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Ben Gamari pushed to branch wip/backports-9.6 at <a href="https://gitlab.haskell.org/ghc/ghc" style="color: #1068bf;">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/a886fcc8f7743829700f2af154a1918e0bf53190" style="color: #1068bf;">a886fcc8</a></strong>
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<span> by Sebastian Graf </span> <i> at 2023-01-18T12:30:25-05:00 </i>
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<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "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: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>Handle shadowing in DmdAnal (#22718)
Previously, when we had a shadowing situation like
```hs
f x = ... -- demand signature <1L><1L>
main = ... \f -> f 1 ...
```
we'd happily use the shadowed demand signature at the call site inside the
lambda. Of course, that's wrong and solution is simply to remove the demand
signature from the `AnalEnv` when we enter the lambda.
This patch does so for all binding constructs Core.
In #22718 the issue was caused by LetUp not shadowing away the existing demand
signature for the let binder in the let body. The resulting absent error is
fickle to reproduce; hence no reproduction test case. #17478 would help.
Fixes #22718.
It appears that TcPlugin_Rewrite regresses by ~40% on Darwin. It is likely that
DmdAnal was exploiting ill-scoped analysis results.
Metric increase ['bytes allocated'] (test_env=x86_64-darwin-validate):
TcPlugin_Rewrite
(cherry picked from commit e3fff7512bbf989386faaa1dccafdad1deabde84)
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<strong style="font-weight: bold;"><a href="https://gitlab.haskell.org/ghc/ghc/-/commit/991b9ca567389114e8bfd7bd9c5483a1602b2427" style="color: #1068bf;">991b9ca5</a></strong>
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<span> by Ben Gamari </span> <i> at 2023-01-18T12:31:21-05:00 </i>
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<pre class="commit-message" style='white-space: pre-wrap; display: block; font-size: 0.8125rem; color: #303030; position: relative; font-family: "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: #fafafa; border-radius: 2px; margin: 0; padding: 8px 12px; border: 1px solid #dbdbdb;'>Accept performance metric changes
Metric Decrease:
MultiLayerModulesTH_OneShot
T21839c
T21839r
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