Port newlib hypotf

build.rs

@@ -26,7 +26,7 @@ mod musl_reference_tests {
 
     // These files are all internal functions or otherwise miscellaneous, not
     // defining a function we want to test.
-    const IGNORED_FILES: &[&str] = &["fenv.rs"];
+    const IGNORED_FILES: &[&str] = &["fenv.rs", "musl/"];
 
     struct Function {
         name: String,

src/math/hypotf.rs

@@ -3,41 +3,111 @@ use core::f32;
 use super::sqrtf;
 
 #[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
-pub fn hypotf(mut x: f32, mut y: f32) -> f32 {
-    let x1p90 = f32::from_bits(0x6c800000); // 0x1p90f === 2 ^ 90
-    let x1p_90 = f32::from_bits(0x12800000); // 0x1p-90f === 2 ^ -90
-
-    let mut uxi = x.to_bits();
-    let mut uyi = y.to_bits();
-    let uti;
-    let mut z: f32;
-
-    uxi &= -1i32 as u32 >> 1;
-    uyi &= -1i32 as u32 >> 1;
-    if uxi < uyi {
-        uti = uxi;
-        uxi = uyi;
-        uyi = uti;
+pub fn hypotf(x: f32, y: f32) -> f32 {
+    let mut ha = f32::to_bits(x) as i32;
+    ha &= 0x7fffffff;
+
+    let mut hb = f32::to_bits(y) as i32;
+    hb &= 0x7fffffff;
+
+    if hb > ha {
+        let temp = ha;
+        ha = hb;
+        hb = temp;
     }
 
-    x = f32::from_bits(uxi);
-    y = f32::from_bits(uyi);
-    if uyi == 0xff << 23 {
-        return y;
+    let mut a = f32::from_bits(ha as u32); /* a <- |a| */
+    let mut b = f32::from_bits(hb as u32); /* b <- |b| */
+    if (ha - hb) > 0xf000000 {
+        return a + b;
+    } /* x/y > 2**30 */
+    let mut k: u32 = 0;
+    if ha > 0x58800000 {
+        /* a>2**50 */
+        if ha >= 0x7f800000 {
+            /* Inf or NaN */
+            let mut w = a + b; /* for sNaN */
+            if ha == 0x7f800000 {
+                w = a;
+            }
+            if hb == 0x7f800000 {
+                w = b;
+            }
+            return w;
+        }
+        /* scale a and b by 2**-60 */
+        ha -= 0x5d800000;
+        hb -= 0x5d800000;
+        k += 60;
+        a = f32::from_bits(ha as u32);
+        b = f32::from_bits(hb as u32);
+    }
+    if hb < 0x26800000 {
+        /* b < 2**-50 */
+        if hb <= 0x007fffff {
+            /* subnormal b or 0 */
+            if hb == 0 {
+                return a;
+            };
+            let t1 = f32::from_bits(0x3f000000); /* t1=2^126 */
+            b *= t1;
+            a *= t1;
+            k -= 126;
+        } else {
+            /* scale a and b by 2^60 */
+            ha += 0x5d800000; /* a *= 2^60 */
+            hb += 0x5d800000; /* b *= 2^60 */
+            k -= 60;
+            a = f32::from_bits(ha as u32);
+            b = f32::from_bits(hb as u32);
+        }
+    }
+    /* medium size a and b */
+    let mut w = a - b;
+    if w > b {
+        let t1 = f32::from_bits((ha as u32) & 0xfffff000);
+        let t2 = a - t1;
+        w = sqrtf(t1 * t1 - (b * (-b) - t2 * (a + t1)));
+    } else {
+        a = a + a;
+        let y1 = f32::from_bits((hb as u32) & 0xfffff000);
+        let y2 = b - y1;
+        let t1 = f32::from_bits((ha as u32) + 0x00800000);
+        let t2 = a - t1;
+        w = sqrtf(t1 * y1 - (w * (-w) - (t1 * y2 + t2 * b)));
     }
-    if uxi >= 0xff << 23 || uyi == 0 || uxi - uyi >= 25 << 23 {
-        return x + y;
+    if k != 0 {
+        let t1 = f32::from_bits(0x3f800000 + (k << 23));
+        return t1 * w;
+    } else {
+        return w;
+    };
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use core::f32::*;
+
+    #[test]
+    fn sanity_check() {
+        assert_eq!(hypotf(0.0, 0.0), 0.0);
+        assert_eq!(hypotf(0.0, -10.0), 10.0);
+        assert_eq!(hypotf(3.0, 4.0), 5.0);
+        assert_eq!(hypotf(-3.0, 4.0), 5.0);
+        assert_eq!(hypotf(4.0, 3.0), 5.0);
+        assert_eq!(hypotf(9.0, 10.0), 13.453624);
+        assert_eq!(hypotf(1.0, 1.0), sqrtf(2.0));
     }
 
