added codegen test for issue 112169

Author: SadiinsoSnowfall

tests/codegen/issues/issue-112169.rs

@@ -0,0 +1,28 @@
+//@ 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: define{{.*}}i32 @issue_112169(){{.*}}{
+#[no_mangle]
+pub fn issue_112169() -> i32 {
+    // CHECK-NOT: icmp
+    // CHECK-NOT: add
+    // CHECK-NOT: br
+    // CHECK: ret i32 102
+    // CHECK-NOT: icmp
+    // CHECK-NOT: add
+    // CHECK-NOT: br
+    let mut s = 0;
+
+    for i in 0..102 {
+        if i == 0 {
+            s = i;
+        }
+
+        s += 1;
+    }
+
+    s
+}