Prazek created this revision.
Prazek added reviewers: rsmith, majnemer, rjmccall.
Prazek added a subscriber: cfe-commits.
It wasn't always safe to generate assumption loads. Last time build failed on
linking of classes like FenceInst because
it didn't introduce any new virtual function, and it had implicit virtual
destructor.
http://reviews.llvm.org/D12385
Files:
lib/CodeGen/CGCXXABI.h
lib/CodeGen/CGClass.cpp
lib/CodeGen/CGVTables.cpp
lib/CodeGen/ItaniumCXXABI.cpp
lib/CodeGen/MicrosoftCXXABI.cpp
test/CodeGenCXX/template-instantiation.cpp
test/CodeGenCXX/thunks.cpp
test/CodeGenCXX/vtable-assume-load.cpp
test/CodeGenCXX/vtable-available-externally.cpp
Index: test/CodeGenCXX/vtable-available-externally.cpp
===================================================================
--- test/CodeGenCXX/vtable-available-externally.cpp
+++ test/CodeGenCXX/vtable-available-externally.cpp
@@ -184,8 +184,8 @@
} // Test8
namespace Test9 {
-// all virtual functions are outline, so we can assume that it will
-// be generated in translation unit where foo is defined
+// All virtual functions are outline, so we can assume that it will
+// be generated in translation unit where foo is defined.
// CHECK-TEST9-DAG: @_ZTVN5Test91AE = available_externally unnamed_addr constant
// CHECK-TEST9-DAG: @_ZTVN5Test91BE = available_externally unnamed_addr constant
struct A {
@@ -217,23 +217,23 @@
};
void A::foo() {}
-// Because key function is inline we will generate vtable as linkonce_odr
+// Because key function is inline we will generate vtable as linkonce_odr.
// CHECK-TEST10-DAG: @_ZTVN6Test101DE = linkonce_odr unnamed_addr constant
struct D : A {
void bar();
};
inline void D::bar() {}
-// because B has outline key function then we can refer to
+// Because B has outline all virtual functions, we can refer to them.
// CHECK-TEST10-DAG: @_ZTVN6Test101BE = available_externally unnamed_addr constant
struct B : A {
void foo();
void bar();
};
// C's key function (car) is outline, but C has inline virtual function so we
// can't guarantee that we will be able to refer to bar from name
-// so (at the moment) we can't emit vtable available_externally
+// so (at the moment) we can't emit vtable available_externally.
// CHECK-TEST10-DAG: @_ZTVN6Test101CE = external unnamed_addr constant
struct C : A {
void bar() {} // defined in body - not key function
@@ -365,4 +365,3 @@
}
}
-
Index: test/CodeGenCXX/vtable-assume-load.cpp
===================================================================
--- test/CodeGenCXX/vtable-assume-load.cpp
+++ test/CodeGenCXX/vtable-assume-load.cpp
@@ -6,7 +6,9 @@
// RUN: FileCheck --check-prefix=CHECK3 --input-file=%t.ll %s
// RUN: FileCheck --check-prefix=CHECK4 --input-file=%t.ll %s
// RUN: FileCheck --check-prefix=CHECK-MS --input-file=%t.ms.ll %s
-
+// RUN: FileCheck --check-prefix=CHECK6 --input-file=%t.ll %s
+// RUN: FileCheck --check-prefix=CHECK7 --input-file=%t.ll %s
+// RUN: FileCheck --check-prefix=CHECK8 --input-file=%t.ll %s
namespace test1 {
struct A {
@@ -150,17 +152,17 @@
}
} // test4
-namespace test5 {
+namespace testMS {
struct __declspec(novtable) S {
virtual void foo();
};
void g(S &s) { s.foo(); }
// if struct has novtable specifier, then we can't generate assumes
-// CHECK-MS-LABEL: define void @"\01?test@test5@@YAXXZ"()
-// CHECK-MS: call x86_thiscallcc %"struct.test5::S"* @"\01??0S@test5@@QAE@XZ"(
+// CHECK-MS-LABEL: define void @"\01?test@testMS@@YAXXZ"()
+// CHECK-MS: call x86_thiscallcc %"struct.testMS::S"* @"\01??0S@testMS@@QAE@XZ"(
// CHECK-MS-NOT: @llvm.assume
// CHECK-MS-LABEL: }
@@ -170,3 +172,123 @@
}
} // test5
+
+namespace test6 {
+// CHECK6: @_ZTVN5test61AE = external
+struct A {
+ A();
+ virtual void foo();
+ virtual ~A() {}
+};
+struct B : A {
+ B();
+};
+// Because A's vtable is external, it's safe to generate assumption loads.
+// CHECK6-LABEL: define void @_ZN5test61gEv()
+// CHECK6: call void @_ZN5test61AC1Ev(
+// CHECK6: call void @llvm.assume(
+
+// We can't emit assumption loads for B, because if we would refer to vtable
+// it would refer to functions that will not be able to find (like implicit
+// inline destructor).
