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<h3>
Sebastian Graf pushed to branch wip/dmdanal-precise-exn
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/0da186c1b5a47e08e91c1c674d46c040c83932fc">0da186c1</a></strong>
<div>
<span>by Krzysztof Gogolewski</span>
<i>at 2020-04-14T07:55:20-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Change zipWith to zipWithEqual in a few places
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/074c1ccd3f8c3fcab117e336316173e8e869230a">074c1ccd</a></strong>
<div>
<span>by Andreas Klebinger</span>
<i>at 2020-04-14T07:55:55-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Small change to the windows ticker.
We already have a function to go from time to ms so use it.
Also expand on the state of timer resolution.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/b69cc8842aa7e2df52b92a9c9ad3b9d8dcf624ab">b69cc884</a></strong>
<div>
<span>by Alp Mestanogullari</span>
<i>at 2020-04-14T07:56:38-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">hadrian: get rid of unnecessary levels of nesting in source-dist
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/d0c3b0696f1ca809ebd83b5fc2c0b911cde38e77">d0c3b069</a></strong>
<div>
<span>by Julien Debon</span>
<i>at 2020-04-14T07:57:16-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">doc (Foldable): Add examples to Data.Foldable
See #17929
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/5b08e0c06e038448a63aa9bd7f163b23d824ba4b">5b08e0c0</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-04-14T23:28:20-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">StgCRun: Enable unwinding only on Linux
It's broken on macOS due and SmartOS due to assembler differences
(#15207) so let's be conservative in enabling it. Also, refactor things
to make the intent clearer.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/27cc2e7b1c1268e59c9d16b4530f27c0d40e9464">27cc2e7b</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-04-14T23:28:57-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts: Don't mark evacuate_large as inline
This function has two callsites and is quite large. GCC consequently
decides not to inline and warns instead. Given the situation, I can't
blame it. Let's just remove the inline specifier.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/9853fc5e3556e733b56976b0a2fce9e82130a9ef">9853fc5e</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-04-14T23:29:48-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">base: Enable large file support for OFD locking impl.
Not only is this a good idea in general but this should also avoid
issue #17950 by ensuring that off_t is 64-bits.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/7b41f21bbfa9e266ba6654b08c3f9fec549c8bca">7b41f21b</a></strong>
<div>
<span>by Matthew Pickering</span>
<i>at 2020-04-14T23:30:24-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Hadrian: Make -i paths absolute
The primary reason for this change is that ghcide does not work with
relative paths. It also matches what cabal and stack do, they always
pass absolute paths.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/41230e2601703df0233860be3f7d53f3a01bdbe5">41230e26</a></strong>
<div>
<span>by Daniel Gröber</span>
<i>at 2020-04-14T23:31:01-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Zero out pinned block alignment slop when profiling
The heap profiler currently cannot traverse pinned blocks because of
alignment slop. This used to just be a minor annoyance as the whole block
is accounted into a special cost center rather than the respective object's
CCS, cf. #7275. However for the new root profiler we would like to be able
to visit _every_ closure on the heap. We need to do this so we can get rid
of the current 'flip' bit hack in the heap traversal code.
Since info pointers are always non-zero we can in principle skip all the
slop in the profiler if we can rely on it being zeroed. This assumption
caused problems in the past though, commit a586b33f8e ("rts: Correct
handling of LARGE ARR_WORDS in LDV profiler"), part of !1118, tried to use
the same trick for BF_LARGE objects but neglected to take into account that
shrink*Array# functions don't ensure that slop is zeroed when not
compiling with profiling.
Later, commit 0c114c6599 ("Handle large ARR_WORDS in heap census (fix
as we will only be assuming slop is zeroed when profiling is on.
This commit also reduces the ammount of slop we introduce in the first
place by calculating the needed alignment before doing the allocation for
small objects where we know the next available address. For large objects
we don't know how much alignment we'll have to do yet since those details
are hidden behind the allocateMightFail function so there we continue to
allocate the maximum additional words we'll need to do the alignment.
So we don't have to duplicate all this logic in the cmm code we pull it
into the RTS allocatePinned function instead.
Metric Decrease:
T7257
haddock.Cabal
haddock.base
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/15fa9bd6dd2d0b8d1fcd7135c85ea0d60853340d">15fa9bd6</a></strong>
<div>
<span>by Daniel Gröber</span>
<i>at 2020-04-14T23:31:01-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts: Expand and add more notes regarding slop
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/caf3f444bcc29f75145834207da00d938c08c2d3">caf3f444</a></strong>
<div>
<span>by Daniel Gröber</span>
<i>at 2020-04-14T23:31:01-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts: allocatePinned: Fix confusion about word/byte units
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/c3c0f662df06500a11970fd391d0a88e081a5296">c3c0f662</a></strong>
<div>
<span>by Daniel Gröber</span>
<i>at 2020-04-14T23:31:01-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts: Underline some Notes as is conventional
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/e149dea9bb89b77d34f50075946d6b4751a974f0">e149dea9</a></strong>
<div>
<span>by Daniel Gröber</span>
<i>at 2020-04-14T23:31:38-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts: Fix nomenclature in OVERWRITING_CLOSURE macros
The additional commentary introduced by commit 8916e64e5437 ("Implement
shrinkSmallMutableArray# and resizeSmallMutableArray#.") unfortunately got
this wrong. We set 'prim' to true in overwritingClosureOfs because we
_don't_ want to call LDV_recordDead().
