[turbofan] Implement sharing of context-independent code.

src/hydrogen-instructions.h

Index: src/hydrogen-instructions.h
diff --git a/src/hydrogen-instructions.h b/src/hydrogen-instructions.h
index 36ca5efb26c15d4a6229931d1cf7517ebe6f3aca..8c6dea742c5956bbb3b067532d5e736a86f92a6a 100644
--- a/src/hydrogen-instructions.h
+++ b/src/hydrogen-instructions.h
@@ -5980,6 +5980,11 @@ class HObjectAccess final {
                          SharedFunctionInfo::kOptimizedCodeMapOffset);
   }
 
+  static HObjectAccess ForOptimizedCodeMapSharedCode() {
+    return HObjectAccess(kInobject, FixedArray::OffsetOfElementAt(
+                                        SharedFunctionInfo::kSharedCodeIndex));
+  }
+
   static HObjectAccess ForFunctionContextPointer() {
     return HObjectAccess(kInobject, JSFunction::kContextOffset);
   }