Repository : ssh://darcs.haskell.org//srv/darcs/ghc On branch : supercompiler
http://hackage.haskell.org/trac/ghc/changeset/07302b1cc7adb6faedb6739d2dd007054bba63f7 >--------------------------------------------------------------- commit 07302b1cc7adb6faedb6739d2dd007054bba63f7 Author: Max Bolingbroke <batterseapo...@hotmail.com> Date: Wed Jul 4 18:15:32 2012 +0100 Restrict stack pruning to preserve effectivness of NOINLINE and friends >--------------------------------------------------------------- .../Supercompile/Evaluator/Evaluate.hs | 19 ++++++++++++++++++- 1 files changed, 18 insertions(+), 1 deletions(-) diff --git a/compiler/supercompile/Supercompile/Evaluator/Evaluate.hs b/compiler/supercompile/Supercompile/Evaluator/Evaluate.hs index 10f9b9a..0fb500c 100644 --- a/compiler/supercompile/Supercompile/Evaluator/Evaluate.hs +++ b/compiler/supercompile/Supercompile/Evaluator/Evaluate.hs @@ -24,6 +24,7 @@ import TyCon import Type import PrelRules import Id +import IdInfo (isShortableIdInfo) import DataCon import Pair import BasicTypes @@ -662,8 +663,24 @@ gc _state@(deeds0, Heap h ids, k, in_e) | x' `elemVarSet` live = (h_pending_kvs, M.insert x' hb h_output, live `unionVarSet` heapBindingFreeVars hb `unionVarSet` varBndrFreeVars x') | otherwise = ((x', hb) : h_pending_kvs, h_output, live) + -- NB: doing this is cool yet also dangerous at the same time. What if we have: + -- {-# NOINLINE foo #-} + -- foo = \x -> e + -- + -- root = case foo 100 of \Delta + -- + -- After normalisation + GCing (including dropping dead update frames) we will basically get: + -- case (\x -> e) 100 of \Delta + -- + -- So this is really bad because we have lost the NOINLINE information! + -- Of course, this is also sometimes cool because it turns non-normalising beta-reductions into manifestly normalising ones. + -- + -- My compromise is to allow dumping only those binders with "shortable" IdInfo, where shortability + -- is a notion stolen from GHCs simplifier. + -- + -- TODO: perhaps this same check should be applied in the Update frame compressor, though that would destroy some stack invariants pruneLiveStack :: Deeds -> Stack -> FreeVars -> (Deeds, Stack) - pruneLiveStack init_deeds k live = trainFoldr (\kf (deeds, k_live) -> if (case tagee kf of Update x' -> x' `elemVarSet` live; _ -> True) + pruneLiveStack init_deeds k live = trainFoldr (\kf (deeds, k_live) -> if (case tagee kf of Update x' | isShortableIdInfo (idInfo x') -> x' `elemVarSet` live; _ -> True) then (deeds, kf `Car` k_live) else (deeds `releaseStackFrameDeeds` kf, k_live)) (\gen deeds -> (deeds, Loco gen)) init_deeds k _______________________________________________ Cvs-ghc mailing list Cvs-ghc@haskell.org http://www.haskell.org/mailman/listinfo/cvs-ghc
