Improve gradient sample code

Unroll loops
Remove control flow
Remove dynamic indexing

com.unity.shadergraph/Editor/Data/Nodes/Input/Gradient/SampleGradientNode.cs

             return
                 @"
 {
-    int colorKey1 = 0;
-    int colorKey2 = Gradient.colorsLength-1;
-    for(int c1 = 0; c1 < Gradient.colorsLength; c1++)
+    {precision}3 color = Gradient.colors[0].rgb;
+    [unroll]
+    for (int c = 1; c < 8; c++) 
-        if(Gradient.colors[c1].w <= Time)
-            colorKey1 = c1;
-        else
-            break;
+        {precision} colorPos = saturate((Time - Gradient.colors[c-1].w) / (Gradient.colors[c].w - Gradient.colors[c-1].w)) * step(c, Gradient.colorsLength-1);
+        color = lerp(color, Gradient.colors[c].rgb, lerp(colorPos, step(0.01, colorPos), Gradient.type));
-    for(int c2 = Gradient.colorsLength-1; c2 >= 0; c2--)
+#ifndef UNITY_COLORSPACE_GAMMA
+    color = SRGBToLinear(color);
+#endif
+    {precision} alpha = Gradient.alphas[0].x;
+    [unroll]
+    for (int a = 1; a < 8; a++) 
-        if(Gradient.colors[c2].w >= Time)
-            colorKey2 = c2;
-        else
-            break;
+        {precision} alphaPos = saturate((Time - Gradient.alphas[a-1].y) / (Gradient.alphas[a].y - Gradient.alphas[a-1].y)) * step(a, Gradient.alphasLength-1);
+        alpha = lerp(alpha, Gradient.alphas[a].x, lerp(alphaPos, step(0.01, alphaPos), Gradient.type));
-    int alphaKey1 = 0;
-    int alphaKey2 = Gradient.alphasLength-1;
-    for(int a1 = 0; a1 < Gradient.alphasLength; a1++)
-    {
-        if(Gradient.alphas[a1].y <= Time)
-            alphaKey1 = a1;
-        else
-            break;
-    }
-    for(int a2 = Gradient.alphasLength-1; a2 >= 0; a2--)
-    {
-        if(Gradient.alphas[a2].y >= Time)
-            alphaKey2 = a2;
-        else
-            break;
-    }
-
-    if(Gradient.type == 1)
-    {
-        float colorPos = min(1, max(0, (Time - Gradient.colors[colorKey1].w) / (Gradient.colors[colorKey2].w - Gradient.colors[colorKey1].w)));
-        float3 color = lerp(Gradient.colors[colorKey1].rgb, Gradient.colors[colorKey2].rgb, step(0.01, colorPos));
-        float alphaPos = min(1, max(0, (Time - Gradient.alphas[alphaKey1].y) / (Gradient.alphas[alphaKey2].y - Gradient.alphas[alphaKey1].y)));
-        float alpha = lerp(Gradient.alphas[alphaKey1].r, Gradient.alphas[alphaKey2].r, step(0.01, alphaPos));
-        Out = float4(color, alpha);
-    }
-    else
-    {
-        float colorPos = min(1, max(0, (Time - Gradient.colors[colorKey1].w) / (Gradient.colors[colorKey2].w - Gradient.colors[colorKey1].w)));
-        float3 color = lerp(Gradient.colors[colorKey1].rgb, Gradient.colors[colorKey2].rgb, colorPos);
-        float alphaPos = min(1, max(0, (Time - Gradient.alphas[alphaKey1].y) / (Gradient.alphas[alphaKey2].y - Gradient.alphas[alphaKey1].y)));
-        float alpha = lerp(Gradient.alphas[alphaKey1].r, Gradient.alphas[alphaKey2].r, alphaPos);
-        Out = float4(color, alpha);
-    }
+    Out = {precision}4(color, alpha);
 }
 ";
         }