Add nexttoward and signbit

Author: gnzlbg

crates/libm/src/math/mod.rs

@@ -149,6 +149,8 @@ mod modf;
 mod modff;
 mod nextafter;
 mod nextafterf;
+mod nexttoward;
+mod nexttowardf;
 mod pow;
 mod powf;
 mod remainder;
@@ -159,6 +161,8 @@ mod round;
 mod roundf;
 mod scalbn;
 mod scalbnf;
+mod signbit;
+mod signbitf;
 mod sin;
 mod sincos;
 mod sincosf;
@@ -263,6 +267,8 @@ pub use self::modf::modf;
 pub use self::modff::modff;
 pub use self::nextafter::nextafter;
 pub use self::nextafterf::nextafterf;
+pub use self::nexttoward::nexttoward;
+pub use self::nexttowardf::nexttowardf;
 pub use self::pow::pow;
 pub use self::powf::powf;
 pub use self::remainder::remainder;

crates/libm/src/math/nexttoward.rs

@@ -0,0 +1,43 @@
+use super::signbit::signbit;
+
+#[inline]
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub extern "C" fn nexttoward(x: f64, y: /*long double*/ f64) -> f64 {
+    let mut ux_i = x.to_bits();
+    if x.is_nan() || y.is_nan() {
+        return x + y;
+    }
+
+    if x == y {
+        return y;
+    }
+    if x == 0.0 {
+        ux_i = 1;
+        if signbit(y) != 0 {
+            ux_i |= 1_u64 << 63;
+        }
+    } else if x < y {
+        if signbit(x) != 0 {
+            ux_i -= 1;
+        } else {
+            ux_i += 1;
+        }
+    } else {
+        if signbit(x) != 0 {
+            ux_i += 1;
+        } else {
+            ux_i -= 1;
+        }
+    }
+    let e = ux_i >> 52 & 0x7ff;
+    // raise overflow if ux.f is infinite and x is finite
+    if e == 0x7ff {
+        force_eval!(x + x);
+    }
+    // raise underflow if ux.f is subnormal or zero
+    let ux_f = f64::from_bits(ux_i);
+    if e == 0 {
+        force_eval!(x * x + ux_f * ux_f);
+    }
+    ux_f
+}

crates/libm/src/math/nexttowardf.rs

@@ -0,0 +1,44 @@
+use super::signbit::signbit;
+use super::signbitf::signbitf;
+
+#[inline]
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub extern "C" fn nexttowardf(x: f32, y: f64) -> f32 {
+    let mut ux_i = x.to_bits();
+    if x.is_nan() || y.is_nan() {
+        return (x as f64 + y) as f32;
+    }
+
+    if x == y as f32 {
+        return y as f32;
+    }
+    if x == 0.0 {
+        ux_i = 1;
+        if signbit(y) != 0 {
+            ux_i |= 0x8000_0000_u32;
+        }
+    } else if x < (y as f32) {
+        if signbitf(x) != 0 {
+            ux_i -= 1;
+        } else {
+            ux_i += 1;
+        }
+    } else {
+        if signbitf(x) != 0 {
+            ux_i += 1;
+        } else {
+            ux_i -= 1;
+        }
+    }
+    let e = ux_i.wrapping_shr(0x7f80_0000_u32);
+    // raise overflow if ux.f is infinite and x is finite
+    if e == 0x7f80_0000_u32 {
+        force_eval!(x + x);
+    }
+    // raise underflow if ux.f is subnormal or zero
+    let ux_f = f32::from_bits(ux_i);
+    if e == 0 {
+        force_eval!(x * x + ux_f * ux_f);
+    }
+    ux_f
+}

crates/libm/src/math/signbit.rs

@@ -0,0 +1,5 @@
+#[inline]
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub(crate) extern "C" fn signbit(x: f64) -> i32 {
+    (x.to_bits() >> 63) as i32
+}

crates/libm/src/math/signbitf.rs

@@ -0,0 +1,5 @@
+#[inline]
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub(crate) extern "C" fn signbitf(x: f32) -> i32 {
+    (x.to_bits() >> 31) as i32
+}