Re: Weird "missing hi file" problem with a serializable Core patch

By the time we do CorePrep, the hi files should already have been written.

I don't think so. When we generate real code we write the interface after the backend has generated the output object. See Note [Writing interface files] in GHC.Driver.Main Cheers, Sylvain On 17/09/2020 12:17, Cheng Shao wrote:

Hi Ben,

The -ddump-if-trace output is attached here. The error is produced when compiling GHC.Types in ghc-prim.

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Note that interface files are written after the Core pipeline is run. Sorry for the confusion, I didn't mean the Core simplifier pipeline. I mean the "Core -> Iface -> Core" roundtrip I tried to perform using the output of CorePrep. By the time we do CorePrep, the hi files should already have been written.

On Wed, Sep 16, 2020 at 11:48 PM Ben Gamari wrote:

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Cheng Shao writes:

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Hi all,

Following a short chat in #ghc last week, I did a first attempt of reusing existing Iface logic to implement serialization for codegen-related Core. The implementation is included in the attached patch (~100 loc). As a quick and dirty validation of whether it works, I also modified the codegen pipeline logic to do a roundtrip: after CorePrep, the Core bits are converted to Iface, then we immediately convert it back and use it for later compiling.

With the patch applied, stage-1 GHC would produce a "missing hi file" error like:

: Bad interface file: _build/stage1/libraries/ghc-prim/build/GHC/Types.hi _build/stage1/libraries/ghc-prim/build/GHC/Types.hi: openBinaryFile: does not exist (No such file or directory)

Hi Cheng,

Which module is being compiled when this error is produced? Could you provide -ddump-if-trace output for the failing compilation?

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The error surprises me, since by the time we perform the Core-to-Core roundtrip, the .hi file should already have been written to disk. Is there anything obviously wrong with the implementation? I'd appreciate any pointers or further questions, thanks a lot!

Note that interface files are written after the Core pipeline is run.

Cheers,

- Ben

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