Merge branch 'jiwaszki/fuse_mul_fc_luci_pass' into jiwaszki/fuse_mul_fc

compiler/luci/pass/src/FuseMulWithFullyConnectedPass.cpp

@@ -118,7 +118,39 @@ bool fuse_mul_with_fc(luci::CircleMul *mul)
   luci::CircleFullyConnected *fc = nullptr;
   luci::CircleConst *multiplication = nullptr;
   RETURN_FALSE_UNLESS(luci::fill(&fc, &multiplication).with_commutative_args_of(mul));
-  // Make sure that FullyConnected has only one successor:
+  /**
+   *  Make sure that FullyConnected has only one successor.
+   *
+   *  If the FullyConnected output is connected to more nodes,
+   *  this pass will replace node with new fused FullyConnected.
+   *  Thus pass success will only introduce extra FullyConnected
+   *  without reducing overall number of nodes.
+   *  Which tends to increase model's size and degrades model's performance.
+   *  Thus one successor is required to benefit from this pass.
+   *
+   *  Example graph that illustrates the described scenario:
+   *
+   *  BEFORE
+   *                |
+   *      [CircleFullyConnected]
+   *                |
+   *        +-------+----------------+
+   *        |                        |
+   *        |                        |
+   *  [Other Node]              [CircleMul]
+   *        |                        |
+   *
+   *  AFTER
+   *                |
+   *      [CircleFullyConnected]
+   *                |
+   *        +-------+-----------------------+
+   *        |                               |
+   *        |                               |
+   *  [Other Node]       [New CircleFullyConnected Fused with Mul]
+   *        |                               |
+   *
+   */
   RETURN_FALSE_UNLESS(loco::succs(fc).size() == 1);
   // Allow only FLOAT32 data type:
   RETURN_FALSE_UNLESS(fc->dtype() == loco::DataType::FLOAT32);
@@ -194,18 +226,10 @@ bool FuseMulWithFullyConnectedPass::run(loco::Graph *g)
   bool changed = false;
   for (auto node : loco::active_nodes(loco::output_nodes(g)))
   {
-    auto mul = dynamic_cast<luci::CircleMul *>(node);
-    if (not mul)
-      continue;
-
-    switch (mul->dtype())
+    if (auto mul = dynamic_cast<luci::CircleMul *>(node))
     {
-      case loco::DataType::FLOAT32:
-        if (fuse_mul_with_fc(mul))
-          changed = true;
-        break;
-      default:
-        break;
+      if (fuse_mul_with_fc(mul))
+        changed = true;
     }
   }