[wasm] New attempt to implement the Int64Lowering of phis.

test/unittests/compiler/graph-unittest.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_UNITTESTS_COMPILER_GRAPH_UNITTEST_H_
 #define V8_UNITTESTS_COMPILER_GRAPH_UNITTEST_H_
 
 #include "src/compiler/common-operator.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/typer.h"
@@ skipping 11 matching lines @@
 namespace compiler {
 
 using ::testing::Matcher;
 
 
 class GraphTest : public TestWithContext, public TestWithIsolateAndZone {
  public:
   explicit GraphTest(int num_parameters = 1);
   ~GraphTest() override;
 
- protected:
   Node* start() { return graph()->start(); }
   Node* end() { return graph()->end(); }
 
   Node* Parameter(int32_t index = 0);
   Node* Float32Constant(volatile float value);
   Node* Float64Constant(volatile double value);
   Node* Int32Constant(int32_t value);
   Node* Uint32Constant(uint32_t value) {
     return Int32Constant(bit_cast<int32_t>(value));
   }
@@ skipping 32 matching lines @@
 
  private:
   Typer typer_;
 };
 
 }  //  namespace compiler
 }  //  namespace internal
 }  //  namespace v8
 
 #endif  // V8_UNITTESTS_COMPILER_GRAPH_UNITTEST_H_