Further Divsteps30 improvement

Author: peterdettman

crypto/src/math/raw/Mod.cs

@@ -278,21 +278,19 @@ private static int Divsteps30(int eta, int f0, int g0, int[] t)
                 Debug.Assert((u * f0 + v * g0) == f << i);
                 Debug.Assert((q * f0 + r * g0) == g << i);
 
-                int p = -(g & 1);
-                int s = eta >> 31;
+                int c1 = eta >> 31;
+                int c2 = -(g & 1);
 
-                int c1 = p & s;
-                int c2 = p & ~s;
+                int x = (f ^ c1) - c1;
+                int y = (u ^ c1) - c1;
+                int z = (v ^ c1) - c1;
 
-                eta = (eta ^ c1) - (c1 + 1);
-
-                g += f & c2;
-                q += u & c2;
-                r += v & c2;
+                g += x & c2;
+                q += y & c2;
+                r += z & c2;
 
-                g -= f & c1;
-                q -= u & c1;
-                r -= v & c1;
+                c1 &= c2;
+                eta = (eta ^ c1) - (c1 + 1);
 
                 f += g & c1;
                 u += q & c1;