[turbofan][arm64] Match fneg for -0.0 - x pattern.

test/unittests/compiler/arm64/instruction-selector-arm64-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 "test/unittests/compiler/instruction-selector-unittest.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
@@ skipping 2239 matching lines @@
   m.Return(n);
   Stream s = m.Build();
   ASSERT_EQ(1U, s.size());
   EXPECT_EQ(kArm64Clz32, s[0]->arch_opcode());
   ASSERT_EQ(1U, s[0]->InputCount());
   EXPECT_EQ(s.ToVreg(p0), s.ToVreg(s[0]->InputAt(0)));
   ASSERT_EQ(1U, s[0]->OutputCount());
   EXPECT_EQ(s.ToVreg(n), s.ToVreg(s[0]->Output()));
 }
 
+
+TEST_F(InstructionSelectorTest, Float64SubWithMinusZero) {
+  StreamBuilder m(this, kMachFloat64, kMachFloat64);
+  Node* const p0 = m.Parameter(0);
+  Node* const n = m.Float64Sub(m.Float64Constant(-0.0), p0);
+  m.Return(n);
+  Stream s = m.Build();
+  ASSERT_EQ(1U, s.size());
+  EXPECT_EQ(kArm64Float64Neg, s[0]->arch_opcode());
+  ASSERT_EQ(1U, s[0]->InputCount());
+  EXPECT_EQ(s.ToVreg(p0), s.ToVreg(s[0]->InputAt(0)));
+  ASSERT_EQ(1U, s[0]->OutputCount());
+  EXPECT_EQ(s.ToVreg(n), s.ToVreg(s[0]->Output()));
+}
+
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8