M2compiler-V3/compiler/src/Lower.mod

IMPLEMENTATION MODULE Lower;
(* Scalar/boolean/control-flow walk (L0-L2): see Lower.def and
   docs/plan-lower.md.  The mutually recursive walkers are declared in
   Lower.def (gm2's link pass rejects FORWARD, V3 has no whole-module
   pass, so a definition-visible declaration breaks the cycle). *)

IMPORT AST, SymTab, QbeGen;

(* ---------------- self-contained symbol tables (zero SymTab surface) ----
   Flat arrays only, no ARRAY OF RECORD: a record's array field loses its
   length word in static array data, and V3 miscompiles that when the
   field is passed as an open array (docs/wip/nested-array-field-bug.mod).
   Names live in flat CHAR arrays indexed manually at slot * 64. *)

CONST
  MaxSym  = 8192;   (* whole-session: >4096 vars/consts/params *)
  MaxName = 63;
  MaxProc = 2048;   (* whole-session: the compiler declares >1200 procs *)
  MaxImp  = 512;    (* per-unit imports *)
  MaxPar  = 32;
  HashSize = 16384; (* power of two > MaxSym, MaxProc: open addressing *)
  MaxCFold = 256;   (* named compile-time set constants per session *)
  MaxCFoldW = 16;   (* mask words (512 bits); wider sets are a 230 *)

VAR
  symName  : ARRAY [0 .. MaxSym * 64 - 1] OF CHAR;
  symKind  : ARRAY [0 .. MaxSym - 1] OF INTEGER;
  symTy    : ARRAY [0 .. MaxSym - 1] OF SymTab.TypeIndex;
  symVal   : ARRAY [0 .. MaxSym * 64 - 1] OF CHAR;  (* const value, flat *)
  nSyms    : CARDINAL;
  procName : ARRAY [0 .. MaxProc * 64 - 1] OF CHAR;
  procUid  : ARRAY [0 .. MaxProc - 1] OF CARDINAL;
  procRes  : ARRAY [0 .. MaxProc - 1] OF SymTab.TypeIndex;
  procDep  : ARRAY [0 .. MaxProc - 1] OF CARDINAL;
  procExt  : ARRAY [0 .. MaxProc - 1] OF BOOLEAN;
  procVa   : ARRAY [0 .. MaxProc - 1] OF BOOLEAN;  (* C varargs *)
  procNpar : ARRAY [0 .. MaxProc - 1] OF CARDINAL;
  parTy    : ARRAY [0 .. MaxProc * MaxPar - 1] OF SymTab.TypeIndex;
  parVar   : ARRAY [0 .. MaxProc * MaxPar - 1] OF BOOLEAN;
  parName  : ARRAY [0 .. MaxProc * MaxPar * 64 - 1] OF CHAR;
  nProcs   : CARDINAL;
  (* Open-addressing indexes into symName/procName: entry = index+1,
     0 = empty.  A whole-session linear scan is too slow (thousands of
     lookups over thousands of entries), so FindSym/FindProc hash. *)
  symHash  : ARRAY [0 .. HashSize - 1] OF INTEGER;
  procHash : ARRAY [0 .. HashSize - 1] OF INTEGER;
  (* Per-unit imports (FROM M IMPORT P): the exact proc entry for a
     name, so an unqualified call resolves to the imported proc even
     when another module declares the same name.  Reset each unit. *)
  impProc  : ARRAY [0 .. MaxImp - 1] OF INTEGER;
  impName  : ARRAY [0 .. MaxImp * 64 - 1] OF CHAR;
  nImps    : CARDINAL;
  (* Record-array globals too large to expand inline: their template is
     emitted with their data and their elements are initialised by a
     run-time loop (QbeGen.InitRecArray) in the unit's init.  Per unit. *)
  nCountInit : CARDINAL;
  countArr : ARRAY [0 .. 63] OF SymTab.Name;
  countTyp : ARRAY [0 .. 63] OF SymTab.TypeIndex;
  (* GOTO/labels: user label name -> QbeGen label, per procedure. *)
  nUserLab : CARDINAL;
  userLabNm : ARRAY [0 .. 255 * 64 - 1] OF CHAR;
  userLabQ : ARRAY [0 .. 255] OF QbeGen.QVal;
  (* Scoping: each symbol records the procedure that owns it (-1 =
     module level); FindSym searches the emitted procedure's chain
     innermost-first so common names (s, i, k) do not collide across
     procedures. *)
  symOwner : ARRAY [0 .. MaxSym - 1] OF INTEGER;
  procParent : ARRAY [0 .. MaxProc - 1] OF INTEGER;
  procSymBase : ARRAY [0 .. MaxProc - 1] OF CARDINAL;
  procSymTop : ARRAY [0 .. MaxProc - 1] OF CARDINAL;
  scopeStack : ARRAY [0 .. MaxProc - 1] OF INTEGER;
  scopeTop : CARDINAL;
  curScopeProc : INTEGER;   (* owner while parsing: enclosing proc *)
  emitProc : INTEGER;       (* owner while emitting: current proc *)
  qualUid : CARDINAL;       (* uid of the last M.P alias resolved *)
  qualIsVar : BOOLEAN;      (* last M.P alias is a proc-typed variable *)
  withRec  : ARRAY [0 .. 15] OF SymTab.TypeIndex;
  withTop  : CARDINAL;
  curMethCls : SymTab.TypeIndex;   (* class bound by the last obj.Method *)
  curImplCls : SymTab.TypeIndex;   (* class whose implementation is open *)
  curUnitName : SymTab.Name;       (* unit being re-emitted (LowerSession) *)
  (* Compile-time set constants (SET CONSTs): masks the grammar computes
     and Lower re-emits as pooled static data.  Name-keyed, latest wins,
     exactly like symVal. *)
  cfoldN    : CARDINAL;
  cfoldName : ARRAY [0 .. MaxCFold * 64 - 1] OF CHAR;
  cfoldW    : ARRAY [0 .. MaxCFold - 1] OF CARDINAL;
  cfoldLo   : ARRAY [0 .. MaxCFold - 1] OF INTEGER;
  cfoldMask : ARRAY [0 .. MaxCFold * MaxCFoldW - 1] OF CARDINAL;

