GHC Core simplifier question: turn off all passes?

[Christopher Done]

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 <rae at cs.brynmawr.edu> 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 <rahulmutt at gmail.com> 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 <chrisdone at 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 at haskell.org
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-devs
>
>
>
>
> --
> Rahul Muttineni
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