Minor math tweaks + ipow32f/ipow64f (AssemblyScript#428)

Author: MaxGraey

std/assembly/math.ts

@@ -343,8 +343,7 @@ export namespace NativeMath {
     t = reinterpret<f64>((reinterpret<u64>(t) + 0x80000000) & 0xFFFFFFFFC0000000);
     var s = t * t;
     r = x / s;
-    var w = t + t;
-    r = (r - t) / (w + r);
+    r = (r - t) / (2 * t + r);
     t = t + t * r;
     return t;
   }
@@ -402,10 +401,7 @@ export namespace NativeMath {
     hx &= 0x7FFFFFFF;
     if (hx >= 0x4086232B) {
       if (isNaN(x)) return x;
-      if (x > overflow) {
-        x *= Ox1p1023;
-        return x;
-      }
+      if (x > overflow)  return x * Ox1p1023;
       if (x < underflow) return 0;
     }
     var hi: f64, lo: f64 = 0;
@@ -819,8 +815,9 @@ export namespace NativeMath {
       if (iy >= 0x43400000) yisint = 2;
       else if (iy >= 0x3FF00000) {
         k = (iy >> 20) - 0x3FF;
-        let offset = select<i32>(52, 20, k > 20) - k;
-        let Ly = select<i32>(ly, iy, k > 20);
+        let kcond = k > 20;
+        let offset = select<i32>(52, 20, kcond) - k;
+        let Ly = select<i32>(ly, iy, kcond);
         let jj = Ly >> offset;
         if ((jj << offset) == Ly) yisint = 2 - (jj & 1);
       }
@@ -842,19 +839,24 @@ export namespace NativeMath {
     }
     var ax = builtin_abs<f64>(x), z: f64;
     if (lx == 0) {
-      if (ix == 0x7FF00000 || ix == 0 || ix == 0x3FF00000) {
+      if (ix == 0 || ix == 0x7FF00000 || ix == 0x3FF00000) {
         z = ax;
         if (hy < 0) z = 1.0 / z;
         if (hx < 0) {
-          if (((ix - 0x3FF00000) | yisint) == 0) z = (z - z) / (z - z);
-          else if (yisint == 1) z = -z;
+          if (((ix - 0x3FF00000) | yisint) == 0) {
+            let d = z - z;
+            z = d / d;
+          } else if (yisint == 1) z = -z;
         }
         return z;
       }
     }
     var s = 1.0;
     if (hx < 0) {
-      if (yisint == 0) return (x - x) / (x - x);
+      if (yisint == 0) {
+        let d = x - x;
+        return d / d;
+      }
       if (yisint == 1) s = -1.0;
     }
     var t1: f64, t2: f64, p_h: f64, p_l: f64, r: f64, t: f64, u: f64, v: f64, w: f64;
@@ -1105,7 +1107,10 @@ export namespace NativeMath {
     var ey = <i64>(uy >> 52 & 0x7FF);
     var sx = ux >> 63;
     var uy1 = uy << 1;
-    if (uy1 == 0 || ex == 0x7FF || isNaN<f64>(y)) return (x * y) / (x * y);
+    if (uy1 == 0 || ex == 0x7FF || isNaN<f64>(y)) {
+      let m = x * y;
+      return m / m;
+    }
     var ux1 = ux << 1;
     if (ux1 <= uy1) {
       if (ux1 == uy1) return 0 * x;
@@ -1157,7 +1162,10 @@ export namespace NativeMath {
     var ex = <i64>(ux >> 52 & 0x7FF);
     var ey = <i64>(uy >> 52 & 0x7FF);
     var sx = <i32>(ux >> 63);
-    if (uy << 1 == 0 || ex == 0x7FF || isNaN(y)) return (x * y) / (x * y);
+    if (uy << 1 == 0 || ex == 0x7FF || isNaN(y)) {
+      let m = x * y;
+      return m / m;
+    }
     if (ux << 1 == 0) return x;
     var uxi = ux;
     if (!ex) {
@@ -1236,7 +1244,7 @@ function expo2f(x: f32): f32 { // exp(x)/2 for x >= log(DBL_MAX)
   const                        // see: musl/src/math/__expo2f.c
     k    = <u32>235,
     kln2 = reinterpret<f32>(0x4322E3BC); // 0x1.45c778p+7f
-  var scale = reinterpret<f32>(<u32>(0x7F + k / 2) << 23);
+  var scale = reinterpret<f32>(<u32>(0x7F + (k >> 1)) << 23);
   return NativeMathf.exp(x - kln2) * scale * scale;
 }
 
