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<h3 style="margin-top: 20px; margin-bottom: 10px;">
Sebastian Graf pushed to branch wip/T20749 at <a href="https://gitlab.haskell.org/ghc/ghc">Glasgow Haskell Compiler / GHC</a>
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Commits:
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<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/d8baa1bdeea1753afc939a20119d3ce555301167">d8baa1bd</a></strong>
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<span> by Simon Peyton Jones </span> <i> at 2023-12-08T15:40:37+00:00 </i>
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<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;'>Take care when simplifying unfoldings
This MR fixes a very subtle bug exposed by #24242.
See Note [Environment for simplLetUnfolding].
I also updated a bunch of Notes on shadowing
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<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/03ca551d370d057bb7670bcae4e114677af6dec6">03ca551d</a></strong>
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<span> by Simon Peyton Jones </span> <i> at 2023-12-08T15:54:50-05:00 </i>
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<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;'>Comments only in FloatIn
Relevant to #3458
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<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/50c787793df3225c2286eb3247b14c1ef24f15d0">50c78779</a></strong>
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<span> by Simon Peyton Jones </span> <i> at 2023-12-08T15:54:50-05:00 </i>
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<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;'>Comments only in SpecConstr
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<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/9431e1953b29b2fe3e383b038258877efe9f6595">9431e195</a></strong>
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<span> by Simon Peyton Jones </span> <i> at 2023-12-08T15:54:50-05:00 </i>
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<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 #22238
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<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/7e06ea591af29d0d9c2cd36998b0f75a778a5f2a">7e06ea59</a></strong>
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<span> by Sebastian Graf </span> <i> at 2023-12-09T17:39:54+01:00 </i>
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<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;'>CorePrep: Attach evaldUnfolding to floats to detect more values
See `Note [Pin evaluatedness on floats]`.
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<li>
<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/12b80370a82b4191558aef01eb7203035193c0a2">12b80370</a></strong>
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<span> by Sebastian Graf </span> <i> at 2023-12-09T17:40:27+01:00 </i>
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<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;'>Make DataCon workers strict in strict fields (#20749)
This patch tweaks `exprIsConApp_maybe`, `exprIsHNF` and friends, and Demand
Analysis so that they exploit and maintain strictness of DataCon workers. See
`Note [Strict fields in Core]` for details.
Very little needed to change, and it puts field seq insertion done by Tag
Inference into a new perspective: That of *implementing* strict field semantics.
Before Tag Inference, DataCon workers are strict. Afterwards they are
effectively lazy and field seqs happen around use sites. History has shown
that there is no other way to guarantee taggedness and thus the STG Strict Field
Invariant.
Knock-on changes:
* `exprIsHNF` previously used `exprOkForSpeculation` on unlifted arguments
instead of recursing into `exprIsHNF`. That regressed the termination
analysis in CPR analysis (which simply calls out to `exprIsHNF`), so I made
it call `exprOkForSpeculation`, too.
* There's a small regression in Demand Analysis, visible in the changed test
output of T16859: Previously, a field seq on a variable would give that
variable a "used exactly once" demand, now it's "used at least once",
because `dmdTransformDataConSig` accounts for future uses of the field
that actually all go through the case binder (and hence won't re-enter the
potential thunk). The difference should hardly be observable.
* The Simplifier's fast path for data constructors only applies to lazy
data constructors now. I observed regressions involving Data.Binary.Put's
`Pair` data type.
* Unfortunately, T21392 does no longer reproduce after this patch, so I marked
it as "not broken" in order to track whether we regress again in the future.
Fixes #20749, the satisfying conclusion of an annoying saga (cf. the ideas
in #21497 and #22475).
Co-Authored-By: Jaro Reinders <jaro.reinders@gmail.com>
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