158d72d728
Set the writable and dead_on_unwind attributes for sret arguments. These indicate that the argument points to writable memory (and it's legal to introduce spurious writes to it on entry to the function) and that the argument memory will not be used if the call unwinds. This enables additional MemCpyOpt/DSE/LICM optimizations.
28 lines
724 B
C++
28 lines
724 B
C++
// RUN: %clang_cc1 -triple=i686 -emit-llvm -o - %s | FileCheck %s
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struct X;
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typedef void (X::*memptr)();
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struct A {
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virtual memptr f();
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};
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struct B {
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virtual memptr f();
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};
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struct C : A, B {
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C();
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memptr f() override __attribute__((noinline)) { return nullptr; };
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};
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C::C() {}
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// Make sure the member pointer is returned from the thunk via the return slot.
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// Because of the tail call, the return value cannot be copied into a local
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// alloca. (PR39901)
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// CHECK-LABEL: define linkonce_odr void @_ZThn4_N1C1fEv(ptr dead_on_unwind noalias writable sret({ i32, i32 }) align 4 %agg.result, ptr noundef %this)
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// CHECK: tail call void @_ZN1C1fEv(ptr dead_on_unwind writable sret({ i32, i32 }) align 4 %agg.result
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