t27c silicon: wire bitstream_reuse.t27 -- blocked by the no-growth rule for hand-written code #8295

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1. gHashTag commented on Oct 9, 2026

   

   gHashTag

   on Oct 9, 2026

   OwnerAuthor

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   The 32-line glue, built and compiled locally against master 1ab051f. Apply with git apply once the way forward is chosen:

   diff --git a/bootstrap/src/main.rs b/bootstrap/src/main.rs
   index 1bf18d68d..0ba14acaf 100644
   --- a/bootstrap/src/main.rs
   +++ b/bootstrap/src/main.rs
   @@ -117,6 +117,10 @@ mod silicon_queue;
    #[path = "../gen/rust/verified/bench_agent.rs"]
    #[allow(dead_code, unused_parens, unused_mut, unused_assignments, unused_variables, non_snake_case, non_upper_case_globals, clippy::all)]
    mod bench_agent;
   +// specs/verified/bitstream_reuse.t27 (#8095): when `t27c silicon` loads a bitstream it built before.
   +#[path = "../gen/rust/verified/bitstream_reuse.rs"]
   +#[allow(dead_code, unused_parens, unused_mut, unused_assignments, unused_variables, non_snake_case, non_upper_case_globals, clippy::all)]
   +mod bitstream_reuse;
    mod phi_f64_literals;
    mod weight_bram;
    mod bitnet_pipeline;
   diff --git a/bootstrap/src/service.rs b/bootstrap/src/service.rs
   index bc5887859..beada1e3f 100644
   --- a/bootstrap/src/service.rs
   +++ b/bootstrap/src/service.rs
   @@ -4246,6 +4246,25 @@ pub fn run_silicon(
        let mut derived_chain: Option<u32> = None;
    
        let mut seen_sites: Vec<u32> = Vec::new();
   +    // #8095: load a bitstream built before from the same inputs by the same tools (specs/verified/bitstream_reuse.t27).
   +    use crate::bitstream_reuse as br;
   +    let bit_path = tmp.join(format!("{stem}.bit"));
   +    let tools = [chipdb.clone(), pnr.clone(), xr.join("utils/fasm2frames.py"), PathBuf::from(run(Command::new("which").arg("xc7frames2bit")).1.trim())];
   +    let xdc_in = tops.last().map(|t| Path::new(t).with_extension("xdc")).filter(|p| p.exists());
   +    let mut key_in = format!("{}|{}|{pnr_seed:?}|{}|{}", run(Command::new("yosys").arg("-V")).1.trim(), run(Command::new("git").arg("-C").arg(&db).args(["rev-parse", "HEAD"])).1.trim(), br::BIT_RECIPE, env!("CARGO_PKG_VERSION"));
   +    for f in sources.iter().map(PathBuf::from).chain(xdc_in).chain(tools) { key_in += &format!("|{}", crate::sha256_hex(&std::fs::read(&f).unwrap_or_default())); }
   +    let cache = PathBuf::from(std::env::var_os("HOME").unwrap_or_default()).join(".cache/t27/bitstreams").join(crate::sha256_hex(key_in.as_bytes()));
   +    let (cached_bit, cached_chain) = (std::fs::read(cache.join("design.bit")).ok(), std::fs::read_to_string(cache.join("chain")).ok());
   +    let intact = cached_bit.as_deref().map(crate::sha256_hex) == std::fs::read_to_string(cache.join("bit.sha256")).ok();
   +    let decision = br::bit_decision(std::env::var_os("T27_SILICON_REBUILD").is_some(), cached_bit.is_some(), cached_chain.is_some(), intact);
   +    'build: {
   +    if decision == br::BIT_REUSE {
   +        std::fs::write(&bit_path, cached_bit.as_deref().unwrap_or_default())?;
   +        derived_chain = cached_chain.and_then(|c| c.trim().parse().ok());
   +        let note = format!("same inputs, same tools: {} (T27_SILICON_REBUILD=1 rebuilds)", cache.display());
   +        stages.push(Stage { name: "bitstream REUSED", secs: 0.0, code: Some(0), artefact: file_len(&bit_path), note });
   +        break 'build;
   +    }
        for attempt in 0..6u32 {
            let t = Instant::now();
            let chparam = match chain_override {
   @@ -4609,7 +4628,6 @@ pub fn run_silicon(
        });
    
        // ---- bitstream, ONLY from non-empty frames ----
   -    let bit_path = tmp.join(format!("{stem}.bit"));
        let frames_ok = file_len(&frames_path).map(|(_, n)| n > 0).unwrap_or(false);
        let t = Instant::now();
        let c = if frames_ok {
   @@ -4634,12 +4652,21 @@ pub fn run_silicon(
                "SKIPPED: empty frames would still yield a 9.7 MB .bit (T169)".into()
            },
        });
   +    }
    
        let build_ok = print_table(&stages);
        if !build_ok {
            println!("FAIL -- the build did not complete. Nothing was loaded.");
            std::process::exit(1);
        }
   +    if br::may_store(decision, build_ok, stages.iter().any(|s| s.name == "BSCAN chain == site" && s.ok())) {
   +        let bit = std::fs::read(&bit_path)?;
   +        std::fs::create_dir_all(&cache)?;
   +        std::fs::write(cache.join("design.bit"), &bit)?;
   +        std::fs::write(cache.join("chain"), derived_chain.map(|c| c.to_string()).unwrap_or_default())?;
   +        std::fs::write(cache.join("bit.sha256"), crate::sha256_hex(&bit))?; // last: a torn entry reads CORRUPT
   +        println!("  bitstream stored for reuse: {}", cache.display());
   +    }
    
        if skip_hardware {
            println!("PASS (build only) -- rerun without --skip-hardware to load and read.");
2. tri-claw

   added

   queen-shaped

   on Oct 9, 2026
3. gHashTag

   added 4 commits that reference this issue on Oct 9, 2026

   t27c silicon reuses its bitstream; math_compare's Pell code moves to …

   ...

   This issue will close once commit 9fe8ab0 is merged into the 'master' branch.

   9fe8ab0

   Pay for the bitstream-reuse glue by deleting a ported script, not mat…

   ...

   This issue will close once commit 39e70f3 is merged into the 'master' branch.

   39e70f3

   Merge origin/master into claude/bitstream-reuse-wire (Closes #8295)

   This issue will close once commit 0d57372 is merged into the 'master' branch.

   0d57372

   bitstream reuse: the venv in the key, and every 10th hit is audited (C…

   ...

   This issue will close once commit 47ef800 is merged into the 'master' branch.

   47ef800
4. gHashTag

   closed this as completedin #8296on Oct 9, 2026
5. gHashTag

   added 2 commits that reference this issue on Oct 9, 2026

   t27c silicon reuses its bitstream; a ported script pays for the glue (C…

   ...

   This issue will close once commit 2ba048e is merged into the 'master' branch.

   2ba048e

   t27b: the node scans of lower.rs move to specs/tri/t27b/ast_scan.t27 (C…

   ...

   This issue will close once commit e4338f4 is merged into the 'master' branch.

   e4338f4