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<div class="content">
<h3 style="margin-top: 20px; margin-bottom: 10px;">
Simon Peyton Jones pushed to branch wip/T21623
at <a href="https://gitlab.haskell.org/ghc/ghc" style="color: #1068bf;">Glasgow Haskell Compiler / GHC</a>
</h3>
<h4 style="margin-top: 10px; margin-bottom: 10px;">
Commits:
</h4>
<ul>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/c2d73cb47562a86da76dae217d15f0dbd2b05b0e" style="color: #1068bf;">c2d73cb4</a></strong>
<div>
<span>by Andreas Klebinger</span>
<i>at 2022-09-28T15:07:30-04:00</i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>Apply some tricks to speed up core lint.
Below are the noteworthy changes and if given their impact on compiler
allocations for a type heavy module:
* Use the oneShot trick on LintM
* Use a unboxed tuple for the result of LintM: ~6% reduction
* Avoid a thunk for the result of typeKind in lintType: ~5% reduction
* lint_app: Don't allocate the error msg in the hot code path: ~4%
reduction
* lint_app: Eagerly force the in scope set: ~4%
* nonDetCmpType: Try to short cut using reallyUnsafePtrEquality#: ~2%
* lintM: Use a unboxed maybe for the `a` result: ~12%
* lint_app: make go_app tail recursive to avoid allocating the go function
as heap closure: ~7%
* expandSynTyCon_maybe: Use a specialized data type
For a less type heavy module like nofib/spectral/simple compiled with
-O -dcore-lint allocations went down by ~24% and compile time by ~9%.
-------------------------
Metric Decrease:
T1969
-------------------------
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/b74b6191d7c442dffdfc9a9e2a6d476d7b3a28f2" style="color: #1068bf;">b74b6191</a></strong>
<div>
<span>by sheaf</span>
<i>at 2022-09-28T15:08:10-04:00</i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>matchLocalInst: do domination analysis
When multiple Given quantified constraints match a Wanted, and there is
a quantified constraint that dominates all others, we now pick it
to solve the Wanted.
See Note [Use only the best matching quantified constraint].
For example:
[G] d1: forall a b. ( Eq a, Num b, C a b ) => D a b
[G] d2: forall a . C a Int => D a Int
[W] {w}: D a Int
When solving the Wanted, we find that both Givens match, but we pick
the second, because it has a weaker precondition, C a Int, compared
to (Eq a, Num Int, C a Int). We thus say that d2 dominates d1;
see Note [When does a quantified instance dominate another?].
This domination test is done purely in terms of superclass expansion,
in the function GHC.Tc.Solver.Interact.impliedBySCs. We don't attempt
to do a full round of constraint solving; this simple check suffices
for now.
Fixes #22216 and #22223
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/2a53ac1877bbd29de432c0aca442904e9da96c4e" style="color: #1068bf;">2a53ac18</a></strong>
<div>
<span>by Simon Peyton Jones</span>
<i>at 2022-09-28T17:49:09-04:00</i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>Improve aggressive specialisation
This patch fixes #21286, by not unboxing dictionaries in
worker/wrapper (ever). The main payload is tiny:
* In `GHC.Core.Opt.DmdAnal.finaliseArgBoxities`, do not unbox
dictionaries in `get_dmd`. See Note [Do not unbox class dictionaries]
in that module
* I also found that imported wrappers were being fruitlessly
specialised, so I fixed that too, in canSpecImport.
See Note [Specialising imported functions] point (2).
In doing due diligence in the testsuite I fixed a number of
other things:
* Improve Note [Specialising unfoldings] in GHC.Core.Unfold.Make,
and Note [Inline specialisations] in GHC.Core.Opt.Specialise,
and remove duplication between the two. The new Note describes
how we specialise functions with an INLINABLE pragma.
And simplify the defn of `spec_unf` in `GHC.Core.Opt.Specialise.specCalls`.
* Improve Note [Worker/wrapper for INLINABLE functions] in
GHC.Core.Opt.WorkWrap.
And (critially) make an actual change which is to propagate the
user-written pragma from the original function to the wrapper; see
`mkStrWrapperInlinePrag`.
