I second Rahul in that -ddump-ds is what you want. But the desugarer actually does a quick "simple-optimization" pass before -ddump-ds. If you really want the raw desugarer output, you'll need -ddump-ds *and* a DEBUG build of GHC. See the code in Desugar here: https://github.com/ghc/ghc/blob/master/compiler/deSugar/Desugar.hs#L159 Richard

On Apr 7, 2017, at 9:05 AM, Rahul Muttineni wrote:

Hi Chris,

I think you're looking for -ddump-ds which outputs the Core just after the desugarer is done. -ddump-simpl gives the Core after the simplifier is run.

Hope that helps, Rahul

On Fri, Apr 7, 2017 at 6:25 PM, Christopher Done mailto:chrisdone@gmail.com> wrote: Hi all,

Just checking, if I want to see the Haskell code desugared to core BEFORE any simplification passes, is this the way to do it?

bash-3.2$ cat > X.hs module X where it = (\x -> x * 2) 123 bash-3.2$ stack exec -- ghc -ddump-simpl X.hs -fforce-recomp -fmax-simplifier-iterations=0 -O0 [1 of 1] Compiling X ( X.hs, X.o )

==================== Tidy Core ==================== Result size of Tidy Core = {terms: 11, types: 3, coercions: 0}

-- RHS size: {terms: 4, types: 1, coercions: 0} it :: Integer [GblId, Str=DmdType] it = * @ Integer GHC.Num.$fNumInteger 123 2

I was a bit surprised that the lambda is collapsed already with optimizations turned off and the simplifier iterations set to 0. I changed this to (\x -> x * x) and it produced a let instead. Is this just one of the things the HS->Core desugarer decides to do?

Ciao! _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org mailto:ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs

-- Rahul Muttineni _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs

Thanks all, I'll try looking at the innards of the desugarer! On 7 April 2017 at 15:24, Christopher Done wrote:

Indeed, it seems that even with -ddump-ds that there's a replacement of immediatelly-applied-lambdas ((\x->x) a => a).

I'm using the GHC API (but running the exe with flags reproduced my problem), so perhaps I could call `desugarModule` with all the simplifier rules deleted or something?

--- Output with -ddump-ds

bash-3.2$ stack exec -- ghc -ddump-ds X.hs -fforce-recomp -fmax-simplifier-iterations=0 -O0 [1 of 1] Compiling X ( X.hs, X.o )

==================== Desugar (after optimization) ==================== Result size of Desugar (after optimization) = {terms: 11, types: 3, coercions: 0}

-- RHS size: {terms: 4, types: 1, coercions: 0} it :: Integer [LclIdX, Str=DmdType] it = * @ Integer GHC.Num.$fNumInteger 123 2

-- RHS size: {terms: 5, types: 0, coercions: 0} X.$trModule :: GHC.Types.Module [LclIdX, Str=DmdType] X.$trModule = GHC.Types.Module (GHC.Types.TrNameS "main"#) (GHC.Types.TrNameS "X"#)

On 7 April 2017 at 15:09, Richard Eisenberg wrote:

...

I second Rahul in that -ddump-ds is what you want. But the desugarer actually does a quick "simple-optimization" pass before -ddump-ds. If you really want the raw desugarer output, you'll need -ddump-ds *and* a DEBUG build of GHC. See the code in Desugar here: https://github.com/ghc/ghc/blob/master/compiler/deSugar/Desugar.hs#L159

Richard

On Apr 7, 2017, at 9:05 AM, Rahul Muttineni wrote:

Hi Chris,

I think you're looking for -ddump-ds which outputs the Core just after the desugarer is done. -ddump-simpl gives the Core after the simplifier is run.

Hope that helps, Rahul

On Fri, Apr 7, 2017 at 6:25 PM, Christopher Done wrote:

...

Hi all,

Just checking, if I want to see the Haskell code desugared to core BEFORE any simplification passes, is this the way to do it?

bash-3.2$ cat > X.hs module X where it = (\x -> x * 2) 123 bash-3.2$ stack exec -- ghc -ddump-simpl X.hs -fforce-recomp -fmax-simplifier-iterations=0 -O0 [1 of 1] Compiling X ( X.hs, X.o )

==================== Tidy Core ==================== Result size of Tidy Core = {terms: 11, types: 3, coercions: 0}

-- RHS size: {terms: 4, types: 1, coercions: 0} it :: Integer [GblId, Str=DmdType] it = * @ Integer GHC.Num.$fNumInteger 123 2

I was a bit surprised that the lambda is collapsed already with optimizations turned off and the simplifier iterations set to 0. I changed this to (\x -> x * x) and it produced a let instead. Is this just one of the things the HS->Core desugarer decides to do?

Ciao! _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs

-- Rahul Muttineni _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs