1 files changed, 46 insertions, 0 deletions
diff --git a/src/test/ui/numbers-arithmetic/u128-as-f32.rs b/src/test/ui/numbers-arithmetic/u128-as-f32.rs
new file mode 100644
index 000000000..839ce932d
--- /dev/null
+++ b/src/test/ui/numbers-arithmetic/u128-as-f32.rs
@@ -0,0 +1,46 @@
+// run-pass
+
+#![feature(test)]
+#![deny(overflowing_literals)]
+extern crate test;
+
+use test::black_box;
+
+macro_rules! test {
+    ($val:expr, $src_ty:ident -> $dest_ty:ident, $expected:expr) => ({
+        {
+            const X: $src_ty = $val;
+            const Y: $dest_ty = X as $dest_ty;
+            assert_eq!(Y, $expected,
+                        "const eval {} -> {}", stringify!($src_ty), stringify!($dest_ty));
+        }
+        // black_box disables constant evaluation to test run-time conversions:
+        assert_eq!(black_box::<$src_ty>($val) as $dest_ty, $expected,
+                    "run-time {} -> {}", stringify!($src_ty), stringify!($dest_ty));
+    });
+}
+
+pub fn main() {
+    // nextDown(f32::MAX) = 2^128 - 2 * 2^104
+    const SECOND_LARGEST_F32: f32 = 340282326356119256160033759537265639424.;
+
+    // f32::MAX - 0.5 ULP and smaller should be rounded down
+    test!(0xfffffe00000000000000000000000000, u128 -> f32, SECOND_LARGEST_F32);
+    test!(0xfffffe7fffffffffffffffffffffffff, u128 -> f32, SECOND_LARGEST_F32);
+    test!(0xfffffe80000000000000000000000000, u128 -> f32, SECOND_LARGEST_F32);
+    // numbers within < 0.5 ULP of f32::MAX it should be rounded to f32::MAX
+    test!(0xfffffe80000000000000000000000001, u128 -> f32, f32::MAX);
+    test!(0xfffffeffffffffffffffffffffffffff, u128 -> f32, f32::MAX);
+    test!(0xffffff00000000000000000000000000, u128 -> f32, f32::MAX);
+    test!(0xffffff00000000000000000000000001, u128 -> f32, f32::MAX);
+    test!(0xffffff7fffffffffffffffffffffffff, u128 -> f32, f32::MAX);
+    // f32::MAX + 0.5 ULP and greater should be rounded to infinity
+    test!(0xffffff80000000000000000000000000, u128 -> f32, f32::INFINITY);
+    test!(0xffffff80000000f00000000000000000, u128 -> f32, f32::INFINITY);
+    test!(0xffffff87ffffffffffffffff00000001, u128 -> f32, f32::INFINITY);
+
+    // u128->f64 should not be affected by the u128->f32 checks
+    test!(0xffffff80000000000000000000000000, u128 -> f64,
+          340282356779733661637539395458142568448.0);
+    test!(u128::MAX, u128 -> f64, 340282366920938463463374607431768211455.0);
+}