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Previously, Itanium ABI guard variables were set after initialization was
complete for non-block declared variables with static and thread storage
duration. That resulted in initialization of such variables being restarted
in cases where the variable was referenced while it was still under
construction. Per C++20 [class.cdtor]p2, such references are permitted
(though the value obtained by such an access is unspecified). The late
initialization resulted in recursive reinitialization loops for cases like
this:
template<typename T>
struct ct {
struct mc {
mc() { ct<T>::smf(); }
void mf() const {}
};
thread_local static mc tlsdm;
static void smf() { tlsdm.mf(); }
};
template<typename T>
thread_local typename ct<T>::mc ct<T>::tlsdm;
int main() {
ct<int>::smf();
}
With this change, guard variables are set before initialization is started
so as to avoid such reinitialization loops.
Fixes https://github.com/llvm/llvm-project/issues/57828
Reviewed By: rjmccall
Differential Revision: https://reviews.llvm.org/D135919
111 lines
3.0 KiB
C++
111 lines
3.0 KiB
C++
// RUN: %clang_cc1 -triple x86_64-pc-linux -emit-llvm -o - %s | FileCheck %s
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// RUN: %clang_cc1 -triple x86_64-apple-darwin -emit-llvm -o - %s | \
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// RUN: FileCheck --check-prefix=MACHO %s
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// CHECK: @_ZN5test11A1aE ={{.*}} constant i32 10, align 4
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// CHECK: @_ZN5test212_GLOBAL__N_11AIiE1xE = internal global i32 0, align 4
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// CHECK: @_ZN5test31AIiE1xE = weak_odr global i32 0, comdat, align 4
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// CHECK: @_ZGVN5test31AIiE1xE = weak_odr global i64 0, comdat($_ZN5test31AIiE1xE)
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// MACHO: @_ZGVN5test31AIiE1xE = weak_odr global i64 0
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// MACHO-NOT: comdat
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// CHECK: _ZN5test51U2k0E ={{.*}} global i32 0
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// CHECK: _ZN5test51U2k1E ={{.*}} global i32 0
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// CHECK: _ZN5test51U2k2E ={{.*}} constant i32 76
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// CHECK-NOT: test51U2k3E
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// CHECK-NOT: test51U2k4E
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// PR5564.
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namespace test1 {
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struct A {
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static const int a = 10;
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};
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const int A::a;
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struct S {
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static int i;
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};
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void f() {
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int a = S::i;
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}
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}
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// Test that we don't use guards for initializing template static data
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// members with internal linkage.
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namespace test2 {
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int foo();
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namespace {
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template <class T> struct A {
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static int x;
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};
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template <class T> int A<T>::x = foo();
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template struct A<int>;
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}
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// CHECK-LABEL: define internal void @__cxx_global_var_init()
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// CHECK: [[TMP:%.*]] = call noundef i32 @_ZN5test23fooEv()
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// CHECK-NEXT: store i32 [[TMP]], ptr @_ZN5test212_GLOBAL__N_11AIiE1xE, align 4
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// CHECK-NEXT: ret void
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}
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// Test that we don't use threadsafe statics when initializing
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// template static data members.
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namespace test3 {
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int foo();
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template <class T> struct A {
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static int x;
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};
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template <class T> int A<T>::x = foo();
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template struct A<int>;
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// CHECK-LABEL: define internal void @__cxx_global_var_init.1() {{.*}} comdat($_ZN5test31AIiE1xE)
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// MACHO-LABEL: define internal void @__cxx_global_var_init.1()
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// MACHO-NOT: comdat
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// CHECK: [[GUARDBYTE:%.*]] = load i8, ptr @_ZGVN5test31AIiE1xE
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// CHECK-NEXT: [[UNINITIALIZED:%.*]] = icmp eq i8 [[GUARDBYTE]], 0
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// CHECK-NEXT: br i1 [[UNINITIALIZED]]
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// CHECK: store i8 1, ptr @_ZGVN5test31AIiE1xE
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// CHECK-NEXT: [[TMP:%.*]] = call noundef i32 @_ZN5test33fooEv()
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// CHECK-NEXT: store i32 [[TMP]], ptr @_ZN5test31AIiE1xE, align 4
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// CHECK-NEXT: br label
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// CHECK: ret void
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}
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// Test that we can fold member lookup expressions which resolve to static data
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// members.
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namespace test4 {
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struct A {
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static const int n = 76;
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};
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int f(A *a) {
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// CHECK-LABEL: define{{.*}} i32 @_ZN5test41fEPNS_1AE
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// CHECK: ret i32 76
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return a->n;
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}
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}
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// Test that static data members in unions behave properly.
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namespace test5 {
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union U {
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static int k0;
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static const int k1;
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static const int k2 = 76;
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static const int k3;
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static const int k4 = 81;
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};
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int U::k0;
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const int U::k1 = (k0 = 9, 42);
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const int U::k2;
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// CHECK: store i32 9, ptr @_ZN5test51U2k0E
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// CHECK: store i32 {{.*}}, ptr @_ZN5test51U2k1E
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// CHECK-NOT: store {{.*}} ptr @_ZN5test51U2k2E
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}
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