add codegen test for slice::Iter::fold

Author: the8472

tests/codegen/slice-iter-fold.rs

@@ -0,0 +1,14 @@
+// ignore-debug: the debug assertions get in the way
+// compile-flags: -O
+// min-llvm-version: 16
+#![crate_type = "lib"]
+
+// CHECK-LABEL: @slice_fold_to_last
+#[no_mangle]
+pub fn slice_fold_to_last(slice: &[i32]) -> Option<&i32> {
+    // CHECK-NOT: loop
+    // CHECK-NOT: br
+    // CHECK-NOT: call
+    // CHECK: ret
+    slice.iter().fold(None, |_, i| Some(i))
+}