Marge Bot pushed to branch wip/marge_bot_batch_merge_job at Glasgow Haskell Compiler / GHC Commits: 5d0ab71a by fendor at 2026-07-27T17:31:05-04:00 Introduce global unit database cache As a first step for better sharing of `UnitInfo` across `UnitEnv`, we introduce a new datatype called `ExternalUnitDatabases`. It primarily serves as an in-memory representation of *all* `UnitDatabase`s across `UnitEnv`. This means, if multiple `HomeUnitEnv`s depend on the same database, one way or another, we make sure that we don't parse from disk every time. Instead, we store the in-memory representation in `ExternalUnitDatabases`. `ExternalUnitDatabaseCache` is the equivalent of `ExternalUnitState` in the `UnitEnv`. It is a mutable variable wrapping `ExternalUnitDatabases`. The mutable `ExternalUnitDatabaseCache` is used in `initUnits` to make sure we don't parse the same unit database multiple times. Almost by accident, we change the semantics of `initUnits` to honour modifications to `packageDBFlags`. The inability to change `packageDBFlags` while also reusing the already parsed `UnitDatabase`s was reported in #26423 as a bug. Hence, we think this behaviour change is warranted and acceptable, especially since it comes with a breaking change to the `initUnits` API. Add regression test for #26423 Closes #26423 - - - - - 6cce494a by fendor at 2026-07-27T17:31:05-04:00 Introduce UnitIndex for global external unit caching `UnitInfo`s have been observed to cause a lot of memory usage in #27500. Especially with multiple home units, as the same (external) units are processed from scratch, even though most of the time we end up with exactly the same `UnitInfo`. We introduce a `UnitEnv` global cache that allows us to store external unit information that is used across all `HomeUnitEnv`s. The most important change in this commit is the introduction of the `UnitIndex`. It stores a global mapping of `UnitId` -> `UnitInfo`, and `initUnits` always uses the cached `UnitInfo` entry to populate each `HomeUnitEnv`'s `UnitState`. This allows us to ensure the following property:
Each `UnitInfo` should be alive exactly once in GHC.
All `UnitState`s should reference 'UnitInfo's stored in the 'UnitIndex'. This ensured by calling 'initUnits' with the 'UnitIndex'. In addition, the `ExternalUnitDatabases` may also hold a reference to each on-disk representation of `UnitInfo`. This means, we impose an hard upper bound on the number of `UnitInfo`s alive in the GHC session:
The number of alive `UnitInfo`s closure objects must be the sum of all loaded unit database times two.
We add performance regression tests that make sure the number of live `UnitInfo` cannot exceed this threshold. Closes #27500 ------------------------- Metric Decrease: MultiComponentModules MultiComponentModulesRecomp MultiComponentModulesRecomp100 mhu-perf LinkableUsage02 ------------------------- These metrics increases are especially notable, as we are not even sharing anything big but merely the global package database with 50 entries. It shows how careful sharing of `UnitInfo` can improve memory usage. We expect this to be much more notable when the whole cabal package database is shared across multiple home units. `LinkableUsage02` metric decreases on unreg and i386 platform, only. --- Technical details To share the `UnitInfo`s correctly, it is important that we extract the `WireMap` into the `UnitIndex`. At the moment of writing, `WireMap` must be globally the same for all `HomeUnitEnv`s. This is important, as we could otherwise not cache the "fully-resolved" `UnitInfo`, as we don't change the `UnitId` or `unitAbiHash` when resolving wired-in units. Thus, there could be ambiguities, when the `WireMap` is not the same for all `UnitState`s across the `UnitEnv`. We consider a `UnitInfo` fully-resolved, if wired-in units have been updated, the `UnitInfo` has been validated and variables in the unit config, such as `${pkgroot}` have been resolved. Updating the wired-in units requires the `WireMap` to be globally the same. - - - - - f8e3bee9 by Zubin Duggal at 2026-07-27T17:31:49-04:00 testsuite: skip runtime stats tests on debugged compilers Debugged flavours build the boot libraries without optimisation, so the runtime numbers do not match the baselines. - - - - - 1e326770 by Zubin Duggal at 2026-07-27T17:31:50-04:00 testsuite: mark #20706 tests fragile rather than broken Whether the static linux linker issues manifest depends on the host toolchain. - - - - - c0b13cbe by Zubin Duggal at 2026-07-27T17:31:50-04:00 testsuite: exclude libnuma from mostly-static It needs static system libraries (libnuma.a) that many platforms do not ship. Fixes #26914 - - - - - 76322136 by Alan Zimmerman at 2026-07-28T10:32:08-04:00 EPA: ClsInstDecl with decls as [LHsDecl GhcPs] in GhcPs Similar to 4fdfe75731e01dad7d7fa474c2703d0d3965afb1, this commit changes the as-parsed representation of class instance declarations to [LHsDecl GhcPs], and only separates them by type from the renamer onward. This also allows us to remove all the AnnSortKey machinery for exact printing, as it is now no longer needed. - - - - - a2e94c6b by Cheng Shao at 