<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" "http://www.w3.org/TR/REC-html40/loose.dtd">
<html lang="en">
<head>
<meta content="text/html; charset=US-ASCII" http-equiv="Content-Type">
<title>
GitLab
</title>



<style>img {
max-width: 100%; height: auto;
}
</style>
</head>
<body>
<div class="content">

<h3>
Sebastian Graf pushed to branch wip/T18078
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/c23cda9d796064f2bb914a916990ede540679a39">c23cda9d</a></strong>
<div>
<span>by Simon Peyton Jones</span>
<i>at 2020-06-09T10:53:57+02:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Implement cast worker/wrapper properly

The cast worker/wrapper transformation transforms
   x = e |> co
into
   y = e
   x = y |> co

This is done by the simplifier, but we were being
careless about transferring IdInfo from x to y,
and about what to do if x is a NOINLNE function.
This resulted in a series of bugs:
     #17673, #18093, #18078.

This patch fixes all that:

* Main change is in GHC.Core.Opt.Simplify, and
  the new prepareBinding function, which does this
  cast worker/wrapper transform.
  See Note [Cast worker/wrappers].

* There is quite a bit of refactoring around
  prepareRhs, makeTrivial etc.  It's nicer now.

* Some wrappers from strictness and cast w/w, notably those for
  a function with a NOINLINE, should inline very late. There
  wasn't really a mechanism for that, which was an existing bug
  really; so I invented a new finalPhase = Phase (-1).  It's used
  for all simplifier runs after the user-visible phase 2,1,0 have
  run.  (No new runs of the simplifier are introduced thereby.)

  See new Note [Compiler phases] in GHC.Types.Basic;
  the main changes are in GHC.Core.Opt.Driver

* Doing this made me trip over two places where the AnonArgFlag on a
  FunTy was being lost so we could end up with (Num a -> ty)
  rather than (Num a => ty)
    - In coercionLKind/coercionRKind
    - In contHoleType in the Simplifier

  I fixed the former by defining mkFunctionType and using it in
  coercionLKind/RKind.

  I could have done the same for the latter, but the information
  is almost to hand.  So I fixed the latter by
    - adding sc_hole_ty to ApplyToVal (like ApplyToTy),
    - adding as_hole_ty to ValArg (like TyArg)
    - adding sc_fun_ty to StrictArg
  Turned out I could then remove ai_type from ArgInfo.  This is
  just moving the deck chairs around, but it worked out nicely.

  See the new Note [AnonArgFlag] in GHC.Types.Var

* When looking at the 'arity decrease' thing (#18093) I discovered
  that stable unfoldings had a much lower arity than the actual
  optimised function.  That's what led to the arity-decrease
  message.  Simple solution: eta-expand.

  It's described in Note [Eta-expand stable unfoldings]
  in GHC.Core.Opt.Simplify

* I also discovered that unsafeCoerce wasn't being inlined if
  the context was boring.  So (\x. f (unsafeCoerce x)) would
  create a thunk -- yikes!  I fixed that by making inlineBoringOK
  a bit cleverer: see Note [Inline unsafeCoerce] in GHC.Core.Unfold.

  I also found that unsafeCoerceName was unused, so I removed it.

I made a test case for #18078, and a very similar one for #17673.

The net effect of all this on nofib is very modest, but positive:

--------------------------------------------------------------------------------
        Program           Size    Allocs   Runtime   Elapsed  TotalMem
--------------------------------------------------------------------------------
           anna          -0.4%     -0.1%     -3.1%     -3.1%      0.0%
 fannkuch-redux          -0.4%     -0.3%     -0.1%     -0.1%      0.0%
       maillist          -0.4%     -0.1%     -7.8%     -1.0%    -14.3%
      primetest          -0.4%    -15.6%     -7.1%     -6.6%      0.0%
--------------------------------------------------------------------------------
            Min          -0.9%    -15.6%    -13.3%    -14.2%    -14.3%
            Max          -0.3%      0.0%    +12.1%    +12.4%      0.0%
 Geometric Mean          -0.4%     -0.2%     -2.3%     -2.2%     -0.1%

