Add some float tests from libcore

Author: antoyo

tests/run/core-float.rs

@@ -0,0 +1,80 @@
+// Compiler:
+//
+// Run-time:
+//   status: 0
+
+// TODO: remove these tests (extracted from libcore) when we run the libcore tests in the CI of the
+// Rust repo.
+
+#![feature(core_intrinsics)]
+
+use std::f32::consts;
+use std::intrinsics;
+
+const EXP_APPROX: Float = 1e-6;
+const ZERO: Float = 0.0;
+const ONE: Float = 1.0;
+
+macro_rules! assert_biteq {
+    ($left:expr, $right:expr $(,)?) => {{
+        let l = $left;
+        let r = $right;
+
+        // Hack to coerce left and right to the same type
+        let mut _eq_ty = l;
+        _eq_ty = r;
+
+        // Hack to get the width from a value
+        assert!(l.to_bits() == r.to_bits());
+    }};
+}
+
+macro_rules! assert_approx_eq {
+    ($a:expr, $b:expr $(,)?) => {{
+        assert_approx_eq!($a, $b, $crate::num::floats::lim_for_ty($a))
+    }};
+    ($a:expr, $b:expr, $lim:expr) => {{
+        let (a, b) = (&$a, &$b);
+        let diff = (*a - *b).abs();
+        assert!(
+            diff <= $lim,
+        );
+    }};
+}
+
+type Float = f32;
+const fn flt (x: Float) -> Float { x }
+
+fn test_exp() {
+    assert_biteq!(1.0, flt(0.0).exp());
+    assert_approx_eq!(consts::E, flt(1.0).exp(), EXP_APPROX);
+    assert_approx_eq!(148.41315910257660342111558004055227962348775, flt(5.0).exp(), EXP_APPROX);
+
+    let inf: Float = Float::INFINITY;
+    let neg_inf: Float = Float::NEG_INFINITY;
+    let nan: Float = Float::NAN;
+    assert_biteq!(inf, inf.exp());
+    assert_biteq!(0.0, neg_inf.exp());
+    assert!(nan.exp().is_nan());
+}
+
+#[inline(never)]
+fn my_abs(num: f32) -> f32 {
+    unsafe { intrinsics::fabs(num) }
+}
+
+fn test_abs() {
+    assert_biteq!(Float::INFINITY.abs(), Float::INFINITY);
+    assert_biteq!(ONE.abs(), ONE);
+    assert_biteq!(ZERO.abs(), ZERO);
+    assert_biteq!((-ZERO).abs(), ZERO);
+    assert_biteq!((-ONE).abs(), ONE);
+    assert_biteq!(Float::NEG_INFINITY.abs(), Float::INFINITY);
+    assert_biteq!((ONE / Float::NEG_INFINITY).abs(), ZERO);
+    assert!(Float::NAN.abs().is_nan());
+}
+
+fn main() {
+    test_abs();
+    test_exp();
+}