* Write new Note [Specialising imported functions] in
GHC.Core.Opt.Specialise
All this has a big effect on some compile times. This is
compiler/perf, showing only changes over 1%:
Metrics: compile_time/bytes allocated
-------------------------------------
LargeRecord(normal) -50.2% GOOD
ManyConstructors(normal) +1.0%
MultiLayerModulesTH_OneShot(normal) +2.6%
PmSeriesG(normal) -1.1%
T10547(normal) -1.2%
T11195(normal) -1.2%
T11276(normal) -1.0%
T11303b(normal) -1.6%
T11545(normal) -1.4%
T11822(normal) -1.3%
T12150(optasm) -1.0%
T12234(optasm) -1.2%
T13056(optasm) -9.3% GOOD
T13253(normal) -3.8% GOOD
T15164(normal) -3.6% GOOD
T16190(normal) -2.1%
T16577(normal) -2.8% GOOD
T16875(normal) -1.6%
T17836(normal) +2.2%
T17977b(normal) -1.0%
T18223(normal) -33.3% GOOD
T18282(normal) -3.4% GOOD
T18304(normal) -1.4%
T18698a(normal) -1.4% GOOD
T18698b(normal) -1.3% GOOD
T19695(normal) -2.5% GOOD
T5837(normal) -2.3%
T9630(normal) -33.0% GOOD
WWRec(normal) -9.7% GOOD
hard_hole_fits(normal) -2.1% GOOD
hie002(normal) +1.6%
geo. mean -2.2%
minimum -50.2%
maximum +2.6%
I diligently investigated some of the big drops.
* Caused by not doing w/w for dictionaries:
T13056, T15164, WWRec, T18223
* Caused by not fruitlessly specialising wrappers
LargeRecord, T9630
For runtimes, here is perf/should+_run:
Metrics: runtime/bytes allocated
--------------------------------
T12990(normal) -3.8%
T5205(normal) -1.3%
T9203(normal) -10.7% GOOD
haddock.Cabal(normal) +0.1%
haddock.base(normal) -1.1%
haddock.compiler(normal) -0.3%
lazy-bs-alloc(normal) -0.2%
------------------------------------------
geo. mean -0.3%
minimum -10.7%
maximum +0.1%
I did not investigate exactly what happens in T9203.
Nofib is a wash:
+-------------------------------++--+-----------+-----------+
| || | tsv (rel) | std. err. |
+===============================++==+===========+===========+
| real/anna || | -0.13% | 0.0% |
| real/fem || | +0.13% | 0.0% |
| real/fulsom || | -0.16% | 0.0% |
| real/lift || | -1.55% | 0.0% |
| real/reptile || | -0.11% | 0.0% |
| real/smallpt || | +0.51% | 0.0% |
| spectral/constraints || | +0.20% | 0.0% |
| spectral/dom-lt || | +1.80% | 0.0% |
| spectral/expert || | +0.33% | 0.0% |
+===============================++==+===========+===========+
| geom mean || | | |
+-------------------------------++--+-----------+-----------+
I spent quite some time investigating dom-lt, but it's pretty
complicated. See my note on !7847. Conclusion: it's just a delicate
inlining interaction, and we have plenty of those.
Metric Decrease:
LargeRecord
T13056
T13253
T15164
T16577
T18223
T18282
T18698a
T18698b
T19695
T9630
WWRec
hard_hole_fits
T9203
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/addeefc054b64286dfc231d394885bfdecfd261d" style="color: #1068bf;">addeefc0</a></strong>
<div>
<span>by Simon Peyton Jones</span>
<i>at 2022-09-28T17:49:09-04:00</i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>Refactor UnfoldingSource and IfaceUnfolding
I finally got tired of the way that IfaceUnfolding reflected
a previous structure of unfoldings, not the current one. This
MR refactors UnfoldingSource and IfaceUnfolding to be simpler
and more consistent.
It's largely just a refactor, but in UnfoldingSource (which moves
to GHC.Types.Basic, since it is now used in IfaceSyn too), I
distinguish between /user-specified/ and /system-generated/ stable
unfoldings.
data UnfoldingSource
= VanillaSrc
| StableUserSrc -- From a user-specified pragma
| StableSystemSrc -- From a system-generated unfolding
| CompulsorySrc
This has a minor effect in CSE (see the use of isisStableUserUnfolding
in GHC.Core.Opt.CSE), which I tripped over when working on
specialisation, but it seems like a Good Thing to know anyway.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/7be6f9a459b2fb0cdf7d1d26a373f7d4f89f7499" style="color: #1068bf;">7be6f9a4</a></strong>
<div>
<span>by Simon Peyton Jones</span>
<i>at 2022-09-28T17:49:09-04:00</i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>INLINE/INLINEABLE pragmas in Foreign.Marshal.Array
Foreign.Marshal.Array contains many small functions, all of which are
overloaded, and which are critical for performance. Yet none of them
had pragmas, so it was a fluke whether or not they got inlined.
This patch makes them all either INLINE (small ones) or
INLINEABLE and hence specialisable (larger ones).
