Compiler pipeline

The compiler is a sequence of components. Each component controls one domain. No two components share a domain.

Stages

Stage	Component	Input	Output
Preprocess	aihc-cpp	Haskell source with CPP directives	Haskell source
Parse	aihc-parser	Haskell source	Surface syntax tree
Resolve	aihc-resolve	Parsed surface modules	The same tree with binding resolution, use resolution, exports, and resolve diagnostics
Type check	aihc-tc	Resolved surface tree	The same tree with types, kinds, evidence, and type diagnostics
Desugar	aihc FC modules	Type-checked surface tree	System FC program and System FC diagnostics
Lower	aihc GRIN modules	System FC program	Strict GRIN program and GRIN diagnostics
Generate	aihc Lir modules and back ends	GRIN program	Lir, then native code, LLVM IR, or WebAssembly

aihc-cpp and aihc-parser live in their own repositories. The other components live in the aihc repository.

Boundaries

Each component does the work of its own domain only.

• aihc-resolve does name resolution only.
• aihc-tc does Haskell type checks only. It does not do name resolution.
• The FC modules desugar to System FC. They do not do Haskell type checks. They can lint types that are already in System FC.
• The GRIN modules do closure conversion, run-time operations, and GRIN transformations. They keep the semantics that System FC gives. They can remove types and coercions. They do not reconstruct Haskell type information.

If a downstream component needs an upstream fact, change the upstream component. Then, use its output in the downstream component.

Intermediate languages

Language	Purpose
System FC	The typed core language. The optimizer works on this language.
GRIN	A strict, first-order language with explicit heap operations.
Lir	A low-level language close to machine code. The back ends consume it.

Use --keep-core, --keep-grin, and --keep-lir to inspect the intermediate programs of a build. See Debug options.