On Thu, Aug 12 2021, Simon Peyton Jones wrote:
> Repro case is something like
> * Here is a source or files
> * Compile like this
> * Look at the generated Core...observe silly thing happening
Tried my best here:
https://gitlab.haskell.org/ghc/ghc/-/issues/20237
Any help on this would be
ll-users@haskell.org
| Subject: Re: Avoiding construction of dead dictionaries
|
|
| On Mon, Aug 09 2021, Simon Peyton Jones wrote:
|
| > Could you offer a small repro case, with a pointer to evidence that it
| matters in practice, and open a ticket?
|
| I'll try my best, but I'm unsu
On Mon, Aug 09 2021, Simon Peyton Jones wrote:
> Could you offer a small repro case, with a pointer to evidence that it
> matters in practice, and open a ticket?
I'll try my best, but I'm unsure how I would generate evidence. Could
you give me a hint?
Is there any way to see how far
Hi Mike
| The right-hand argument of <+ leads to a dictionary construction that is a
| proof of a certain property, but the dictionary itself ends up being dead,
| like so:
|
|case $w$dOpCon_r2kGJ ...
|of
|{ (# ww1_s27L3 #) -> ... }
| ^
|
Hi all,
On 09/08/2021 16:31, Brandon Allbery wrote:
We haven't figured out what they did, but the other day we had someone
in #haskell with an infinite loop evaluating a dictionary. So
apparently it is possible for a dictionary to be bottom somehow.
I managed to do something like this once:
ut things would be a bit more uniform. If there was a real
> advantage to doing this, it’d definitely be worth measuring the perf cost
> (if any).
>
>
>
> Simon
>
>
>
> *From:* Glasgow-haskell-users *On
> Behalf Of *Brandon Allbery
> *Sent:* 09 August 2021 16:32
...@deinprogramm.de
Subject: Re: Avoiding construction of dead dictionaries
We haven't figured out what they did, but the other day we had someone in
#haskell with an infinite loop evaluating a dictionary. So apparently it is
possible for a dictionary to be bottom somehow.
On Mon, Aug 9, 2021 at 1
We haven't figured out what they did, but the other day we had someone in
#haskell with an infinite loop evaluating a dictionary. So apparently it is
possible for a dictionary to be bottom somehow.
On Mon, Aug 9, 2021 at 11:27 AM Tom Smeding wrote:
> Hi Mike,
>
>
> > But wouldn't that imply
Hi Mike,
> But wouldn't that imply that ghc can build dictionary-construction code
> that evaluates to bottom? Can that happen?
I assume no, but here the dictionary is embedded as a field in the GADT, right?
So if the data value is bottom, there is not even a dictionary to be found, let
alone
Thanks for thinking about this one!
On Fri, Aug 06 2021, Tom Smeding wrote:
> Would it not be unsound for ghc to elide dictionary construction here?
> After all, the right-hand side might actually be a bottom
> (e.g. undefined) at run-time, in which case the pattern match cannot
> succeed
Would it not be unsound for ghc to elide dictionary construction here? After
all, the right-hand side might actually be a bottom (e.g. undefined) at
run-time, in which case the pattern match cannot succeed according to the
semantics of Haskell. I suspect that if you make the pattern match lazy
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