add codegen test for issue-118392, 71096

Author: tesuji

tests/codegen/issues/issue-118392.rs

@@ -0,0 +1,11 @@
+//@ compile-flags: -O
+//@ min-llvm-version: 18
+#![crate_type = "lib"]
+
+// CHECK-LABEL: @div2
+// CHECK: ashr i32 %a, 1
+// CHECK-NEXT: ret i32
+#[no_mangle]
+pub fn div2(a: i32) -> i32 {
+    a.div_euclid(2)
+}