[turbofan] Float32Abs and Float64Abs are supported by all backends.

src/compiler/mips64/instruction-selector-mips64.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/base/adapters.h"
 #include "src/base/bits.h"
 #include "src/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
@@ skipping 1253 matching lines @@
   Node* left = node->InputAt(0);
   Node* right = node->InputAt(1);
   Emit(kMips64Float64InsertHighWord32, g.DefineSameAsFirst(node),
        g.UseRegister(left), g.UseRegister(right));
 }
 
 
 // static
 MachineOperatorBuilder::Flags
 InstructionSelector::SupportedMachineOperatorFlags() {
-  return MachineOperatorBuilder::kFloat32Abs |
-         MachineOperatorBuilder::kFloat64Abs |
-         MachineOperatorBuilder::kFloat64RoundDown |
+  return MachineOperatorBuilder::kFloat64RoundDown |
          MachineOperatorBuilder::kFloat64RoundTruncate;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8