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.
22 lines
539 B
C++
22 lines
539 B
C++
// RUN: %clang_cc1 -emit-llvm %s -o - -triple=ppc64-windows-msvc | FileCheck %s
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// The purpose of this test is to see that we do something reasonable for
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// architectures where we haven't checked what MSVC does.
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struct A {
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A() : a(42) {}
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A(const A &o) : a(o.a) {}
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~A() {}
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int a;
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};
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struct B {
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A foo(A o);
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};
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A B::foo(A x) {
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return x;
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}
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// CHECK-LABEL: define{{.*}} void @"?foo@B@@QEAA?AUA@@U2@@Z"(ptr {{[^,]*}} %this, ptr dead_on_unwind noalias writable sret(%struct.A) align 4 %agg.result, ptr dead_on_return noundef %x)
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