[Turbofan] Simplify operand canonicalization on archs with simple FP aliasing.

src/compiler/register-allocator.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/compiler/linkage.h"
 #include "src/compiler/register-allocator.h"
 #include "src/string-stream.h"
 
 namespace v8 {
@@ skipping 2052 matching lines @@
       for (int i = 0; i < config()->num_allocatable_double_registers(); ++i) {
         int code = config()->GetAllocatableDoubleCode(i);
         if (!IsOutputFPRegisterOf(instr, MachineRepresentation::kFloat64,
                                   code)) {
           TopLevelLiveRange* range =
               FixedFPLiveRangeFor(code, MachineRepresentation::kFloat64);
           range->AddUseInterval(curr_position, curr_position.End(),
                                 allocation_zone());
         }
       }
-      for (int i = 0; i < config()->num_allocatable_float_registers(); ++i) {
-        int code = config()->GetAllocatableFloatCode(i);
-        if (!IsOutputFPRegisterOf(instr, MachineRepresentation::kFloat32,
-                                  code)) {
-          TopLevelLiveRange* range =
-              FixedFPLiveRangeFor(code, MachineRepresentation::kFloat32);
-          range->AddUseInterval(curr_position, curr_position.End(),
-                                allocation_zone());
+      // Preserve fixed float registers on archs with non-simple aliasing.
+      if (!kSimpleFPAliasing) {
+        for (int i = 0; i < config()->num_allocatable_float_registers(); ++i) {
+          int code = config()->GetAllocatableFloatCode(i);
+          if (!IsOutputFPRegisterOf(instr, MachineRepresentation::kFloat32,
+                                    code)) {
+            TopLevelLiveRange* range =
+                FixedFPLiveRangeFor(code, MachineRepresentation::kFloat32);
+            range->AddUseInterval(curr_position, curr_position.End(),
+                                  allocation_zone());
+          }
         }
       }
     }
 
     for (size_t i = 0; i < instr->InputCount(); i++) {
       InstructionOperand* input = instr->InputAt(i);
       if (input->IsImmediate() || input->IsExplicit()) {
         continue;  // Ignore immediates and explicitly reserved registers.
       }
       LifetimePosition use_pos;
@@ skipping 1675 matching lines @@
         }
       }
     }
   }
 }
 
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8