GHC Core simplifier question: turn off all passes?

[Christopher Done]

Thanks all, I'll try looking at the innards of the desugarer!

On 7 April 2017 at 15:24, Christopher Done <chrisdone at gmail.com> 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.$trModule =
>   GHC.Types.Module
>     (GHC.Types.TrNameS "main"#) (GHC.Types.TrNameS "X"#)
>
> On 7 April 2017 at 15:09, Richard Eisenberg <rae at cs.brynmawr.edu> wrote:
>> I second Rahul in that -ddump-ds is what you want. But the desugarer
>> actually does a quick "simple-optimization" pass before -ddump-ds. If you
>> really want the raw desugarer output, you'll need -ddump-ds *and* a DEBUG
>> build of GHC. See the code in Desugar here:
>> https://github.com/ghc/ghc/blob/master/compiler/deSugar/Desugar.hs#L159
>>
>> Richard
>>
>> On Apr 7, 2017, at 9:05 AM, Rahul Muttineni <rahulmutt at gmail.com> wrote:
>>
>> Hi Chris,
>>
>> I think you're looking for -ddump-ds which outputs the Core just after the
>> desugarer is done. -ddump-simpl gives the Core after the simplifier is run.
>>
>> Hope that helps,
>> Rahul
>>
>> On Fri, Apr 7, 2017 at 6:25 PM, Christopher Done <chrisdone at gmail.com>
>> wrote:
>>>
>>> Hi all,
>>>
>>> Just checking, if I want to see the Haskell code desugared to core
>>> BEFORE any simplification passes, is this the way to do it?
>>>
>>> bash-3.2$ 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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>>