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<h3>
Ryan Scott pushed to branch wip/T18021
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/75fc1ed58bb9adb3f472e1529d368c0fff479353">75fc1ed5</a></strong>
<div>
<span>by Sylvain Henry</span>
<i>at 2020-11-28T15:40:23-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Hadrian: fix detection of ghc-pkg for cross-compilers
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/7cb5df9617544dc3bdf85b719feaaa5d15f01c2c">7cb5df96</a></strong>
<div>
<span>by Sylvain Henry</span>
<i>at 2020-11-28T15:40:23-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">hadrian: fix ghc-pkg uses (#17601)
Make sure ghc-pkg doesn't read the compiler "settings" file by passing
--no-user-package-db.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/e3fd4226a08ac6cd4abe9f25f764e518de66834a">e3fd4226</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-11-28T15:40:23-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">gitlab-ci: Introduce a nightly cross-compilation job
This adds a job to test cross-compilation from x86-64 to AArch64 with
Hadrian.
Fixes #18234
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/698d3d9648e9cb6b3757269e21ce4fa1692a1a3b">698d3d96</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-11-28T15:41:00-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">gitlab-ci: Only deploy GitLab Pages in ghc/ghc>
The deployments are quite large and yet are currently only served for
the ghc/ghc> project.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/625726f988852f5779825a954609d187d9865dc1">625726f9</a></strong>
<div>
<span>by David Eichmann</span>
<i>at 2020-11-28T15:41:37-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">ghc-heap: partial TSO/STACK decoding
Co-authored-by: Sven Tennie <sven.tennie@gmail.com>
Co-authored-by: Matthew Pickering <matthewtpickering@gmail.com>
Co-authored-by: Ben Gamari <bgamari.foss@gmail.com>
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/22ea9c296906ad3a8fed384bcf6fb35d4b6ca814">22ea9c29</a></strong>
<div>
<span>by Andreas Klebinger</span>
<i>at 2020-11-28T15:42:13-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Small optimization to CmmSink.
Inside `regsUsedIn` we can avoid some thunks by specializing the
recursion. In particular we avoid the thunk for `(f e z)` in the
MachOp/Load branches, where we know this will evaluate to z.
Reduces allocations for T3294 by ~1%.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/bba42c62220a437f52e7d30cbfa67e93b4cab06e">bba42c62</a></strong>
<div>
<span>by John Ericson</span>
<i>at 2020-11-28T15:42:49-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Make primop handler indentation more consistent
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/c82bc8e9d444d6d61198f3bfbcc7c5bb5f6ce13c">c82bc8e9</a></strong>
<div>
<span>by John Ericson</span>
<i>at 2020-11-28T15:42:49-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Cleanup some primop constructor names
Harmonize the internal (big sum type) names of the native vs fixed-sized
number primops a bit. (Mainly by renaming the former.)
No user-facing names are changed.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/ae14f160c64d20880486ba365348ef3900c84a60">ae14f160</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-11-28T15:43:25-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">testsuite: Mark T14702 as fragile on Windows
Due to #18953.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/1bc104b029b4f043cac42253ee2387f4d574abca">1bc104b0</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-11-29T15:33:18-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">withTimings: Emit allocations counter
This will allow us to back out the allocations per compiler pass from
the eventlog. Note that we dump the allocation counter rather than the
difference since this will allow us to determine how much work is done
*between* `withTiming` blocks.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/e992ea84248e2ac9f9d439cd9b25745e8c41e32d">e992ea84</a></strong>
<div>
<span>by GHC GitLab CI</span>
<i>at 2020-11-29T15:33:54-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">ThreadPaused: Don't zero slop until free vars are pushed
When threadPaused blackholes a thunk it calls `OVERWRITING_CLOSURE` to
zero the slop for the benefit of the sanity checker. Previously this was
done *before* pushing the thunk's free variables to the update
remembered set. Consequently we would pull zero'd pointers to the update
remembered set.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/e82cd140e510a792031247a8f414ade48382703b">e82cd140</a></strong>
<div>
<span>by GHC GitLab CI</span>
<i>at 2020-11-29T15:33:54-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">nonmoving: Fix regression from TSAN work
The TSAN rework (specifically aad1f803) introduced a subtle regression
in GC.c, swapping `g0` in place of `gen`. Whoops!