+
+// CHECK6-LABEL: call void @_ZN5test61BC1Ev(
+// CHECK6-NOT: call void @llvm.assume(
+// CHECK6-LABEL: }
+void g() {
+ A *a = new A;
+ B *b = new B;
+}
+
+}
+
+namespace test7 {
+// Because A's key function is defined here, vtable is generated in this TU
+// CHECK7: @_ZTVN5test71AE = unnamed_addr constant
+struct A {
+ A();
+ virtual void foo();
+ virtual void bar();
+};
+void A::foo() {}
+
+// CHECK7-LABEL: define void @_ZN5test71gEv()
+// CHECK7: call void @_ZN5test71AC1Ev(
+// CHECK7: call void @llvm.assume(
+// CHECK7-LABEL: }
+void g() {
+ A *a = new A();
+ a->bar();
+}
+}
+
+namespace test8 {
+
+struct A {
+ virtual void foo();
+ virtual void bar();
+};
+
+// CHECK8-DAG: @_ZTVN5test81BE = available_externally unnamed_addr constant
+struct B : A {
+ B();
+ void foo();
+ void bar();
+};
+
+// CHECK8-DAG: @_ZTVN5test81CE = linkonce_odr unnamed_addr constant
+struct C : A {
+ C();
+ void bar();
+ void foo() {}
+};
+inline void C::bar() {}
+
+// CHECK8-DAG: @_ZTVN5test81DE = external unnamed_addr constant
+struct D : A {
+ D();
+ void foo();
+ void inline bar();
+};
+void D::bar() {}
+
+// CHECK8-DAG: @_ZTVN5test81EE = linkonce_odr unnamed_addr constant
+struct E : A {
+ E();
+};
+
+// CHECK8-LABEL: define void @_ZN5test81bEv()
+// CHECK8: call void @llvm.assume(
+// CHECK8-LABEL: }
+void b() {
+ B b;
+ b.bar();
+}
+
+// Vtable is generated in this TU, but C has inline virtual functions which
+// prohibits as from generating assumption loads.
+// CHECK8-LABEL: define void @_ZN5test81cEv()
+// CHECK8-NOT: call void @llvm.assume(
+// CHECK8-LABEL: }
+void c() {
+ C c;
+ c.bar();
+}
+
+// CHECK8-LABEL: define void @_ZN5test81dEv()
+// CHECK8: call void @llvm.assume(
+// CHECK8-LABEL: }
+void d() {
+ D d;
+ d.bar();
+}
+
+// CHECK8-LABEL: define void @_ZN5test81eEv()
+// CHECK8: call void @llvm.assume(
+// CHECK8-LABEL: }
+void e() {
+ E e;
+ e.bar();
+}
+}
+
Index: test/CodeGenCXX/thunks.cpp
===================================================================
--- test/CodeGenCXX/thunks.cpp
+++ test/CodeGenCXX/thunks.cpp
@@ -398,11 +398,13 @@
// Checking with opt
// CHECK-OPT-LABEL: define internal void @_ZThn8_N6Test4B12_GLOBAL__N_11C1fEv(%"struct.Test4B::(anonymous namespace)::C"* %this) unnamed_addr #0 align 2
+// This is from Test5:
+// CHECK-OPT-LABEL: define linkonce_odr void @_ZTv0_n24_N5Test51B1fEv
+
// This is from Test10:
// CHECK-OPT-LABEL: define linkonce_odr void @_ZN6Test101C3fooEv
// CHECK-OPT-LABEL: define linkonce_odr void @_ZThn8_N6Test101C3fooEv
-// This is from Test5:
-// CHECK-OPT-LABEL: define linkonce_odr void @_ZTv0_n24_N5Test51B1fEv
+
// CHECK: attributes [[NUW]] = { nounwind uwtable{{.*}} }
Index: test/CodeGenCXX/template-instantiation.cpp
===================================================================
--- test/CodeGenCXX/template-instantiation.cpp
+++ test/CodeGenCXX/template-instantiation.cpp
@@ -1,7 +1,5 @@
// RUN: %clang_cc1 %s -O1 -disable-llvm-optzns -triple=x86_64-apple-darwin10 -emit-llvm -o - | FileCheck %s
-// CHECK: @_ZTVN5test018stdio_sync_filebufIA4_iEE = linkonce_odr unnamed_addr constant
-
// CHECK: @_ZN7PR100011xE = global
// CHECK-NOT: @_ZN7PR100014kBarE = external global i32
//
@@ -14,6 +12,7 @@
// CHECK: @_ZN7PR100011SIiE3arrE = linkonce_odr global [3 x i32]
// CHECK-NOT: @_ZN7PR100011SIiE3arr2E = linkonce_odr global [3 x i32]A
+// CHECK: @_ZTVN5test018stdio_sync_filebufIA4_iEE = linkonce_odr unnamed_addr constant
// CHECK-NOT: _ZTVN5test31SIiEE
// CHECK-NOT: _ZTSN5test31SIiEE
Index: lib/CodeGen/MicrosoftCXXABI.cpp
===================================================================
--- lib/CodeGen/MicrosoftCXXABI.cpp
+++ lib/CodeGen/MicrosoftCXXABI.cpp
@@ -106,8 +106,7 @@
QualType DestTy) override;
bool EmitBadCastCall(CodeGenFunction &CGF) override;
