Crate rucc_lower 

The typed AST to IR walk: SSA construction and ABI-directed lowering.

Design: spec/08-ir.md. Layer rank 9, see spec/18-package-layout.md.

What is here so far

lower, the walk from the typed tree to the IR, and Ssa, the SSA construction by Braun’s algorithm that it drives: the thing that lets a local variable become a value without ever having been a stack slot.

The walk is in four files, one per level of the thing it walks. unit is the translation unit: objects with static storage, their images, and the functions. body is one function: the statements, the control flow, and the expressions. repr is the answer to what a C type is once the IR is the one asking, and abi is the answer to how a call travels, which is the target’s rather than C’s.

What it does not build yet is reported rather than mislowered. A statement expression, va_arg, a variable length array, a computed goto and inline asm each become a diagnostic, so a program that uses one fails to compile rather than compiling into something that is not what it says.

Every crate in the workspace is published, and publishing implies a promise. This one is tier 3: its Rust API is explicitly unstable and will change without a major version bump. Depend on the rucc binary’s behaviour, not on this.

Structs

Context

Everything the walk reads, which is a checked translation unit and the target it is for.

Lowered

What the walk produced.

Ssa

The state of an SSA construction over one function.

Var

A variable, which is somewhere in the source that can be written more than once.

Constants

MILESTONE

The milestone in spec/17-milestones.md that fills this crate in.

Functions

lower

Walks a checked translation unit and builds the IR for it.