PROCEDURE CopyN (src: ARRAY OF CHAR; VAR dst: ARRAY OF CHAR);
  VAR i: CARDINAL;
  BEGIN
    i := 0;
    WHILE (i < MaxName) AND (src[i] # CHR(0)) DO dst[i] := src[i]; INC(i) END;
    dst[i] := CHR(0)
  END CopyN;

PROCEDURE CopySpan (VAR src: ARRAY OF CHAR; VAR dst: ARRAY OF CHAR;
                    srcOff, dstOff: CARDINAL);
(* src is a VAR open array on purpose: gm2 copies a value open-array
   formal to a stack VLA of its full length, which overflows the stack
   for the multi-megabyte tables below. *)
  VAR i: CARDINAL;
  BEGIN
    i := 0;
    WHILE (i < MaxName) AND (src[srcOff + i] # CHR(0)) DO
      dst[dstOff + i] := src[srcOff + i]; INC(i)
    END;
    dst[dstOff + i] := CHR(0)
  END CopySpan;

PROCEDURE HashStr (name: ARRAY OF CHAR): CARDINAL;
  VAR h: CARDINAL; i: CARDINAL;
  BEGIN
    h := 5381; i := 0;
    WHILE (i <= HIGH(name)) AND (name[i] # CHR(0)) DO
      h := (h * 33 + VAL(CARDINAL, ORD(name[i]))) MOD HashSize; INC(i)
    END;
    RETURN h
  END HashStr;

