Design model

Platform spec article

Design model

Back to Lowering contract ◎ Open feature in platform map

Spec standingStandard

Owner

Piotr Mikstacki pmikstacki@cybernomad.it

Submitter

Piotr Mikstacki pmikstacki@cybernomad.it

Current document

ADRs (3)

1. 0001-feature-hub-authority Feature hub authority Accepted

   This feature hub owns normative MUST/SHOULD contract text for Lowering contract.

   Context

   Sibling articles under this feature previously restated requirements in inconsistent forms.

   Decision

   This feature hub owns normative MUST/SHOULD contract text. Sibling articles must not redefine hub requirements and should link here for authority.

   Consequences

   Contract changes start on the hub or in linked ADRs, then propagate to articles and implementation anchors.

   Verification anchors

   • site/website/src/content/docs/platform-spec/compiler/codegen-and-ir/lowering-contract/index.mdx
   • article bundle under the same feature directory.

   Open full ADR page

2. 0002-spec-over-implementation-notes Specification over implementation notes Accepted

   Platform-spec text supersedes informal crate comments for Lowering contract.

   Context

   Implementation crates accumulated informal notes that diverged from published contracts.

   Decision

   Normative platform-spec prose and ADRs under this feature supersede informal comments in implementation crates until explicitly migrated into spec text.

   Consequences

   Engineers file spec/ADR updates when behavior changes; crate comments are non-authoritative for conformance arguments.

   Verification anchors

   • compiler/crates/beskid_codegen
   • compiler/crates/beskid_codegen
   • compiler/crates/beskid_engine/src/jit_module.rs

   Open full ADR page

3. 0003-cranelift-lowering-single-entry Cranelift lowering via lower_source Accepted

   Lowering was split across experimental paths.

   Context

   Lowering was split across experimental paths.

   Decision

   beskid_codegen::lower_source is the single lowering entry producing CodegenArtifact consumed by JitModule.

   Consequences

   Experimental IR dumps must not bypass this entry in release builds.

   Verification anchors

   • compiler/crates/beskid_codegen
   • compiler/crates/beskid_engine/src/jit_module.rs.

   Open full ADR page

Articles

• Contracts and edge cases Normative guarantees and known edge cases for `Lowering contract`. article Standard
• Design model Conceptual model for `Lowering contract` and its subsystem boundaries. article Standard
• Examples Practical examples that demonstrate `Lowering contract` behavior. article Standard
• FAQ and troubleshooting Common questions and debugging guidance for `Lowering contract`. article Standard
• Flow and algorithm End-to-end control flow and major algorithmic steps for `Lowering contract`. article Standard
• Verification and traceability How `Lowering contract` requirements map to tests and implementation anchors. article Standard

History

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Completeness

OKfeature · 2 SpecSection(s) · 1 H2 heading(s)

Section id	Required	Found
what-this-feature-specifies	yes	yes
implementation-anchors	yes	yes

Full tree: run pnpm verify:platform-spec-layout (writes src/generated/platform-spec-layout-report.json).

Related spec docs

• Area
  Codegen and IR

  Parent area

• Feature
  Stage ordering and artifacts

  Pipeline ordering that lowering must follow

• Domain
  Execution

  Lowered artifacts are consumed by execution backends

• Feature
  Lowering contract

  Parent feature hub

Lowering boundary

Lowering is the last semantic gate before any backend runs. Inputs are a post-merge program snapshot (HIR + ModuleIndex + resolved types); output is an immutable CodegenArtifact containing Cranelift modules, data descriptors, extern imports, and debug metadata.

Backends must not re-run parse, mod host, or semantic rules on the artifact.

flowchart TB
  subgraph analysis [beskid_analysis]
    hir[HIR + ModuleIndex]
  end
  subgraph codegen [beskid_codegen]
    lower[lower_program / lower_source]
    art[CodegenArtifact]
  end
  subgraph backends [beskid_engine]
    jit[JitModule]
    aot[AOT object emit]
  end
  hir --> lower --> art
  art --> jit
  art --> aot

Artifact contents

Slice	Role
CLIF modules	Per-compilation-unit functions and globals
Builtin imports	declare_builtin_imports from BUILTIN_SPECS
ExternImport rows	User contract symbols for link step
Type descriptors	GC layout + array/string shapes for alloc

Invariants

• Lowering runs only when syntax_generation_id matches the merged tree used by semantic rules (stage ordering).
• Panic/abort paths use AbiReturnKind::Never imports so unreachable blocks are correct.
• JIT and AOT consume the same artifact type; divergence happens only after CodegenArtifact is sealed.

Code anchors

• beskid_codegen::lower_source in compiler/crates/beskid_codegen
• CodegenArtifact construction in compiler/crates/beskid_codegen
• JitModule in compiler/crates/beskid_engine/src/jit_module.rs
• Runtime smoke: compiler/crates/beskid_tests/src/runtime/jit.rs