[ET-VK] Modify conv 2d pw op shader and dispatch settings to linearly…

… dispatch work accounting for linearity texture to improve performance.

This diff modifies the convolution 2D pointwise op shader and dispatch settings to linearly dispatch work accounting for linearity texture to improve performance.

Differential Revision: [D67683411](https://our.internmc.facebook.com/intern/diff/D67683411/)

ghstack-source-id: 259692390
Pull Request resolved: #7452

backends/vulkan/runtime/graph/ops/glsl/conv2d_pw.glsl

@@ -40,7 +40,12 @@ layout(local_size_x_id = 0, local_size_y_id = 1, local_size_z_id = 2) in;
  * size is only 1x1, making it easier to re-use loaded texels from t_kernel.
  */
 void main() {
-  const u16vec3 gpos = u16vec3(gl_GlobalInvocationID);
+  const uint16_t out_limits_y_scaled = uint16_t((out_limits.y + TILE_SIZE - 1) / TILE_SIZE);
+
+  const u16vec3 gpos = u16vec3(
+    gl_GlobalInvocationID.x / (out_limits_y_scaled * out_limits.z),
+    (gl_GlobalInvocationID.x / out_limits.z) % out_limits_y_scaled,
+    gl_GlobalInvocationID.x % out_limits.z);
 
   // Output position for TILE_SIZE = 2
   // +--------+--------+

backends/vulkan/runtime/graph/ops/impl/Convolution.cpp

@@ -372,6 +372,10 @@ void add_conv2d_node(
 
   utils::uvec3 wg_size = create_conv2d_global_wg_size(graph, method, out);
 
+  if (method == Conv2dMethod::Pointwise) {
+    wg_size = {wg_size[0] * wg_size[1] * wg_size[2], 1, 1};
+  }
+
   graph.execute_nodes().emplace_back(new DispatchNode(
       graph,
       shader,