[turbofan] Optimized lowering of DYNAMIC_LOCAL lookup slot loads.

test/unittests/compiler/js-typed-lowering-unittest.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/code-factory.h"
 #include "src/compiler/access-builder.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/js-operator.h"
 #include "src/compiler/js-typed-lowering.h"
 #include "src/compiler/machine-operator.h"
@@ skipping 909 matching lines @@
         IsPhi(kMachAnyTagged, _, _,
               IsMerge(IsIfTrue(IsBranch(
                           IsObjectIsSmi(IsLoadContext(
                               ContextAccess(i, Context::EXTENSION_INDEX, false),
                               context)),
                           control)),
                       _)));
   }
 }
 
+
+// -----------------------------------------------------------------------------
+// JSLoadDynamicContext
+
+
+TEST_F(JSTypedLoweringTest, JSLoadDynamicContext) {
+  Node* const context = Parameter(Type::Any());
+  Node* const frame_state = EmptyFrameState();
+  Node* const effect = graph()->start();
+  Node* const control = graph()->start();
+  Handle<String> name = factory()->object_string();
+  for (int i = 0; i < DynamicContextAccess::kMaxCheckDepth; ++i) {
+    uint32_t bitset = 1 << i;  // Only single check.
+    Reduction r = Reduce(
+        graph()->NewNode(javascript()->LoadDynamicContext(name, bitset, 23, 42),
+                         context, context, frame_state, effect, control));
+    ASSERT_TRUE(r.Changed());
+    EXPECT_THAT(
+        r.replacement(),
+        IsPhi(kMachAnyTagged,
+              IsLoadContext(ContextAccess(23, 42, false), context), _,
+              IsMerge(
+                  IsIfTrue(IsBranch(
+                      IsReferenceEqual(
+                          Type::Tagged(),
+                          IsLoadContext(
+                              ContextAccess(i, Context::EXTENSION_INDEX, false),
+                              context),
+                          IsNumberConstant(BitEq(0.0))),
+                      control)),
+                  _)));
+  }
+}
+
 #if V8_TURBOFAN_TARGET
 
 // -----------------------------------------------------------------------------
 // JSAdd
 
 
 TEST_F(JSTypedLoweringTest, JSAddWithString) {
   TRACED_FOREACH(LanguageMode, language_mode, kLanguageModes) {
     Node* lhs = Parameter(Type::String(), 0);
     Node* rhs = Parameter(Type::String(), 1);
@@ skipping 109 matching lines @@
   EXPECT_THAT(r.replacement(),
               IsFinish(IsAllocate(IsNumberConstant(Context::SizeFor(
                                       Context::MIN_CONTEXT_SLOTS)),
                                   effect, control),
                        _));
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8