Revert^4 "Partial LSE analysis & store removal"

We incorrectly handled merging unknowns in some situations.
Specifically in cases where we are unable to materialize loop-phis we
could end up with PureUnknowns which could end up hiding stores that
need to be kept.

In an unrelated issue we were incorrectly considering some values as
escapes when live at the point of an invoke. Since
SearchPhiPlaceholdersForKeptStores used a more precise notion of
escapes we could end up removing stores without being able to replace
the values.

This reverts commit 2316b3a0779f3721a78681f5c70ed6624ecaebef.
This unreverts commit b6837f0350ff66c13582b0e94178dd5ca283ff0a
This reverts commit fe270426c8a2a69a8f669339e83b86fbf40e25a1.
This unreverts commit bb6cda60e4418c0ab557ea4090e046bed8206763.

Bug: 67037140
Bug: 173120044

Reason for revert: Fixed issue causing incorrect store elimination
Test: ./test.py --host
Test: Boot cuttlefish
      atest FrameworksServicesTests:com.android.server.job.BackgroundRestrictionsTest#testPowerWhiteList

Change-Id: I2ebae9ccfaf5169d551c5019b547589d0fce1dc9
diff --git a/compiler/optimizing/execution_subgraph_test.h b/compiler/optimizing/execution_subgraph_test.h
new file mode 100644
index 0000000..13cb2bc
--- /dev/null
+++ b/compiler/optimizing/execution_subgraph_test.h
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2020 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_COMPILER_OPTIMIZING_EXECUTION_SUBGRAPH_TEST_H_
+#define ART_COMPILER_OPTIMIZING_EXECUTION_SUBGRAPH_TEST_H_
+
+#include "android-base/macros.h"
+
+namespace art {
+
+class HGraph;
+class ExecutionSubgraph;
+
+class ExecutionSubgraphTestHelper {
+ public:
+  static bool CalculateValidity(HGraph* graph, const ExecutionSubgraph* subgraph);
+
+ private:
+  ExecutionSubgraphTestHelper() = delete;
+
+  DISALLOW_COPY_AND_ASSIGN(ExecutionSubgraphTestHelper);
+};
+}  // namespace art
+
+#endif  // ART_COMPILER_OPTIMIZING_EXECUTION_SUBGRAPH_TEST_H_