Files
clang-p2996/clang/test/CodeGenCXX/RelativeVTablesABI/parent-vtable-in-comdat.cpp
Leonard Chan cf8ff75bad [clang][RelativeVTablesABI] Use dso_local_equivalent rather than emitting stubs
Thanks to D77248, we can bypass the use of stubs altogether and use PLT
relocations if they are available for the target. LLVM and LLD support the
R_AARCH64_PLT32 relocation, so we can also guarantee a static PLT relocation on AArch64.
Not emitting these stubs saves a lot of extra binary size.

Differential Revision: https://reviews.llvm.org/D83812
2020-11-30 16:02:35 -08:00

43 lines
2.2 KiB
C++

// Cross comdat example
// Parent VTable is in a comdat section.
// RUN: %clang_cc1 %s -triple=aarch64 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
// RUN: %clang_cc1 %s -triple=x86_64 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables | FileCheck %s
// A::foo() has a comdat since it is an inline function
// CHECK: $_ZN1A3fooEv = comdat any
// CHECK: $_ZTV1A = comdat any
// CHECK: $_ZTS1A = comdat any
// The VTable for A has its own comdat section bc it has no key function
// CHECK: $_ZTI1A = comdat any
// CHECK: $_ZTI1A.rtti_proxy = comdat any
// The VTable for A is emitted here and in a comdat section since it has no key function, and is used in this module when creating an instance of A.
// CHECK: @_ZTV1A.local = linkonce_odr hidden unnamed_addr constant { [3 x i32] } { [3 x i32] [i32 0, i32 trunc (i64 sub (i64 ptrtoint ({ i8*, i8* }** @_ZTI1A.rtti_proxy to i64), i64 ptrtoint (i32* getelementptr inbounds ({ [3 x i32] }, { [3 x i32] }* @_ZTV1A.local, i32 0, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (void (%class.A*)* dso_local_equivalent @_ZN1A3fooEv to i64), i64 ptrtoint (i32* getelementptr inbounds ({ [3 x i32] }, { [3 x i32] }* @_ZTV1A.local, i32 0, i32 0, i32 2) to i64)) to i32)] }, comdat($_ZTV1A), align 4
// CHECK: @_ZTVN10__cxxabiv117__class_type_infoE = external global i8*
// CHECK: @_ZTS1A = linkonce_odr constant [3 x i8] c"1A\00", comdat, align 1
// CHECK: @_ZTI1A = linkonce_odr constant { i8*, i8* } { i8* getelementptr inbounds (i8, i8* bitcast (i8** @_ZTVN10__cxxabiv117__class_type_infoE to i8*), i32 8), i8* getelementptr inbounds ([3 x i8], [3 x i8]* @_ZTS1A, i32 0, i32 0) }, comdat, align 8
// CHECK: @_ZTI1A.rtti_proxy = hidden unnamed_addr constant { i8*, i8* }* @_ZTI1A, comdat
// CHECK: @_ZTV1A = linkonce_odr unnamed_addr alias { [3 x i32] }, { [3 x i32] }* @_ZTV1A.local
// CHECK: define linkonce_odr void @_ZN1A3fooEv(%class.A* {{.*}}%this) unnamed_addr #{{[0-9]+}} comdat
class A {
public:
inline virtual void foo() {}
};
class B : public A {
public:
void foo() override;
};
void A_foo(A *a);
void A_foo(A *a) { a->foo(); }
// func() is only used to emit a vtable.
void func() {
A a;
A_foo(&a);
}