[Git][ghc/ghc][wip/simplifier-tweaks] 23 commits: Improve toInteger @Word32 on 64-bit platforms

Simon Peyton Jones (@simonpj) gitlab at gitlab.haskell.org
Tue Mar 26 13:59:46 UTC 2024



Simon Peyton Jones pushed to branch wip/simplifier-tweaks at Glasgow Haskell Compiler / GHC


Commits:
8a8ac65a by Matthew Craven at 2024-03-23T00:20:52-04:00
Improve toInteger @Word32 on 64-bit platforms

On 64-bit platforms, every Word32 fits in an Int, so we can
convert to Int# without having to perform the overflow check
integerFromWord# uses internally.

- - - - -
0c48f2b9 by Apoorv Ingle at 2024-03-23T00:21:28-04:00
Fix for #24552 (see testcase T24552)

Fixes for a bug in desugaring pattern synonyms matches, introduced
while working on  on expanding `do`-blocks in #18324

The `matchWrapper` unecessarily (and incorrectly) filtered out the
default wild patterns in a match. Now the wild pattern alternative is
simply ignored by the pm check as its origin is `Generated`.
The current code now matches the expected semantics according to the language spec.

- - - - -
b72705e9 by Simon Peyton Jones at 2024-03-23T00:22:04-04:00
Print more info about kinds in error messages

This fixes #24553, where GHC unhelpfully said

  error: [GHC-83865]
    • Expected kind ‘* -> * -> *’, but ‘Foo’ has kind ‘* -> * -> *’

See Note [Showing invisible bits of types in error messages]

- - - - -
8f7cfc7e by Tristan Cacqueray at 2024-03-23T00:22:44-04:00
docs: remove the don't use float hint

This hint is outdated, ``Complex Float`` are now specialised,
and the heap space suggestion needs more nuance so it should
be explained in the unboxed/storable array documentation.

- - - - -
5bd8ed53 by Andreas Klebinger at 2024-03-23T16:18:33-04:00
NCG: Fix a bug in jump shortcutting.

When checking if a jump has more than one destination account for the
possibility of some jumps not being representable by a BlockId.

We do so by having isJumpishInstr return a `Maybe BlockId` where Nothing
represents non-BlockId jump destinations.

Fixes #24507

- - - - -
8d67f247 by Ben Gamari at 2024-03-23T16:19:09-04:00
docs: Drop old release notes, add for 9.12.1

- - - - -
7db8c992 by Cheng Shao at 2024-03-25T13:45:46-04:00
rts: fix clang compilation on aarch64

This patch fixes function prototypes in ARMOutlineAtomicsSymbols.h
which causes "error: address argument to atomic operation must be a
pointer to _Atomic type" when compiling with clang on aarch64.

- - - - -
237194ce by Sylvain Henry at 2024-03-25T13:46:27-04:00
Lexer: fix imports for Alex 3.5.1 (#24583)

- - - - -
810660b7 by Cheng Shao at 2024-03-25T22:19:16-04:00
libffi-tarballs: bump libffi-tarballs submodule to libffi 3.4.6

This commit bumps the libffi-tarballs submodule to libffi 3.4.6, which
includes numerous upstream libffi fixes, especially
https://github.com/libffi/libffi/issues/760.

- - - - -
d2ba41e8 by Alan Zimmerman at 2024-03-25T22:19:51-04:00
EPA: do not duplicate comments in signature RHS

- - - - -
d1371219 by Simon Peyton Jones at 2024-03-26T11:39:22+00:00
Several improvements to the handling of coercions

* Make `mkSymCo` and `mkInstCo` smarter
  Fixes #23642

* Fix return role of `SelCo` in the coercion optimiser.
  Fixes #23617

* Make the coercion optimiser `opt_trans_rule` work better for newtypes
  Fixes #23619

- - - - -
1eebfb65 by Simon Peyton Jones at 2024-03-26T11:39:22+00:00
FloatOut: improve floating for join point

See the new Note [Floating join point bindings].

* Completely get rid of the complicated join_ceiling nonsense, which
  I have never understood.

* Do not float join points at all, except perhaps to top level.

