[Git][ghc/ghc][wip/sand-witch/pattern- at a-binders] 10 commits: Add -fpolymorphic-specialisation flag (off by default at all optimisation levels)

Andrei Borzenkov (@sand-witch) gitlab at gitlab.haskell.org
Fri Jun 30 08:39:41 UTC 2023 


Andrei Borzenkov pushed to branch wip/sand-witch/pattern- at a-binders at Glasgow Haskell Compiler / GHC


Commits:
9f01d14b by Matthew Pickering at 2023-06-29T04:13:41-04:00
Add -fpolymorphic-specialisation flag (off by default at all optimisation levels)

Polymorphic specialisation has led to a number of hard to diagnose
incorrect runtime result bugs (see #23469, #23109, #21229, #23445) so
this commit introduces a flag `-fpolymorhphic-specialisation` which
allows users to turn on this experimental optimisation if they are
willing to buy into things going very wrong.

Ticket #23469

- - - - -
b1e611d5 by Ben Gamari at 2023-06-29T04:14:17-04:00
Rip out runtime linker/compiler checks

We used to choose flags to pass to the toolchain at runtime based on the
platform running GHC, and in this commit we drop all of those runtime
linker checks

Ultimately, this represents a change in policy: We no longer adapt at
runtime to the toolchain being used, but rather make final decisions
about the toolchain used at /configure time/
(we have deleted Note [Run-time linker info] altogether!).

This works towards the goal of having all toolchain configuration logic
living in the same place, which facilities the work towards a
runtime-retargetable GHC (see #19877).

As of this commit, the runtime linker/compiler logic was moved to
autoconf, but soon it, and the rest of the existing toolchain
configuration logic, will live in the standalone ghc-toolchain program
(see !9263)

In particular, what used to be done at runtime is now as follows:
* The flags -Wl,--no-as-needed for needed shared libs are configured
  into settings
* The flag -fstack-check is configured into settings
* The check for broken tables-next-to-code was outdated
* We use the configured c compiler by default as the assembler program
* We drop `asmOpts` because we already configure -Qunused-arguments flag
  into settings (see !10589)

Fixes #23562

Co-author: Rodrigo Mesquita (@alt-romes)

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8b35e8ca by Ben Gamari at 2023-06-29T18:46:12-04:00
Define FFI_GO_CLOSURES

The libffi shipped with Apple's XCode toolchain does not contain a
definition of the FFI_GO_CLOSURES macro, despite containing references
to said macro. Work around this by defining the macro, following the
model of a similar workaround in OpenJDK [1].

[1] https://github.com/openjdk/jdk17u-dev/pull/741/files

- - - - -
d7ef1704 by Ben Gamari at 2023-06-29T18:46:12-04:00
base: Fix incorrect CPP guard

This was guarded on `darwin_HOST_OS` instead of `defined(darwin_HOST_OS)`.

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7c7d1f66 by Ben Gamari at 2023-06-29T18:46:48-04:00
rts/Trace: Ensure that debugTrace arguments are used

As debugTrace is a macro we must take care to ensure that
the fact is clear to the compiler lest we see warnings.

- - - - -
cb92051e by Ben Gamari at 2023-06-29T18:46:48-04:00
rts: Various warnings fixes

- - - - -
dec81dd1 by Ben Gamari at 2023-06-29T18:46:48-04:00
hadrian: Ignore warnings in unix and semaphore-compat

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1e5b2642 by Andrei Borzenkov at 2023-06-30T12:39:32+04:00
Draft: Type patterns (22478, 18986)

Improved name resolution and type checking of type patterns in constructors:

1. HsTyPat: a new dedicated data type that represents type patterns in
   HsConPatDetails instead of reusing HsPatSigType

2. rnHsTyPat: a new function that renames a type
   pattern and collects its binders into three groups:
    - explicitly bound type variables, excluding locally bound
      variables
    - implicitly bound type variables from kind signatures
      (only if ScopedTypeVariables are enabled)
    - named wildcards (only from kind signatures)
2a. rnHsPatSigTypeBindingVars: removed in favour of rnHsTyPat
2b. rnImplcitTvBndrs: removed because no longer needed

