[x86] Improve code generation for context materialization.

src/compiler/x64/code-generator-x64.cc

Index: src/compiler/x64/code-generator-x64.cc
diff --git a/src/compiler/x64/code-generator-x64.cc b/src/compiler/x64/code-generator-x64.cc
index db5a448adc9a0ee689421edeedbd843c58ad2dba..be28bf74d589b5ef08359d6349af79a277c88ef6 100644
--- a/src/compiler/x64/code-generator-x64.cc
+++ b/src/compiler/x64/code-generator-x64.cc
@@ -1309,9 +1309,18 @@ void CodeGenerator::AssembleMove(InstructionOperand* source,
         case Constant::kExternalReference:
           __ Move(dst, src.ToExternalReference());
           break;
-        case Constant::kHeapObject:
-          __ Move(dst, src.ToHeapObject());
+        case Constant::kHeapObject: {
+          Handle<HeapObject> src_object = src.ToHeapObject();
+          if (info()->IsOptimizing() &&
+              src_object.is_identical_to(info()->context())) {
+            // Loading the context from the frame is way cheaper than
+            // materializing the actual context heap object address.
+            __ movp(dst, Operand(rbp, StandardFrameConstants::kContextOffset));
+          } else {
+            __ Move(dst, src_object);
+          }
           break;
+        }
         case Constant::kRpoNumber:
           UNREACHABLE();  // TODO(dcarney): load of labels on x64.
           break;