1 files changed, 122 insertions, 0 deletions
diff --git a/tests/mir-opt/sroa/structs.rs b/tests/mir-opt/sroa/structs.rs
new file mode 100644
index 000000000..7946eeaea
--- /dev/null
+++ b/tests/mir-opt/sroa/structs.rs
@@ -0,0 +1,122 @@
+// unit-test: ScalarReplacementOfAggregates
+// compile-flags: -Cpanic=abort
+// no-prefer-dynamic
+
+struct Tag(usize);
+
+#[repr(C)]
+struct S(Tag, Tag, Tag);
+
+impl Drop for Tag {
+    #[inline(never)]
+    fn drop(&mut self) {}
+}
+
+pub fn dropping() {
+    S(Tag(0), Tag(1), Tag(2)).1;
+}
+
+pub fn enums(a: usize) -> usize {
+    if let Some(a) = Some(a) { a } else { 0 }
+}
+
+pub fn structs(a: f32) -> f32 {
+    struct U {
+        _foo: usize,
+        a: f32,
+    }
+
+    U { _foo: 0, a }.a
+}
+
+pub fn unions(a: f32) -> u32 {
+    union Repr {
+        f: f32,
+        u: u32,
+    }
+    unsafe { Repr { f: a }.u }
+}
+
+#[derive(Copy, Clone)]
+struct Foo {
+    a: u8,
+    b: (),
+    c: &'static str,
+    d: Option<isize>,
+}
+
+fn g() -> u32 {
+    3
+}
+
+pub fn flat() {
+    let Foo { a, b, c, d } = Foo { a: 5, b: (), c: "a", d: Some(-4) };
+    let _ = a;
+    let _ = b;
+    let _ = c;
+    let _ = d;
+}
+
+#[repr(C)]
+struct Escaping {
+    a: u32,
+    b: u32,
+    c: u32,
+}
+
+fn f(a: *const u32) {
+    println!("{}", unsafe { *a.add(2) });
+}
+
+// `f` uses the `&e.a` to access `e.c`. This is UB according to Miri today; however,
+// T-opsem has not finalized that decision and as such rustc should not rely on
+// it. If SROA were to rely on it, it would be (almost) correct to turn `e` into
+// three distinct locals - one for each field - and pass a reference to only one
+// of them to `f`. However, this would lead to a miscompilation because `b` and `c`
+// might no longer appear right after `a` in memory.
+pub fn escaping() {
+    f(&Escaping { a: 1, b: 2, c: g() }.a);
+}
+
+fn copies(x: Foo) {
+    let y = x;
+    let t = y.a;
+    let u = y.c;
+    let z = y;
+    let a = z.b;
+}
+
+fn ref_copies(x: &Foo) {
+    let y = *x;
+    let t = y.a;
+    let u = y.c;
+}
+
+fn constant() {
+    const U: (usize, u8) = (5, 9);
+    let y = U;
+    let t = y.0;
+    let u = y.1;
+}
+
+fn main() {
+    dropping();
+    enums(5);
+    structs(5.);
+    unions(5.);
+    flat();
+    escaping();
+    copies(Foo { a: 5, b: (), c: "a", d: Some(-4) });
+    ref_copies(&Foo { a: 5, b: (), c: "a", d: Some(-4) });
+    constant();
+}
+
+// EMIT_MIR structs.dropping.ScalarReplacementOfAggregates.diff
+// EMIT_MIR structs.enums.ScalarReplacementOfAggregates.diff
+// EMIT_MIR structs.structs.ScalarReplacementOfAggregates.diff
+// EMIT_MIR structs.unions.ScalarReplacementOfAggregates.diff
+// EMIT_MIR structs.flat.ScalarReplacementOfAggregates.diff
+// EMIT_MIR structs.escaping.ScalarReplacementOfAggregates.diff
+// EMIT_MIR structs.copies.ScalarReplacementOfAggregates.diff
+// EMIT_MIR structs.ref_copies.ScalarReplacementOfAggregates.diff
+// EMIT_MIR structs.constant.ScalarReplacementOfAggregates.diff