M2compiler-V3/docs/summary_two-phase-lower1.md

Lower phase — slice 1 (relations, booleans, short-circuit)

Branch ast-stage-c. Suite 181/181; self-hosting fixpoint OK (3,104,868 bytes; L0 was 3,090,949). Plan: docs/plan-lower.md.

What landed

Lower now covers, in addition to L0:

• Relations = # < <= > >= on scalar operands → QbeGen.Cmp(op, …) (AST.Op* mapped to SymTab.Op*), result BOOLEAN.
• NOT / ~ → QbeGen.NotQ.
• Short-circuit AND (Term) and OR (SimExpr): the walk brackets the RHS with DelayBegin/DelayEnd, then emits the same merge block (Slot4, NewLabel ×3, Jnz, EmitLabel, DelayFlush, StoreW, Jmp, LoadW, CopyOp) as the grammar — so the temp/label counters line up and the image is byte-identical.
• TRUE/FALSE constants in LowerDesign.
• CanLower accepts scalar classes INT/BOOLEAN/CHAR/UCHAR/ENUM.

Verified

gen_ssa/TLower1L.ssa (a program with (x<y) AND (y>0) and NOT (x=y) OR (x<=y)) is byte-identical to the legacy image (lower_ok t_lower1.mod).

Next

L2: control flow (IF/WHILE/REPEAT/LOOP/FOR/RETURN/HALT) — statements, so CanBody grows and LowerUnit walks statement nodes.