* Some refactoring around wantToFloat, to treat Rec and NonRec more
  uniformly

- - - - -
ccf34222 by Simon Peyton Jones at 2024-03-26T11:39:22+00:00
Improve eta-expansion through call stacks

See Note [Eta expanding through CallStacks] in GHC.Core.Opt.Arity

This is a one-line change, that fixes an inconsistency
-               || isCallStackPredTy ty
+               || isCallStackPredTy ty || isCallStackTy ty

- - - - -
1c4a2e14 by Simon Peyton Jones at 2024-03-26T11:39:22+00:00
Spelling, layout, pretty-printing only

- - - - -
e5e487da by Simon Peyton Jones at 2024-03-26T11:39:22+00:00
Improve exprIsConApp_maybe a little

Eliminate a redundant case at birth.  This sometimes reduces
Simplifier iterations.

See Note [Case elim in exprIsConApp_maybe].

- - - - -
42fd4071 by Simon Peyton Jones at 2024-03-26T11:39:22+00:00
Inline GHC.HsToCore.Pmc.Solver.Types.trvVarInfo

When exploring compile-time regressions after meddling with the Simplifier, I
discovered that GHC.HsToCore.Pmc.Solver.Types.trvVarInfo was very delicately
balanced.  It's a small, heavily used, overloaded function and it's important
that it inlines. By a fluke it was before, but at various times in my journey it
stopped doing so.  So I just added an INLINE pragma to it; no sense in depending
on a delicately-balanced fluke.

- - - - -
5e37b4d5 by Simon Peyton Jones at 2024-03-26T11:39:22+00:00
Slight improvement in WorkWrap

Ensure that WorkWrap preserves lambda binders, in case of join points.  Sadly I
have forgotten why I made this change (it was while I was doing a lot of
meddling in the Simplifier, but
  * it does no harm,
  * it is slightly more efficient, and
  * presumably it made something better!

Anyway I have kept it in a separate commit.

- - - - -
d4c04c9f by Simon Peyton Jones at 2024-03-26T11:39:22+00:00
Use named record fields for the CastIt { ... } data constructor

This is a pure refactor

- - - - -
f330f0ab by Simon Peyton Jones at 2024-03-26T11:39:22+00:00
Remove a long-commented-out line

Pure refactoring

- - - - -
0edce85a by Simon Peyton Jones at 2024-03-26T11:39:22+00:00
Simplifier improvements

This MR started as: allow the simplifer to do more in one pass,
arising from places I could see the simplifier taking two iterations
where one would do.  But it turned into a larger project, because
these changes unexpectedly made inlining blow up, especially join
points in deeply-nested cases.

The main changes are below.  There are also many new or rewritten Notes.

Avoiding simplifying repeatedly
~~~~~~~~~~~~~~~
See Note [Avoiding simplifying repeatedly]

* The SimplEnv now has a seInlineDepth field, which says how deep
  in unfoldings we are.  See Note [Inline depth] in Simplify.Env.
  Currently used only for the next point: avoiding repeatedly
  simplifying coercions.

* Avoid repeatedly simplifying coercions.
  see Note [Avoid re-simplifying coercions] in Simplify.Iteration
  As you'll see from the Note, this makes use of the seInlineDepth.

* Allow Simplify.Iteration.simplAuxBind to inline used-once things.
  This is another part of Note [Post-inline for single-use things], and
  is really good for reducing simplifier iterations in situations like
      case K e of { K x -> blah }
  wher x is used once in blah.

* Make GHC.Core.SimpleOpt.exprIsConApp_maybe do some simple case
  elimination.  Note [Case elim in exprIsConApp_maybe]

postInlineUnconditionally
~~~~~~~~~~~~~~~~~~~~~~~~~
* Allow Simplify.Utils.postInlineUnconditionally to inline variables
  that are used exactly once. See Note [Post-inline for single-use things].

* Do not postInlineUnconditionally join point, ever.
  Doing so does not reduce allocation, which is the main point,
  and with join points that are used a lot it can bloat code.
  See point (1) of Note [Duplicating join points] in
  GHC.Core.Opt.Simplify.Iteration.

* Do not postInlineUnconditionally a strict (demanded) binding.
  It will not allocate a thunk (it'll turn into a case instead)
  so again the main point of inlining it doesn't hold.  Better
  to check per-call-site.

