[Turbofan] Revert FP register aliasing support on Arm.

src/compiler/instruction.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_COMPILER_INSTRUCTION_H_
 #define V8_COMPILER_INSTRUCTION_H_
 
 #include <deque>
 #include <iosfwd>
 #include <map>
@@ skipping 589 matching lines @@
          LocationOperand::cast(this)->location_kind() ==
              LocationOperand::STACK_SLOT &&
          LocationOperand::cast(this)->representation() ==
              MachineRepresentation::kSimd128;
 }
 
 uint64_t InstructionOperand::GetCanonicalizedValue() const {
   if (IsAllocated() || IsExplicit()) {
     MachineRepresentation canonical = MachineRepresentation::kNone;
     if (IsFPRegister()) {
-      if (kSimpleFPAliasing) {
-        // We treat all FP register operands the same for simple aliasing.
-        canonical = MachineRepresentation::kFloat64;
-      } else {
-        // We need to distinguish FP register operands of different reps when
-        // aliasing is not simple (e.g. ARM).
-        canonical = LocationOperand::cast(this)->representation();
-      }
+      // We treat all FP register operands the same for simple aliasing.
+      canonical = MachineRepresentation::kFloat64;
     }
     return InstructionOperand::KindField::update(
         LocationOperand::RepresentationField::update(this->value_, canonical),
         LocationOperand::EXPLICIT);
   }
   return this->value_;
 }
 
 // Required for maps that don't care about machine type.
 struct CompareOperandModuloType {
@@ skipping 864 matching lines @@
 
 
 std::ostream& operator<<(std::ostream& os,
                          const PrintableInstructionSequence& code);
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_INSTRUCTION_H_