PROCEDURE SpanEq (VAR arr: ARRAY OF CHAR; off: CARDINAL;
                  name: ARRAY OF CHAR): BOOLEAN;
  VAR j: CARDINAL;
  BEGIN
    j := 0;
    WHILE (j < MaxName) AND (name[j] # CHR(0)) DO
      IF arr[off + j] # name[j] THEN RETURN FALSE END;
      INC(j)
    END;
    RETURN arr[off + j] = name[j]
  END SpanEq;

PROCEDURE HashPut (VAR htab: ARRAY OF INTEGER; VAR names: ARRAY OF CHAR;
                   name: ARRAY OF CHAR; idx: CARDINAL);
(* Insert idx, replacing an existing entry with the same name so the
   latest declaration wins (the linear scan used to search backward). *)
  VAR h: CARDINAL;
  BEGIN
    h := HashStr(name);
    LOOP
      IF htab[h] = 0 THEN htab[h] := VAL(INTEGER, idx) + 1; RETURN END;
      IF SpanEq(names, VAL(CARDINAL, htab[h] - 1) * 64, name) THEN
        htab[h] := VAL(INTEGER, idx) + 1; RETURN
      END;
      h := (h + 1) MOD HashSize
    END
  END HashPut;

PROCEDURE HashGet (VAR htab: ARRAY OF INTEGER; VAR names: ARRAY OF CHAR;
                   name: ARRAY OF CHAR): INTEGER;
  VAR h: CARDINAL;
  BEGIN
    h := HashStr(name);
    LOOP
      IF htab[h] = 0 THEN RETURN -1 END;
      IF SpanEq(names, VAL(CARDINAL, htab[h] - 1) * 64, name) THEN
        RETURN htab[h] - 1
      END;
      h := (h + 1) MOD HashSize
    END
  END HashGet;

PROCEDURE Reset;
  VAR i: CARDINAL;
  BEGIN
    nSyms := 0; nProcs := 0;
    scopeTop := 0; curScopeProc := -1; emitProc := -1;
    i := 0;
    WHILE i < HashSize DO symHash[i] := 0; procHash[i] := 0; INC(i) END
  END Reset;

PROCEDURE NoteVar (name: ARRAY OF CHAR; kind: INTEGER; t: SymTab.TypeIndex);
  BEGIN
    IF nSyms >= MaxSym THEN RETURN END;
    CopySpan(name, symName, 0, nSyms * 64);
    symKind[nSyms] := kind; symTy[nSyms] := t;
    symOwner[nSyms] := curScopeProc;
    HashPut(symHash, symName, name, nSyms);
    INC(nSyms)
  END NoteVar;

PROCEDURE NoteConstVal (val: ARRAY OF CHAR);
(* Records the evaluated value of the CONST just entered by NoteVar.
   Const values are per-unit and cross-module names collide (every
   module has EOL), so they live here, not in SymTab. *)
  BEGIN
    IF nSyms > 0 THEN CopySpan(val, symVal, 0, (nSyms - 1) * 64) END
  END NoteConstVal;

PROCEDURE ScopeEnter;
(* Called at a procedure heading, before NoteProc.  Pushes the enclosing
   procedure as the parent scope. *)
  BEGIN
    IF scopeTop <= HIGH(scopeStack) THEN
      scopeStack[scopeTop] := curScopeProc;
      INC(scopeTop)
    END
  END ScopeEnter;

PROCEDURE ScopeLeave;
  BEGIN
    IF curScopeProc >= 0 THEN procSymTop[curScopeProc] := nSyms END;
    IF scopeTop > 0 THEN
      DEC(scopeTop);
      curScopeProc := scopeStack[scopeTop]
    END
  END ScopeLeave;

