[project @ 2000-09-07 16:32:23 by simonpj]
A list of simplifier-related stuff, triggered by looking at GHC's performance. I don't guarantee that this lot will lead to a uniform improvement over 4.08, but it it should be a bit better. More work probably required. * Make the simplifier's Stop continuation record whether the expression being simplified is the RHS of a thunk, or (say) the body of a lambda or case RHS. In the thunk case we want to be a bit keener about inlining if the type of the thunk is amenable to update in place. * Fix interestingArg, which was being too liberal, and hence doing too much inlining. * Extended CoreUtils.exprIsCheap to make two more things cheap: - case (coerce x) of ... - let x = y +# z This makes a bit more eta expansion happen. It was provoked by a program of Marcin's. * MkIface.ifaceBinds. Make sure that we emit rules for things (like class operations) that don't get a top-level binding in the interface file. Previously such rules were silently forgotten. * Move transformRhs to *after* simplification, which makes it a little easier to do, and means that the arity it computes is readily available to completeBinding. This gets much better arities. * Do coerce splitting in completeBinding. This gets good code for newtype CInt = CInt Int test:: CInt -> Int test x = case x of 1 -> 2 2 -> 4 3 -> 8 4 -> 16 _ -> 0 * Modify the meaning of "arity" so that during compilation it means "if you apply this function to fewer args, it will do virtually no work". So, for example f = coerce t (\x -> e) has arity at least 1. When a function is exported, it's arity becomes the number of exposed, top-level lambdas, which is subtly different. But that's ok. I removed CoreUtils.exprArity altogether: it looked only at the exposed lambdas. Instead, we use exprEtaExpandArity exclusively. All of this makes I/O programs work much better.
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