-    z = 1.;
-    if uxi >= (0x7f + 60) << 23 {
-        z = x1p90;
-        x *= x1p_90;
-        y *= x1p_90;
-    } else if uyi < (0x7f - 60) << 23 {
-        z = x1p_90;
-        x *= x1p90;
-        y *= x1p90;
+    /// The spec: https://en.cppreference.com/w/c/numeric/math/hypot
+    #[test]
+    fn spec_tests() {
+        assert!(hypotf(0.0, NAN).is_nan());
+        assert!(hypotf(NAN, 0.0).is_nan());
+        assert!(hypotf(NAN, NAN).is_nan());
+        assert_eq!(hypotf(INFINITY, NAN), INFINITY);
+        assert_eq!(hypotf(INFINITY, 0.0), INFINITY);
     }
-    z * sqrtf((x as f64 * x as f64 + y as f64 * y as f64) as f32)
 }
+

src/math/mod.rs

@@ -348,3 +348,10 @@ fn with_set_low_word(f: f64, lo: u32) -> f64 {
 fn combine_words(hi: u32, lo: u32) -> f64 {
     f64::from_bits((hi as u64) << 32 | lo as u64)
 }
+
+// Test that the old code continues to build
+#[cfg(test)]
+#[allow(dead_code)]
+mod musl {
+    mod hypotf;
+}

src/math/musl/hypotf.rs

@@ -0,0 +1,44 @@
+use core::f64;
+
+// Note: This should be just super::sqrtf once sqrtf is moved into the musl module
+use super::super::sqrtf;
+
+#[cfg_attr(all(test, assert_no_panic), no_panic::no_panic)]
+pub fn hypotf(mut x: f32, mut y: f32) -> f32 {
+    let x1p90 = f32::from_bits(0x6c800000); // 0x1p90f === 2 ^ 90
+    let x1p_90 = f32::from_bits(0x12800000); // 0x1p-90f === 2 ^ -90
+
+    let mut uxi = x.to_bits();
+    let mut uyi = y.to_bits();
+    let uti;
+    let mut z: f32;
+
+    uxi &= -1i32 as u32 >> 1;
+    uyi &= -1i32 as u32 >> 1;
+    if uxi < uyi {
+        uti = uxi;
+        uxi = uyi;
+        uyi = uti;
+    }
+
+    x = f32::from_bits(uxi);
+    y = f32::from_bits(uyi);
+    if uyi == 0xff << 23 {
+        return y;
+    }
+    if uxi >= 0xff << 23 || uyi == 0 || uxi - uyi >= 25 << 23 {
+        return x + y;
+    }
+
+    z = 1.;
+    if uxi >= (0x7f + 60) << 23 {
+        z = x1p90;
+        x *= x1p_90;
+        y *= x1p_90;
+    } else if uyi < (0x7f - 60) << 23 {
+        z = x1p_90;
+        x *= x1p90;
+        y *= x1p90;
+    }
+    z * sqrtf((x as f64 * x as f64 + y as f64 * y as f64) as f32)
+}