PROCEDURE ReenterScopeProc (ty: INTEGER);
(* Restores a previously noted proc entry as current for the re-parse
   pass (its registration ran once in the skip pass): pushes the
   current owner and resumes ty, so the Block-end ScopeLeave pops back
   and nested NoteProc/NoteVar attach under the right parent. *)
  BEGIN
    IF (ty < 0) OR (ty >= VAL(INTEGER, nProcs)) THEN RETURN END;
    IF scopeTop <= HIGH(scopeStack) THEN
      scopeStack[scopeTop] := curScopeProc;
      INC(scopeTop)
    END;
    curScopeProc := ty
  END ReenterScopeProc;

PROCEDURE CurScopeProc (): INTEGER;
(* The proc entry NoteProc most recently made current (ty stamped on the
   NkProcDecl); captured by the parser's span table for the re-parse. *)
  BEGIN
    RETURN curScopeProc
  END CurScopeProc;

PROCEDURE NoteProc (name: ARRAY OF CHAR; uid: CARDINAL;
                    res: SymTab.TypeIndex; depth: CARDINAL; ext: BOOLEAN);
  BEGIN
    IF nProcs >= MaxProc THEN RETURN END;
    CopySpan(name, procName, 0, nProcs * 64);
    procUid[nProcs] := uid; procRes[nProcs] := res;
    procDep[nProcs] := depth; procExt[nProcs] := ext;
    procNpar[nProcs] := 0;
    procParent[nProcs] := curScopeProc;
    procSymBase[nProcs] := nSyms;
    curScopeProc := VAL(INTEGER, nProcs);
    HashPut(procHash, procName, name, nProcs);
    INC(nProcs)
  END NoteProc;

PROCEDURE AliasProc (name: ARRAY OF CHAR; uid: CARDINAL;
                     res: SymTab.TypeIndex; depth: CARDINAL; ext: BOOLEAN);
(* A generic procedure formal bound to an actual procedure: add a
   proc-table entry so calls through the formal resolve to the actual,
   without disturbing the scope stack (unlike NoteProc). *)
  BEGIN
    IF nProcs >= MaxProc THEN RETURN END;
    CopySpan(name, procName, 0, nProcs * 64);
    procUid[nProcs] := uid; procRes[nProcs] := res;
    procDep[nProcs] := depth; procExt[nProcs] := ext;
    procNpar[nProcs] := 0;
    procParent[nProcs] := -1;
    procSymBase[nProcs] := nSyms;
    HashPut(procHash, procName, name, nProcs);
    INC(nProcs)
  END AliasProc;

PROCEDURE MarkProcExternal;
(* The grammar calls this from the EXTERNAL branch, after NoteProc, so
   the walk records that the callee takes no static link. *)
  BEGIN
    IF nProcs > 0 THEN procExt[nProcs - 1] := TRUE END
  END MarkProcExternal;

PROCEDURE NoteCProc (name: ARRAY OF CHAR);
(* FROM libc IMPORT P: note its signature (real prototypes for the
   known C functions, permissive no-result varargs otherwise).  NoteProc
   sets curScopeProc; restore it so the next import is not seen as
   nested. *)
  VAR save: INTEGER; i: CARDINAL;
  BEGIN
    save := curScopeProc;
    curScopeProc := -1;
    NoteProc(name, 0, SymTab.ProcRes(name), 0, TRUE);
    curScopeProc := save;
    IF nProcs > 0 THEN
      procExt[nProcs - 1] := TRUE;
      procVa[nProcs - 1] := SymTab.Varargs(name);
      procParent[nProcs - 1] := -1;
      i := 0;
      WHILE i < SymTab.ProcNPar(name) DO
        NoteParam("", SymTab.ParamType(name, i),
                  SymTab.ParamIsVar(name, i));
        INC(i)
      END
    END
  END NoteCProc;

