#855: Improvements to SpecConstr -------------------------------------+------------------------------------- Reporter: simonpj | Owner: (none) Type: task | Status: new Priority: normal | Milestone: ⊥ Component: Compiler | Version: 6.4.2 Resolution: | Keywords: SpecConstr Operating System: Unknown/Multiple | Architecture: Type of failure: Runtime | Unknown/Multiple performance bug | Test Case: N/A Blocked By: | Blocking: 915 Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by sgraf): A quick update: `ex1` is optimized to similar code as above, but without resorting to forced `SPEC` now. E.g., inference of `ArgOcc`s is now much better, because it looks at occs from specialised RHSs now (specialising for lambdas gives rise to new occs). This entailed a rewrite of the spec loop. Also I had to pass on occs from recursive calls to achieve something like the static argument transformation. I'll write things up in a wiki page once I'm done trying to optimize `ex{2,3}`. This is the code currently generated for `ex1`: {{{ -- RHS size: {terms: 41, types: 23, coercions: 0, joins: 3/3} Main.$wex1 [InlPrag=NOINLINE] :: GHC.Prim.Int# -> GHC.Prim.Int# [GblId, Arity=1, Caf=NoCafRefs, Str=<S,U>, Unf=OtherCon []] Main.$wex1 = \ (ww_s4m8 :: GHC.Prim.Int#) -> joinrec { $s$wgo_s4or :: GHC.Prim.Int# -> GHC.Prim.Int# -> GHC.Prim.Int# -> Bool -> GHC.Prim.Int# [LclId[JoinId(4)], Arity=4, Str=<S,U><S,U><L,A><L,A>] $s$wgo_s4or (sc_s4oq :: GHC.Prim.Int#) (sc1_s4op :: GHC.Prim.Int#) _ [Occ=Dead] _ [Occ=Dead] = jump $s$wgo2_s4nk sc1_s4op sc_s4oq; $s$wgo1_s4o0 :: GHC.Prim.Int# -> GHC.Prim.Int# -> GHC.Prim.Int# -> GHC.Prim.Int# [LclId[JoinId(3)], Arity=3, Str=<S,U><S,U><S,U>] $s$wgo1_s4o0 (sc_s4nZ :: GHC.Prim.Int#) (sc1_s4nY :: GHC.Prim.Int#) (sc2_s4nX :: GHC.Prim.Int#) = jump $s$wgo_s4or (GHC.Prim.+# sc2_s4nX sc_s4nZ) sc1_s4nY sc_s4nZ GHC.Types.False; $s$wgo2_s4nk [Occ=LoopBreaker] :: GHC.Prim.Int# -> GHC.Prim.Int# -> GHC.Prim.Int# [LclId[JoinId(2)], Arity=2, Str=<S,U><S,U>, Unf=OtherCon []] $s$wgo2_s4nk (sc_s4nj :: GHC.Prim.Int#) (sc1_s4ni :: GHC.Prim.Int#) = case GHC.Prim.<# sc_s4nj ww_s4m8 of { __DEFAULT -> sc1_s4ni; 1# -> jump $s$wgo1_s4o0 (GHC.Prim.*# sc_s4nj sc_s4nj) (GHC.Prim.+# sc_s4nj 1#) sc1_s4ni }; } in jump $s$wgo2_s4nk 1# 0# }}} `-flate-dmd-anal` gets rid of the superfluous `$s$wgo_s4or`, but what pass is responsible for contracting the recursive group into a single binding (by inlining until we hit the loopbreaker)? -- Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/855#comment:20> GHC <http://www.haskell.org/ghc/> The Glasgow Haskell Compiler