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1. matthewjasper

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   major-changeA proposal to make a major change to rustcA proposal to make a major change to rustc

   on Jul 4, 2020
2. rustbot commented on Jul 4, 2020

   

   rustbot

   on Jul 4, 2020

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   This issue is not meant to be used for technical discussion. There is a Zulip stream for that. Use this issue to leave procedural comments, such as volunteering to review, indicating that you second the proposal (or third, etc), or raising a concern that you would like to be addressed.
3. rustbot

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   on Jul 4, 2020
4. oli-obk commented on Jul 6, 2020

   

   oli-obk

   on Jul 6, 2020

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5. rustbot

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   final-comment-periodThe FCP has started, most (if not all) team members are in agreementThe FCP has started, most (if not all) team members are in agreement

   on Jul 6, 2020
6. spastorino

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   on Jul 8, 2020
7. matthewjasper

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   and removed

   final-comment-periodThe FCP has started, most (if not all) team members are in agreementThe FCP has started, most (if not all) team members are in agreement

   finished-final-comment-periodThe FCP has finished, action upon the disposition label needs to be takenThe FCP has finished, action upon the disposition label needs to be taken

   on Jul 20, 2020
8. matthewjasper

   closed this as completedon Jul 20, 2020
9. spastorino

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   on Jul 22, 2020
10. extf33 commented on Sep 5, 2023

    

    extf33

    on Sep 5, 2023

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    @matthewjasper

    Hello, I came across this issue while looking for a way to serialize/deserialize the MIR Body.
    I have two questions.

    1. Where in the rustc code is the decode() method, which is associated with the MIR Body (as mentioned below), used?

       • https://github.com/rust-lang/rust/blob/04374cd74264b9d3b7d2d3df08ae38df8af4d020/compiler/rustc_middle/src/ty/codec.rs#L420
       • https://github.com/rust-lang/rust/blob/04374cd74264b9d3b7d2d3df08ae38df8af4d020/compiler/rustc_middle/src/ty/codec.rs#L266-L275
       • https://github.com/rust-lang/rust/blob/04374cd74264b9d3b7d2d3df08ae38df8af4d020/compiler/rustc_middle/src/query/on_disk_cache.rs#L787-L794

    2. Is it possible to serialize the MIR Body to a file (during a MIR pass) and then load it back by deserializing it?
       If so, how should the code be written?
       I thought of a logic like the one below.

       use crate::MirPass;
       use rustc_middle::mir::*;
       use rustc_middle::ty::TyCtxt;
       use rustc_serialize::opaque::{FileEncoder, MemDecoder};
       use rustc_serialize::{Decodable, Encodable};
       use std::fs;
       
       pub struct MirSerDe;
       
       impl<'tcx> MirPass<'tcx> for MirSerDe {
           fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
               let tmpfile = tempfile::NamedTempFile::new().unwrap();
               let tmpfile = tmpfile.path();
       
               // Serialize
               let mut encoder = FileEncoder::new(&tmpfile).unwrap();
               Encodable::encode(body, &mut encoder);
               encoder.finish().unwrap();
       
               // Deserialize
               let data = fs::read(&tmpfile).unwrap();
               let mut decoder = MemDecoder::new(&data[..], 0);
               let decoded = Decodable::decode(&mut decoder);
       
               assert_eq!(body, decoded);
           }
       }
11. matthewjasper commented on Sep 5, 2023

    

    matthewjasper

    on Sep 5, 2023

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    Zulip (or a new issue if you have a suitable repository for it) might be a better place to discuss this than this Github issue, but to answer your questions:

    1. There is one decode call here:
       https://github.com/rust-lang/rust/blob/af488be5f82b5e1010f7b52bc4fcda697793950d/compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs#L88
       and another here:
       https://github.com/rust-lang/rust/blob/b402182d4e0b00254c1afd0620547e2ee42ae336/compiler/rustc_middle/src/query/on_disk_cache.rs#L532
    2. I don't think we have support for this. You'll need a decoder that implements TyDecoder and encoder that implements TyEncoder and neither of the current types used for this would be suitable. You could try implementing your own. What do you actually want to do here? Why can't you keep the MIR in memory