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<div class="content">

<h3 style="margin-top: 20px; margin-bottom: 10px;">
Matthew Craven pushed to branch wip/T24264 at <a href="https://gitlab.haskell.org/ghc/ghc">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/1c79526a0ee0060dc692478926f6d0228c853a33">1c79526a</a></strong>
<div>
<span> by Finley McIlwaine </span> <i> at 2023-12-15T12:24:40-08:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>Late plugins
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/000c3302c6520430ca4c702d55d8eaeec61c9997">000c3302</a></strong>
<div>
<span> by Finley McIlwaine </span> <i> at 2023-12-15T12:24:40-08:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>withTiming on LateCCs and late plugins
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/be4551acf4ed705a1c3384db6a537f61000da688">be4551ac</a></strong>
<div>
<span> by Finley McIlwaine </span> <i> at 2023-12-15T12:24:40-08:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>add test for late plugins
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/7c29da9f2650e6b849d50efbbe1ac82b4f52f8fc">7c29da9f</a></strong>
<div>
<span> by Finley McIlwaine </span> <i> at 2023-12-15T12:24:40-08:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>Document late plugins
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/9a52ae46a33b490161e1e3e1cc70caa46c60488a">9a52ae46</a></strong>
<div>
<span> by Ben Gamari </span> <i> at 2023-12-20T07:07:26-05:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>Fix thunk update ordering

Previously we attempted to ensure soundness of concurrent thunk update
by synchronizing on the access of the thunk's info table pointer field.
This was believed to be sufficient since the indirectee (which may
expose a closure allocated by another core) would not be examined
until the info table pointer update is complete.

However, it turns out that this can result in data races in the presence
of multiple threads racing a update a single thunk. For instance,
consider this interleaving under the old scheme:

            Thread A                             Thread B
            ---------                            ---------
    t=0     Enter t
      1     Push update frame
      2     Begin evaluation

      4     Pause thread
      5     t.indirectee=tso
      6     Release t.info=BLACKHOLE

      7     ... (e.g. GC)

      8     Resume thread
      9     Finish evaluation
      10    Relaxed t.indirectee=x

      11                                         Load t.info
      12                                         Acquire fence
      13                                         Inspect t.indirectee

      14    Release t.info=BLACKHOLE

Here Thread A enters thunk `t` but is soon paused, resulting in `t`
being lazily blackholed at t=6. Then, at t=10 Thread A finishes
evaluation and updates `t.indirectee` with a relaxed store.

Meanwhile, Thread B enters the blackhole. Under the old scheme this
would introduce an acquire-fence but this would only synchronize with
Thread A at t=6. Consequently, the result of the evaluation, `x`, is not
visible to Thread B, introducing a data race.

We fix this by treating the `indirectee` field as we do all other
mutable fields. This means we must always access this field with
acquire-loads and release-stores.

See #23185.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/f4b535382db3e7879dd4b9312ed64d6586339f1f">f4b53538</a></strong>
<div>
<span> by Vladislav Zavialov </span> <i> at 2023-12-20T07:08:02-05:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>docs: Fix link to 051-ghc-base-libraries.rst

The proposal is no longer available at the previous URL.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/f7e21fabffa1c61ce16687362fbb0b85921421a6">f7e21fab</a></strong>
<div>
<span> by Matthew Pickering </span> <i> at 2023-12-21T14:57:40+00:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>hadrian: Build all executables in bin/ folder

In the end the bindist creation logic copies them all into the bin
folder. There is no benefit to building a specific few binaries in the
lib/bin folder anymore.

This also removes the ad-hoc logic to copy the touchy and unlit
executables from stage0 into stage1. It takes <1s to build so we might
as well just build it.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/0038d052c8c80b4b430bb2aa1c66d5280be1aa95">0038d052</a></strong>
<div>
<span> by Zubin Duggal </span> <i> at 2023-12-22T23:28:00-05:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>testsuite: mark jspace as fragile on i386.

This test has been flaky for some time and has been failing consistently on
i386-linux since 8e0446df landed.

See #24261
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/dfd670a0fcd38e5c169fbc7980fa433a9eb371a0">dfd670a0</a></strong>
<div>
<span> by Ben Bellick </span> <i> at 2023-12-24T10:10:31-05:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>Deprecate -ddump-json and introduce -fdiagnostics-as-json

Addresses #19278

This commit deprecates the underspecified -ddump-json flag and
introduces a newer, well-specified flag -fdiagnostics-as-json.

Also included is a JSON schema as part of the documentation.

The -ddump-json flag will be slated for removal shortly after this merge.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/609e6225c44c8e90c3847400b8db832b308e9b32">609e6225</a></strong>
<div>
<span> by Ben Bellick </span> <i> at 2023-12-24T10:10:31-05:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>Deprecate -ddump-json and introduce -fdiagnostics-as-json

Addresses #19278

This commit deprecates the underspecified -ddump-json flag and
introduces a newer, well-specified flag -fdiagnostics-as-json.

Also included is a JSON schema as part of the documentation.

The -ddump-json flag will be slated for removal shortly after this merge.
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/865513b2becb15664e7f2373773afafb39553a79">865513b2</a></strong>
<div>
<span> by Ömer Sinan Ağacan </span> <i> at 2023-12-24T10:11:13-05:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>Fix BNF in user manual 6.6.8.2: formal syntax for instance declarations
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/c247b6befe6a599688bad0a3383424f7ea12d5f2">c247b6be</a></strong>
<div>
<span> by Zubin Duggal </span> <i> at 2023-12-25T16:01:23-05:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>docs: document permissibility of -XOverloadedLabels (#24249)

Document the permissibility introduced by
https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0170-unrestricted-overloadedlabels.rst
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/e5b7eb59c47b8e1ac39b0f9a9c5a261896e14fa3">e5b7eb59</a></strong>
<div>
<span> by Ömer Sinan Ağacan </span> <i> at 2023-12-25T16:02:03-05:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>Fix a code block syntax in user manual sec. 6.8.8.6
</pre>
</li>
<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/1a41aab8266ffb40d560a4aa6b347fd2c138856a">1a41aab8</a></strong>
<div>
<span> by Matthew Craven </span> <i> at 2023-12-28T18:04:16-05:00 </i>
</div>
<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 14px; color: #333238; position: relative; font-family: var(--default-mono-font, "GitLab Mono"),"JetBrains Mono","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: #fbfafd; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dcdcde;'>StgToCmm: Detect some no-op case-continuations

...and generate no code for them. Fixes #24264.
</pre>
</li>
</ul>
<h4 style="margin-top: 10px; margin-bottom: 10px;">
30 changed files:
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compiler/GHC/Core/LateCC.hs
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compiler/GHC/Driver/Config/Logger.hs
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compiler/GHC/Driver/Errors.hs
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compiler/GHC/Driver/Flags.hs
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compiler/GHC/Driver/Main.hs
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compiler/GHC/Driver/Monad.hs
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compiler/GHC/Driver/Plugins.hs
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compiler/GHC/Driver/Session.hs
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compiler/GHC/Types/Error.hs
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