0371dff995
When using the relative vtable ABI, if a vtable is not dso_local, it's given private linkage (if not COMDAT) or hidden visibility (if COMDAT) to make it dso_local (to place it in rodata instead of data.rel.ro), and an alias generated with the original linkage and visibility. This alias could later be removed from the symbol table, e.g. if using a version script, at which point we lose all symbol information about the vtable. Use internal linkage instead of private linkage to avoid this. While I'm here, clarify the comment about why COMDAT vtables can't use internal (or private) linkage, and associate it with the else block where hidden visibility is applied instead of internal linkage.
49 lines
2.6 KiB
C++
49 lines
2.6 KiB
C++
// Multiple inheritance.
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// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -o - -emit-llvm -fhalf-no-semantic-interposition | FileCheck %s
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// VTable for C contains 2 sub-vtables (represented as 2 structs). The first contains the components for B and the second contains the components for C. The RTTI ptr in both arrays still point to the RTTI struct for C.
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// The component for bar() instead points to a thunk which redirects to C::bar() which overrides B::bar().
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// Now that we have a class with 2 parents, the offset to top in the second array is non-zero.
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// CHECK: @_ZTV1C.local = internal unnamed_addr constant { [4 x i32], [3 x i32] } { [4 x i32] [i32 0, i32 trunc (i64 sub (i64 ptrtoint (ptr @_ZTI1C.rtti_proxy to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [4 x i32], [3 x i32] }, ptr @_ZTV1C.local, i32 0, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @_ZN1C3fooEv to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [4 x i32], [3 x i32] }, ptr @_ZTV1C.local, i32 0, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @_ZN1C3barEv to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [4 x i32], [3 x i32] }, ptr @_ZTV1C.local, i32 0, i32 0, i32 2) to i64)) to i32)], [3 x i32] [i32 -8, i32 trunc (i64 sub (i64 ptrtoint (ptr @_ZTI1C.rtti_proxy to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [4 x i32], [3 x i32] }, ptr @_ZTV1C.local, i32 0, i32 1, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (ptr dso_local_equivalent @_ZThn8_N1C3barEv to i64), i64 ptrtoint (ptr getelementptr inbounds ({ [4 x i32], [3 x i32] }, ptr @_ZTV1C.local, i32 0, i32 1, i32 2) to i64)) to i32)] }, align 4
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// CHECK: @_ZTV1C ={{.*}} unnamed_addr alias { [4 x i32], [3 x i32] }, ptr @_ZTV1C.local
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// CHECK: define{{.*}} void @_Z8C_foobarP1C(ptr noundef %c) local_unnamed_addr
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// CHECK-NEXT: entry:
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// CHECK-NEXT: [[vtable:%[a-z0-9]+]] = load ptr, ptr %c, align 8
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// Offset 0 to get first method
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// CHECK-NEXT: [[ptr1:%[0-9]+]] = tail call ptr @llvm.load.relative.i32(ptr [[vtable]], i32 0)
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// CHECK-NEXT: call void [[ptr1]](ptr {{[^,]*}} %c)
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// CHECK-NEXT: [[vtable:%[a-z0-9]+]] = load ptr, ptr %c, align 8
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// Offset by 4 to get the next bar()
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// CHECK-NEXT: [[ptr2:%[0-9]+]] = tail call ptr @llvm.load.relative.i32(ptr [[vtable]], i32 4)
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// CHECK-NEXT: call void [[ptr2]](ptr {{[^,]*}} %c)
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// CHECK-NEXT: ret void
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// CHECK-NEXT: }
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class A {
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public:
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virtual void foo();
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};
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class B {
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virtual void bar();
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};
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class C : public A, public B {
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public:
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void foo() override;
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void bar() override;
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};
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void C::foo() {}
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void C::bar() {}
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void C_foobar(C *c) {
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c->foo();
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c->bar();
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}
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