Fixes #18997.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/35a5207e8277800b77af90d74cdd235d29a901e6">35a5207e</a></strong>
<div>
<span>by GHC GitLab CI</span>
<i>at 2020-11-29T15:33:54-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts/Messages: Add missing write barrier in THROWTO message update
After a THROWTO message has been handle the message closure is
overwritten by a NULL message. We must ensure that the original
closure's pointers continue to be visible to the nonmoving GC.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/0120829f47ed9ebd02ffd552d71e45cca3bdc9f6">0120829f</a></strong>
<div>
<span>by GHC GitLab CI</span>
<i>at 2020-11-29T15:33:54-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">nonmoving: Add missing write barrier in shrinkSmallByteArray
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/8a4d8fb62abde3b79043e8915ee538aaabe2d97c">8a4d8fb6</a></strong>
<div>
<span>by GHC GitLab CI</span>
<i>at 2020-11-29T15:33:54-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Updates: Don't zero slop until closure has been pushed
Ensure that the the free variables have been pushed to the update
remembered set before we zero the slop.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/2793cfdc8f7dca8461149d54882286a76f52ff84">2793cfdc</a></strong>
<div>
<span>by GHC GitLab CI</span>
<i>at 2020-11-29T15:33:54-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">OSThreads: Fix error code checking
pthread_join returns its error code and apparently doesn't set errno.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/e391a16f919e5bebf75355e8dd1542cdc5656198">e391a16f</a></strong>
<div>
<span>by GHC GitLab CI</span>
<i>at 2020-11-29T15:33:54-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">nonmoving: Don't join to mark_thread on shutdown
The mark thread is not joinable as we detach from it on creation.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/60d088aba238c7265adf76840ec1d883373b0e20">60d088ab</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-11-29T15:33:54-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">nonmoving: Add reference to Ueno 2016
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/3aa603620ef5a6aae1778278aa9914f344ab526e">3aa60362</a></strong>
<div>
<span>by GHC GitLab CI</span>
<i>at 2020-11-29T15:33:54-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">nonmoving: Ensure that evacuated large objects are marked
See Note [Non-moving GC: Marking evacuated objects].
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/8d304a99d2d0c17fb49c0589c0525817d515c0d0">8d304a99</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-11-30T10:15:22-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts/m32: Refactor handling of allocator seeding
Previously, in an attempt to reduce fragmentation, each new allocator
would map a region of M32_MAX_PAGES fresh pages to seed itself. However,
this ends up being extremely wasteful since it turns out that we often
use fewer than this. Consequently, these pages end up getting freed
which, ends up fragmenting our address space more than than we would
have if we had naively allocated pages on-demand.
Here we refactor m32 to avoid this waste while achieving the
fragmentation mitigation previously desired. In particular, we move all
page allocation into the global m32_alloc_page, which will pull a page
from the free page pool. If the free page pool is empty we then refill
it by allocating a region of M32_MAP_PAGES and adding them to the pool.
Furthermore, we do away with the initial seeding entirely. That is, the
allocator starts with no active pages: pages are rather allocated on an
as-needed basis.
On the whole this ends up being a pleasingly simple change,
simultaneously making m32 more efficient, more robust, and simpler.
Fixes #18980.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/b66292890d5fe0791c291f4fc427f1ab1d0f5c15">b6629289</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-11-30T10:15:58-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts: Use CHECK instead of assert
Use the GHC wrappers instead of <assert.h>.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/9f4efa6a5e5d43c81d7e61b27f7cd6e3f812b1ea">9f4efa6a</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-11-30T10:15:58-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts/linker: Replace some ASSERTs with CHECK
In the past some people have confused ASSERT, which is for checking
internal invariants, which CHECK, which should be used when checking
things that might fail due to bad input (and therefore should be enabled
even in the release compiler). Change some of these cases in the linker
to use CHECK.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/0f8a4655e39bed1ca39820abdd3df9db5706b036">0f8a4655</a></strong>
<div>
<span>by Ryan Scott</span>
<i>at 2020-11-30T10:16:34-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Allow deploy:pages job to fail
See #18973.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/49ebe369165c85ae4c2382b40e34bfa4f1e9da25">49ebe369</a></strong>
<div>
<span>by chessai</span>
<i>at 2020-11-30T19:47:40-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Optimisations in Data.Foldable (T17867)
This PR concerns the following functions from `Data.Foldable`:
* minimum
* maximum
* sum
* product
* minimumBy
* maximumBy
- Default implementations of these functions now use `foldl'` or `foldMap'`.