3. collect_pat: updated to collect type variable binders from type patterns
   (this means that types and terms use the same infrastructure to detect
   conflicting bindings, unused variables and name shadowing)
3a. CollVarTyVarBinders: a new CollectFlag constructor that enables
    collection of type variables

4. tcHsTyPat: a new function that typechecks type patterns, capable of
   handling polymorphic kinds.
   See Note [Type patterns: binders and unifiers]

Examples of code that is now accepted:

   f = \(P @a) -> \(P @a) -> ...  -- triggers -Wname-shadowing

   g :: forall a. Proxy a -> ...
   g (P @a) = ...                 -- also triggers -Wname-shadowing

   h (P @($(TH.varT (TH.mkName "t")))) = ...
                                  -- t is bound at splice time

   j (P @(a :: (x,x))) = ...      -- (x,x) is no longer rejected

   data T where
     MkT :: forall (f :: forall k. k -> Type).
       f Int -> f Maybe -> T
   k :: T -> ()
   k (MkT @f (x :: f Int) (y :: f Maybe)) = ()
                                  -- f :: forall k. k -> Type

Examples of code that is rejected with better error messages:

  f (Left @a @a _) = ...
  -- new message:
  --     • Conflicting definitions for ‘a’
  --       Bound at: Test.hs:1:11
  --                 Test.hs:1:14

Examples of code that is now rejected:

  {-# OPTIONS_GHC -Werror=unused-matches #-}
  f (P @a) = ()
  -- Defined but not used: type variable ‘a’

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5956c7bd by Andrei Borzenkov at 2023-06-30T12:39:32+04:00
Add more notes and comments to the patch

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9da7d3d5 by Andrei Borzenkov at 2023-06-30T12:39:32+04:00
Apply Simon's suggestions about documentation

- - - - -


30 changed files:

- compiler/GHC/Core/Opt/Specialise.hs
- compiler/GHC/Driver/Backend.hs
- compiler/GHC/Driver/CodeOutput.hs
- compiler/GHC/Driver/DynFlags.hs
- compiler/GHC/Driver/Flags.hs
- compiler/GHC/Driver/Main.hs
- compiler/GHC/Driver/Pipeline/Execute.hs
- compiler/GHC/Driver/Session.hs
- compiler/GHC/Hs/Instances.hs
- compiler/GHC/Hs/Pat.hs
- compiler/GHC/Hs/Type.hs
- compiler/GHC/Hs/Utils.hs
- compiler/GHC/HsToCore/Quote.hs
- compiler/GHC/Iface/Ext/Ast.hs
- compiler/GHC/Linker/ExtraObj.hs
- compiler/GHC/Parser/PostProcess.hs
- compiler/GHC/Parser/Types.hs
- compiler/GHC/Rename/HsType.hs
- compiler/GHC/Rename/Pat.hs
- compiler/GHC/Rename/Splice.hs
- compiler/GHC/Rename/Splice.hs-boot
- compiler/GHC/Rename/Utils.hs
- compiler/GHC/SysTools.hs
- − compiler/GHC/SysTools/Info.hs
- compiler/GHC/SysTools/Tasks.hs
- compiler/GHC/Tc/Errors/Ppr.hs
- compiler/GHC/Tc/Errors/Types.hs
- compiler/GHC/Tc/Gen/HsType.hs
- compiler/GHC/Tc/Gen/Pat.hs
- compiler/GHC/Tc/Utils/TcMType.hs


The diff was not included because it is too large.


View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/19f42c6793547def0cd5d5d29a6f4a0072146a4d...9da7d3d5e775392e563b714a00f552bf9cabd887

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/19f42c6793547def0cd5d5d29a6f4a0072146a4d...9da7d3d5e775392e563b714a00f552bf9cabd887
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