llvm-project/clang/test/CodeGenCXX/thiscall-struct-return.cpp

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C++

// For MSVC ABI compatibility, all structures returned by value using the
// thiscall calling convention must use the hidden parameter.
//
// RUN: %clang_cc1 -triple i386-PC-Win32 %s -fms-compatibility -O0 -emit-llvm -o - | FileCheck %s
// This structure would normally be returned via EAX
struct S {
int i;
};
// This structure would normally be returned via EAX/EDX
struct M {
int i;
int j;
};
class C {
public:
C() {}
struct S __attribute__((thiscall)) Small() const {
struct S s = { 0 };
return s;
}
struct M __attribute__((thiscall)) Medium() const {
struct M m = { 0 };
return m;
}
};
// CHECK: define void @_Z4testv()
void test( void ) {
// CHECK: call void @_ZN1CC1Ev(%class.C* [[C:%.+]])
C c;
// CHECK: call x86_thiscallcc void @_ZNK1C5SmallEv(%struct.S* sret %{{.+}}, %class.C* [[C]])
(void)c.Small();
// CHECK: call x86_thiscallcc void @_ZNK1C6MediumEv(%struct.M* sret %{{.+}}, %class.C* [[C]])
(void)c.Medium();
}