- All have been marked with INLINEABLE to make room for further optimisations.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/4d79ef6599f44b5ab33cbd89fec96ebfac0794a1">4d79ef65</a></strong>
<div>
<span>by chessai</span>
<i>at 2020-11-30T19:47:40-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Apply suggestion to libraries/base/Data/Foldable.hs</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/6af074cecdee533791943af1191541f82abc34c4">6af074ce</a></strong>
<div>
<span>by chessai</span>
<i>at 2020-11-30T19:47:40-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Apply suggestion to libraries/base/Data/Foldable.hs</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/ab334262a605b0ebc228096d8af88a55aa5ea6b8">ab334262</a></strong>
<div>
<span>by Viktor Dukhovni</span>
<i>at 2020-11-30T19:48:17-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">dirty MVAR after mutating TSO queue head
While the original head and tail of the TSO queue may be in the same
generation as the MVAR, interior elements of the queue could be younger
after a GC run and may then be exposed by putMVar operation that updates
the queue head.
Resolves #18919
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/5eb163f321fdc9a3dbb5e02a157b7f8194e70fcc">5eb163f3</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-11-30T19:48:53-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts/linker: Don't allow shared libraries to be loaded multiple times
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/490aa14dbc98e4713f913c4417d454e53b8b278a">490aa14d</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-11-30T19:48:53-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts/linker: Initialise CCSs from native shared objects
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/6ac3db5fefbac6bea6c8fd0ac64daf036d9a8e60">6ac3db5f</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-11-30T19:48:53-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts/linker: Move shared library loading logic into Elf.c
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/b6698d73fa9811795ca37ba0b704aa430c390345">b6698d73</a></strong>
<div>
<span>by GHC GitLab CI</span>
<i>at 2020-11-30T19:48:53-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts/linker: Don't declare dynamic objects with image_mapped
This previously resulted in warnings due to spurious unmap failures.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/b94a65afe1e270245cd5b9fe03d59b726dfba8c4">b94a65af</a></strong>
<div>
<span>by jneira</span>
<i>at 2020-11-30T19:49:31-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Include tried paths in findToolDir error
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/72a87fbc7a95c012be260d1a14374e2b06ed0a36">72a87fbc</a></strong>
<div>
<span>by Richard Eisenberg</span>
<i>at 2020-12-01T19:57:41-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Move core flattening algorithm to Core.Unify
This sets the stage for a later change, where this
algorithm will be needed from GHC.Core.InstEnv.
This commit also splits GHC.Core.Map into
GHC.Core.Map.Type and GHC.Core.Map.Expr,
in order to avoid module import cycles
with GHC.Core.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/0dd45d0adbade7eaae973b09b4d0ff1acb1479b8">0dd45d0a</a></strong>
<div>
<span>by Richard Eisenberg</span>
<i>at 2020-12-01T19:57:41-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Bump the # of commits searched for perf baseline
The previous value of 75 meant that a feature branch with
more than 75 commits would get spurious CI passes.
This affects #18692, but does not fix that ticket, because
if a baseline cannot be found, we should fail, not succeed.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/8bb52d9186655134e3e06b4dc003e060379f5417">8bb52d91</a></strong>
<div>
<span>by Richard Eisenberg</span>
<i>at 2020-12-01T19:57:41-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Remove flattening variables
This patch redesigns the flattener to simplify type family applications
directly instead of using flattening meta-variables and skolems. The key new
innovation is the CanEqLHS type and the new CEqCan constraint (Ct). A CanEqLHS
is either a type variable or exactly-saturated type family application; either
can now be rewritten using a CEqCan constraint in the inert set.
