Cycles Refactor: Add SSE Utility code from Embree for cleaner SSE code.

This makes the code a bit easier to understand, and might come in handy
if we want to reuse more Embree code.

Differential Revision: https://developer.blender.org/D482

Code by Brecht, with fixes by Lockal, Sergey and myself.

intern/cycles/render/curves.cpp

@@ -46,8 +46,9 @@ void curvebounds(float *lower, float *upper, float3 *p, int dim)
 	float discroot = curve_coef[2] * curve_coef[2] - 3 * curve_coef[3] * curve_coef[1];
 	float ta = -1.0f;
 	float tb = -1.0f;
+
 	if(discroot >= 0) {
-		discroot = sqrt(discroot);
+		discroot = sqrtf(discroot);
 		ta = (-curve_coef[2] - discroot) / (3 * curve_coef[3]);
 		tb = (-curve_coef[2] + discroot) / (3 * curve_coef[3]);
 		ta = (ta > 1.0f || ta < 0.0f) ? -1.0f : ta;
@@ -56,20 +57,21 @@ void curvebounds(float *lower, float *upper, float3 *p, int dim)
 
 	*upper = max(p1[dim],p2[dim]);
 	*lower = min(p1[dim],p2[dim]);
+
 	float exa = p1[dim];
 	float exb = p2[dim];
-	float t2;
-	float t3;
+
 	if(ta >= 0.0f) {
-		t2 = ta * ta;
-		t3 = t2 * ta;
+		float t2 = ta * ta;
+		float t3 = t2 * ta;
 		exa = curve_coef[3] * t3 + curve_coef[2] * t2 + curve_coef[1] * ta + curve_coef[0];
 	}
 	if(tb >= 0.0f) {
-		t2 = tb * tb;
-		t3 = t2 * tb;
+		float t2 = tb * tb;
+		float t3 = t2 * tb;
 		exb = curve_coef[3] * t3 + curve_coef[2] * t2 + curve_coef[1] * tb + curve_coef[0];
 	}
+
 	*upper = max(*upper, max(exa,exb));
 	*lower = min(*lower, min(exa,exb));
 }