See Note [Specialising array operations] in that module.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/b0c89dfaf9f8aeda9dd69a9583fd29150099aa27" style="color: #1068bf;">b0c89dfa</a></strong>
<div>
<span>by Jade Lovelace</span>
<i>at 2022-09-28T17:49:49-04:00</i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>Export OnOff from GHC.Driver.Session
I was working on fixing an issue where HLS was trying to pass its
DynFlags to HLint, but didn't pass any of the disabled language
extensions, which HLint would then assume are on because of their
default values.
Currently it's not possible to get any of the "No" flags because the
`DynFlags.extensions` field can't really be used since it is [OnOff
Extension] and OnOff is not exported.
So let's export it.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/2f050687e75ffe6fbf140cacd15fd916d2997499" style="color: #1068bf;">2f050687</a></strong>
<div>
<span>by Bodigrim</span>
<i>at 2022-09-28T17:50:28-04:00</i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>Avoid Data.List.group; prefer Data.List.NonEmpty.group
This allows to avoid further partiality, e. g., map head . group is
replaced by map NE.head . NE.group, and there are less panic calls.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/6642e892df720fdeb111eaf2a145fda603406a33" style="color: #1068bf;">6642e892</a></strong>
<div>
<span>by Simon Peyton Jones</span>
<i>at 2022-09-28T23:26:39+01:00</i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>Start work
Not ready for review
More progress
Wibbles
Stage1 compiles
More wibbles
More wibbles
More -- almost working
Comments
Wibbles
Wibbles
Wibble inlineId
Wibbles
Infinite loop somewhere
More wibbles. Maybe can build stage2
Make FuNCo a thing by itself
Wibble
Wibble
Wibbles
Fix OptCoercion
Wibble
Wibble to optCoercion
Replace SORT with TYPE and CONSTRAINT
Wibble
Delete unused import
Delete TypeOrConstraint from ghc-prim:GHC.Types
Move from NthCo to SelCo
Wibbles
Wibbles in RepType
Wibble
Add mkWpEta
Really add mkWpEta
Wibble Typeable binds etc
Improve error messages
More wibbles, mainly to error messages
Wibbles
Wibbles to errors
Wibbles
But especially: treat Constraint as Typeable
More wibbles
More changes
* Move role into SelTyCon
* Get rid of mkTcSymCo and friends
Unused variable
Wibbles
Wibble
Accept error message changes
Refactoring...
Remove tc functions like tcKind, tcGetTyVar.
Move tyConsOfType, occCheckExpand to TyCo.FVs.
Introduce GHC.Core.TyCo.Compare
Lots of import changes!
Update haddock submodule (I hope)
Wibbles (notably: actually add GHC.Core.TyCo.Compare)
Wibbles
Wibble output of T16575
Wibbles
More wibbles
Remove infinite loop in T1946
See Note [ForAllTy and type equality]
Deal with rejigConRes
Needs a Note to be written by Richard
Some renaming
AnonArgFlag --> FunTyFlag
ArgFlag --> ForAllTyFlag
Update haddock submodule
Rename TyCoBinder to ForAllTyBinder
Wibbles
Update haddock
Wibble
Update unix submodule
I think I accidentally got it out of sync with HEAD;
this puts it back.
Rename TyCoBinder to PiTyBinder
Update Haddock submodule
Wrap dictionaries in tuples
This fixes the kind bugs in arrow desugaring. Needs some Notes,
but I want to try CI.
More on boxing data cons
Rebase and update GHC.Tc.Errors/GHC.Tc.Errors.Ppr
Revert accidental changes in SameOccInfo
fixes mod180, tcfail182
Wibbles in error messages
..plus eqType comes from GHC.Core.TyCo.Compare
Wibbles
More wibbles
Reaedy for RAE review
Fix fragile rule setup in GHC.Float
See Note [realToFrac natural-to-float]
Wibbles
More wibbles
Remove unused import
Remove another unused import
Wibbles
Update haddock submodule
Respond to Sam's suggestions
Wibbles
Wibbles
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/60388ccc9989a1f2bb59678b19eb2566e9a5173c" style="color: #1068bf;">60388ccc</a></strong>
<div>
<span>by Simon Peyton Jones</span>
<i>at 2022-09-28T23:54:58+01:00</i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "Menlo", "DejaVu Sans Mono", "Liberation Mono", "Consolas", "Ubuntu Mono", "Courier New", "andale mono", "lucida console", monospace; word-break: break-all; word-wrap: break-word; background-color: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>Wibbles
</pre>
</li>
</ul>
<h4 style="margin-top: 10px; margin-bottom: 10px;">18 changed files:</h4>
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<a href="#d0d96a6d03668aeab20ebe05e2c4ccb798c7e64c" style="color: #1068bf;">
compiler/GHC.hs
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<p style="font-size: small; color: #666;">
—
<br>
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