Whenever possible use length passed to the List constructor for bounds checks instead of loading it…

runtime/vm/intermediate_language_x64.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intermediate_language.h"
 
 #include "lib/error.h"
@@ skipping 2254 matching lines @@
     __ cmpq(FieldAddress(receiver, length_offset), Immediate(imm));
     __ j(BELOW_EQUAL, deopt);
   } else {
     Register index = locs()->in(1).reg();
     __ cmpq(index, FieldAddress(receiver, length_offset));
     __ j(ABOVE_EQUAL, deopt);
   }
 }
 
 
+LocationSummary* CheckBoundInstr::MakeLocationSummary() const {
+  const intptr_t kNumInputs = 2;
+  const intptr_t kNumTemps = 0;
+  LocationSummary* locs =
+      new LocationSummary(kNumInputs, kNumTemps, LocationSummary::kNoCall);
+  locs->set_in(0, Location::RequiresRegister());
+  locs->set_in(1, Location::RegisterOrConstant(index()));
+  return locs;
+}
+
+
+void CheckBoundInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
+  Register length = locs()->in(0).reg();
+
+  Label* deopt = compiler->AddDeoptStub(deopt_id(),
+                                        kDeoptLoadIndexedFixedArray);
+
+  if (locs()->in(1).IsConstant()) {
+    const Object& constant = locs()->in(1).constant();
+    ASSERT(constant.IsSmi());
+    const int64_t imm =
+        reinterpret_cast<int64_t>(constant.raw());
+    __ cmpq(length, Immediate(imm));
+    __ j(BELOW_EQUAL, deopt);
+  } else {
+    Register index = locs()->in(1).reg();
+    __ cmpq(index, length);
+    __ j(ABOVE_EQUAL, deopt);
+  }
+}
+
+
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64