For some reason they are ignored, or at least the rewritten code looks as if only a single pass was done. I have facts represented like this: data AssignmentFactBot a = Bottom | Const (M.Map a CmmExpr) I initialize the entry node with: g' <- dataflowPassFwd graph [(entry_blk, Const M.empty)] $ analRewFwd cpLattice cpTransfer (cpRewrite dflags) And lattice is initialized with Bottom. Now the join function: joinCpFacts old Bottom = panic "AAAAAAAAAAA" joinCpFacts (Const old) (Const new) = ... joinCpFacts Bottom Bottom = panic "Joining bottom with bottom" joinCpFacts Bottom (Const _) = panic "Joining bottom with const" Two last panics are intended - they should never happen. The first one is for debugging purposes and surprisingly it is never called - only the second equation is. I'm puzzled. Where did I go wrong? Janek ----- Oryginalna wiadomość ----- Od: "Edward Z. Yang" <ezyang@MIT.EDU> Do: "Jan Stolarek" <jan.stolarek@p.lodz.pl> DW: "Simon Peyton-Jones" <simonpj@microsoft.com>, "ghc-devs" <ghc-devs@haskell.org> Wysłane: wtorek, 30 lipiec 2013 20:40:53 Temat: Re: Two Hoopl questions What happens when you put a loop in your code? Edward Excerpts from Jan Stolarek's message of Tue Jul 30 08:34:44 -0700 2013:
I'll allow myself to ask my second question again:
2) In my algorithm I need to initialize all of the blocks in a graph with bottom element of a lattice, except for the entry block, which needs some other initial values. I've written something like this:
cmmCopyPropagation dflags graph = do let entry_blk = g_entry graph g' <- dataflowPassFwd graph [(entry_blk, (Top, Top))] $ analRewFwd cpLattice cpTransfer cpRewrite return . fst $ g'
cpLattice = DataflowLattice "copy propagation" (Bottom, Bottom) cpJoin
However, it seems that Bottom values passed to cpLattice are ignored - I could replace second parameter to DataflowLattice with `undefined` and the code would still run without causing an error. Is there something obviously wrong in the way I pass initial fact values to dataflowPassFwd, or should I look for the problem in other parts of my code?
Janek