Prazek created this revision.
We can emit vtable definition having inline function
if they are all emitted.
https://reviews.llvm.org/D33437
Files:
include/clang/AST/VTableBuilder.h
lib/CodeGen/CGVTables.cpp
lib/CodeGen/CodeGenModule.cpp
lib/CodeGen/CodeGenModule.h
lib/CodeGen/ItaniumCXXABI.cpp
test/CodeGenCXX/vtable-available-externally.cpp
test/CodeGenCXX/vtable-linkage.cpp
Index: test/CodeGenCXX/vtable-linkage.cpp
===================================================================
--- test/CodeGenCXX/vtable-linkage.cpp
+++ test/CodeGenCXX/vtable-linkage.cpp
@@ -145,12 +145,14 @@
// F<int> is an explicit template instantiation declaration without a
// key function, so its vtable should have external linkage.
// CHECK-DAG: @_ZTV1FIiE = external unnamed_addr constant
-// CHECK-OPT-DAG: @_ZTV1FIiE = external unnamed_addr constant
+// CHECK-OPT-DAG: @_ZTV1FIiE = available_externally unnamed_addr constant
// E<int> is an explicit template instantiation declaration. It has a
// key function is not instantiated, so we know that vtable definition
// will be generated in TU where key function will be defined
-// so we can mark it as available_externally (only with optimizations)
+// so we can mark it as external (without optimizations) and
+// available_externally (with optimizations) because all of the inline
+// virtual functions have been emitted.
// CHECK-DAG: @_ZTV1EIiE = external unnamed_addr constant
// CHECK-OPT-DAG: @_ZTV1EIiE = available_externally unnamed_addr constant
Index: test/CodeGenCXX/vtable-available-externally.cpp
===================================================================
--- test/CodeGenCXX/vtable-available-externally.cpp
+++ test/CodeGenCXX/vtable-available-externally.cpp
@@ -12,6 +12,7 @@
// RUN: FileCheck --check-prefix=CHECK-TEST14 %s < %t.opt
// RUN: FileCheck --check-prefix=CHECK-TEST15 %s < %t.opt
// RUN: FileCheck --check-prefix=CHECK-TEST16 %s < %t.opt
+// RUN: FileCheck --check-prefix=CHECK-TEST17 %s < %t.opt
#include <typeinfo>
@@ -274,8 +275,8 @@
virtual D& operator=(const D&);
};
-// Cannot emit B's vtable available_externally, because we cannot create
-// a reference to the inline virtual B::operator= function.
+// Cannot emit D's vtable available_externally, because we cannot create
+// a reference to the inline virtual D::operator= function.
// CHECK-TEST11: @_ZTVN6Test111DE = external unnamed_addr constant
struct D : C {
virtual void key();
@@ -391,3 +392,30 @@
}
}
+namespace Test17 {
+// This test checks if we emit vtables opportunistically.
+// CHECK-TEST17-DAG: @_ZTVN6Test171AE = available_externally
+// CHECK-TEST17-DAG: @_ZTVN6Test171BE = external
+
+struct A {
+ virtual void key();
+ virtual void bar() {}
+};
+
+// We won't gonna use deleting destructor for this type, which will disallow
+// emitting vtable as available_externally
+struct B {
+ virtual void key();
+ virtual ~B() {}
+};
+
+void testcaseA() {
+ A a;
+ a.bar(); // this forces to emit definition of bar
+}
+
+void testcaseB() {
+ B b; // This only forces emitting of complete object destructor
+}
+
+} // namespace Test17
Index: lib/CodeGen/ItaniumCXXABI.cpp
===================================================================
--- lib/CodeGen/ItaniumCXXABI.cpp
+++ lib/CodeGen/ItaniumCXXABI.cpp
@@ -366,20 +366,30 @@
void emitCXXStructor(const CXXMethodDecl *MD, StructorType Type) override;
private:
- bool hasAnyVirtualInlineFunction(const CXXRecordDecl *RD) const {
- const auto &VtableLayout =
- CGM.getItaniumVTableContext().getVTableLayout(RD);
-
- for (const auto &VtableComponent : VtableLayout.vtable_components()) {
- // Skip empty slot.
- if (!VtableComponent.isUsedFunctionPointerKind())
- continue;
-
- const CXXMethodDecl *Method = VtableComponent.getFunctionDecl();
- if (Method->getCanonicalDecl()->isInlined())
- return true;
- }
- return false;
+ bool hasAnyUnusedVirtualInlineFunction(const CXXRecordDecl *RD) const {
+ const auto &VtableLayout =
+ CGM.getItaniumVTableContext().getVTableLayout(RD);
+
+ for (const auto &VtableComponent : VtableLayout.vtable_components()) {
+ // Skip empty slot.
