Re: Typeable

I'll take a look in the next few days. I'm concerned about that performance regression -- we'll need to get a handle on it. Enjoy your holiday! Richard On Mar 26, 2015, at 8:48 AM, Simon Peyton Jones wrote:

Iavor, Richard, and others

We always thought it was the Right Thing to generate the runtime representation for a TyCon (used in Typeable type representations) at the definition site of the type, not “on the fly”. I thought I’d do this.

But it was a LOT harder than I expected. I have spent a ridiculous amount of time on it over the last three weeks. Sigh.

However (a) it’s done, (b) I did a lot of other tidying up (as usual). So I’m keen to use it.

Would you like to take a look? It’s on branch wip/T9858-typeable-spj. Relevant log messages below.

Unsurprisingly, some perf/compiler tests get a bit slower (see below).

More surprisingly, there are two perf/should_run tests that get worse

perf/should_run T5205 [stat not good enough] (normal)

perf/should_run lazy-bs-alloc [stat not good enough] (normal)

This is much more surprising: neither seems to have anything much to do with Typeable. But I can’t investigate before I go on holiday. Would anyone else like to?

It’s all up to date wrt HEAD.

Simon

commit fcd18c42b6ae2e73a9f4c67dbe6d994b0f8468c8 Author: Simon Peyton Jones Date: Thu Mar 26 11:06:12 2015 +0000

Remove a redndant 'return'

commit a6200759fd2f3f0e901cb2092e148bf31abb08b4 Author: Simon Peyton Jones Date: Mon Mar 23 14:53:53 2015 +0000

Error message wibbles

These are associated with - new instance reporting - typeable changes in -ddump-simpl output - -ddump-types being a bit less verbose - some renaming of type variables in debugger output (no idea why this happens)

commit fe510d911b6cf61d6884b8b42d8771d4aea3229f Author: Simon Peyton Jones Date: Mon Mar 23 14:50:23 2015 +0000

Generate Typeble info at definition sites

This patch implements the idea floated in #9858, namely that we should generate type-representation information at the data type declaration site, rather than when solving a Typeable constraint.

However, this turned out quite a bit harder than I expected. I still think it's the right thing to do, and it's done now, but it was quite a struggle.

See particularly * Note [Grand plan for Typeable] in TcTypeable (which is a new module) * Note [The overall promotion story] in DataCon (clarifies existing stuff)

The most painful bit was that to generate Typeable instances (ie TyConRepName bindings) for every TyCon is tricky for types in ghc-prim etc: - we need to have enough data types around to *define* a TyCon - many of these types are wired-in

Also, to minimise the code generated for each data type, I wanted to generate pure data, not CAFs with unpackCString# stuff floating about.

Performance ~~~~~~~~~~~ Three perf/compiler tests start to allocate quite a bit more. This isn't surprising, because they all allocate zillions of data types, with practically no other code, esp T1969

T1969: GHC allocates 30% more T5642: GHC allocates 14% more T9872d: GHC allocates 5% more

I'm treating this as acceptable. The payoff comes in Typeable-heavy code.

Remaining to do ~~~~~~~~~~~~~~~ * I think that "TyCon" and "Module" are over-generic names to use for the runtime type representations used in GHC.Typeable. Better might be "TrTyCon" and "TrModule". But I have not yet done this

* Add more info the the "TyCon" e.g. source location where it was defined

* Use the new "Module" type to help with Trac #10068

* It would be possible to generate TyConRepName (ie Typeable instances) selectively rather than all the time. We'd need to persist the information in interface files. Lacking a motivating reason I have not done this, but it would not be difficult.

Refactoring ~~~~~~~~~~~ As is so often the case, I ended up refactoring more than I intended. In particular

* In TyCon, - a type *family* (whether type or data) is repesented by a FamilyTyCon - a algebraic data type (including data/newtype instances) is represented by AlgTyCon This wasn't true before; a data family was represented as an AlgTyCon. There are some corresponding changes in IfaceSyn.

Also get rid of the (unhelpfully named) tyConParent.

* In TyCon define 'Promoted', isomorphic to Maybe, used when things are optionally promoted; and use it elsewhere in GHC.

* Each TyCon, including promoted TyCons, contains its TyConRepName, if it has one. This is, in effect, the name of its Typeable instance.

* I added PatSynId, DefMethId, and ReflectionId to the IdInfo.IdDetails type. They are used for debugging only, namely to suppress excessive output in -ddump-types.

* Tidy up the generation of PrelInfo.knownKeyNames

* Move newImplicitBinder from IfaceEnv to BuildTyCl

* PrelNames.conName renamed to dcQual for consistency with varQual, tcQual

* Move mkDefaultMethodIds, mkRecSelBinds from TcTyClsDecls to TcTyDecls

commit 021e6f583a1159b0a3581ab1713d560cadc2bdf7 Author: Simon Peyton Jones Date: Mon Mar 23 14:32:31 2015 +0000

tcRnDeclsi can use tcRnSrcDecls

I'm not sure why tcRnDeclsi didn't call tcRnSrcDecls before, but now it does. About 20 lines of code vanish. Hooray.

commit 6473d110ab1aa22a5933e405b59e3f597562ce02 Author: Simon Peyton Jones Date: Fri Mar 20 12:38:42 2015 +0000

Implement lookupGlobal in TcEnv, and use it

This localises the (revolting) initTcForLookup function, exposing instead the more civilised interface for lookupGlobal

commit 7078a11f50e3af9139dd5ceef032e89047677833 Author: Simon Peyton Jones Date: Fri Mar 20 12:36:22 2015 +0000

Comments and white space

commit 48512df5751a07fd503f0ba523e5504d09ee258d Author: Simon Peyton Jones Date: Fri Mar 20 12:27:59 2015 +0000

Improve the error messages for class instance errors

See Note [Displaying potential instances]. simonpj@cam-05-unx:~/code/HEAD-5$