[Git][ghc/ghc][wip/T21754] 3 commits: Demand: Clear distinction between Call SubDmd and eval Dmd (#21717)

[Sebastian Graf (@sgraf812)]

Sebastian Graf pushed to branch wip/T21754 at Glasgow Haskell Compiler / GHC


Commits:
aeafdba5 by Sebastian Graf at 2022-09-27T15:14:54+02:00
Demand: Clear distinction between Call SubDmd and eval Dmd (#21717)

In #21717 we saw a reportedly unsound strictness signature due to an unsound
definition of plusSubDmd on Calls. This patch contains a description and the fix
to the unsoundness as outlined in `Note [Call SubDemand vs. evaluation Demand]`.

This fix means we also get rid of the special handling of `-fpedantic-bottoms`
in eta-reduction. Thanks to less strict and actually sound strictness results,
we will no longer eta-reduce the problematic cases in the first place, even
without `-fpedantic-bottoms`.

So fixing the unsoundness also makes our eta-reduction code simpler with less
hacks to explain. But there is another, more unfortunate side-effect:
We *unfix* #21085, but fortunately we have a new fix ready:
See `Note [mkCall and plusSubDmd]`.

There's another change:
I decided to make `Note [SubDemand denotes at least one evaluation]` a lot
simpler by using `plusSubDmd` (instead of `lubPlusSubDmd`) even if both argument
demands are lazy. That leads to less precise results, but in turn rids ourselves
from the need for 4 different `OpMode`s and the complication of
`Note [Manual specialisation of lub*Dmd/plus*Dmd]`. The result is simpler code
that is in line with the paper draft on Demand Analysis.

I left the abandoned idea in `Note [Unrealised opportunity in plusDmd]` for
posterity. The fallout in terms of regressions is negligible, as the testsuite
and NoFib shows.

```
        Program         Allocs    Instrs
--------------------------------------------------------------------------------
         hidden          +0.2%     -0.2%
         linear          -0.0%     -0.7%
--------------------------------------------------------------------------------
            Min          -0.0%     -0.7%
            Max          +0.2%     +0.0%
 Geometric Mean          +0.0%     -0.0%
```

Fixes #21717.

- - - - -
9b1595c8 by Ross Paterson at 2022-09-27T14:12:01-04:00
implement proposal 106 (Define Kinds Without Promotion) (fixes #6024)

includes corresponding changes to haddock submodule

- - - - -
3bf718f7 by Sebastian Graf at 2022-09-28T10:38:45+02:00
Boxity: Don't update Boxity unless worker/wrapper follows (#21754)

A small refactoring in our Core Opt pipeline and some new functions for
transfering argument boxities from one signature to another to facilitate
`Note [Don't change boxity without worker/wrapper]`.

Fixes #21754.

- - - - -


30 changed files:

- compiler/GHC/Core/DataCon.hs
- compiler/GHC/Core/Opt/Arity.hs
- compiler/GHC/Core/Opt/DmdAnal.hs
- compiler/GHC/Core/Opt/Pipeline.hs
- compiler/GHC/Core/Opt/Pipeline/Types.hs
- compiler/GHC/Core/Opt/Simplify/Utils.hs
- compiler/GHC/Driver/Config/Core/Lint.hs
- compiler/GHC/Driver/Session.hs
- compiler/GHC/Hs/Decls.hs
- compiler/GHC/HsToCore/Quote.hs
- compiler/GHC/Parser.y
- compiler/GHC/Parser/PostProcess.hs
- compiler/GHC/Rename/Module.hs
- compiler/GHC/Rename/Names.hs
- compiler/GHC/Tc/Errors/Ppr.hs
- compiler/GHC/Tc/Errors/Types.hs
- compiler/GHC/Tc/TyCl.hs
- compiler/GHC/Tc/TyCl/Instance.hs
- compiler/GHC/ThToHs.hs
- compiler/GHC/Types/Demand.hs
- compiler/GHC/Types/Error/Codes.hs
- compiler/GHC/Types/TyThing.hs
- compiler/Language/Haskell/Syntax/Decls.hs
- docs/users_guide/9.6.1-notes.rst
- docs/users_guide/exts/data_kinds.rst
- + docs/users_guide/exts/type_data.rst
- docs/users_guide/exts/types.rst
- libraries/Cabal
- libraries/ghc-boot-th/GHC/LanguageExtensions/Type.hs
- testsuite/tests/arityanal/should_compile/Arity11.stderr


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View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/f2e39aade432ec323deb7f0d7f40716ce47a7539...3bf718f71ec57e09e20a93344c8e04ebdc49eb34

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