[turbofan] Remove some clever-but-wrong bits from select lowering.

test/unittests/compiler/select-lowering-unittest.cc

-// 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.
-
-#include "src/compiler/select-lowering.h"
-#include "test/unittests/compiler/graph-unittest.h"
-#include "test/unittests/compiler/node-test-utils.h"
-#include "testing/gmock-support.h"
-
-using testing::AllOf;
-using testing::Capture;
-using testing::CaptureEq;
-using testing::Not;
-
-namespace v8 {
-namespace internal {
-namespace compiler {
-
-class SelectLoweringTest : public GraphTest {
- public:
-  SelectLoweringTest() : GraphTest(5), lowering_(graph(), common()) {}
-
- protected:
-  Reduction Reduce(Node* node) { return lowering_.Reduce(node); }
-
- private:
-  SelectLowering lowering_;
-};
-
-
-TEST_F(SelectLoweringTest, SelectWithSameConditions) {
-  Node* const p0 = Parameter(0);
-  Node* const p1 = Parameter(1);
-  Node* const p2 = Parameter(2);
-  Node* const p3 = Parameter(3);
-  Node* const p4 = Parameter(4);
-  Node* const s0 = graph()->NewNode(
-      common()->Select(MachineRepresentation::kWord32), p0, p1, p2);
-
-  Capture<Node*> branch;
-  Capture<Node*> merge;
-  {
-    Reduction const r = Reduce(s0);
-    ASSERT_TRUE(r.Changed());
-    EXPECT_THAT(
-        r.replacement(),
-        IsPhi(
-            MachineRepresentation::kWord32, p1, p2,
-            AllOf(CaptureEq(&merge),
-                  IsMerge(IsIfTrue(CaptureEq(&branch)),
-                          IsIfFalse(AllOf(CaptureEq(&branch),
-                                          IsBranch(p0, graph()->start())))))));
-  }
-  {
-    Reduction const r = Reduce(graph()->NewNode(
-        common()->Select(MachineRepresentation::kWord32), p0, p3, p4));
-    ASSERT_TRUE(r.Changed());
-    EXPECT_THAT(r.replacement(), IsPhi(MachineRepresentation::kWord32, p3, p4,
-                                       CaptureEq(&merge)));
-  }
-  {
-    // We must not reuse the diamond if it is reachable from either else/then
-    // values of the Select, because the resulting graph can not be scheduled.
-    Reduction const r = Reduce(graph()->NewNode(
-        common()->Select(MachineRepresentation::kWord32), p0, s0, p0));
-    ASSERT_TRUE(r.Changed());
-    EXPECT_THAT(r.replacement(), IsPhi(MachineRepresentation::kWord32, s0, p0,
-                                       Not(CaptureEq(&merge))));
-  }
-}
-
-}  // namespace compiler
-}  // namespace internal
-}  // namespace v8