PROCEDURE NoteProcNode (n: AST.Node);
(* Records the proc-table index in the NkProcDecl's ty field, so
   LowerDecls can find the exact entry.  FindProc(name) would return the
   last duplicate (e.g. the two nested `Sep`s), giving the wrong uid and
   the wrong scope for its locals. *)
  BEGIN
    IF nProcs > 0 THEN AST.SetTy(n, VAL(INTEGER, nProcs - 1)) END
  END NoteProcNode;

PROCEDURE ProcInfoIdx (pi: INTEGER; VAR uid: CARDINAL;
                       VAR res: SymTab.TypeIndex; VAR depth: CARDINAL;
                       VAR ext: BOOLEAN; VAR npar: CARDINAL): BOOLEAN;
  BEGIN
    IF (pi < 0) OR (pi >= VAL(INTEGER, nProcs)) THEN RETURN FALSE END;
    uid := procUid[pi]; res := procRes[pi]; depth := procDep[pi];
    ext := procExt[pi]; npar := procNpar[pi];
    IF npar > MaxPar THEN npar := MaxPar END;
    RETURN TRUE
  END ProcInfoIdx;

PROCEDURE ParamInfoIdx (pi: INTEGER; i: CARDINAL;
                        VAR t: SymTab.TypeIndex; VAR isVar: BOOLEAN;
                        VAR pn: ARRAY OF CHAR): BOOLEAN;
  BEGIN
    IF (pi < 0) OR (pi >= MaxProc)
       OR (i >= procNpar[pi]) OR (procNpar[pi] > MaxPar) THEN
      RETURN FALSE
    END;
    t := parTy[VAL(CARDINAL, pi) * MaxPar + i];
    isVar := parVar[VAL(CARDINAL, pi) * MaxPar + i];
    CopySpan(parName, pn, VAL(CARDINAL, pi) * MaxPar * 64 + i * 64, 0);
    RETURN TRUE
  END ParamInfoIdx;

PROCEDURE SetProcRes (t: SymTab.TypeIndex);
  BEGIN
    IF nProcs > 0 THEN procRes[nProcs - 1] := t END
  END SetProcRes;

PROCEDURE NoteParam (name: ARRAY OF CHAR; t: SymTab.TypeIndex; isVar: BOOLEAN);
  VAR j: CARDINAL;
  BEGIN
    IF nProcs = 0 THEN RETURN END;
    j := procNpar[nProcs - 1];
    IF j >= MaxPar THEN RETURN END;
    CopySpan(name, parName, 0, (nProcs - 1) * MaxPar * 64 + j * 64);
    parTy[(nProcs - 1) * MaxPar + j] := t;
    parVar[(nProcs - 1) * MaxPar + j] := isVar;
    procNpar[nProcs - 1] := j + 1
  END NoteParam;

PROCEDURE NameEq (i: CARDINAL; name: ARRAY OF CHAR): BOOLEAN;
  VAR j: CARDINAL;
  BEGIN
    j := 0;
    WHILE (j < MaxName) AND (name[j] # CHR(0)) DO
      IF symName[i * 64 + j] # name[j] THEN RETURN FALSE END;
      INC(j)
    END;
    RETURN symName[i * 64 + j] = name[j]
  END NameEq;

PROCEDURE FindSym (name: ARRAY OF CHAR; VAR kind: INTEGER;
                   VAR t: SymTab.TypeIndex): BOOLEAN;
(* Locals/params of the emitted procedure (and its enclosing procedures)
   shadow module-level symbols, so walk the scope chain innermost-first
   and only then fall back to the hash for a module-level symbol. *)
  VAR i: INTEGER; owner: INTEGER;
  BEGIN
    owner := emitProc;
    WHILE owner >= 0 DO
      (* procSymTop is unset for headings that never ScopeLeave (class
         method declarations); fall back to the whole table then. *)
      IF procSymTop[owner] > 0 THEN
        i := VAL(INTEGER, procSymTop[owner]) - 1
      ELSE i := VAL(INTEGER, nSyms) - 1
      END;
      WHILE i >= VAL(INTEGER, procSymBase[owner]) DO
        IF (symOwner[i] = owner) AND NameEq(VAL(CARDINAL, i), name) THEN
          kind := symKind[i]; t := symTy[i]; RETURN TRUE
        END;
        DEC(i)
      END;
      owner := procParent[owner]
    END;
    i := HashGet(symHash, symName, name);
    IF (i >= 0) AND (symOwner[i] = -1) THEN
      kind := symKind[i]; t := symTy[i]; RETURN TRUE
    END;
    RETURN FALSE
  END FindSym;

