Add codegen test for issue 112169

Author: SadiinsoSnowfall

tests/codegen/issues/issue-112169-long-iterator-unroll.rs

@@ -0,0 +1,23 @@
+//@ compile-flags: -O
+#![crate_type = "lib"]
+
+// Test that simple iterator-based loops of length > 101 are fully optimized away.
+// See <https://github.com/rust-lang/rust/issues/112169>
+
+// CHECK-LABEL: issue_112169()
+#[no_mangle]
+pub fn issue_112169() -> i32 {
+    // CHECK-NEXT: {{.*}}:
+    // CHECK-NEXT: ret i32 102
+    let mut s = 0;
+
+    for i in 0..102 {
+        if i == 0 {
+            s = i;
+        }
+
+        s += 1;
+    }
+
+    s
+}