-We can optimise the function-entry code as follows.
-\begin{itemize}
-
-\item If the ``function'' is not updatable, we can jump directly to its
- entry code, rather than indirecting via the info pointer in the
- closure. (For updatable thunks we must go via the closure, in
- case it has been updated.)
-
-\item If the former bullet applies, and the application we are
- compiling gives the function as many arguments as it needs, we
- can jump to its fast-entry code. (This only applies if the
- function has one or more args, because zero-arg closures have
- no fast-entry code.)
-
-\item If the function is a top-level non-constructor or imported, there
- is no need to make Node point to its closure. In order for
- this to be right, we need to ensure that:
- \begin{itemize}
- \item If such closures are updatable then they push their
- static address in the update frame, not Node. Actually
- we create a black hole and push its address.
-
- \item The arg satisfaction check should load Node before jumping to
- UpdatePAP.
-
- \item Top-level constructor closures need careful handling. If we are to
- jump direct to the constructor code, we must load Node first, even
- though they are top-level. But if we go to their ``own''
- standard-entry code (which loads Node and then jumps to the
- constructor code) we don't need to load Node.
- \end{itemize}
-\end{itemize}
-
-
-{\em Top level constructors (@mkStaticConEntryInfo@)}
-
-\begin{verbatim}
- x = {y,ys} \ {} Cons {y,ys} -- Std form constructor
-\end{verbatim}
-
-x-closure: Cons-info-table, y-closure, ys-closure
-
-x-entry: Node = x-closure; jump( Cons-entry )
-
-x's EntryInfo in its own module:
-\begin{verbatim}
- Base-label = Cons -- Not x!!
- NodeMustPoint = True
- ClosureClass = Constructor
-\end{verbatim}
-
- So if x is entered, Node will be set up and
- we'll jump direct to the Cons code.
-
-x's EntryInfo in another module: (which may not know that x is a constructor)
-\begin{verbatim}
- Base-label = x -- Is x!!
- NodeMustPoint = False -- All imported things have False
- ClosureClass = non-committal
-\end{verbatim}
-
- If x is entered, we'll jump to x-entry, which will set up Node
- before jumping to the standard Cons code
-
-{\em Top level non-constructors (@mkStaticEntryInfo@)}
-\begin{verbatim}
- x = ...
-\end{verbatim}
-
-For updatable thunks, x-entry must push an allocated BH in update frame, not Node.
-
-For non-zero arity, arg satis check must load Node before jumping to
- UpdatePAP.
projects / ghc-hetmet.git / blobdiff