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"
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