@@ -1424,7 +1432,7 @@ export namespace NativeMathf {
     if (iy == 0) {
       switch (m) {
         case 0:
-        case 1: return y;
+        case 1: return  y;
         case 2: return  pi;
         case 3: return -pi;
       }
@@ -1538,12 +1546,8 @@ export namespace NativeMathf {
     hx &= 0x7FFFFFFF;
     if (hx >= 0x42AEAC50) {
       if (hx >= 0x42B17218) {
-        if (!sign_) {
-          x *= Ox1p127f;
-          return x;
-        } else {
-          if (hx >= 0x42CFF1B5) return 0;
-        }
+        if (!sign_) return x * Ox1p127f;
+        else if (hx >= 0x42CFF1B5) return 0;
       }
     }
     var hi: f32, lo: f32;
@@ -1889,8 +1893,9 @@ export namespace NativeMathf {
       if (iy >= 0x4B800000) yisint = 2;
       else if (iy >= 0x3F800000) {
         k = (iy >> 23) - 0x7F;
-        j = iy >> (23 - k);
-        if ((j << (23 - k)) == iy) yisint = 2 - (j & 1);
+        let ki = 23 - k;
+        j = iy >> ki;
+        if ((j << ki) == iy) yisint = 2 - (j & 1);
       }
     }
     if (iy == 0x7F800000) { // y is +-inf
@@ -1909,14 +1914,20 @@ export namespace NativeMathf {
       z = ax;
       if (hy < 0) z = 1.0 / z;
       if (hx < 0) {
-        if (((ix - 0x3F800000) | yisint) == 0) z = (z - z) / (z - z);
+        if (((ix - 0x3F800000) | yisint) == 0) {
+          let d = z - z;
+          z = d / d;
+        }
         else if (yisint == 1) z = -z;
       }
       return z;
     }
     var sn = <f32>1.0;
     if (hx < 0) {
-      if (yisint == 0) return (x - x) / (x - x);
+      if (yisint == 0) {
+        let d = x - x;
+        return d / d;
+      }
       if (yisint == 1) sn = -1.0;
     }
     var t1: f32, t2: f32, r: f32, s: f32, t: f32, u: f32, v: f32, w: f32, p_h: f32, p_l: f32;
@@ -2159,7 +2170,10 @@ export namespace NativeMathf {
     var ey = <i32>(uy >> 23 & 0xFF);
     var sx = ux & 0x80000000;
     var uy1 = uy << 1;
-    if (uy1 == 0 || ex == 0xFF || isNaN<f32>(y)) return (x * y) / (x * y);
+    if (uy1 == 0 || ex == 0xFF || isNaN<f32>(y)) {
+      let m = x * y;
+      return m / m;
+    }
     var ux1 = ux << 1;
     if (ux1 <= uy1) {
       if (ux1 == uy1) return 0 * x;
@@ -2380,3 +2394,27 @@ export function ipow64(x: i64, e: i32): i64 {
   }
   return out;
 }
+
+export function ipow32f(x: f32, e: i32): f32 {
+  var sign = e >> 31;
+  e = (e + sign) ^ sign; // abs(e)
+  var out: f32 = 1;
+  while (e) {
+    out *= select<f32>(x, 1.0, e & 1);
+    e >>= 1;
+    x *= x;
+  }
+  return sign ? <f32>1.0 / out : out;
+}
+
+export function ipow64f(x: f64, e: i32): f64 {
+  var sign = e >> 31;
+  e = (e + sign) ^ sign; // abs(e)
+  var out = 1.0;
+  while (e) {
+    out *= select(x, 1.0, e & 1);
+    e >>= 1;
+    x *= x;
+  }
+  return sign ? 1.0 / out : out;
+}