From 7e39134874fb8315ea941c661f32394eaf667c3b Mon Sep 17 00:00:00 2001
From: Eugene Zhulenev <ezhulenev@google.com>
Date: Wed, 13 May 2020 15:05:25 -0700
Subject: [PATCH] [Grappler] Do not add control edges from placeholder inputs
 in function inlining

PiperOrigin-RevId: 311412339
Change-Id: Ie40c0c44f1d6b42b53c259f8ad92d171577cd9c7
---
 tensorflow/core/grappler/optimizers/function_optimizer.cc | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tensorflow/core/grappler/optimizers/function_optimizer.cc b/tensorflow/core/grappler/optimizers/function_optimizer.cc
index eaccff3b127..ed3af955c13 100644
--- a/tensorflow/core/grappler/optimizers/function_optimizer.cc
+++ b/tensorflow/core/grappler/optimizers/function_optimizer.cc
@@ -1122,7 +1122,15 @@ void AddStrictInputSemantics(Node* caller, Graph* g) {
 
   VLOG(3) << "Add control edges from all data inputs to enforce strict "
              "semantics with regard to function inputs";
+
+  // Do not add control edges from placeholders, because it will prevent
+  // pruning, and they can't produce any side effects anyway.
+  const auto is_placeholder = [](const Node* node) -> bool {
+    return node->type_string() == "Placeholder";
+  };
+
   for (const Node* node : data_inputs) {
+    if (is_placeholder(node)) continue;
     g->AddControlEdge(g->FindNodeId(node->id()), caller,
                       /*allow_duplicates=*/true);
   }