Update unreachable_enum_default_branch.rs

Author: dianqk

tests/codegen/enum/uninhabited_enum_default_branch.rs

@@ -0,0 +1,43 @@
+//@ compile-flags: -O
+
+#![crate_type = "lib"]
+
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord)]
+pub struct Int(u32);
+
+const A: Int = Int(201);
+const B: Int = Int(270);
+const C: Int = Int(153);
+
+// The code is from https://github.com/rust-lang/rust/issues/119520.
+// This code will basically turn into `matches!(x.partial_cmp(&A), Some(Greater | Equal))`.
+// The otherwise branch must be `Less`.
+// CHECK-LABEL: @implicit_match(
+// CHECK-SAME: [[TMP0:%.*]])
+// CHECK-NEXT:  start:
+// CHECK-NEXT:    [[TMP1:%.*]] = add i32 [[TMP0]], -201
+// CHECK-NEXT:    icmp ult i32 [[TMP1]], 70
+// CHECK-NEXT:    icmp eq i32 [[TMP0]], 153
+// CHECK-NEXT:    [[SPEC_SELECT:%.*]] = or i1
+// CHECK-NEXT:    ret i1 [[SPEC_SELECT]]
+#[no_mangle]
+pub fn implicit_match(x: Int) -> bool {
+    (x >= A && x <= B)
+        || x == C
+}
+
+// The code is from https://github.com/rust-lang/rust/issues/110097.
+// We expect it to generate the same optimized code as a full match.
+// CHECK-LABEL: @if_let(
+// CHECK-NEXT:  start:
+// CHECK-NEXT: insertvalue
+// CHECK-NEXT: insertvalue
+// CHECK-NEXT: ret
+#[no_mangle]
+pub fn if_let(val: Result<i32, ()>) -> Result<i32, ()> {
+    if let Ok(x) = val {
+        Ok(x)
+    } else {
+        Err(())
+    }
+}