d1fd72343c
The idea is that the CC1 default for ELF should set dso_local on default
visibility external linkage definitions in the default -mrelocation-model pic
mode (-fpic/-fPIC) to match COFF/Mach-O and make output IR similar.
The refactoring is made available by 2820a2ca3a.
Currently only x86 supports local aliases. We move the decision to the driver.
There are three CC1 states:
* -fsemantic-interposition: make some linkages interposable and make default visibility external linkage definitions dso_preemptable.
* (default): selected if the target supports .Lfoo$local: make default visibility external linkage definitions dso_local
* -fhalf-no-semantic-interposition: if neither option is set or the target does not support .Lfoo$local: like -fno-semantic-interposition but local aliases are not used. So references can be interposed if not optimized out.
Add -fhalf-no-semantic-interposition to a few tests using the half-based semantic interposition behavior.
30 lines
1.5 KiB
C++
30 lines
1.5 KiB
C++
// Check the layout of the vtable for a child class that inherits a virtual
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// function but does not override it.
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// RUN: %clang_cc1 %s -triple=aarch64-unknown-fuchsia -O1 -S -o - -emit-llvm -fexperimental-relative-c++-abi-vtables -fhalf-no-semantic-interposition | FileCheck %s
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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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// The VTable for B should look similar to the vtable for A but the component for foo() should point to A::foo() and the component for bar() should point to B::bar().
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// CHECK: @_ZTV1B.local = private unnamed_addr constant { [4 x i32] } { [4 x i32] [i32 0, i32 trunc (i64 sub (i64 ptrtoint ({ i8*, i8*, i8* }** @_ZTI1B.rtti_proxy to i64), i64 ptrtoint (i32* getelementptr inbounds ({ [4 x i32] }, { [4 x i32] }* @_ZTV1B.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 ({ [4 x i32] }, { [4 x i32] }* @_ZTV1B.local, i32 0, i32 0, i32 2) to i64)) to i32), i32 trunc (i64 sub (i64 ptrtoint (void (%class.B*)* dso_local_equivalent @_ZN1B3barEv to i64), i64 ptrtoint (i32* getelementptr inbounds ({ [4 x i32] }, { [4 x i32] }* @_ZTV1B.local, i32 0, i32 0, i32 2) to i64)) to i32)] }, align 4
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// CHECK: @_ZTV1B ={{.*}} unnamed_addr alias { [4 x i32] }, { [4 x i32] }* @_ZTV1B.local
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class B : public A {
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public:
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virtual void bar();
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};
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void A::foo() {}
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void B::bar() {}
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void A_foo(A *a) {
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a->foo();
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}
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void B_foo(B *b) {
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b->foo();
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}
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