PUBLIC
PUBLIC
Trust me when I say I understand your frustration. It is even more frustrating
for me not to be able to just send a Github repo link containing my code...
I'll try to make an MWE that demonstrates the problem but it will probably take
quite some time. I was hoping that maybe there's some known gotcha that I'm not
aware of - for example (see my other thread), I just discovered that setting
optimization flags one by one isn't equal to setting them wholesale with -On,
so I was *not* running specialisation in my normal (per-module) pipeline at
all! Unfortunately, now that I've discovered this and made sure optLevel is set
to at least 1, I am still seeing the polymorphic default implementation of >>
as the only one :/
I also tried to be cheeky about the binding order and put the whole collected
CoreProgram into a single Rec binder to test your guess, since that should make
the actual textual order irrelevant. Unfortunately, that sill doesn't change
anything :/
From: Simon Peyton Jones <simo...@microsoft.com>
Sent: Monday, October 11, 2021 3:33 PM
To: Erdi, Gergo <gergo.e...@sc.com>; Matthew Pickering
<matthewtpicker...@gmail.com>
Cc: Montelatici, Raphael Laurent <raphael.montelat...@sc.com>; 'GHC'
<ghc-devs@haskell.org>
Subject: [External] RE: Specialisation doesn't kick in (RE: Instantiation of
overloaded definition *in Core*)
PUBLIC
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Bank and our clients.
It's incredibly hard to debug this sort of thing remotely, without the ability
to reproduce it. First, you are using a variant of GHC, with changes that we
can only guess at. Second, even with unmodified GHC I often find that
unexpected things happen - until I dig deeper and it becomes obvious!
There is one odd thing about your dump: it seems to be in reverse dependency
order, with functions being defined before they are used, rather than after.
That would certainly stop the specialiser from working. The occurrence
analyser would sort this out (literally). But that's a total guess.
Simon
PS: I am leaving Microsoft at the end of November 2021, at which point
simo...@microsoft.com<mailto:simo...@microsoft.com> will cease to work. Use
simon.peytonjo...@gmail.com<mailto:simon.peytonjo...@gmail.com> instead. (For
now, it just forwards to simo...@microsoft.com<mailto:simo...@microsoft.com>.)
From: Erdi, Gergo <gergo.e...@sc.com<mailto:gergo.e...@sc.com>>
Sent: 11 October 2021 03:58
To: Simon Peyton Jones <simo...@microsoft.com<mailto:simo...@microsoft.com>>;
Matthew Pickering
<matthewtpicker...@gmail.com<mailto:matthewtpicker...@gmail.com>>
Cc: Montelatici, Raphael Laurent
<raphael.montelat...@sc.com<mailto:raphael.montelat...@sc.com>>; 'GHC'
<ghc-devs@haskell.org<mailto:ghc-devs@haskell.org>>
Subject: RE: Specialisation doesn't kick in (RE: Instantiation of overloaded
definition *in Core*)
PUBLIC
PUBLIC
Hi Simon, Matt & others,
It took me until now to be able to try out GHC HEAD, mostly because I had to
adapt to all the GHC.Unit.* refactorings. However, now I am on
a466b02492f73a43c6cb9ce69491fc85234b9559 which includes the commit Simon
pointed out. My original plan was to expose the first half of specProgram, i.e.
the part that calls `go binds`. I did that because I want to apply
specialisation on collected whole-program Core, not just whatever would be in
scope for a Core-to-Core plugin pass, so I am not writing a CoreM and I don't
even have a ModGuts at hand.
However, I found out from Matt's email on this thread that this is not going to
be enough and eventually I'll need to figure out how I intend to apply the
rewrite rules that come out of this. So for now, I am just turning on
specialization in the normal pipeline by setting Opt_Specialise,
Opt_SpecialiseAggressively, and Opt_CrossModuleSpecialise. And I'm still not
seeing $dm>> being specialized.