PROCEDURE GetConstVal (name: ARRAY OF CHAR; VAR v: ARRAY OF CHAR): BOOLEAN;
  VAR i: INTEGER;
  BEGIN
    i := HashGet(symHash, symName, name);
    IF (i >= 0) AND (symKind[i] = SymTab.KindConst) THEN
      CopySpan(symVal, v, VAL(CARDINAL, i) * 64, 0);
      IF v[0] # CHR(0) THEN RETURN TRUE END
    END;
    (* a literal propagated with its enum type lives only in SymTab *)
    v[0] := CHR(0);
    RETURN SymTab.GetSymVal(name, v)
  END GetConstVal;

PROCEDURE SetConstVal (name: ARRAY OF CHAR; val: ARRAY OF CHAR);
(* Refresh a CONST's recorded value after Lower re-emits its aggregate
   constructor (the grammar's value was suppressed under NoEmit). *)
  VAR i: INTEGER;
  BEGIN
    i := HashGet(symHash, symName, name);
    IF i >= 0 THEN CopySpan(val, symVal, 0, VAL(CARDINAL, i) * 64) END
  END SetConstVal;

PROCEDURE ProcNameEq (i: CARDINAL; name: ARRAY OF CHAR): BOOLEAN;
  VAR j: CARDINAL;
  BEGIN
    j := 0;
    WHILE (j < MaxName) AND (name[j] # CHR(0)) DO
      IF procName[i * 64 + j] # name[j] THEN RETURN FALSE END;
      INC(j)
    END;
    RETURN procName[i * 64 + j] = name[j]
  END ProcNameEq;

PROCEDURE ProcVisible (i: INTEGER): BOOLEAN;
(* TRUE when proc i is nested directly in the emitted procedure or one
   of its enclosing procedures (or is module-level). *)
  VAR owner: INTEGER;
  BEGIN
    owner := emitProc;
    WHILE owner >= 0 DO
      IF procParent[i] = owner THEN RETURN TRUE END;
      owner := procParent[owner]
    END;
    RETURN procParent[i] = -1
  END ProcVisible;

PROCEDURE ImpNameEq (i: CARDINAL; name: ARRAY OF CHAR): BOOLEAN;
  BEGIN
    RETURN SpanEq(impName, i * 64, name)
  END ImpNameEq;

PROCEDURE FindProc (name: ARRAY OF CHAR): INTEGER;
(* Scope-aware: a nested procedure (e.g. one of two `Sep`s) must resolve
   to the one in the emitted procedure's chain, not the last duplicate.
   The current unit's imports win over any same-named proc. *)
  VAR i: INTEGER; owner: INTEGER;
  BEGIN
    i := 0;
    WHILE i < VAL(INTEGER, nImps) DO
      IF ImpNameEq(VAL(CARDINAL, i), name) THEN RETURN impProc[i] END;
      INC(i)
    END;
    i := HashGet(procHash, procName, name);
    IF (i >= 0) AND ProcVisible(i) THEN RETURN i END;
    owner := emitProc;
    WHILE owner >= 0 DO
      i := VAL(INTEGER, nProcs) - 1;
      WHILE i > 0 DO
        DEC(i);
        IF (procParent[i] = owner) AND ProcNameEq(VAL(CARDINAL, i), name) THEN
          RETURN i
        END
      END;
      owner := procParent[owner]
    END;
    i := VAL(INTEGER, nProcs) - 1;
    WHILE i > 0 DO
      DEC(i);
      IF (procParent[i] = -1) AND ProcNameEq(VAL(CARDINAL, i), name) THEN
        RETURN i
      END
    END;
    RETURN -1
  END FindProc;