- bool canEmitAvailableExternallyVTable(
- const CXXRecordDecl *RD) const override {
+ bool canEmitUnusedVTable(const CXXRecordDecl *RD) const override {
return false;
}
Index: lib/CodeGen/ItaniumCXXABI.cpp
===================================================================
--- lib/CodeGen/ItaniumCXXABI.cpp
+++ lib/CodeGen/ItaniumCXXABI.cpp
@@ -229,7 +229,7 @@
void emitVirtualInheritanceTables(const CXXRecordDecl *RD) override;
- bool canEmitAvailableExternallyVTable(const CXXRecordDecl *RD) const override;
+ bool canEmitUnusedVTable(const CXXRecordDecl *RD) const override;
void setThunkLinkage(llvm::Function *Thunk, bool ForVTable, GlobalDecl GD,
bool ReturnAdjustment) override {
@@ -1523,8 +1523,7 @@
VTables.EmitVTTDefinition(VTT, CGM.getVTableLinkage(RD), RD);
}
-bool ItaniumCXXABI::canEmitAvailableExternallyVTable(
- const CXXRecordDecl *RD) const {
+bool ItaniumCXXABI::canEmitUnusedVTable(const CXXRecordDecl *RD) const {
// We don't emit available_externally vtables if we are in -fapple-kext mode
// because kext mode does not permit devirtualization.
if (CGM.getLangOpts().AppleKext)
Index: lib/CodeGen/CGVTables.cpp
===================================================================
--- lib/CodeGen/CGVTables.cpp
+++ lib/CodeGen/CGVTables.cpp
@@ -682,7 +682,7 @@
static bool shouldEmitAvailableExternallyVTable(const CodeGenModule &CGM,
const CXXRecordDecl *RD) {
return CGM.getCodeGenOpts().OptimizationLevel > 0 &&
- CGM.getCXXABI().canEmitAvailableExternallyVTable(RD);
+ CGM.getCXXABI().canEmitUnusedVTable(RD);
}
/// Compute the required linkage of the v-table for the given class.
@@ -832,11 +832,11 @@
/// we define that v-table?
static bool shouldEmitVTableAtEndOfTranslationUnit(CodeGenModule &CGM,
const CXXRecordDecl *RD) {
- // If vtable is internal then it has to be done
+ // If vtable is internal then it has to be done.
if (!CGM.getVTables().isVTableExternal(RD))
return true;
- // If it's external then maybe we will need it as available_externally
+ // If it's external then maybe we will need it as available_externally.
return shouldEmitAvailableExternallyVTable(CGM, RD);
}
Index: lib/CodeGen/CGClass.cpp
===================================================================
--- lib/CodeGen/CGClass.cpp
+++ lib/CodeGen/CGClass.cpp
@@ -1857,8 +1857,15 @@
// with a vtable. We don't do this for base subobjects for two reasons:
// first, it's incorrect for classes with virtual bases, and second, we're
// about to overwrite the vptrs anyway.
+ // We also have to make sure if we can refer to vtable:
+ // - If vtable is external then it's safe to use it (for availabe_externally
+ // CGVTables will make sure it can emit it).
+ // - Otherwise we can refer to vtable if it's unused.
+ // FIXME: If vtable is used by ctor/dtor, we are always safe to refer to it.
if (CGM.getCodeGenOpts().OptimizationLevel > 0 &&
- ClassDecl->isDynamicClass() && Type != Ctor_Base)
+ ClassDecl->isDynamicClass() && Type != Ctor_Base &&
+ (CGM.getVTables().isVTableExternal(ClassDecl) ||
+ CGM.getCXXABI().canEmitUnusedVTable(ClassDecl)))
EmitVTableAssumptionLoads(ClassDecl, This);
}
Index: lib/CodeGen/CGCXXABI.h
===================================================================
--- lib/CodeGen/CGCXXABI.h
+++ lib/CodeGen/CGCXXABI.h
@@ -218,8 +218,7 @@
virtual void emitThrow(CodeGenFunction &CGF, const CXXThrowExpr *E) = 0;
virtual llvm::GlobalVariable *getThrowInfo(QualType T) { return nullptr; }
- virtual bool canEmitAvailableExternallyVTable(
- const CXXRecordDecl *RD) const = 0;
+ virtual bool canEmitUnusedVTable(const CXXRecordDecl *RD) const = 0;
virtual void emitBeginCatch(CodeGenFunction &CGF, const CXXCatchStmt *C) = 0;
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