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gemmini-mlir

The out-of-tree target home for gemmini (Berkeley systolic-array accelerator, chipyard/generators/gemmini), modeled by Merlin as a tensor_resident target.

This repo is the single per-target home under the <target>-mlir convention (gemmini-mlir, rvv-mlir, atlas-mlir, radiance-mlir, …). Merlin hooks up to it natively: it fetches this repo into its generated-target home (out/build/generated/gemmini/) and discovers the target with zero extra configuration — the reference backend below self-registers via the contract's plugin.backend.

Layout

  • contracts/target_contract.yaml — the Merlin capability manifest (intent + the ABI encoding surface RTL facts cannot ground) and the plugin.backend: backend declaration.
  • contracts/residual.yaml — the human-authored residual the capability deriver reproduces.
  • backend/ — the reference backend, a Python package evicted from Merlin core's runtime/backends/. Importing it self-registers the gemmini backend in Merlin's registry:
    • backend/gemmini.py — compile + run on the oracle, parse output, gate.
    • backend/gemmini_codegen.py — command buffer → bare-metal C via low-level libgemmini intrinsics.
    • backend/gemmini_codegen_mlir.py — command buffer → LLVM-dialect RoCC MLIR (.insn on stock LLVM).
    • backend/__init__.py — registers under the package name and exposes the codegen submodules.
  • evidence_concepts.yaml — per-target concept vocabulary for the evidence pass.
  • AGENT.md — the target's agent-facing brief.

The reference backend imports Merlin internals (merlin.runtime.*); it is loaded by Merlin's out-of-tree backend loader (merlin.runtime.backends.base) by file path, so it is not a standalone distribution — it travels with an installed Merlin.

Branch model — one branch per champion experiment

  • main is the target base: the contract + the reference backend + metadata. This is what Merlin fetches by default, and what every champion experiment forks from.
  • Each champion experiment (a certified/hand codegen package) is its own branch, forked from main so it inherits the reference backend, and adding its buildable codegen payload (payload/, .merlin/ provenance, CMake, tools/<target>-opt/). Example: baseline carries the hand_v0 codegen champion (tagged v0-hand_v0).

The history of each branch is that champion's promotion trail; the tags mark promoted versions.

How Merlin fetches this repo

merlin-target-fetch gemmini                 # fetch main (base + reference backend)
merlin-target-fetch gemmini --champion baseline   # fetch a champion-experiment branch

This clones the repo into out/build/generated/gemmini/, where Merlin's target registry resolves it with zero env and loads the plugin.backend.