Vendor things

third-party/vendor/psm/examples/on_stack_fibo.rs

@@ -0,0 +1,77 @@
+extern crate psm;
+
+psm::psm_stack_manipulation! {
+    yes {
+        use std::alloc;
+
+        #[inline(never)]
+        fn fib(n: usize, stack_limit: *mut u8) -> Option<u64> {
+            // match psm::StackDirection::new() {
+            //     psm::StackDirection::Ascending => if psm::stack_pointer() > stack_limit {
+            //         return None;
+            //     }
+            //     psm::StackDirection::Descending => if psm::stack_pointer() < stack_limit {
+            //         return None;
+            //     }
+            // }
+
+            match n {
+                0 => Some(0),
+                1 => Some(1),
+                _ => fib(n - 1, stack_limit).and_then(|x| fib(n - 2, stack_limit).map(|y| x + y)),
+            }
+        }
+
+        const STACK_ALIGN: usize = 4096;
+        const STACK_REDLINE: usize = 512;
+        const FIB_COUNTS: [(usize, u64); 3] = [
+            (8, 21),
+            (16, 987),
+            (32, 2178309),
+        ];
+
+
+        fn main() {
+            let mut stack_size = 1024 * 128;
+            unsafe {
+                for &(n, expected) in FIB_COUNTS.iter() {
+                    loop {
+                        println!("fib({}) with {} bytes of stack", n, stack_size - STACK_REDLINE);
+                        let layout = alloc::Layout::from_size_align(stack_size, STACK_ALIGN).unwrap();
+                        let new_stack = alloc::alloc(layout);
+                        assert!(!new_stack.is_null(), "allocations must succeed!");
+                        let max_stack = match psm::StackDirection::new() {
+                            psm::StackDirection::Ascending =>
+                                new_stack.offset((stack_size - STACK_REDLINE) as isize),
+                            psm::StackDirection::Descending =>
+                                new_stack.offset(STACK_REDLINE as isize),
+                        };
+                        let result = psm::on_stack(new_stack, stack_size, || {
+                            fib(n, max_stack)
+                        });
+                        alloc::dealloc(new_stack, layout);
+                        if let Some(res) = result {
+                            assert_eq!(res, expected);
+                            println!("fib({}) = {}", n, res);
+                            break;
+                        } else {
+                            println!("Stack not large enough!");
+                            stack_size *= 2;
+                        }
+                    }
+                }
+            }
+        }
+
+    }
+    no {
+        fn main() {
+            eprintln!("Stack manipulation not supported by this target");
+        }
+    }
+}
+
+#[test]
+fn run_example() {
+    main()
+}