+ if (!VtableComponent.isUsedFunctionPointerKind())
+ continue;
+
+ const CXXMethodDecl *Method = VtableComponent.getFunctionDecl();
+ if (!Method->getCanonicalDecl()->isInlined())
+ continue;
+
+ StringRef Name = CGM.getMangledName(VtableComponent.getGlobalDecl());
+ auto *Entry = CGM.GetGlobalValue(Name);
+ // This checks if virtual inline function has already been emitted.
+ // Note that it is possible that this inline function would be emitted
+ // after trying to emit vtable speculatively. Because of this we do
+ // an extra pass after emitting all deferred vtables to find and emit
+ // these vtables opportunistically.
+ if (!Entry || Entry->isDeclaration())
+ return true;
+ }
+ return false;
}
bool isVTableHidden(const CXXRecordDecl *RD) const {
@@ -1687,11 +1697,11 @@
if (CGM.getLangOpts().AppleKext)
return false;
- // If we don't have any inline virtual functions, and if vtable is not hidden,
- // then we are safe to emit available_externally copy of vtable.
+ // If we don't have any not emitted inline virtual function, and if vtable is
+ // not hidden, then we are safe to emit available_externally copy of vtable.
// FIXME we can still emit a copy of the vtable if we
// can emit definition of the inline functions.
- return !hasAnyVirtualInlineFunction(RD) && !isVTableHidden(RD);
+ return !hasAnyUnusedVirtualInlineFunction(RD) && !isVTableHidden(RD);
}
static llvm::Value *performTypeAdjustment(CodeGenFunction &CGF,
Address InitialPtr,
Index: lib/CodeGen/CodeGenModule.h
===================================================================
--- lib/CodeGen/CodeGenModule.h
+++ lib/CodeGen/CodeGenModule.h
@@ -341,6 +341,9 @@
/// A queue of (optional) vtables to consider emitting.
std::vector<const CXXRecordDecl*> DeferredVTables;
+ /// A queue of (optional) vtables that may be emitted opportunistically.
+ std::vector<const CXXRecordDecl *> OpportunisticVTables;
+
/// List of global values which are required to be present in the object file;
/// bitcast to i8*. This is used for forcing visibility of symbols which may
/// otherwise be optimized out.
@@ -1278,6 +1281,10 @@
/// Emit any needed decls for which code generation was deferred.
void EmitDeferred();
+ /// Try to emit external vtables as available_externally if they have emitted
+ /// all inlined virtual functions.
+ void EmitVTablesOpportunistically();
+
/// Call replaceAllUsesWith on all pairs in Replacements.
void applyReplacements();
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -382,6 +382,7 @@
void CodeGenModule::Release() {
EmitDeferred();
+ EmitVTablesOpportunistically();
applyGlobalValReplacements();
applyReplacements();
checkAliases();
@@ -1373,6 +1374,20 @@
}
}
+void CodeGenModule::EmitVTablesOpportunistically() {
+ // Only emit speculated vtables with optimizations.
+ if (CodeGenOpts.OptimizationLevel == 0)
+ return;
+ llvm::dbgs() << "opurtinistic\n";
+ for (const CXXRecordDecl *RD : OpportunisticVTables) {
+ assert(getVTables().isVTableExternal(RD) &&
+ "This queue should only contain external vtables");
+ if (getCXXABI().canSpeculativelyEmitVTable(RD))
+ VTables.GenerateClassData(RD);
+ }
+ OpportunisticVTables.clear();
+}
+
void CodeGenModule::EmitGlobalAnnotations() {
if (Annotations.empty())
return;
Index: lib/CodeGen/CGVTables.cpp
===================================================================
--- lib/CodeGen/CGVTables.cpp
+++ lib/CodeGen/CGVTables.cpp
@@ -901,6 +901,8 @@
for (const CXXRecordDecl *RD : DeferredVTables)
if (shouldEmitVTableAtEndOfTranslationUnit(*this, RD))
VTables.GenerateClassData(RD);
+ else
+ OpportunisticVTables.push_back(RD);
assert(savedSize == DeferredVTables.size() &&
"deferred extra vtables during vtable emission?");
Index: include/clang/AST/VTableBuilder.h
===================================================================
--- include/clang/AST/VTableBuilder.h
+++ include/clang/AST/VTableBuilder.h
@@ -154,6 +154,18 @@
bool isRTTIKind() const { return isRTTIKind(getKind()); }
+ GlobalDecl getGlobalDecl() const {
+ assert(isUsedFunctionPointerKind() &&
+ "GlobalDecl can be created only from virtual function");
+ if (getKind() == CK_FunctionPointer)
+ return GlobalDecl(getFunctionDecl());
+
+ auto *DtorDecl = cast<CXXDestructorDecl>(getFunctionDecl());
+ if (getKind() == CK_CompleteDtorPointer)
+ return GlobalDecl(DtorDecl, CXXDtorType::Dtor_Complete);
+ return GlobalDecl(DtorDecl, CXXDtorType::Dtor_Deleting);
+ }
+
private:
static bool isFunctionPointerKind(Kind ComponentKind) {
return isUsedFunctionPointerKind(ComponentKind) ||
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