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[clang][RelativeVTables] Make the rtti_proxy LinkOnceODR instead of External linkage #67755

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Merged
merged 1 commit into from
Oct 4, 2023
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[clang][RelativeVTables] Make the rtti_proxy LinkOnceODR instead of External linkage #67755

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12 changes: 10 additions & 2 deletions clang/lib/CodeGen/CGVTables.cpp
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Expand Up @@ -639,8 +639,16 @@ void CodeGenVTables::addRelativeComponent(ConstantArrayBuilder &builder,
// want the stub/proxy to be emitted for properly calculating the offset.
// Examples where there would be no symbol emitted are available_externally
// and private linkages.
auto stubLinkage = vtableHasLocalLinkage ? llvm::GlobalValue::InternalLinkage
: llvm::GlobalValue::ExternalLinkage;
//
// `internal` linkage results in STB_LOCAL Elf binding while still manifesting a
// local symbol.
//
// `linkonce_odr` linkage results in a STB_DEFAULT Elf binding but also allows for
// the rtti_proxy to be transparently replaced with a GOTPCREL reloc by a
// target that supports this replacement.
auto stubLinkage = vtableHasLocalLinkage
? llvm::GlobalValue::InternalLinkage
: llvm::GlobalValue::LinkOnceODRLinkage;

llvm::Constant *target;
if (auto *func = dyn_cast<llvm::Function>(globalVal)) {
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3 changes: 1 addition & 2 deletions clang/test/CodeGenCXX/RelativeVTablesABI/child-vtable-in-comdat.cpp
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Expand Up @@ -8,7 +8,6 @@
// CHECK-DAG: $_ZTS1B = comdat any
// CHECK-DAG: $_ZTI1B = comdat any
// CHECK-DAG: $_ZTI1B.rtti_proxy = comdat any
// CHECK-DAG: $_ZTI1A.rtti_proxy = comdat any

// VTable for B is emitted here since we access it when creating an instance of B. The VTable is also linkonce_odr and in its own comdat.
// CHECK-DAG: @_ZTV1B.local = linkonce_odr hidden unnamed_addr constant { [3 x i32] } { [3 x i32] [i32 0, i32 trunc (i64 sub (i64 ptrtoint (ptr @_ZTI1B.rtti_proxy to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [3 x i32] }, ptr @_ZTV1B.local, i32 0, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @_ZN1B3fooEv to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [3 x i32] }, ptr @_ZTV1B.local, i32 0, i32 0, i32 2) to i64)) to i32)] }, comdat($_ZTV1B), align 4
Expand All @@ -18,7 +17,7 @@
// CHECK-DAG: @_ZTS1B =
// CHECK-DAG: @_ZTI1A =
// CHECK-DAG: @_ZTI1B =
// CHECK-DAG: @_ZTI1B.rtti_proxy = hidden unnamed_addr constant ptr @_ZTI1B, comdat
// CHECK-DAG: @_ZTI1B.rtti_proxy = linkonce_odr hidden unnamed_addr constant ptr @_ZTI1B, comdat

// We will emit a vtable for B here, so it does have an alias, but we will not
// emit one for A.
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2 changes: 1 addition & 1 deletion clang/test/CodeGenCXX/RelativeVTablesABI/parent-vtable-in-comdat.cpp
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Expand Up @@ -18,7 +18,7 @@
// CHECK: @_ZTVN10__cxxabiv117__class_type_infoE = external global [0 x ptr]
// CHECK: @_ZTS1A = linkonce_odr constant [3 x i8] c"1A\00", comdat, align 1
// CHECK: @_ZTI1A = linkonce_odr constant { ptr, ptr } { ptr getelementptr inbounds (i8, ptr @_ZTVN10__cxxabiv117__class_type_infoE, i32 8), ptr @_ZTS1A }, comdat, align 8
// CHECK: @_ZTI1A.rtti_proxy = hidden unnamed_addr constant ptr @_ZTI1A, comdat
// CHECK: @_ZTI1A.rtti_proxy = linkonce_odr hidden unnamed_addr constant ptr @_ZTI1A, comdat
// CHECK: @_ZTV1A = linkonce_odr unnamed_addr alias { [3 x i32] }, ptr @_ZTV1A.local

