[ET-VK] Applying bias after sum calculation in conv2d pw shader to improve performance.

Pull Request resolved: #11150

This diff improves the performance of the conv2d pw shader by changing the order of operations to apply bias after the sum calculation.
ghstack-source-id: 286652108
@exported-using-ghexport

Differential Revision: [D75450662](https://our.internmc.facebook.com/intern/diff/D75450662/)

Author: trivedivivek

backends/vulkan/runtime/graph/ops/glsl/conv2d_pw_s1p0.glsl

@@ -79,14 +79,9 @@ void main() {
   // Tuple of consecutive 4 elements represents a single output texel.
   float sum[TILE_SIZE_X * TILE_SIZE_Y * 4];
 
-  const vec4 bias = texelFetch(t_bias, ivec2(out_pos_z, 0), 0);
-
   // Initialize the output array with the bias value
-  for (int i = 0; i < TILE_SIZE_X * TILE_SIZE_Y * 4; i += 4) {
-    sum[i] = bias.x;
-    sum[i + 1] = bias.y;
-    sum[i + 2] = bias.z;
-    sum[i + 3] = bias.w;
+  for (int i = 0; i < TILE_SIZE_X * TILE_SIZE_Y * 4; i++) {
+    sum[i] = 0;
   }
 
   int z4 = 0;
@@ -157,10 +152,13 @@ void main() {
     }
   }
 
+  const vec4 bias = texelFetch(t_bias, ivec2(out_pos_z, 0), 0);
+
   for (int i = 0; i < TILE_SIZE_X * TILE_SIZE_Y; ++i) {
     const ivec3 pos_l = ivec3(pos[i * 2], pos[i * 2 + 1], out_pos_z);
     if (all(lessThan(pos_l.xy, out_limits.xy))) {
-      imageStore(t_out, pos_l, op(vec4(sum[i * 4], sum[i * 4 + 1], sum[i * 4 + 2], sum[i * 4 + 3]), out_min, out_max));
+      const vec4 out_sum = vec4(sum[i * 4], sum[i * 4 + 1], sum[i * 4 + 2], sum[i * 4 + 3]);
+      imageStore(t_out, pos_l, op(out_sum + bias, out_min, out_max));
     }
   }
 }