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Simplifying fast_atan2f()

--- a/src/analysis.c

+++ b/src/analysis.c

@@ -115,26 +115,20 @@

 #define cE ((float)M_PI/2)

 static OPUS_INLINE float fast_atan2f(float y, float x) {

    float x2, y2;

-   /* Should avoid underflow on the values we'll get */

-   if (ABS16(x)+ABS16(y)<1e-9f)

-   {

-      x*=1e12f;

-      y*=1e12f;

-   }

    x2 = x*x;

    y2 = y*y;

+   /* For very small values, we don't care about the answer, so

+      we can just return 0. */

+   if (x2 + y2 < 1e-18f)

+   {

+      return 0;

+   }

    if(x2<y2){

       float den = (y2 + cB*x2) * (y2 + cC*x2);

-      if (den!=0)

-         return -x*y*(y2 + cA*x2) / den + (y<0 ? -cE : cE);

-      else

-         return (y<0 ? -cE : cE);

+      return -x*y*(y2 + cA*x2) / den + (y<0 ? -cE : cE);

    }else{

       float den = (x2 + cB*y2) * (x2 + cC*y2);

-      if (den!=0)

-         return  x*y*(x2 + cA*y2) / den + (y<0 ? -cE : cE) - (x*y<0 ? -cE : cE);

-      else

-         return (y<0 ? -cE : cE) - (x*y<0 ? -cE : cE);

+      return  x*y*(x2 + cA*y2) / den + (y<0 ? -cE : cE) - (x*y<0 ? -cE : cE);

    }

 }