Rollup merge of #145355 - clubby789:option-match-eq, r=nikic

Add codegen test for issue 122734

Closes #122734

Author: Zalathar

tests/codegen-llvm/issues/issue-122734-match-eq.rs

@@ -0,0 +1,78 @@
+//@ min-llvm-version: 21
+//@ compile-flags: -Copt-level=3 -Zmerge-functions=disabled
+//! Tests that matching + eq on `Option<FieldlessEnum>` produces a simple compare with no branching
+
+#![crate_type = "lib"]
+
+#[derive(PartialEq)]
+pub enum TwoNum {
+    A,
+    B,
+}
+
+#[derive(PartialEq)]
+pub enum ThreeNum {
+    A,
+    B,
+    C,
+}
+
+// CHECK-LABEL: @match_two
+#[no_mangle]
+pub fn match_two(a: Option<TwoNum>, b: Option<TwoNum>) -> bool {
+    // CHECK-NEXT: start:
+    // CHECK-NEXT: icmp eq i8
+    // CHECK-NEXT: ret
+    match (a, b) {
+        (Some(x), Some(y)) => x == y,
+        (Some(_), None) => false,
+        (None, Some(_)) => false,
+        (None, None) => true,
+    }
+}
+
+// CHECK-LABEL: @match_three
+#[no_mangle]
+pub fn match_three(a: Option<ThreeNum>, b: Option<ThreeNum>) -> bool {
+    // CHECK-NEXT: start:
+    // CHECK-NEXT: icmp eq
+    // CHECK-NEXT: ret
+    match (a, b) {
+        (Some(x), Some(y)) => x == y,
+        (Some(_), None) => false,
+        (None, Some(_)) => false,
+        (None, None) => true,
+    }
+}
+
+// CHECK-LABEL: @match_two_ref
+#[no_mangle]
+pub fn match_two_ref(a: &Option<TwoNum>, b: &Option<TwoNum>) -> bool {
+    // CHECK-NEXT: start:
+    // CHECK-NEXT: load i8
+    // CHECK-NEXT: load i8
+    // CHECK-NEXT: icmp eq i8
+    // CHECK-NEXT: ret
+    match (a, b) {
+        (Some(x), Some(y)) => x == y,
+        (Some(_), None) => false,
+        (None, Some(_)) => false,
+        (None, None) => true,
+    }
+}
+
+// CHECK-LABEL: @match_three_ref
+#[no_mangle]
+pub fn match_three_ref(a: &Option<ThreeNum>, b: &Option<ThreeNum>) -> bool {
+    // CHECK-NEXT: start:
+    // CHECK-NEXT: load i8
+    // CHECK-NEXT: load i8
+    // CHECK-NEXT: icmp eq
+    // CHECK-NEXT: ret
+    match (a, b) {
+        (Some(x), Some(y)) => x == y,
+        (Some(_), None) => false,
+        (None, Some(_)) => false,
+        (None, None) => true,
+    }
+}