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

… dispatch work accounting for linearity texture to improve performance. (#7501)

Pull Request resolved: #7452

This diff modifies the convolution 2D pointwise op shader and dispatch settings to linearly dispatch work accounting for linearity texture to improve performance.
ghstack-source-id: 260166247
@exported-using-ghexport

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

Co-authored-by: Vivek Trivedi <5340687+trivedivivek@users.noreply.github.com>

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,