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<h3>
Simon Peyton Jones pushed to branch wip/T18412
at <a href="https://gitlab.haskell.org/ghc/ghc">Glasgow Haskell Compiler / GHC</a>
</h3>
<h4>
Commits:
</h4>
<ul>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/9ad072b487fe528947f817b0417933a6cd1941b7">9ad072b4</a></strong>
<div>
<span>by Simon Peyton Jones</span>
<i>at 2020-07-13T14:52:49-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Use dumpStyle when printing inlinings
This just makes debug-printing consistent,
and more informative.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/e78c4efb8735eb97f17e7b4ca35e305b0766f78a">e78c4efb</a></strong>
<div>
<span>by Simon Peyton Jones</span>
<i>at 2020-07-13T14:52:49-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Comments only
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/7ccb760b1a8034b28171d7540712fd195f65d1fd">7ccb760b</a></strong>
<div>
<span>by Simon Peyton Jones</span>
<i>at 2020-07-13T14:52:49-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Reduce result discount in conSize
Ticket #18282 showed that the result discount given by conSize
was massively too large. This patch reduces that discount to
a constant 10, which just balances the cost of the constructor
application itself.
Note [Constructor size and result discount] elaborates, as
does the ticket #18282.
Reducing result discount reduces inlining, which affects perf. I
found that I could increase the unfoldingUseThrehold from 80 to 90 in
compensation; in combination with the result discount change I get
these overall nofib numbers:
Program Size Allocs Runtime Elapsed TotalMem
--------------------------------------------------------------------------------
boyer -0.2% +5.4% -3.2% -3.4% 0.0%
cichelli -0.1% +5.9% -11.2% -11.7% 0.0%
compress2 -0.2% +9.6% -6.0% -6.8% 0.0%
cryptarithm2 -0.1% -3.9% -6.0% -5.7% 0.0%
gamteb -0.2% +2.6% -13.8% -14.4% 0.0%
genfft -0.1% -1.6% -29.5% -29.9% 0.0%
gg -0.0% -2.2% -17.2% -17.8% -20.0%
life -0.1% -2.2% -62.3% -63.4% 0.0%
mate +0.0% +1.4% -5.1% -5.1% -14.3%
parser -0.2% -2.1% +7.4% +6.7% 0.0%
primetest -0.2% -12.8% -14.3% -14.2% 0.0%
puzzle -0.2% +2.1% -10.0% -10.4% 0.0%
rsa -0.2% -11.7% -3.7% -3.8% 0.0%
simple -0.2% +2.8% -36.7% -38.3% -2.2%
wheel-sieve2 -0.1% -19.2% -48.8% -49.2% -42.9%
--------------------------------------------------------------------------------
Min -0.4% -19.2% -62.3% -63.4% -42.9%
Max +0.3% +9.6% +7.4% +11.0% +16.7%
Geometric Mean -0.1% -0.3% -17.6% -18.0% -0.7%
I'm ok with these numbers, remembering that this change removes
an *exponential* increase in code size in some in-the-wild cases.
I investigated compress2. The difference is entirely caused by this
function no longer inlining
WriteRoutines.$woutputCodes
= \ (w :: [CodeEvent]) ->
let result_s1Sr
= case WriteRoutines.outputCodes_$s$woutput w 0# 0# 8# 9# of
(# ww1, ww2 #) -> (ww1, ww2)
in (# case result_s1Sr of (x, _) ->
map @Int @Char WriteRoutines.outputCodes1 x
, case result_s1Sr of { (_, y) -> y } #)
It was right on the cusp before, driven by the excessive result
discount. Too bad!
