# Lower phase — slice 2 (control flow)

Branch `ast-stage-c`.  Suite **182/182**; self-hosting fixpoint **OK**
(**3,123,487 bytes**; L1 was 3,104,868).  Plan: `docs/plan-lower.md`.

## What landed

`LowerStmt` (sequence iteration + statement dispatch merged, so **no
`FORWARD`** — gm2's whole-program pass rejects it) now emits:

- `IF`/`ELSIF`/`ELSE` — flattening the AST's nested-`NkIf` chain into the
  grammar's single shared `lEnd`, threading `lElse`, exactly as the
  grammar does.
- `WHILE`, `REPEAT`, `LOOP` + `EXIT` (via `PushLoop`/`TopLoop`).
- `FOR` **without `BY`** (`cslew`/`add` loop), with the same
  `StoreVar`/`LoadVar`/`Op3` order.
- `HALT`.

`CanStmt` mirrors the same shapes; `FOR` with a `BY` clause stays out of
the subset (needs constant evaluation).

## Finding

`FORWARD` declarations in `Lower.mod` broke gm2's whole-program pass
("too many errors in pass 3") even though `-c` compiled the module.
Merging the mutually-recursive bodies (`CanBody`↔`CanStat`,
`LowerBody`↔`LowerIf`) into single dispatching procedures removed it.

## Verified

`gen_ssa/TLower2L.ssa` — a program with `IF`/`ELSIF`/`ELSE`, `WHILE`,
`REPEAT`, `LOOP`/`EXIT`, `FOR` and a conditional `HALT` — is
**byte-identical** to the legacy image (`lower_ok t_lower2.mod`).

## Next

L3: procedures/functions (headers, params, locals, `RETURN`, calls) —
`BeginFunc`/`FuncParam`/`EndFuncHeader`/`EndFunc`/`CallBegin`…  This is
where `LowerUnit` starts walking declaration bodies, not just the program
body.