Metric Decrease:
  T5631
  T13701
  T14697
  T15164
Metric Increase:
  T12150
  T12234
  T12425
</pre>
</li>
</ul>
<h4>30 changed files:</h4>
<ul>
<li class="file-stats">
<a href="#0887cf39c5cdf9cf8d6758f410d7dab3023c0d77">
compiler/GHC/Builtin/Names.hs
</a>
</li>
<li class="file-stats">
<a href="#783e5dae6e86931f06700fc088fb7d48c8a07386">
compiler/GHC/Core/Coercion.hs
</a>
</li>
<li class="file-stats">
<a href="#446b4afbe6836b950115a619acea24ddde19dc90">
compiler/GHC/Core/Opt/CSE.hs
</a>
</li>
<li class="file-stats">
<a href="#c1bf6b849619bc8d7ef37a97d993dbfaa9966f7b">
compiler/GHC/Core/Opt/CprAnal.hs
</a>
</li>
<li class="file-stats">
<a href="#f2f5de8b9f31451d693079c2a2d27fb47b18a3f4">
compiler/GHC/Core/Opt/Driver.hs
</a>
</li>
<li class="file-stats">
<a href="#f168a93cde5e2aec2441d6331dfe500172df4af3">
compiler/GHC/Core/Opt/Simplify.hs
</a>
</li>
<li class="file-stats">
<a href="#48fbb5cdea308650de5756521feb28ec68819b9b">
compiler/GHC/Core/Opt/Simplify/Utils.hs
</a>
</li>
<li class="file-stats">
<a href="#b6a5ba32bafb8fbda933538b3007e755fef6f101">
compiler/GHC/Core/Opt/SpecConstr.hs
</a>
</li>
<li class="file-stats">
<a href="#5b215b0e109123e4bef5434854f18e2f61c45b88">
compiler/GHC/Core/Opt/WorkWrap.hs
</a>
</li>
<li class="file-stats">
<a href="#11ffe98a94d798427bc600e4fcfe899407536346">
compiler/GHC/Core/SimpleOpt.hs
</a>
</li>
<li class="file-stats">
<a href="#84c9d3ba34173297e7d7747e02caa2e004b164fc">
compiler/GHC/Core/Type.hs
</a>
</li>
<li class="file-stats">
<a href="#2811a7297b8aa206197ac1f5dabd0818e3c7ec5a">
compiler/GHC/Core/Unfold.hs
</a>
</li>
<li class="file-stats">
<a href="#1a7aba0daeafab195716dd25432479804a55ab60">
compiler/GHC/Core/Utils.hs
</a>
</li>
<li class="file-stats">
<a href="#a5d27de4e3111a69f69902c65ecf7b3379f7c49a">
compiler/GHC/CoreToStg/Prep.hs
</a>
</li>
<li class="file-stats">
<a href="#166e3514d27c63ef7e86af29830d9e8b2a31c8b1">
compiler/GHC/Types/Basic.hs
</a>
</li>
<li class="file-stats">
<a href="#261c0c5029eb34eb7436b087d77314f377ff8223">
compiler/GHC/Types/Id/Make.hs
</a>
</li>
<li class="file-stats">
<a href="#5dac619989e8509003cf7b463c100f5cc56072a3">
compiler/GHC/Types/Var.hs
</a>
</li>
<li class="file-stats">
<a href="#f35faa85de2e0a75cdaa452eb7336a09c677d450">
compiler/GHC/Utils/Binary.hs
</a>
</li>
<li class="file-stats">
<a href="#98b46afb652ad9b66a276d3c312d1262c3838642">
libraries/base/Unsafe/Coerce.hs
</a>
</li>
<li class="file-stats">
<a href="#f7296c640c970ad9c7ff46e3e4854d4ab2dd7c14">
testsuite/tests/codeGen/should_compile/debug.stdout
</a>
</li>
<li class="file-stats">
<a href="#71247aaad504d89a31c398d6edd6cfc090975b86">
testsuite/tests/deSugar/should_compile/T2431.stderr
</a>
</li>
<li class="file-stats">
<a href="#b788976ba3555853d385fd1c6246444c972d749f">
testsuite/tests/perf/compiler/T16473.stdout
</a>
</li>
<li class="file-stats">
<a href="#6e2ce964ea02e92c2202946150700a3219beed86">
testsuite/tests/simplCore/should_compile/T13143.stderr
</a>
</li>
<li class="file-stats">
<a href="#bed56c1799aaab17a90f7de64953a3c8b0b8de48">
<span class="new-file">
+
testsuite/tests/simplCore/should_compile/T17673.hs
</span>
</a>
</li>
<li class="file-stats">
<a href="#b60bc5262db8520abdfa01f255cd29eec5891d15">
<span class="new-file">
+
testsuite/tests/simplCore/should_compile/T17673.stderr
</span>
</a>
</li>
<li class="file-stats">
<a href="#05c47cd4b4d1fb1924b29f5b95b19813a5ce9fcd">
<span class="new-file">
+
testsuite/tests/simplCore/should_compile/T18078.hs
</span>
</a>
</li>
<li class="file-stats">
<a href="#d714e0dbbb2f419378e3fdd77e8efff312ad2e41">
<span class="new-file">
+
testsuite/tests/simplCore/should_compile/T18078.stderr
</span>
</a>
</li>
<li class="file-stats">
<a href="#ae44213f400f8badeaf992dd66c7c6bfd26ffd60">
testsuite/tests/simplCore/should_compile/T3772.stdout
</a>
</li>
<li class="file-stats">
<a href="#0e264f20bcb9f21ef8f19196ea35fb751107dd1f">
testsuite/tests/simplCore/should_compile/T7360.stderr
</a>
</li>
<li class="file-stats">
<a href="#e9ed289bdfe6bcb0204e76be84b2f377004a5d3d">
testsuite/tests/simplCore/should_compile/T7865.stdout
</a>
</li>
</ul>
<h5>The diff was not included because it is too large.</h5>

</div>
<div class="footer" style="margin-top: 10px;">
<p style="font-size: small; color: #777;">

<br>
<a href="https://gitlab.haskell.org/ghc/ghc/-/commit/c23cda9d796064f2bb914a916990ede540679a39">View it on GitLab</a>.
<br>
You're receiving this email because of your account on gitlab.haskell.org.
If you'd like to receive fewer emails, you can
adjust your notification settings.
<script type="application/ld+json">{"@context":"http://schema.org","@type":"EmailMessage","action":{"@type":"ViewAction","name":"View Commit","url":"https://gitlab.haskell.org/ghc/ghc/-/commit/c23cda9d796064f2bb914a916990ede540679a39"}}</script>


</p>
</div>
</body>
</html>