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.
108 lines
2.4 KiB
C++
108 lines
2.4 KiB
C++
// RUN: %clang_cc1 -std=c++1z -emit-llvm -triple x86_64-linux-gnu -o - %s | FileCheck %s
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struct A {
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A(int);
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A(A&&);
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A(const A&);
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~A();
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operator bool();
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int arr[10];
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};
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A f();
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void h();
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// CHECK-LABEL: define {{.*}} @_Z1gv(
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void g() {
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// CHECK: %[[A:.*]] = alloca
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// CHECK-NOT: alloca
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// CHECK-NOT: call
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// CHECK: call {{.*}} @_Z1fv(ptr dead_on_unwind writable sret({{.*}}) align 4 %[[A]])
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A a = A( A{ f() } );
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// CHECK-NOT: call
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// CHECK: call void @_Z1hv(
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h();
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// CHECK-NOT: call
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// CHECK: call void @_ZN1AD1Ev(ptr {{[^,]*}} %[[A]])
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// CHECK-NOT: call
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// CHECK-LABEL: }
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}
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void f(A);
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// CHECK-LABEL: define {{.*}} @_Z1hv(
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void h() {
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// CHECK: %[[A:.*]] = alloca
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// CHECK-NOT: alloca
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// CHECK-NOT: call
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// CHECK: call {{.*}} @_Z1fv(ptr dead_on_unwind writable sret({{.*}}) align 4 %[[A]])
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// CHECK-NOT: call
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// CHECK: call {{.*}} @_Z1f1A(ptr noundef %[[A]])
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f(f());
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// CHECK-NOT: call
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// CHECK: call void @_ZN1AD1Ev(ptr {{[^,]*}} %[[A]])
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// CHECK: call void @_Z1hv(
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h();
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// CHECK-NOT: call
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// CHECK-LABEL: }
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}
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// We still pass classes with trivial copy/move constructors and destructors in
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// registers, even if the copy is formally omitted.
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struct B {
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B(int);
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int n;
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};
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B fB();
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void fB(B);
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// CHECK-LABEL: define {{.*}} @_Z1iv(
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void i() {
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// CHECK: %[[B:.*]] = alloca
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// CHECK-NOT: alloca
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// CHECK-NOT: call
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// CHECK: %[[B_N:.*]] = call i32 @_Z2fBv()
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// CHECK-NOT: call
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// CHECK: store i32 %[[B_N]],
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// CHECK-NOT: call
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// CHECK: %[[B_N:.*]] = load i32
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// CHECK-NOT: call
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// CHECK: call void @_Z2fB1B(i32 %[[B_N]])
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fB(fB());
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// CHECK-LABEL: }
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}
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// CHECK-LABEL: define {{.*}} @_Z1jv(
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void j() {
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// CHECK: alloca ptr
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// CHECK: %[[OUTERTEMP:.*]] = alloca %{{.*}}
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// CHECK: %[[INNERTEMP:.*]] = alloca %{{.*}}
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// CHECK: call void @_ZN1AC1Ei(ptr {{.*}} %[[INNERTEMP]], i32 noundef 1)
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// CHECK: call noundef zeroext i1 @_ZN1AcvbEv(ptr {{.*}} %[[INNERTEMP]])
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// CHECK: br i1
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//
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// CHECK: call void @_ZN1AC1EOS_(ptr {{.*}} %[[OUTERTEMP]], ptr {{.*}} %[[INNERTEMP]])
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// CHECK: br label
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//
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// CHECK: call void @_ZN1AC1Ei(ptr {{.*}} %[[OUTERTEMP]], i32 noundef 2)
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// CHECK: br label
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//
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// CHECK: call void @_ZN1AD1Ev(ptr {{.*}} %[[INNERTEMP]])
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A &&a = A(1) ?: A(2);
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// CHECK: call void @_Z1iv()
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i();
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// CHECK: call void @_ZN1AD1Ev(ptr {{.*}} %[[OUTERTEMP]])
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}
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