[simd] Disable Simd Scalar lowering for x64, enable tests for all other architectures.

src/compiler/simd-scalar-lowering.cc

 // Copyright 2016 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/compiler/simd-scalar-lowering.h"
 #include "src/compiler/diamond.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
@@ skipping 19 matching lines @@
       placeholder_(
           graph->NewNode(common->Parameter(-2, "placeholder"), graph->start())),
       parameter_count_after_lowering_(-1) {
   DCHECK_NOT_NULL(graph);
   DCHECK_NOT_NULL(graph->end());
   replacements_ = zone->NewArray<Replacement>(graph->NodeCount());
   memset(replacements_, 0, sizeof(Replacement) * graph->NodeCount());
 }
 
 void SimdScalarLowering::LowerGraph() {
+  if (!IsScalarLoweringEnabled()) return;
   stack_.push_back({graph()->end(), 0});
   state_.Set(graph()->end(), State::kOnStack);
   replacements_[graph()->end()->id()].type = SimdType::kInt32;
 
   while (!stack_.empty()) {
     NodeState& top = stack_.back();
     if (top.input_index == top.node->InputCount()) {
       // All inputs of top have already been lowered, now lower top.
       stack_.pop_back();
       state_.Set(top.node, State::kVisited);
@@ skipping 351 matching lines @@
       } else {
         UNREACHABLE();
       }
     }
     ReplaceNode(phi, rep_nodes);
   }
 }
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8