9e0c06d708
Let Clang emit `dead_on_return` attribute on pointer arguments that are passed indirectly, namely, large aggregates that the ABI mandates be passed by value; thus, the parameter is destroyed within the callee. Writes to such arguments are not observable by the caller after the callee returns. This should desirably enable further MemCpyOpt/DSE optimizations. Previous discussion: https://discourse.llvm.org/t/rfc-add-dead-on-return-attribute/86871.
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 dead_on_return noundef %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 dead_on_return noundef %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 dead_on_return noundef %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 dead_on_return noundef %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 dead_on_return noundef %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 dead_on_return noundef %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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