Hannes Siebenhandl pushed to branch wip/fendor/T27202 at Glasgow Haskell Compiler / GHC Commits: 8d8cd01f by Wolfgang Jeltsch at 2026-05-08T09:09:48+02:00 Introduce a cache of home module name providers This contribution introduces to the module graph a cache that maps home module names to sets of units providing them and changes the finder to use that cache. This is a performance optimization, especially for multi-home-unit builds. The particular changes are as follows: * In `GHC.Unit.Module.Graph`, `ModuleGraph` is extended with a new field `mg_home_module_name_providers_map`, exposed as `mgHomeModuleNameProvidersMap`. This is a cache that assigns to each home module name the set of IDs of home units that define it. Operations that construct module graphs are updated such that this cache stays synchronized. * In `GHC.Unit.Finder`, `findImportedModule` is changed to pull `mgHomeModuleNameProvidersMap` from `hsc_mod_graph` and pass it to `findImportedModuleNoHsc`, which now does not search home units in arbitrary order but prioritizes those units that the cache mentions as potential providers of the requested module. In addition, this contribution adds variants of the two multi-component compiler performance tests that use 100 units instead of 20, because with just 20 units the benefits from caching of home module name providers are still negligible. The following table shows the total time needed for running both multi-component tests before and after this contribution and with different numbers of units: | # of units | Before | After | |-----------:|-------:|------:| | 20 | 0:12 | 0:12 | | 100 | 0:47 | 0:42 | | 200 | 3:05 | 2:08 | Note that there seems to be a general overhead of 12 seconds that is not attributable to the actual tests, so that the real running times should be 12 seconds smaller than shown above. Resolves #27055. Co-authored-by: Matthew Pickering <matthewtpickering@gmail.com> Co-authored-by: Fendor <fendor@posteo.de> - - - - - 6ad6c93c by fendor at 2026-05-08T10:31:08+02:00 Fix regression T27202: `:load` and `:add` work in GHCi To fix the regression there are conceptually two major things that we fix: * We don't remove the `importDirs` from `interactive-session` * When `:add`ing a module, we don't try to find them via PackageImports * The PackageImport is wrong as we can't know the package-name at this stage in ghc/UI.hs What does it mean to not remove the `importDirs` from `interactive-session`? It means that, given some initial `DynFlags`, we will use those `importDirs` in `interactive-session`. The initial `DynFlags`, however, depend on how you initialise the GHC session. For a simple session, initialised by ghc -isrc -this-unit-id main It is simple, just use the `DynFlags` given on the cli. Thus, `main` and `interactive-session` will have the same `DynFlags`, except for the `homeUnitId` and `interactive-session` depends on `main` by construction of the GHCi session. What about a multiple home unit session, though? ghc -unit @unit1 -unit @unit2 What are the `DynFlags` in this cli invocation? It shouldn't be either `@unti1` nor `@unit2`, as the order shouldn't matter or any other implicit condition. For consistency, we decide that the initial `DynFlags` are the top `DynFlags` on the cli, ignoring `-unit` flags. Thus, in this example, there are no `importsDirs` regardless of what we might find in `@unit1` and `@unit2`. But in this invocation: ghc -isrc -unit @unit1 -unit @unit2 The `interactive-session` will have the `importsDirs` `src`. Note, `-isrc` will be inherited in `@unit1` and `@unit2`, so you need to explicitly use `-i` to clear the `importsDirs`, in order to avoid accidentally adding `src` as an import directory to all other home units. This fix has been made possible by the improvements introduced in !15888, which avoids ambiguity when a home unit shares the `importsDirs` with the `interactive-session`, on top of being much faster for multiple home units. Adds regression tests for T27202 for `:load`ing and `:add`ing modules that are located in import directories. - - - - - 49 changed files: - + changelog.d/T27202 - compiler/GHC/Unit/Finder.hs - compiler/GHC/Unit/Module/Graph.hs - ghc/GHCi/UI.hs - ghc/Main.hs - testsuite/tests/driver/fat-iface/fat014.stdout - testsuite/tests/ghci/prog018/prog018.stdout - testsuite/tests/ghci/prog020/Makefile - testsuite/tests/ghci/prog020/all.T - testsuite/tests/ghci/prog020/ghci.prog020.script → testsuite/tests/ghci/prog020/ghci.prog020a.script - testsuite/tests/ghci/prog020/ghci.prog020.stderr → testsuite/tests/ghci/prog020/ghci.prog020a.stderr - testsuite/tests/ghci/prog020/ghci.prog020.stdout → testsuite/tests/ghci/prog020/ghci.prog020a.stdout - + testsuite/tests/ghci/prog020/ghci.prog020b.script - + testsuite/tests/ghci/prog020/ghci.prog020b.stderr - + testsuite/tests/ghci/prog020/ghci.prog020b.stdout - + testsuite/tests/ghci/prog023/Makefile - + testsuite/tests/ghci/prog023/all.T - + testsuite/tests/ghci/prog023/prog023a.script - + testsuite/tests/ghci/prog023/prog023a.stdout - + testsuite/tests/ghci/prog023/prog023b.script - + testsuite/tests/ghci/prog023/prog023b.stdout - + testsuite/tests/ghci/prog023/src/A.hs - + testsuite/tests/ghci/prog024/Makefile - + testsuite/tests/ghci/prog024/all.T - + testsuite/tests/ghci/prog024/prog024a.script - + testsuite/tests/ghci/prog024/prog024a.stdout - + testsuite/tests/ghci/prog024/prog024b.script - + testsuite/tests/ghci/prog024/prog024b.stdout - + testsuite/tests/ghci/prog024/prog024c.script - + testsuite/tests/ghci/prog024/prog024c.stderr - + testsuite/tests/ghci/prog024/prog024c.stdout - + testsuite/tests/ghci/prog024/prog024d.script - + testsuite/tests/ghci/prog024/prog024d.stderr - + testsuite/tests/ghci/prog024/prog024d.stdout - + testsuite/tests/ghci/prog024/prog024e.script - + testsuite/tests/ghci/prog024/prog024e.stdout - + testsuite/tests/ghci/prog024/prog024f.script - + testsuite/tests/ghci/prog024/prog024f.stdout - + testsuite/tests/ghci/prog024/src/A.hs - + testsuite/tests/ghci/prog024/src/B.hs - testsuite/tests/ghci/scripts/T13997.stdout - testsuite/tests/ghci/scripts/T1914.stdout - testsuite/tests/ghci/scripts/T20217.stdout - testsuite/tests/ghci/scripts/T8042.stdout - testsuite/tests/ghci/scripts/T8042recomp.stdout - testsuite/tests/ghci/should_run/T10920.stderr - testsuite/tests/perf/compiler/Makefile - testsuite/tests/perf/compiler/all.T - testsuite/tests/perf/compiler/genMultiComp.py The diff was not included because it is too large. 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