e2d7cd685d
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
114 lines
4.4 KiB
C++
114 lines
4.4 KiB
C++
// RUN: %clang_cc1 %s -fno-rtti -triple=i686-pc-win32 -emit-llvm -o - | FileCheck --check-prefix=CHECK32 %s
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// RUN: %clang_cc1 %s -fno-rtti -triple=x86_64-pc-win32 -emit-llvm -o - | FileCheck --check-prefix=CHECK64 %s
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namespace byval_thunk {
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struct Agg {
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Agg();
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Agg(const Agg &);
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~Agg();
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int x;
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};
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struct A { virtual void foo(Agg x); };
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struct B { virtual void foo(Agg x); };
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struct C : A, B { C(); virtual void foo(Agg x); };
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C::C() {} // force emission
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// CHECK32-LABEL: define linkonce_odr dso_local x86_thiscallcc void @"?foo@C@byval_thunk@@W3AEXUAgg@2@@Z"
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// CHECK32: (ptr noundef %this, ptr inalloca(<{ %"struct.byval_thunk::Agg" }>) %0)
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// CHECK32: getelementptr i8, ptr %{{.*}}, i32 -4
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// CHECK32: musttail call x86_thiscallcc void @"?foo@C@byval_thunk@@UAEXUAgg@2@@Z"
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// CHECK32: (ptr noundef %{{.*}}, ptr inalloca(<{ %"struct.byval_thunk::Agg" }>) %0)
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// CHECK32-NEXT: ret void
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// CHECK64-LABEL: define linkonce_odr dso_local void @"?foo@C@byval_thunk@@W7EAAXUAgg@2@@Z"
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// CHECK64: (ptr noundef %this, ptr noundef dead_on_return %x)
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// CHECK64: getelementptr i8, ptr %{{.*}}, i32 -8
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// CHECK64: call void @"?foo@C@byval_thunk@@UEAAXUAgg@2@@Z"
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// CHECK64: (ptr {{[^,]*}} %{{.*}}, ptr noundef dead_on_return %x)
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// CHECK64-NOT: call
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// CHECK64: ret void
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}
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namespace stdcall_thunk {
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struct Agg {
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Agg();
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Agg(const Agg &);
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~Agg();
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int x;
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};
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struct A { virtual void __stdcall foo(Agg x); };
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struct B { virtual void __stdcall foo(Agg x); };
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struct C : A, B { C(); virtual void __stdcall foo(Agg x); };
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C::C() {} // force emission
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// CHECK32-LABEL: define linkonce_odr dso_local x86_stdcallcc void @"?foo@C@stdcall_thunk@@W3AGXUAgg@2@@Z"
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// CHECK32: (ptr inalloca(<{ ptr, %"struct.stdcall_thunk::Agg" }>) %0)
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// CHECK32: %[[this_slot:[^ ]*]] = getelementptr inbounds nuw <{ ptr, %"struct.stdcall_thunk::Agg" }>, ptr %0, i32 0, i32 0
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// CHECK32: load ptr, ptr %[[this_slot]]
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// CHECK32: getelementptr i8, ptr %{{.*}}, i32 -4
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// CHECK32: store ptr %{{.*}}, ptr %[[this_slot]]
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// CHECK32: musttail call x86_stdcallcc void @"?foo@C@stdcall_thunk@@UAGXUAgg@2@@Z"
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// CHECK32: (ptr inalloca(<{ ptr, %"struct.stdcall_thunk::Agg" }>) %0)
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// CHECK32-NEXT: ret void
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// CHECK64-LABEL: define linkonce_odr dso_local void @"?foo@C@stdcall_thunk@@W7EAAXUAgg@2@@Z"
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// CHECK64: (ptr noundef %this, ptr noundef dead_on_return %x)
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// CHECK64: getelementptr i8, ptr %{{.*}}, i32 -8
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// CHECK64: call void @"?foo@C@stdcall_thunk@@UEAAXUAgg@2@@Z"
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// CHECK64: (ptr {{[^,]*}} %{{.*}}, ptr noundef dead_on_return %x)
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// CHECK64-NOT: call
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// CHECK64: ret void
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}
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namespace sret_thunk {
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struct Agg {
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Agg();
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Agg(const Agg &);
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~Agg();
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int x;
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};
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struct A { virtual Agg __cdecl foo(Agg x); };
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struct B { virtual Agg __cdecl foo(Agg x); };
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struct C : A, B { C(); virtual Agg __cdecl foo(Agg x); };
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C::C() {} // force emission
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// CHECK32-LABEL: define linkonce_odr dso_local ptr @"?foo@C@sret_thunk@@W3AA?AUAgg@2@U32@@Z"
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// CHECK32: (ptr inalloca(<{ ptr, ptr, %"struct.sret_thunk::Agg" }>) %0)
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// CHECK32: %[[this_slot:[^ ]*]] = getelementptr inbounds nuw <{ ptr, ptr, %"struct.sret_thunk::Agg" }>, ptr %0, i32 0, i32 0
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// CHECK32: load ptr, ptr %[[this_slot]]
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// CHECK32: getelementptr i8, ptr %{{.*}}, i32 -4
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// CHECK32: store ptr %{{.*}}, ptr %[[this_slot]]
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// CHECK32: %[[rv:[^ ]*]] = musttail call ptr @"?foo@C@sret_thunk@@UAA?AUAgg@2@U32@@Z"
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// CHECK32: (ptr inalloca(<{ ptr, ptr, %"struct.sret_thunk::Agg" }>) %0)
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// CHECK32-NEXT: ret ptr %[[rv]]
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// CHECK64-LABEL: define linkonce_odr dso_local void @"?foo@C@sret_thunk@@W7EAA?AUAgg@2@U32@@Z"
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// CHECK64: (ptr noundef %this, ptr dead_on_unwind noalias writable sret(%"struct.sret_thunk::Agg") align 4 %agg.result, ptr noundef dead_on_return %x)
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// CHECK64: getelementptr i8, ptr %{{.*}}, i32 -8
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// CHECK64: call void @"?foo@C@sret_thunk@@UEAA?AUAgg@2@U32@@Z"
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// CHECK64: (ptr {{[^,]*}} %{{.*}}, ptr dead_on_unwind writable sret(%"struct.sret_thunk::Agg") align 4 %agg.result, ptr noundef dead_on_return %x)
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// CHECK64-NOT: call
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// CHECK64: ret void
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}
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#if 0
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// FIXME: When we extend LLVM IR to allow forwarding of varargs through musttail
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// calls, use this test.
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namespace variadic_thunk {
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struct Agg {
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Agg();
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Agg(const Agg &);
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~Agg();
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int x;
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};
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struct A { virtual void foo(Agg x, ...); };
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struct B { virtual void foo(Agg x, ...); };
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struct C : A, B { C(); virtual void foo(Agg x, ...); };
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C::C() {} // force emission
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}
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#endif
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