Because the flattener no longer reduces all type family applications to
variables, there was some performance degradation if a lengthy type family
application is now flattened over and over (not making progress). To
compensate, this patch contains some extra optimizations in the flattener,
leading to a number of performance improvements.
Close #18875.
Close #18910.
There are many extra parts of the compiler that had to be affected in writing
this patch:
* The family-application cache (formerly the flat-cache) sometimes stores
coercions built from Given inerts. When these inerts get kicked out, we must
kick out from the cache as well. (This was, I believe, true previously, but
somehow never caused trouble.) Kicking out from the cache requires adding a
filterTM function to TrieMap.
* This patch obviates the need to distinguish "blocking" coercion holes from
non-blocking ones (which, previously, arose from CFunEqCans). There is thus
some simplification around coercion holes.
* Extra commentary throughout parts of the code I read through, to preserve
the knowledge I gained while working.
* A change in the pure unifier around unifying skolems with other types.
Unifying a skolem now leads to SurelyApart, not MaybeApart, as documented
in Note [Binding when looking up instances] in GHC.Core.InstEnv.
* Some more use of MCoercion where appropriate.
* Previously, class-instance lookup automatically noticed that e.g. C Int was
a "unifier" to a target [W] C (F Bool), because the F Bool was flattened to
a variable. Now, a little more care must be taken around checking for
unifying instances.
* Previously, tcSplitTyConApp_maybe would split (Eq a => a). This is silly,
because (=>) is not a tycon in Haskell. Fixed now, but there are some
knock-on changes in e.g. TrieMap code and in the canonicaliser.
* New function anyFreeVarsOf{Type,Co} to check whether a free variable
satisfies a certain predicate.
* Type synonyms now remember whether or not they are "forgetful"; a forgetful
synonym drops at least one argument. This is useful when flattening; see
flattenView.
* The pattern-match completeness checker invokes the solver. This invocation
might need to look through newtypes when checking representational equality.
Thus, the desugarer needs to keep track of the in-scope variables to know
what newtype constructors are in scope. I bet this bug was around before but
never noticed.
* Extra-constraints wildcards are no longer simplified before printing.
See Note [Do not simplify ConstraintHoles] in GHC.Tc.Solver.
* Whether or not there are Given equalities has become slightly subtler.
See the new HasGivenEqs datatype.
* Note [Type variable cycles in Givens] in GHC.Tc.Solver.Canonical
explains a significant new wrinkle in the new approach.
* See Note [What might match later?] in GHC.Tc.Solver.Interact, which
explains the fix to #18910.
* The inert_count field of InertCans wasn't actually used, so I removed
it.
Though I (Richard) did the implementation, Simon PJ was very involved
in design and review.
This updates the Haddock submodule to avoid #18932 by adding
a type signature.
-------------------------
Metric Decrease:
T12227
T5030
T9872a
T9872b
T9872c
Metric Increase:
T9872d
-------------------------
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/d66660ba4c491f9937a1a959b009d90f08a4fbee">d66660ba</a></strong>
<div>
<span>by Richard Eisenberg</span>
<i>at 2020-12-01T19:57:41-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Rename the flattener to become the rewriter.
Now that flattening doesn't produce flattening variables,
it's not really flattening anything: it's rewriting. This
change also means that the rewriter can no longer be confused
the core flattener (in GHC.Core.Unify), which is sometimes used
during type-checking.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/add0aeaefd4d823d31315564e924ce8c018fb69e">add0aeae</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-12-01T19:58:17-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts: Introduce mmapAnonForLinker
Previously most of the uses of mmapForLinker were mapping anonymous
memory, resulting in a great deal of unnecessary repetition. Factor this
out into a new helper.
Also fixes a few places where error checking was missing or suboptimal.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/97d71646ddf3814de62573100ed0b224d1588cbc">97d71646</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-12-01T19:58:17-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts/linker: Introduce munmapForLinker
Consolidates munmap calls to ensure consistent error handling.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/d8872af08d205c3067371d56200e68cf2f0c1ffc">d8872af0</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-12-01T19:58:18-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts/Linker: Introduce Windows implementations for mmapForLinker, et al.
