Investigate bytecode serialization

[pepeiborra]

Bytecode itself can be serialised. ResolvedBCO has a Binary instance although that might be too late in the compilation pipeline for you. Specifically the compilation pipeline for bytecode is,

CoreProgram                             \
  ⇓  GHC.CoreToByteCode.schemeTopBind    |
ProtoBCO                                 | GHC.CoreToByteCode.byteCodeGen
  ⇓  GHC.ByteCode.Asm.assembleBCOs       |
CompiledByteCode                        /
  ⇓  GHC.ByteCode.Linker.linkBCO
ResolvedBCO
  ⇓  GHCi.CreateBCO.createBCOs
HValueRef

I haven't thought hard about where the right place in this pipeline would be to persist bytecode.

Originally posted by @bgamari in https://github.com/haskell/ghcide/issues/854#issuecomment-705790631

[pepeiborra]

/cc @josefs

[pepeiborra]

Relevant: it should be possible to serialize core to iface files, taking hints from ezyang/ghc@13615ca. The idea here is that we can preserve the Core produced by the frontend in the interface file such that we can later easily produce restart the compilation pipeline to produce bytecode (which should be quick).

[josefs]

Note that ResolvedBCO contains pointers into memory, so to serialize it we would have to unresolve it. I don't know what the Binary instance is for but it sounds very easy to misuse.

[pepeiborra]

closing as this is a non-actionable documentation ticket