* Improve occurrence analyis for bottoming function calls, to help
  postInlineUnconditionally.  See Note [Bottoming function calls]
  in GHC.Core.Opt.OccurAnal

Inlining generally
~~~~~~~~~~~~~~~~~~
* In GHC.Core.Opt.Simplify.Utils.interestingCallContext,
  use RhsCtxt NonRecursive (not BoringCtxt) for a plain-seq case.
  See Note [Seq is boring]

* In GHC.Core.Opt.Simplify.Utils.interestingArg,
  - return ValueArg for OtherCon [c1,c2, ...], but
  - return NonTrivArg for OtherCon []
  This makes a function a little less likely to inline if all we
  know is that the argument is evaluated, but nothing else.

* isConLikeUnfolding is no longer true for OtherCon {}.
  This propagates to exprIsConLike.  Con-like-ness has /positive/
  information.

Join points
~~~~~~~~~~~
* Be very careful about inlining join points.
  See these two long Notes
    Note [Duplicating join points] in GHC.Core.Opt.Simplify.Iteration
    Note [Inlining join points] in GHC.Core.Opt.Simplify.Inline

* When making join points, don't do so if the join point is so small
  it will immediately be inlined; check uncondInlineJoin.

* In GHC.Core.Opt.Simplify.Inline.tryUnfolding, improve the inlining
  heuristics for join points. In general we /do not/ want to inline
  join points /even if they are small/.  See Note [Duplicating join points]
  GHC.Core.Opt.Simplify.Iteration.

  But sometimes we do: see Note [Inlining join points] in
  GHC.Core.Opt.Simplify.Inline.

* Do not add an unfolding to a join point at birth.  This is a tricky one
  and has a long Note [Do not add unfoldings to join points at birth]
  It shows up in two places
  - In `mkDupableAlt` do not add an inlining
  - (trickier) In `simplLetUnfolding` don't add an unfolding for a
    fresh join point
  I am not fully satisifed with this, but it works and is well documented.

* In GHC.Core.Unfold.sizeExpr, make jumps small, so that we don't penalise
  having a non-inlined join point.

- - - - -
cfd5e4a1 by Simon Peyton Jones at 2024-03-26T11:39:22+00:00
Testsuite message changes from simplifier improvements

- - - - -
2ee2620f by Simon Peyton Jones at 2024-03-26T11:39:22+00:00
Account for bottoming functions in OccurAnal

This fixes #24582, a small but long-standing bug

- - - - -
2cf3c6e7 by Simon Peyton Jones at 2024-03-26T13:59:29+00:00
Move mergeCaseAlts to prepareAlts

This makes it happen on InAlts, which reduces the number of Simplifier
iterations by one.

- - - - -


23 changed files:

- compiler/GHC/CmmToAsm/AArch64/Instr.hs
- compiler/GHC/CmmToAsm/BlockLayout.hs
- compiler/GHC/CmmToAsm/Instr.hs
- compiler/GHC/CmmToAsm/PPC/Instr.hs
- compiler/GHC/CmmToAsm/Reg/Graph/SpillClean.hs
- compiler/GHC/CmmToAsm/Reg/Linear/JoinToTargets.hs
- compiler/GHC/CmmToAsm/Reg/Liveness.hs
- compiler/GHC/CmmToAsm/X86/Instr.hs
- compiler/GHC/Core.hs
- compiler/GHC/Core/Coercion.hs
- compiler/GHC/Core/Coercion/Opt.hs
- compiler/GHC/Core/Map/Type.hs
- compiler/GHC/Core/Opt/Arity.hs
- compiler/GHC/Core/Opt/FloatOut.hs
- compiler/GHC/Core/Opt/Monad.hs
- compiler/GHC/Core/Opt/OccurAnal.hs
- compiler/GHC/Core/Opt/Pipeline.hs
- compiler/GHC/Core/Opt/SetLevels.hs
- compiler/GHC/Core/Opt/Simplify.hs
- compiler/GHC/Core/Opt/Simplify/Env.hs
- compiler/GHC/Core/Opt/Simplify/Inline.hs
- compiler/GHC/Core/Opt/Simplify/Iteration.hs
- compiler/GHC/Core/Opt/Simplify/Monad.hs


The diff was not included because it is too large.


View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/d66a7c832871a7cb537f4f03d555a469ffcb6a31...2cf3c6e74d31c4635d5d47276042ada323523403

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/d66a7c832871a7cb537f4f03d555a469ffcb6a31...2cf3c6e74d31c4635d5d47276042ada323523403
You're receiving this email because of your account on gitlab.haskell.org.


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.haskell.org/pipermail/ghc-commits/attachments/20240326/ec1af6db/attachment-0001.html>


More information about the ghc-commits mailing list