This patch makes the dead_on_return parameter attribute optionally require a number
of bytes to be passed in to specify the number of bytes known to be dead
upon function return/unwind. This is aimed at enabling annotating the
this pointer in C++ destructors with dead_on_return in clang. We need
this to handle cases like the following:
```
struct X {
int n;
~X() {
this[n].n = 0;
}
};
void f() {
X xs[] = {42, -1};
}
```
Where we only certain that sizeof(X) bytes are dead upon return of ~X.
Otherwise DSE would be able to eliminate the store in ~X which would not
be correct.
This patch only does the wiring within IR. Future patches will make
clang emit correct sizing information and update DSE to only delete
stores to objects marked dead_on_return that are provably in bounds of
the number of bytes specified to be dead_on_return.
Reviewers: nikic, alinas, antoniofrighetto
Pull Request: https://github.com/llvm/llvm-project/pull/171712
219 lines
5.6 KiB
C++
219 lines
5.6 KiB
C++
// RUN: %clang_cc1 -triple aarch64-windows -ffreestanding -emit-llvm -O0 \
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// RUN: -x c++ -o - %s | FileCheck %s
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// Pass and return for type size <= 8 bytes.
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// CHECK: define {{.*}} i64 @{{.*}}f1{{.*}}()
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// CHECK: call i64 {{.*}}func1{{.*}}(i64 %0)
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struct S1 {
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int a[2];
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};
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S1 func1(S1 x);
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S1 f1() {
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S1 x;
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return func1(x);
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}
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// Pass and return type size <= 16 bytes.
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// CHECK: define {{.*}} [2 x i64] @{{.*}}f2{{.*}}()
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// CHECK: call [2 x i64] {{.*}}func2{{.*}}([2 x i64] %0)
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struct S2 {
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int a[4];
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};
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S2 func2(S2 x);
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S2 f2() {
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S2 x;
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return func2(x);
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}
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// Pass and return for type size > 16 bytes.
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// CHECK: define {{.*}} void @{{.*}}f3{{.*}}(ptr dead_on_unwind noalias writable sret(%struct.S3) align 4 %agg.result)
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// CHECK: call void {{.*}}func3{{.*}}(ptr dead_on_unwind writable sret(%struct.S3) align 4 %agg.result, ptr noundef dead_on_return %agg.tmp)
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struct S3 {
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int a[5];
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};
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S3 func3(S3 x);
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S3 f3() {
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S3 x;
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return func3(x);
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}
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// Pass and return aggregate (of size < 16 bytes) with non-trivial destructor.
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// Passed directly but returned indirectly.
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// CHECK: define {{.*}} void {{.*}}f4{{.*}}(ptr dead_on_unwind inreg noalias writable sret(%struct.S4) align 4 %agg.result)
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// CHECK: call void {{.*}}func4{{.*}}(ptr dead_on_unwind inreg writable sret(%struct.S4) align 4 %agg.result, [2 x i64] %0)
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struct S4 {
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int a[3];
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~S4();
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};
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S4 func4(S4 x);
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S4 f4() {
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S4 x;
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return func4(x);
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}
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// Pass and return from instance method called from instance method.
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// CHECK: define {{.*}} void @{{.*}}bar@Q1{{.*}}(ptr {{[^,]*}} %this, ptr dead_on_unwind inreg noalias writable sret(%class.P1) align 1 %agg.result)
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// CHECK: call void {{.*}}foo@P1{{.*}}(ptr noundef{{[^,]*}} %ref.tmp, ptr dead_on_unwind inreg writable sret(%class.P1) align 1 %agg.result, i64 %coerce.val.ii)
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class P1 {
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public:
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P1 foo(P1 x);
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};
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class Q1 {
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public:
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P1 bar();
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};
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P1 Q1::bar() {
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P1 p1;
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return P1().foo(p1);
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}
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// Pass and return from instance method called from free function.
