[turbofan]: Elide extra move when accessing stack or frame register

src/compiler/x87/instruction-selector-x87.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/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
 namespace v8 {
@@ skipping 1048 matching lines @@
     VisitCompare(selector, opcode, g.Use(right), g.UseImmediate(left), cont);
   } else {
     VisitCompare(selector, opcode, left, right, cont,
                  node->op()->HasProperty(Operator::kCommutative));
   }
 }
 
 
 void VisitWordCompare(InstructionSelector* selector, Node* node,
                       FlagsContinuation* cont) {
-  X87OperandGenerator g(selector);
-  Int32BinopMatcher m(node);
-  if (m.left().IsLoad() && m.right().IsLoadStackPointer()) {
-    LoadMatcher<ExternalReferenceMatcher> mleft(m.left().node());
-    ExternalReference js_stack_limit =
-        ExternalReference::address_of_stack_limit(selector->isolate());
-    if (mleft.object().Is(js_stack_limit) && mleft.index().Is(0)) {
-      // Compare(Load(js_stack_limit), LoadStackPointer)
-      if (!node->op()->HasProperty(Operator::kCommutative)) cont->Commute();
-      InstructionCode opcode = cont->Encode(kX87StackCheck);
-      if (cont->IsBranch()) {
-        selector->Emit(opcode, g.NoOutput(), g.Label(cont->true_block()),
-                       g.Label(cont->false_block()));
-      } else {
-        DCHECK(cont->IsSet());
-        selector->Emit(opcode, g.DefineAsRegister(cont->result()));
-      }
-      return;
-    }
-  }
   VisitWordCompare(selector, node, kX87Cmp, cont);
 }
 
 
 // Shared routine for word comparison with zero.
 void VisitWordCompareZero(InstructionSelector* selector, Node* user,
                           Node* value, FlagsContinuation* cont) {
   // Try to combine the branch with a comparison.
   while (selector->CanCover(user, value)) {
     switch (value->opcode()) {
@@ skipping 248 matching lines @@
       MachineOperatorBuilder::kFloat32Min |
       MachineOperatorBuilder::kFloat64Max |
       MachineOperatorBuilder::kFloat64Min |
       MachineOperatorBuilder::kWord32ShiftIsSafe;
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8