MustBeEmitted(const ValueDecl *D);
+
+ /// Determine whether the definition can be emitted eagerly, or should be
+ /// delayed until the end of the translation unit. This is relevant for
+ /// definitions whose linkage can change, e.g. implicit function instantions
+ /// which may later be explicitly instantiated.
+ bool MayBeEmittedEagerly(const ValueDecl *D);
/// Check whether we can use a "simpler", more core exceptions personality
/// function.
diff --git a/clang/test/CodeGenCXX/dllexport.cpp b/clang/test/CodeGenCXX/dllexport.cpp
index 5e2b3921c14..cfbc7e10078 100644
--- a/clang/test/CodeGenCXX/dllexport.cpp
+++ b/clang/test/CodeGenCXX/dllexport.cpp
@@ -615,6 +615,21 @@ NonExportedBaseClass::~NonExportedBaseClass() {}
struct __declspec(dllexport) ExportedDerivedClass : NonExportedBaseClass {};
// M32-DAG: weak_odr dllexport x86_thiscallcc void @"\01??1ExportedDerivedClass@@UAE@XZ"
+// Do not assert about generating code for constexpr functions twice during explicit instantiation (PR21718).
+template <typename T> struct ExplicitInstConstexprMembers {
+ // Copy assignment operator
+ // M32-DAG: define weak_odr dllexport x86_thiscallcc dereferenceable(1) %struct.ExplicitInstConstexprMembers* @"\01??4?$ExplicitInstConstexprMembers@X@@QAEAAU0@ABU0@@Z"
+
+ constexpr ExplicitInstConstexprMembers() {}
+ // M32-DAG: define weak_odr dllexport x86_thiscallcc %struct.ExplicitInstConstexprMembers* @"\01??0?$ExplicitInstConstexprMembers@X@@QAE@XZ"
+
+ ExplicitInstConstexprMembers(const ExplicitInstConstexprMembers&) = default;
+ // M32-DAG: define weak_odr dllexport x86_thiscallcc %struct.ExplicitInstConstexprMembers* @"\01??0?$ExplicitInstConstexprMembers@X@@QAE@ABU0@@Z"
+
+ constexpr int f() const { return 42; }
+ // M32-DAG: define weak_odr dllexport x86_thiscallcc i32 @"\01?f@?$ExplicitInstConstexprMembers@X@@QBEHXZ"
+};
+template struct __declspec(dllexport) ExplicitInstConstexprMembers<void>;
//===----------------------------------------------------------------------===//
// Classes with template base classes
diff --git a/clang/test/CodeGenCXX/explicit-instantiation.cpp b/clang/test/CodeGenCXX/explicit-instantiation.cpp
index 5bd06784cfa..6076444c25b 100644
--- a/clang/test/CodeGenCXX/explicit-instantiation.cpp
+++ b/clang/test/CodeGenCXX/explicit-instantiation.cpp
@@ -90,6 +90,19 @@ namespace LateInstantiation {
// CHECK-OPT: define available_externally i32 @_ZN17LateInstantiation1fIiEEiv(
}
+namespace PR21718 {
+// The linkage of a used constexpr member function can change from linkonce_odr
+// to weak_odr after explicit instantiation without errors about defining the
+// same function twice.
+template <typename T>
+struct S {
+// CHECK-LABEL: define weak_odr i32 @_ZN7PR217181SIiE1fEv
+ __attribute__((used)) constexpr int f() { return 0; }
+};
+int g() { return S<int>().f(); }
+template struct S<int>;
+}
+
// Check that we emit definitions from explicit instantiations even when they
// occur prior to the definition itself.
template <typename T> struct S {
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