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// CHECK: define {{.*}} void {{.*}}bar{{.*}}()
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// CHECK: call void {{.*}}foo@P2{{.*}}(ptr noundef{{[^,]*}} %ref.tmp, ptr dead_on_unwind inreg writable sret(%class.P2) align 1 %retval, i64 %coerce.val.ii)
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class P2 {
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public:
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P2 foo(P2 x);
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};
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P2 bar() {
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P2 p2;
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return P2().foo(p2);
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}
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// Pass and return an object with a user-provided constructor (passed directly,
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// returned indirectly)
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// CHECK: define {{.*}} void @{{.*}}f5{{.*}}(ptr dead_on_unwind inreg noalias writable sret(%struct.S5) align 4 %agg.result)
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// CHECK: call void {{.*}}func5{{.*}}(ptr dead_on_unwind inreg writable sret(%struct.S5) align 4 %agg.result, i64 {{.*}})
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struct S5 {
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S5();
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int x;
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};
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S5 func5(S5 x);
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S5 f5() {
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S5 x;
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return func5(x);
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}
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// Pass and return an object with a non-trivial explicitly defaulted constructor
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// (passed directly, returned directly)
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// CHECK: define {{.*}} i8 @"?f6@@YA?AUS6@@XZ"()
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// CHECK: call i8 {{.*}}func6{{.*}}(i64 {{.*}})
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struct S6a {
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S6a();
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};
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struct S6 {
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S6() = default;
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S6a x;
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};
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S6 func6(S6 x);
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S6 f6() {
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S6 x;
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return func6(x);
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}
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// Pass and return an object with a non-trivial implicitly defaulted constructor
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// (passed directly, returned directly)
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// CHECK: define {{.*}} i8 @"?f7@@YA?AUS7@@XZ"()
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// CHECK: call i8 {{.*}}func7{{.*}}(i64 {{.*}})
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struct S7 {
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S6a x;
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};
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S7 func7(S7 x);
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S7 f7() {
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S7 x;
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return func7(x);
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}
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struct S8a {
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~S8a();
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};
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// Pass and return an object with a non-trivial default destructor (passed
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// directly, returne indirectly)
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struct S8 {
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S8a x;
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int y;
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};
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// CHECK: define {{.*}} void {{.*}}?f8{{.*}}(ptr dead_on_unwind inreg noalias writable sret(%struct.S8) align 4 {{.*}})
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// CHECK: call void {{.*}}func8{{.*}}(ptr dead_on_unwind inreg writable sret(%struct.S8) align 4 {{.*}}, i64 {{.*}})
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S8 func8(S8 x);
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S8 f8() {
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S8 x;
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return func8(x);
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}
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// Pass and return an object with a non-trivial copy-assignment operator and
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// a trivial copy constructor (passed directly, returned indirectly)
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// CHECK: define {{.*}} void @"?f9@@YA?AUS9@@XZ"(ptr dead_on_unwind inreg noalias writable sret(%struct.S9) align 4 {{.*}})
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// CHECK: call void {{.*}}func9{{.*}}(ptr dead_on_unwind inreg writable sret(%struct.S9) align 4 {{.*}}, i64 {{.*}})
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struct S9 {
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S9& operator=(const S9&);
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int x;
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};
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S9 func9(S9 x);
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S9 f9() {
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S9 x;
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S9 y = x;
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x = y;
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return func9(x);
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}
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// Pass and return an object with a base class (passed directly, returned
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// indirectly).
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// CHECK: define dso_local void {{.*}}f10{{.*}}(ptr dead_on_unwind inreg noalias writable sret(%struct.S10) align 4 {{.*}})
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// CHECK: call void {{.*}}func10{{.*}}(ptr dead_on_unwind inreg writable sret(%struct.S10) align 4 {{.*}}, [2 x i64] {{.*}})
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struct S10 : public S1 {
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int x;
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};
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S10 func10(S10 x);
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S10 f10() {
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S10 x;
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return func10(x);
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}
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// Pass and return a non aggregate object exceeding > 128 bits (passed
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// indirectly, returned indirectly)
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// CHECK: define dso_local void {{.*}}f11{{.*}}(ptr dead_on_unwind inreg noalias writable sret(%struct.S11) align 8 {{.*}})
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// CHECK: call void {{.*}}func11{{.*}}(ptr dead_on_unwind inreg writable sret(%struct.S11) align 8 {{.*}}, ptr {{.*}})
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struct S11 {
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virtual void f();
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int a[5];
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};
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S11 func11(S11 x);
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S11 f11() {
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S11 x;
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return func11(x);
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}
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// GH86384
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// Pass and return object with template constructor (pass directly,
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// return indirectly).
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// CHECK: define dso_local void @"?f12@@YA?AUS12@@XZ"(ptr dead_on_unwind inreg noalias writable sret(%struct.S12) align 4 {{.*}})
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// CHECK: call void @"?func12@@YA?AUS12@@U1@@Z"(ptr dead_on_unwind inreg writable sret(%struct.S12) align 4 {{.*}}, i64 {{.*}})
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struct S12 {
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template<typename T> S12(T*) {}
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int x;
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};
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S12 func12(S12 x);
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S12 f12() {
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S12 x((int*)0);
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return func12(x);
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}
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