[x86] Faster/shorter code for stack checks.

src/compiler/ia32/instruction-selector-ia32.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/compiler/instruction-selector-impl.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 823 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) {
+  IA32OperandGenerator 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(kIA32StackCheck);
+      if (cont->IsBranch()) {
+        selector->Emit(opcode, g.NoOutput(), g.Label(cont->true_block()),
+                       g.Label(cont->false_block()))->MarkAsControl();
+      } else {
+        DCHECK(cont->IsSet());
+        selector->Emit(opcode, g.DefineAsRegister(cont->result()));
+      }
+      return;
+    }
+  }
   VisitWordCompare(selector, node, kIA32Cmp, 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 260 matching lines @@
     flags |= MachineOperatorBuilder::kFloat64Floor |
              MachineOperatorBuilder::kFloat64Ceil |
              MachineOperatorBuilder::kFloat64RoundTruncate;
   }
   return flags;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8