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/c35d0e03514ce111ff8265426a7b911456984f50">c35d0e03</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-12-01T19:58:18-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts/m32: Introduce NEEDS_M32 macro
Instead of relying on RTS_LINKER_USE_MMAP
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/41c64eb5db50c80e110e47b7ab1c1ee18dada46b">41c64eb5</a></strong>
<div>
<span>by Ben Gamari</span>
<i>at 2020-12-01T19:58:18-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">rts/linker: Use m32 to allocate symbol extras in PEi386
</pre>
</li>
<li>
<strong><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/86a700ecd8ed2265535f5d39b20cd9938c2203d5">86a700ec</a></strong>
<div>
<span>by Ryan Scott</span>
<i>at 2020-12-04T17:54:42-05:00</i>
</div>
<pre class="commit-message" style="white-space: pre-wrap; margin: 0;">Reject dodgy scoping in associated family instance RHSes
Commit e63518f5d6a93be111f9108c0990a1162f88d615 tried to push all of the logic
of detecting out-of-scope type variables on the RHSes of associated type family
instances to `GHC.Tc.Validity` by deleting a similar check in the renamer.
Unfortunately, this commit went a little too far, as there are some corner
cases that `GHC.Tc.Validity` doesn't detect. Consider this example:
```hs
class C a where
data D a
instance forall a. C Int where
data instance D Int = MkD a
```
If this program isn't rejected by the time it reaches the typechecker, then
GHC will believe the `a` in `MkD a` is existentially quantified and accept it.
This is almost surely not what the user wants! The simplest way to reject
programs like this is to restore the old validity check in the renamer
(search for `improperly_scoped` in `rnFamEqn`).
Note that this is technically a breaking change, since the program in the
`polykinds/T9574` test case (which previously compiled) will now be rejected:
```hs
instance Funct ('KProxy :: KProxy o) where
type Codomain 'KProxy = NatTr (Proxy :: o -> *)
```
This is because the `o` on the RHS will now be rejected for being out of scope.
Luckily, this is simple to repair:
```hs
instance Funct ('KProxy :: KProxy o) where
type Codomain ('KProxy @o) = NatTr (Proxy :: o -> *)
```
All of the discussion is now a part of the revamped
`Note [Renaming associated types]` in `GHC.Rename.Module`.
A different design would be to make associated type family instances have
completely separate scoping from the parent instance declaration, much like
how associated type family default declarations work today. See the discussion
beginning at https://gitlab.haskell.org/ghc/ghc/-/issues/18021#note_265729 for
more on this point. This, however, would break even more programs that are
accepted today and likely warrants a GHC proposal before going forward. In the
meantime, this patch fixes the issue described in #18021 in the least invasive
way possible. There are programs that are accepted today that will no longer
be accepted after this patch, but they are arguably pathological programs, and
they are simple to repair.
Fixes #18021.