2026-07-28T10:32:09-04:00 hadrian: implement and use writeFileAtomic to fix race condition This patch implements `writeFileAtomic` in hadrian and change all invocations of shake non-atomic `writeFile'` to use `writeFileAtomic`, to avoid multiple hadrian concurrent invocations overwriting the same in-tree generated file not in the build root directory. Fixes #27536. Additional notes: - `writeFileChanged`/`writeFileChangedBS` cannot be made atomic since it involves reading the file's older version, so their uses are left alone. It doesn't affect #27536 given their outputs are contained in the build root directory. - It's possible to shrink this patch by only making writes outside the build root directory atomic. But I think it's not worth the effort for fine grained distinction here, and atomic writes within the build root directory should also improve robustness of a hadrian build. - In the longer term we do want to make a ghc build only generate files within the build root directory, though that's a lot of work and outside the scope of this particular bugfix. Co-authored-by: Codex <codex@openai.com> - - - - - 100 changed files: - + changelog.d/T26423 - + changelog.d/unit-index - compiler/GHC.hs - compiler/GHC/Driver/Backpack.hs - compiler/GHC/Driver/Env.hs - compiler/GHC/Driver/Main/Hsc.hs - compiler/GHC/Driver/Main/Interactive.hs - compiler/GHC/Driver/Main/Passes.hs - compiler/GHC/Driver/Session/Units.hs - compiler/GHC/Hs/Decls.hs - compiler/GHC/Hs/Instances.hs - compiler/GHC/Hs/Stats.hs - compiler/GHC/Hs/Utils.hs - compiler/GHC/HsToCore/Docs.hs - compiler/GHC/HsToCore/Quote.hs - compiler/GHC/Iface/Ext/Ast.hs - compiler/GHC/Parser.y - compiler/GHC/Parser/Annotation.hs - compiler/GHC/Parser/PostProcess.hs - compiler/GHC/Rename/Module.hs - compiler/GHC/Rename/Names.hs - compiler/GHC/Tc/TyCl.hs - compiler/GHC/Tc/TyCl/Class.hs - compiler/GHC/Tc/TyCl/Instance.hs - compiler/GHC/Tc/Utils/Env.hs - compiler/GHC/ThToHs.hs - compiler/GHC/Types/Unique.hs - compiler/GHC/Unit/Env.hs - + compiler/GHC/Unit/External/Database.hs - + compiler/GHC/Unit/External/Index.hs - + compiler/GHC/Unit/External/ModuleOrigin.hs - + compiler/GHC/Unit/External/Providers.hs - + compiler/GHC/Unit/External/Query.hs - + compiler/GHC/Unit/External/Substitution.hs - + compiler/GHC/Unit/External/Validate.hs - + compiler/GHC/Unit/External/Visibility.hs - + compiler/GHC/Unit/External/Wired.hs - compiler/GHC/Unit/Home/Graph.hs - compiler/GHC/Unit/Info.hs - compiler/GHC/Unit/State.hs - compiler/GHC/Unit/State.hs-boot - compiler/GHC/Unit/Types.hs - compiler/Language/Haskell/Syntax/Decls.hs - compiler/ghc.cabal.in - ghc/GHCi/UI.hs - hadrian/src/Hadrian/Builder/Ar.hs - hadrian/src/Hadrian/Utilities.hs - hadrian/src/Rules/BinaryDist.hs - hadrian/src/Rules/CabalReinstall.hs - hadrian/src/Rules/Documentation.hs - hadrian/src/Rules/Generate.hs - hadrian/src/Rules/Library.hs - hadrian/src/Rules/Nofib.hs - hadrian/src/Rules/Program.hs - hadrian/src/Rules/Register.hs - hadrian/src/Rules/Rts.hs - hadrian/src/Rules/SourceDist.hs - hadrian/src/Rules/Test.hs - hadrian/src/Rules/ToolArgs.hs - testsuite/driver/testlib.py - testsuite/tests/count-deps/CountDepsParser.stdout - + testsuite/tests/driver/T26423/Hello.hs - + testsuite/tests/driver/T26423/Makefile - + testsuite/tests/driver/T26423/T26423.hs - + testsuite/tests/driver/T26423/T26423.stderr - + testsuite/tests/driver/T26423/T26423.stdout - + testsuite/tests/driver/T26423/all.T - + testsuite/tests/driver/T26423/test/Test.hs - + testsuite/tests/driver/T26423/test/test.pkg - + testsuite/tests/driver/TUnitInfo/Foo.hs - + testsuite/tests/driver/TUnitInfo/Makefile - + testsuite/tests/driver/TUnitInfo/all.T - + testsuite/tests/driver/TUnitInfo/genMhu.sh - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space-mhu.stdout - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space-single.stdout - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space.hs - + testsuite/tests/driver/TUnitInfo/generic-unit-info-space.stdout - testsuite/tests/driver/all.T - testsuite/tests/driver/mostly-static/Makefile - testsuite/tests/ghci/T13786/all.T - testsuite/tests/ghci/linking/all.T - testsuite/tests/ghci/linking/dyn/all.T - testsuite/tests/haddock/should_compile_flag_haddock/T17544.stderr - testsuite/tests/package/T20010/all.T - testsuite/tests/parser/should_compile/DumpRenamedAst.stderr - testsuite/tests/plugins/all.T - testsuite/tests/printer/Test24533.stdout - testsuite/tests/rts/all.T - testsuite/tests/rts/linker/all.T - utils/check-exact/ExactPrint.hs - utils/check-exact/Utils.hs - utils/haddock/haddock-api/src/Haddock.hs - utils/haddock/haddock-api/src/Haddock/Backends/Hoogle.hs - utils/haddock/haddock-api/src/Haddock/Backends/LaTeX.hs - utils/haddock/haddock-api/src/Haddock/Backends/Xhtml/Decl.hs - utils/haddock/haddock-api/src/Haddock/Convert.hs - utils/haddock/haddock-api/src/Haddock/GhcUtils.hs - utils/haddock/haddock-api/src/Haddock/Interface/Create.hs - utils/haddock/haddock-api/src/Haddock/Interface/Rename.hs - utils/haddock/haddock-api/src/Haddock/Types.hs The diff was not included because it is too large. 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