clean up pow.c and powf.c

[musl] / src / math / powf.c

diff --git a/src/math/powf.c b/src/math/powf.c
index c78eb12..427c896 100644 (file)
--- a/src/math/powf.c
+++ b/src/math/powf.c
@@ -19,9 +19,6 @@ static const float
 bp[]   = {1.0, 1.5,},
 dp_h[] = { 0.0, 5.84960938e-01,}, /* 0x3f15c000 */
 dp_l[] = { 0.0, 1.56322085e-06,}, /* 0x35d1cfdc */
-zero   =  0.0,
-one    =  1.0,
-two    =  2.0,
 two24  =  16777216.0,  /* 0x4b800000 */
 huge   =  1.0e30,
 tiny   =  1.0e-30,
@@ -60,17 +57,15 @@ float powf(float x, float y)
        ix = hx & 0x7fffffff;
        iy = hy & 0x7fffffff;
 
-       /* y == zero: x**0 = 1 */
+       /* x**0 = 1, even if x is NaN */
        if (iy == 0)
-               return one;
-
-       /* x == 1: 1**y = 1, even if y is NaN */
+               return 1.0f;
+       /* 1**y = 1, even if y is NaN */
        if (hx == 0x3f800000)
-               return one;
-
-       /* y != zero: result is NaN if either arg is NaN */
+               return 1.0f;
+       /* NaN if either arg is NaN */
        if (ix > 0x7f800000 || iy > 0x7f800000)
-               return (x+0.0F) + (y+0.0F);
+               return x + y;
 
        /* determine if y is an odd int when x < 0
         * yisint = 0       ... y is not an integer
@@ -92,17 +87,14 @@ float powf(float x, float y)
        /* special value of y */
        if (iy == 0x7f800000) {  /* y is +-inf */
                if (ix == 0x3f800000)      /* (-1)**+-inf is 1 */
-                       return one;
+                       return 1.0f;
                else if (ix > 0x3f800000)  /* (|x|>1)**+-inf = inf,0 */
-                       return hy >= 0 ? y : zero;
+                       return hy >= 0 ? y : 0.0f;
                else                       /* (|x|<1)**+-inf = 0,inf */
-                       return hy < 0 ? -y : zero;
-       }
-       if (iy == 0x3f800000) {  /* y is +-1 */
-               if (hy < 0)
-                       return one/x;
-               return x;
+                       return hy >= 0 ? 0.0f: -y;
        }
+       if (iy == 0x3f800000)    /* y is +-1 */
+               return hy >= 0 ? x : 1.0f/x;
        if (hy == 0x40000000)    /* y is 2 */
                return x*x;
        if (hy == 0x3f000000) {  /* y is  0.5 */
@@ -115,7 +107,7 @@ float powf(float x, float y)
        if (ix == 0x7f800000 || ix == 0 || ix == 0x3f800000) { /* x is +-0,+-inf,+-1 */
                z = ax;
                if (hy < 0)  /* z = (1/|x|) */
-                       z = one/z;
+                       z = 1.0f/z;
                if (hx < 0) {
                        if (((ix-0x3f800000)|yisint) == 0) {
                                z = (z-z)/(z-z); /* (-1)**non-int is NaN */
@@ -125,15 +117,13 @@ float powf(float x, float y)
                return z;
        }
 
-       n = ((uint32_t)hx>>31) - 1;
-
-       /* (x<0)**(non-int) is NaN */
-       if ((n|yisint) == 0)
-               return (x-x)/(x-x);
-
-       sn = one; /* s (sign of result -ve**odd) = -1 else = 1 */
-       if ((n|(yisint-1)) == 0)  /* (-ve)**(odd int) */
-               sn = -one;
+       sn = 1.0f; /* sign of result */
+       if (hx < 0) {
+               if (yisint == 0) /* (x<0)**(non-int) is NaN */
+                       return (x-x)/(x-x);
+               if (yisint == 1) /* (x<0)**(odd int) */
+                       sn = -1.0f;
+       }
 
        /* |y| is huge */
        if (iy > 0x4d000000) { /* if |y| > 2**27 */
@@ -178,7 +168,7 @@ float powf(float x, float y)
 
                /* compute s = s_h+s_l = (x-1)/(x+1) or (x-1.5)/(x+1.5) */
                u = ax - bp[k];   /* bp[0]=1.0, bp[1]=1.5 */
-               v = one/(ax+bp[k]);
+               v = 1.0f/(ax+bp[k]);
                s = u*v;
                s_h = s;
                GET_FLOAT_WORD(is, s_h);
@@ -257,8 +247,8 @@ float powf(float x, float y)
        w = v - (z - u);
        t = z*z;
        t1 = z - t*(P1+t*(P2+t*(P3+t*(P4+t*P5))));
-       r = (z*t1)/(t1-two) - (w+z*w);
-       z = one - (r - z);
+       r = (z*t1)/(t1-2.0f) - (w+z*w);
+       z = 1.0f - (r - z);
        GET_FLOAT_WORD(j, z);
        j += n<<23;
        if ((j>>23) <= 0)  /* subnormal output */