No longer need `alloca`s for consuming `Result<!, i32>` and similar

In optimized builds GVN gets rid of these already, but in `opt-level=0` we actually make `alloca`s for this, which particularly impacts `?`-style things that use actually-only-one-variant types like this.

1 files changed, 31 insertions, 0 deletions

diff --git a/tests/codegen-llvm/enum/enum-transparent-extract.rs b/tests/codegen-llvm/enum/enum-transparent-extract.rs
new file mode 100644
index 00000000000..c5efb8d472b
--- /dev/null
+++ b/tests/codegen-llvm/enum/enum-transparent-extract.rs
@@ -0,0 +1,31 @@
+//@ compile-flags: -Copt-level=0
+//@ only-64bit
+
+#![crate_type = "lib"]
+
+use std::ops::ControlFlow;
+
+pub enum Never {}
+
+#[no_mangle]
+pub fn make_unmake_result_never(x: i32) -> i32 {
+    // CHECK-LABEL: define i32 @make_unmake_result_never(i32 %x)
+    // CHECK: start:
+    // CHECK-NEXT: ret i32 %x
+
+    let y: Result<i32, Never> = Ok(x);
+    let Ok(z) = y;
+    z
+}
+
+#[no_mangle]
+pub fn extract_control_flow_never(x: ControlFlow<&str, Never>) -> &str {
+    // CHECK-LABEL: define { ptr, i64 } @extract_control_flow_never(ptr align 1 %x.0, i64 %x.1)
+    // CHECK: start:
+    // CHECK-NEXT: %[[P0:.+]] = insertvalue { ptr, i64 } poison, ptr %x.0, 0
+    // CHECK-NEXT: %[[P1:.+]] = insertvalue { ptr, i64 } %[[P0]], i64 %x.1, 1
+    // CHECK-NEXT: ret { ptr, i64 } %[[P1]]
+
+    let ControlFlow::Break(s) = x;
+    s
+}