The reason is because of this "inherently used" distinction made in the LDV
profiler so I rename the variable to be more appropriate.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/1dd3d18c2afd9e6009cd53295d26f8b31ca58fec">1dd3d18c</a></strong>
<div>
<span>by Daniel Gröber</span>
<i>at 2020-04-14T23:31:38-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Remove call to LDV_RECORD_CREATE for array resizing
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/19de2fb090a25ab0d640d0cd5aef09f35e7455a0">19de2fb0</a></strong>
<div>
<span>by Daniel Gröber</span>
<i>at 2020-04-14T23:31:38-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts: Assert LDV_recordDead is not called for inherently used closures
The comments make it clear LDV_recordDead should not be called for
inhererently used closures, so add an assertion to codify this fact.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/0b934e30417a767063625494ecf135c9d6006f71">0b934e30</a></strong>
<div>
<span>by Ryan Scott</span>
<i>at 2020-04-14T23:32:14-04:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Bump template-haskell version to 2.17.0.0
This requires bumping the `exceptions` and `text` submodules to bring
in commits that bump their respective upper version bounds on
`template-haskell`.
Fixes #17645. Fixes #17696.
Note that the new `text` commit includes a fair number of additions
to the Haddocks in that library. As a result, Haddock has to do more
work during the `haddock.Cabal` test case, increasing the number of
allocations it requires. Therefore,
-------------------------
Metric Increase:
haddock.Cabal
-------------------------
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/8b1c64a09f913f6cbcd0430873620772a156a67b">8b1c64a0</a></strong>
<div>
<span>by Sebastian Graf</span>
<i>at 2020-04-15T10:44:28+02:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">DmdAnal: Reflect precise exceptions in demand types
This is part two of the "fixing precise exception" plan in
https://gitlab.haskell.org/ghc/ghc/wikis/fixing-precise-exceptions
and, in combination with !2956, supercedes !2525.
In #13380 and #17676 we saw that we didn't preserve precise exception
semantics in demand analysis. We fixed that with minimal changes in
!2956, but that is terribly unprincipled.
That unprincipledness results in a loss of precision, which is tracked
by these new test cases:
- `T13380b`: Regression in dead code elimination, because !2956 was too
syntactic about `raiseIO#`
- `T13380c`: No need to apply the "IO hack" when the IO action may not
throw a precise exception
- `T13380d`: Demonstrating unsoundness of the "IO hack" when resorting
to manual state token threading and direct use of primops.
More details below.
The "IO hack" (which is a fallback to preserve precise exceptions
semantics and thus soundness, rather than some smart thing that
increases precision) is quite a misnomer and is called
`mayThrowPreciseException` now.
Also there is a slight chance that the IO hack was unsound before,
because it assumes that precise exceptions can only be thrown from a
case scrutinee of type `(# State# RealWorld, _ #)`.
I couldn't come up with a program using the `IO` abstraction that
violates this assumption. But it's easy to do so via manual state token
threading and direct use of primops, see `T13380d`. Also similar code
might be generated by Nested CPR in the (hopefully not too) distant
future.
Hence, we now have a more careful test in `forcesRealWorld` that passes
`T13380d`.
As for *how* we fixed these wrinkles: We augmented the `Divergence`
lattice to a diamond with two new elements forming the middle layer:
- `ExnOrDiv`: Means either `Diverges` (, throws an imprecise exception)
or throws a *precise* exception.
- `ConOrDiv`: Means either `Diverges` (, throws an imprecise exception)
or converges.
See the wiki page for more implementational details:
https://gitlab.haskell.org/ghc/ghc/wikis/fixing-precise-exceptions#replacing-hacks-by-principled-program-analyses
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/b821abb9cc2a0a8bc11323bbf830fd95e1aace85">b821abb9</a></strong>
<div>
<span>by Sebastian Graf</span>
<i>at 2020-04-15T11:16:54+02:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Fix the perf regression in T12227/T12545
But now T9233 fails because we are doing more work. Temporarily marking
as accepted increase.
Metric Increase:
T9233
Metric Decrease:
hie002
</pre>
</li>
</ul>
<h4>30 changed files:</h4>
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<a href="#d0d96a6d03668aeab20ebe05e2c4ccb798c7e64c">
compiler/GHC.hs
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<a href="#8b1482a65a3092c268b853a00aa18286427d1dec">
compiler/GHC/Core/Arity.hs
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<a href="#975dc08a8e7942b32d621f617d5a9c1b668601dd">
compiler/GHC/Core/Coercion/Opt.hs
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<a href="#36a42448a83a9d1f6df8475f03ead2eed199dd8e">
compiler/GHC/Core/Lint.hs
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compiler/GHC/Core/Op/CallArity.hs
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<a href="#1419e35d2402c23209a644b054c5a67aa4463451">
compiler/GHC/Core/Op/DmdAnal.hs
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compiler/GHC/Core/Op/FloatIn.hs
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compiler/GHC/Core/Op/FloatOut.hs
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compiler/GHC/Core/Op/LiberateCase.hs
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compiler/GHC/Core/Op/OccurAnal.hs
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compiler/GHC/Core/Op/Simplify.hs
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compiler/GHC/Core/Unfold.hs
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compiler/GHC/Core/Utils.hs
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compiler/GHC/HsToCore/Expr.hs
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compiler/GHC/Iface/Tidy.hs
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compiler/GHC/Tc/Deriv/Generate.hs
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compiler/GHC/Types/Demand.hs
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compiler/GHC/Types/Id.hs
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