[Turbofan] Allow compiler to elide complex aliasing code.

test/unittests/compiler/instruction-sequence-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/base/utils/random-number-generator.h"
 #include "src/compiler/pipeline.h"
 #include "test/unittests/compiler/instruction-sequence-unittest.h"
 #include "test/unittests/test-utils.h"
 #include "testing/gmock/include/gmock/gmock.h"
 
@@ skipping 49 matching lines @@
   CHECK(instruction_blocks_.empty());
   num_general_registers_ = num_general_registers;
   num_double_registers_ = num_double_registers;
 }
 
 
 RegisterConfiguration* InstructionSequenceTest::config() {
   if (config_.is_empty()) {
     config_.Reset(new RegisterConfiguration(
         num_general_registers_, num_double_registers_, num_general_registers_,
-        num_double_registers_, RegisterConfiguration::OVERLAP,
-        allocatable_codes, allocatable_double_codes, general_register_names_,
+        num_double_registers_, allocatable_codes, allocatable_double_codes,
+        kSimpleFPAliasing ? RegisterConfiguration::OVERLAP
+                          : RegisterConfiguration::COMBINE,
+        general_register_names_,
         double_register_names_,  // float register names
         double_register_names_));
   }
   return config_.get();
 }
 
 
 InstructionSequence* InstructionSequenceTest::sequence() {
   if (sequence_ == nullptr) {
     sequence_ = new (zone())
@@ skipping 420 matching lines @@
 
 
 Instruction* InstructionSequenceTest::AddInstruction(Instruction* instruction) {
   sequence()->AddInstruction(instruction);
   return instruction;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8