</pre>
</li>
</ul>
<h4>30 changed files:</h4>
<ul>
<li class="file-stats">
<a href="#587d266bb27a4dc3022bbed44dfa19849df3044c">
.gitlab-ci.yml
</a>
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<li class="file-stats">
<a href="#157f7634c25bc6366cb7c9c9edb48e819dce38db">
.gitlab/ci.sh
</a>
</li>
<li class="file-stats">
<a href="#451725cc4e5d443a3b7c2adcdf224840f953b7e2">
compiler/GHC/Builtin/primops.txt.pp
</a>
</li>
<li class="file-stats">
<a href="#5c66928780aaad0eb5888511dc4b0b08492c69fa">
compiler/GHC/ByteCode/Types.hs
</a>
</li>
<li class="file-stats">
<a href="#806448db91cc2906ebcc088107220a663d3d43eb">
compiler/GHC/Cmm/CommonBlockElim.hs
</a>
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<li class="file-stats">
<a href="#4fbb1c5f251c38fc01fcde693420ee6d02df7e45">
compiler/GHC/Cmm/Dataflow/Label.hs
</a>
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<li class="file-stats">
<a href="#b1390f6749e1a2dddcae35f88d55623ea6269f56">
compiler/GHC/Cmm/Sink.hs
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<a href="#783e5dae6e86931f06700fc088fb7d48c8a07386">
compiler/GHC/Core/Coercion.hs
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<a href="#b0ab2032bd0c006bb9cda1e5433173de35930f53">
compiler/GHC/Core/Coercion.hs-boot
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<a href="#f10ed7a2470454dfdd8691a08beba67d8b78ee70">
compiler/GHC/Core/Coercion/Axiom.hs
</a>
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<li class="file-stats">
<a href="#975dc08a8e7942b32d621f617d5a9c1b668601dd">
compiler/GHC/Core/Coercion/Opt.hs
</a>
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<li class="file-stats">
<a href="#91648438362e5a35363d2bb7abb04016dedd7d7e">
compiler/GHC/Core/FamInstEnv.hs
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<li class="file-stats">
<a href="#5596bb0f228bd2a308c4391df97375ae879430a8">
compiler/GHC/Core/InstEnv.hs
</a>
</li>
<li class="file-stats">
<a href="#640612f2fdc707ac7ee74f4165a7b86f38aa6249">
<span class="new-file">
+
compiler/GHC/Core/Map/Expr.hs
</span>
</a>
</li>
<li class="file-stats">
<a href="#691eec62dc293d0881c314b38b7363dc88b44c59">
compiler/GHC/Core/Map.hs
→
compiler/GHC/Core/Map/Type.hs
</a>
</li>
<li class="file-stats">
<a href="#446b4afbe6836b950115a619acea24ddde19dc90">
compiler/GHC/Core/Opt/CSE.hs
</a>
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<li class="file-stats">
<a href="#aa79261abf782f3dc603af7fbd5c4b08ed3ddb88">
compiler/GHC/Core/Opt/ConstantFold.hs
</a>
</li>
<li class="file-stats">
<a href="#039e8f5676356ef05c90af828aae48aac7296e47">
compiler/GHC/Core/TyCo/FVs.hs
</a>
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<li class="file-stats">
<a href="#578c7c3857d66d963736ff6742f3433a0e8d01b7">
compiler/GHC/Core/TyCo/Rep.hs
</a>
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<li class="file-stats">
<a href="#4aad0050db1a8a20db8bbca149111de99cb299c9">
compiler/GHC/Core/TyCon.hs
</a>
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<li class="file-stats">
<a href="#d1a980a3e0f207c148bb3ab404696977015bcc56">
compiler/GHC/Core/TyCon/Env.hs
</a>
</li>
<li class="file-stats">
<a href="#84c9d3ba34173297e7d7747e02caa2e004b164fc">
compiler/GHC/Core/Type.hs
</a>
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<li class="file-stats">
<a href="#89a2e0e1a3095c7a42b10f2819049908908080e8">
compiler/GHC/Core/Unify.hs
</a>
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<li class="file-stats">
<a href="#2fefe3125c649bc5377b06a7cca18e785855b79c">
compiler/GHC/Data/Bag.hs
</a>
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<a href="#f4ae6618b39d5ee4af8302b821aa7e38097a84b7">
compiler/GHC/Data/Maybe.hs
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<a href="#87e780e9b5d14cf4e8a52bb125fc352fa8a1d4be">
compiler/GHC/Data/TrieMap.hs
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<li class="file-stats">
<a href="#2e5692f568fd7b67a6b172e2a60469da8392508c">
compiler/GHC/Driver/Flags.hs
</a>
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<li class="file-stats">
<a href="#774d88050336ef660c7a219fb06c480c2fc639bc">
compiler/GHC/Driver/Session.hs
</a>
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<li class="file-stats">
<a href="#c8a27621f82549165d8946ae8e9f467660958059">
compiler/GHC/HsToCore/Monad.hs
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</li>
<li class="file-stats">
<a href="#9095b3c5485a1f2f18a0a43346b7a49dfdd1f65d">
compiler/GHC/HsToCore/Pmc/Solver.hs
</a>
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</ul>
<h5>The diff was not included because it is too large.</h5>
</div>
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