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.
42 lines
1.0 KiB
C++
42 lines
1.0 KiB
C++
// For MSVC ABI compatibility, all structures returned by value using the
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// thiscall calling convention must use the hidden parameter.
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//
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// RUN: %clang_cc1 -triple i386-PC-Win32 %s -fms-compatibility -emit-llvm -o - | FileCheck %s
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// This structure would normally be returned via EAX
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struct S {
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int i;
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};
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// This structure would normally be returned via EAX/EDX
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struct M {
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int i;
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int j;
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};
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class C {
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public:
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C() {}
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struct S __attribute__((thiscall)) Small() const {
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struct S s = { 0 };
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return s;
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}
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struct M __attribute__((thiscall)) Medium() const {
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struct M m = { 0 };
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return m;
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}
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};
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// CHECK-LABEL: define{{.*}} void @_Z4testv()
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void test( void ) {
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// CHECK: call void @_ZN1CC1Ev(ptr {{[^,]*}} [[C:%.+]])
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C c;
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// CHECK: call x86_thiscallcc void @_ZNK1C5SmallEv(ptr dead_on_unwind writable sret(%struct.S) align 4 %{{.+}}, ptr {{[^,]*}} [[C]])
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(void)c.Small();
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// CHECK: call x86_thiscallcc void @_ZNK1C6MediumEv(ptr dead_on_unwind writable sret(%struct.M) align 4 %{{.+}}, ptr {{[^,]*}} [[C]])
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(void)c.Medium();
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}
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