Serialize Core #2813
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Serialize Core #2813
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Some benchmarks here: https://well-typed.com/blog/2022/04/hls-performance/ (this is the |
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I've added the on demand bytecode generation commit to this as well as its a major simplification of the patch, and deletes a bunch of code added by the first commit, along with fixing a few bugs. If required I can split it into multiple PRs but I think it is better to review all the changes at once. See the commit message for a description of the changes. |
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Add a `.hi.core` file format to which we serialize out compiled core after generating it. This core is then read back in on subsequent runs and compiled to bytecode. This greatly speeds up startup times when we need compilation, as we can simply read bytecode off the disk instead of having to recompile a lot of modules This is based off Fat Interface files in GHC: https://gitlab.haskell.org/ghc/ghc/-/merge_requests/7502 - Also add --verify-core-file to do roundtrip testing of core-files - Use closed world assumption for core and .hie files
Adds a new rule `GetLinkable` which is called on demand by hscCompileCoreExprHook whenever a linkable is required for a splice. Adds a MonadUnliftIO instance for Action to faciliate the above We write Core Files whenever a linkable could potentially be required for a file (i.e it is in the transitive closure of a module that uses TH/compile time code execution) However, we only generate byte/object code when such a linkable is really required by a splice (i.e. the module is in the transitive closure of any symbol called from a splice). No linkables are stored in `HiFileResult`. If a linkable is required, then it must be obtained via a call to `GetLinkable`. Also use hashes to do fine grained recompilation checking for TH instead of mod times. This simplifies recompilation checking quite a bit.
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| -- | Find the runtime dependencies by looking at the annotations | ||
| -- serialized in the iface | ||
| parseRuntimeDeps :: [ModIfaceAnnotation] -> ModuleEnv UTCTime | ||
| parseRuntimeDeps :: [ModIfaceAnnotation] -> ModuleEnv BS.ByteString |
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This now collects hashes instead of timestamps, right?
Maybe worth an extended comment.
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I've added a line here and also a bit in Note [Recompilation avoidance in the presence of TH]
No, but there could be perf regressions in projects that use TH and unboxed things on GHC <9.2 (which forces us to use object code), as now we have the overhead of serializing the core file in addition to writing out object code. I don't think this is worth any added complexity to fix. For non TH use cases, I don't think any of the new code paths introduced by this patch should be invoked. |
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lsp-types benchmarks from CI show a nice reduction in number of rebuilds: |
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Is this ultimately going to get into GHC? Or are we going to be on the hook for maintaining this indefinitely? |
Fat interface files are likely to be in GHC 9.6 |
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Serialize core to core files
Add a
.hi.corefile format to which we serialize out compiled core after generating it.This core is then read back in on subsequent runs and compiled to bytecode.
This greatly speeds up startup times when we need compilation, as we can simply read bytecode
off the disk instead of having to recompile a lot of modules
This is based off Fat Interface files in GHC: https://gitlab.haskell.org/ghc/ghc/-/merge_requests/7502