// CHECK: define linkonce_odr void @_ZN1A3fooEv(ptr {{.*}}%this) unnamed_addr #{{[0-9]+}} comdat
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4 changes: 2 additions & 2 deletions clang/test/CodeGenCXX/RelativeVTablesABI/relative-vtables-hwasan.cpp
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Expand Up @@ -6,7 +6,7 @@
/// hwasan-instrumented.
// CHECK-DAG: @_ZTV1A.local = private unnamed_addr constant { [3 x i32] } { [3 x i32] [i32 0, i32 trunc (i64 sub (i64 ptrtoint (ptr @_ZTI1A.rtti_proxy to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [3 x i32] }, ptr @_ZTV1A.local, i32 0, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @_ZN1A3fooEv to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [3 x i32] }, ptr @_ZTV1A.local, i32 0, i32 0, i32 2) to i64)) to i32)] }, no_sanitize_hwaddress, align 4
// CHECK-DAG: @_ZTV1A = unnamed_addr alias { [3 x i32] }, ptr @_ZTV1A.local
// CHECK-DAG: @_ZTI1A.rtti_proxy = hidden unnamed_addr constant ptr @_ZTI1A, no_sanitize_hwaddress, comdat
// CHECK-DAG: @_ZTI1A.rtti_proxy = linkonce_odr hidden unnamed_addr constant ptr @_ZTI1A, no_sanitize_hwaddress, comdat

class A {
public:
Expand All @@ -22,7 +22,7 @@ void A_foo(A *a) {
/// If the vtable happens to be hidden, then the alias is not needed. In this
/// case, the original vtable struct itself should be unsanitized.
// CHECK-DAG: @_ZTV1B = hidden unnamed_addr constant { [3 x i32] } { [3 x i32] [i32 0, i32 trunc (i64 sub (i64 ptrtoint (ptr @_ZTI1B.rtti_proxy to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [3 x i32] }, ptr @_ZTV1B, i32 0, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @_ZN1B3fooEv to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [3 x i32] }, ptr @_ZTV1B, i32 0, i32 0, i32 2) to i64)) to i32)] }, no_sanitize_hwaddress, align 4
// CHECK-DAG: @_ZTI1B.rtti_proxy = hidden unnamed_addr constant ptr @_ZTI1B, no_sanitize_hwaddress, comdat
// CHECK-DAG: @_ZTI1B.rtti_proxy = linkonce_odr hidden unnamed_addr constant ptr @_ZTI1B, no_sanitize_hwaddress, comdat

class __attribute__((visibility("hidden"))) B {
public:
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2 changes: 1 addition & 1 deletion clang/test/CodeGenCXX/RelativeVTablesABI/simple-vtable-definition.cpp
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Expand Up @@ -14,7 +14,7 @@
// CHECK: @_ZTI1A ={{.*}} constant { ptr, ptr } { ptr getelementptr inbounds (i8, ptr @_ZTVN10__cxxabiv117__class_type_infoE, i32 8), ptr @_ZTS1A }, align 8

// The rtti should be in a comdat
// CHECK: @_ZTI1A.rtti_proxy = hidden unnamed_addr constant ptr @_ZTI1A, comdat
// CHECK: @_ZTI1A.rtti_proxy = {{.*}}comdat

// The vtable symbol is exposed through an alias.
// @_ZTV1A = dso_local unnamed_addr alias { [3 x i32] }, ptr @_ZTV1A.local
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4 changes: 2 additions & 2 deletions clang/test/CodeGenCXX/RelativeVTablesABI/type-info.cpp
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Expand Up @@ -13,8 +13,8 @@
// CHECK: @_ZTVN10__cxxabiv120__si_class_type_infoE = external global [0 x ptr]
// CHECK: @_ZTS1B ={{.*}} constant [3 x i8] c"1B\00", align 1
// CHECK: @_ZTI1B ={{.*}} constant { ptr, ptr, ptr } { ptr getelementptr inbounds (i8, ptr @_ZTVN10__cxxabiv120__si_class_type_infoE, i32 8), ptr @_ZTS1B, ptr @_ZTI1A }, align 8
// CHECK: @_ZTI1A.rtti_proxy = hidden unnamed_addr constant ptr @_ZTI1A, comdat
// CHECK: @_ZTI1B.rtti_proxy = hidden unnamed_addr constant ptr @_ZTI1B, comdat
// CHECK: @_ZTI1A.rtti_proxy = linkonce_odr hidden unnamed_addr constant ptr @_ZTI1A, comdat
// CHECK: @_ZTI1B.rtti_proxy = linkonce_odr hidden unnamed_addr constant ptr @_ZTI1B, comdat

// CHECK: define {{.*}}ptr @_Z11getTypeInfov() local_unnamed_addr
// CHECK-NEXT: entry:
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