Happily, the compiler/perf tests show a number of improvements:
T12227 compiler bytes-alloc -6.6%
T12545 compiler bytes-alloc -4.7%
T13056 compiler bytes-alloc -3.3%
T15263 runtime bytes-alloc -13.1%
T17499 runtime bytes-alloc -14.3%
T3294 compiler bytes-alloc -1.1%
T5030 compiler bytes-alloc -11.7%
T9872a compiler bytes-alloc -2.0%
T9872b compiler bytes-alloc -1.2%
T9872c compiler bytes-alloc -1.5%
Metric Decrease:
T12227
T12545
T13056
T15263
T17499
T3294
T5030
T9872a
T9872b
T9872c
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/7f0b671ee8a65913891c07f157b21d77d6c63036">7f0b671e</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-07-13T14:52:49-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">testsuite: Widen acceptance threshold on T5837
This test is positively tiny and consequently the bytes allocated
measurement will be relatively noisy. Consequently I have seen this
fail spuriously quite often.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/52f28cd653f092d4e2e33b37135799bf5068d2c3">52f28cd6</a></strong>
<div>
<span>by Simon Peyton Jones</span>
<i>at 2020-07-14T16:47:35+01:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Allow multiple case branches to have a higher rank type
As #18412 points out, it should be OK for multiple case alternatives
to have a higher rank type, provided they are all the same.
This patch implements that change. It sweeps away
GHC.Tc.Gen.Match.tauifyMultipleBranches, and friends, replacing it
with an enhanced version of fillInferResult.
The basic change to fillInferResult is to permit the case in which
another case alternative has already filled in the result; and in
that case simply unify. It's very simple actually.
See the new Note [fillInferResult] in TcMType
Other refactoring:
- Move all the InferResult code to one place, in GHC.Tc.Utils.TcMType
(previously some of it was in Unify)
- Move tcInstType and friends from TcMType to Instantiate, where it
more properly belongs. (TCMType was getting very long.)
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/20037a90d0a8a24a5dc31603cd2374f769e4f109">20037a90</a></strong>
<div>
<span>by Simon Peyton Jones</span>
<i>at 2020-07-14T16:47:35+01:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Improve typechecking of NPlusK patterns
This patch (due to Richard Eisenberg) improves
documentation of the wrapper returned by tcSubMult
(see Note [Wrapper returned from tcSubMult] in
GHC.Tc.Utils.Unify).
And, more substantially, it cleans up the multiplicity
handling in the typechecking of NPlusKPat
</pre>
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<h4>30 changed files:</h4>
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<a href="#f168a93cde5e2aec2441d6331dfe500172df4af3">
compiler/GHC/Core/Opt/Simplify.hs
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<a href="#578c7c3857d66d963736ff6742f3433a0e8d01b7">
compiler/GHC/Core/TyCo/Rep.hs
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<a href="#84c9d3ba34173297e7d7747e02caa2e004b164fc">
compiler/GHC/Core/Type.hs
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compiler/GHC/Core/Unfold.hs
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compiler/GHC/Core/UsageEnv.hs
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compiler/GHC/Driver/Session.hs
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compiler/GHC/HsToCore/Binds.hs
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compiler/GHC/Tc/Gen/Expr.hs
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compiler/GHC/Tc/Gen/Match.hs
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compiler/GHC/Tc/Gen/Pat.hs
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<a href="#eade747fa0a15693c67617629e286714fce958e4">
compiler/GHC/Tc/Gen/Sig.hs
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compiler/GHC/Tc/Instance/Class.hs
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compiler/GHC/Tc/Instance/Family.hs
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compiler/GHC/Tc/Solver/Flatten.hs
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compiler/GHC/Tc/TyCl/Class.hs
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compiler/GHC/Tc/Types/Evidence.hs
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compiler/GHC/Tc/Utils/Env.hs
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<a href="#59d42d45d27a766c3ef299d73c226697153b7f6e">
compiler/GHC/Tc/Utils/Instantiate.hs
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compiler/GHC/Tc/Utils/TcMType.hs
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compiler/GHC/Tc/Utils/TcType.hs
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compiler/GHC/Tc/Utils/Unify.hs
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testsuite/tests/deSugar/should_compile/T13208.stdout
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testsuite/tests/perf/compiler/T18282.hs
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testsuite/tests/perf/compiler/all.T
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testsuite/tests/simplCore/should_compile/T13143.stderr
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<h5>The diff was not included because it is too large.</h5>
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