CodeStubAssembler can generate code for builtins

src/compiler/linkage.h

Index: src/compiler/linkage.h
diff --git a/src/compiler/linkage.h b/src/compiler/linkage.h
index 3012f56e01f2a3a98695737ed3b719f7e6a685bf..07f835638680895fee3ba3fb3c049cfb181d72ad 100644
--- a/src/compiler/linkage.h
+++ b/src/compiler/linkage.h
@@ -367,6 +367,11 @@ class Linkage : public ZoneObject {
   // Get the location where an incoming OSR value is stored.
   LinkageLocation GetOsrValueLocation(int index) const;
 
+  // A special {Parameter} index for Stub Calls that represents context.
+  static int GetStubCallContextParamIndex(int parameter_count) {
+    return parameter_count + 0;  // Parameter (arity + 0) is special.
+  }
+
   // A special {Parameter} index for JSCalls that represents the new target.
   static int GetJSCallNewTargetParamIndex(int parameter_count) {
     return parameter_count + 0;  // Parameter (arity + 0) is special.