Is this because I define each of "class Monad", "data IO a", "instance Monad
IO", and "main", in four distinct modules? In other words, is this something I
will not be able to try out until I figure out how to make a fake ModGuts and
run a CoreM from outside the normal compilation pipeline, feeding it the
whole-program collected CoreBinds? But if so, why is it that when I feed my
whole program to just specBinds (which I can try easily since it has no
ModGuts/CoreM dependency other than a uniq supply and the CoreProgram), I get
back an empty UsageDetails?
Thanks,
Gergo
For reference, the relevant definitions dumped from GHC with specialization
(supposedly) turned on:
main = $fMonadIO_$c>> @() @() sat_sJg xmain
$fMonadIO_$c>> :: forall a b. IO a -> IO b -> IO b
$fMonadIO_$c>> = \ (@a_aF9) (@b_aFa) -> $dm>> @IO $fMonadIO @a_aF9 @b_aFa;
$dm>> :: forall (m :: Type -> Type) a b. Monad m => m a -> m b -> m b
$dm>>
= \ (@(m_ani :: Type -> Type))
($dMonad_sIi [Occ=Once1] :: Monad m_ani)
(@a_ar4)
(@b_ar5)
(ma_sIj [Occ=Once1] :: m_ani a_ar4)
(mb_sIk [Occ=OnceL1] :: m_ani b_ar5) ->
let {
sat_sIm [Occ=Once1] :: a_ar4 -> m_ani b_ar5
[LclId]
sat_sIm = \ _ [Occ=Dead] -> mb_sIk } in
>>= @m_ani $dMonad_sIi @a_ar4 @b_ar5 ma_sIj sat_sIm
From: Erdi, Gergo
Sent: Thursday, October 7, 2021 9:30 AM
To: Simon Peyton Jones <simo...@microsoft.com<mailto:simo...@microsoft.com>>
Cc: Montelatici, Raphael Laurent
<raphael.montelat...@sc.com<mailto:raphael.montelat...@sc.com>>; GHC
<ghc-devs@haskell.org<mailto:ghc-devs@haskell.org>>
Subject: RE: Specialisation doesn't kick in (RE: Instantiation of overloaded
definition *in Core*)
PUBLIC
Indeed, I am using 9.0.1. I'll try upgrading. Thanks!
From: Simon Peyton Jones <simo...@microsoft.com<mailto:simo...@microsoft.com>>
Sent: Wednesday, October 6, 2021 6:12 PM
To: Erdi, Gergo <gergo.e...@sc.com<mailto:gergo.e...@sc.com>>
Cc: Montelatici, Raphael Laurent
<raphael.montelat...@sc.com<mailto:raphael.montelat...@sc.com>>; GHC
<ghc-devs@haskell.org<mailto:ghc-devs@haskell.org>>
Subject: [External] RE: Specialisation doesn't kick in (RE: Instantiation of
overloaded definition *in Core*)
Grego,
Yes I think that should auto-specialise.
Which version of GHC are you using? Do you have this patch?
commit ef0135934fe32da5b5bb730dbce74262e23e72e8
Author: Simon Peyton Jones simo...@microsoft.com<mailto:simo...@microsoft.com>
Date: Thu Apr 8 22:42:31 2021 +0100
Make the specialiser handle polymorphic specialisation
Here's why I ask. The call
$fMonadIO_$c>> = \ (@a) (@b) -> $dm>> @IO $fMonadIO @a @b
indeed applies $dm>> to $fMonadIO, but it also applies it to a and b. In the
version of GHC you have, maybe that stops the call from floating up to the
definition site, and being used to specialise it.
Can you make a repro case without your plugin?
Simon
PS: I am leaving Microsoft at the end of November 2021, at which point
simo...@microsoft.com<mailto:simo...@microsoft.com> will cease to work. Use
simon.peytonjo...@gmail.com<mailto:simon.peytonjo...@gmail.com> instead. (For
now, it just forwards to simo...@microsoft.com<mailto:simo...@microsoft.com>.)
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