Add a generic version of round

This replaces `round` and `roundf`.

Author: tgross35

etc/function-definitions.json

@@ -685,12 +685,14 @@
     "round": {
         "sources": [
             "src/libm_helper.rs",
+            "src/math/generic/round.rs",
             "src/math/round.rs"
         ],
         "type": "f64"
     },
     "roundf": {
         "sources": [
+            "src/math/generic/round.rs",
             "src/math/roundf.rs"
         ],
         "type": "f32"

src/math/generic/mod.rs

@@ -4,6 +4,7 @@ mod fabs;
 mod fdim;
 mod floor;
 mod rint;
+mod round;
 mod scalbn;
 mod sqrt;
 mod trunc;
@@ -14,6 +15,7 @@ pub use fabs::fabs;
 pub use fdim::fdim;
 pub use floor::floor;
 pub use rint::rint;
+pub use round::round;
 pub use scalbn::scalbn;
 pub use sqrt::sqrt;
 pub use trunc::trunc;

src/math/generic/round.rs

@@ -0,0 +1,46 @@
+use super::super::{Float, MinInt};
+use super::{copysign, trunc};
+
+pub fn round<F: Float>(x: F) -> F {
+    let f0p5 = F::from_parts(false, F::EXP_BIAS - 1, F::Int::ZERO); // 0.5
+    let f0p25 = F::from_parts(false, F::EXP_BIAS - 2, F::Int::ZERO); // 0.25
+
+    trunc(x + copysign(f0p5 - f0p25 * F::EPSILON, x))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn zeroes_f32() {
+        assert_biteq!(round(0.0_f32), 0.0_f32);
+        assert_biteq!(round(-0.0_f32), -0.0_f32);
+    }
+
+    #[test]
+    fn sanity_check_f32() {
+        assert_eq!(round(-1.0_f32), -1.0);
+        assert_eq!(round(2.8_f32), 3.0);
+        assert_eq!(round(-0.5_f32), -1.0);
+        assert_eq!(round(0.5_f32), 1.0);
+        assert_eq!(round(-1.5_f32), -2.0);
+        assert_eq!(round(1.5_f32), 2.0);
+    }
+
+    #[test]
+    fn zeroes_f64() {
+        assert_biteq!(round(0.0_f64), 0.0_f64);
+        assert_biteq!(round(-0.0_f64), -0.0_f64);
+    }
+
+    #[test]
+    fn sanity_check_f64() {
+        assert_eq!(round(-1.0_f64), -1.0);
+        assert_eq!(round(2.8_f64), 3.0);
+        assert_eq!(round(-0.5_f64), -1.0);
+        assert_eq!(round(0.5_f64), 1.0);
+        assert_eq!(round(-1.5_f64), -2.0);
+        assert_eq!(round(1.5_f64), 2.0);
+    }
+}

src/math/round.rs

@@ -1,28 +1,5 @@
-use core::f64;
-
-use super::{copysign, trunc};
-
+/// Round `x` to the nearest integer, breaking ties away from zero.
 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
 pub fn round(x: f64) -> f64 {
-    trunc(x + copysign(0.5 - 0.25 * f64::EPSILON, x))
-}
-
-#[cfg(test)]
-mod tests {
-    use super::round;
-
-    #[test]
-    fn negative_zero() {
-        assert_eq!(round(-0.0_f64).to_bits(), (-0.0_f64).to_bits());
-    }
-
-    #[test]
-    fn sanity_check() {
-        assert_eq!(round(-1.0), -1.0);
-        assert_eq!(round(2.8), 3.0);
-        assert_eq!(round(-0.5), -1.0);
-        assert_eq!(round(0.5), 1.0);
-        assert_eq!(round(-1.5), -2.0);
-        assert_eq!(round(1.5), 2.0);
-    }
+    super::generic::round(x)
 }

src/math/roundf.rs

@@ -1,30 +1,5 @@
-use core::f32;
-
-use super::{copysignf, truncf};
-
+/// Round `x` to the nearest integer, breaking ties away from zero.
 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
 pub fn roundf(x: f32) -> f32 {
-    truncf(x + copysignf(0.5 - 0.25 * f32::EPSILON, x))
-}
-
-// PowerPC tests are failing on LLVM 13: https://github.com/rust-lang/rust/issues/88520
-#[cfg(not(target_arch = "powerpc64"))]
-#[cfg(test)]
-mod tests {
-    use super::roundf;
-
-    #[test]
-    fn negative_zero() {
-        assert_eq!(roundf(-0.0_f32).to_bits(), (-0.0_f32).to_bits());
-    }
-
-    #[test]
-    fn sanity_check() {
-        assert_eq!(roundf(-1.0), -1.0);
-        assert_eq!(roundf(2.8), 3.0);
-        assert_eq!(roundf(-0.5), -1.0);
-        assert_eq!(roundf(0.5), 1.0);
-        assert_eq!(roundf(-1.5), -2.0);
-        assert_eq!(roundf(1.5), 2.0);
-    }
+    super::generic::round(x)
 }