PROCEDURE FindProcByUid (uid: CARDINAL): INTEGER;
(* Exact proc entry for a module-qualified call (M.P): the base name may
   be duplicated across modules, but the uid is unique. *)
  VAR i: INTEGER;
  BEGIN
    i := VAL(INTEGER, nProcs);
    WHILE i > 0 DO
      DEC(i);
      IF procUid[i] = uid THEN RETURN i END
    END;
    RETURN -1
  END FindProcByUid;

PROCEDURE NoteImportedProc (name: ARRAY OF CHAR);
(* FROM M IMPORT P (a procedure): remember the exact proc entry so an
   unqualified call resolves to the imported proc, not a same-named
   proc declared in another module.  Reset at each unit. *)
  VAR pi: INTEGER;
  BEGIN
    IF SymTab.SymKind(name) # SymTab.KindProc THEN RETURN END;
    pi := FindProcByUid(SymTab.ProcUid(name));
    IF pi < 0 THEN RETURN END;
    IF nImps >= MaxImp THEN RETURN END;
    impProc[nImps] := pi;
    CopySpan(name, impName, 0, nImps * 64);
    INC(nImps)
  END NoteImportedProc;

PROCEDURE Resolve (nm: ARRAY OF CHAR; VAR k: INTEGER;
                   VAR t: SymTab.TypeIndex): BOOLEAN;
  VAR kind: INTEGER; ti: SymTab.TypeIndex;
  BEGIN
    IF FindSym(nm, kind, ti) THEN k := kind; t := ti; RETURN TRUE END;
    IF SymTab.Lookup(nm) THEN k := SymTab.SymKind(nm); t := SymTab.SymType(nm);
      RETURN TRUE
    END;
    (* A bare procedure used as a value: it lives in the proc table.
       Sibling method names must fall through so LowerDesign can bind
       THIS, so exclude methods of the open class implementation. *)
    IF FindProc(nm) >= 0 THEN
      IF (curImplCls = SymTab.InvalidType)
         OR NOT SymTab.MethodExists(curImplCls, nm) THEN
        k := SymTab.KindProc; t := SymTab.InvalidType; RETURN TRUE
      END
    END;
    RETURN FALSE
  END Resolve;

PROCEDURE ProcInfo (nm: ARRAY OF CHAR; VAR uid: CARDINAL;
                    VAR res: SymTab.TypeIndex; VAR depth: CARDINAL;
                    VAR ext: BOOLEAN; VAR npar: CARDINAL): BOOLEAN;
  VAR i: INTEGER;
  BEGIN
    i := FindProc(nm);
    IF (i < 0) OR (i >= MaxProc) THEN RETURN FALSE END;
    uid := procUid[i]; res := procRes[i]; depth := procDep[i];
    ext := procExt[i]; npar := procNpar[i];
    IF npar > MaxPar THEN npar := MaxPar END;
    RETURN TRUE
  END ProcInfo;

PROCEDURE ParamInfo (nm: ARRAY OF CHAR; i: CARDINAL;
                     VAR t: SymTab.TypeIndex; VAR isVar: BOOLEAN;
                     VAR pn: ARRAY OF CHAR): BOOLEAN;
  VAR k: INTEGER;
  BEGIN
    k := FindProc(nm);
    IF (k < 0) OR (k >= MaxProc) THEN RETURN FALSE END;
    IF (i >= procNpar[k]) OR (procNpar[k] > MaxPar) THEN RETURN FALSE END;
    t := parTy[VAL(CARDINAL, k) * MaxPar + i];
    isVar := parVar[VAL(CARDINAL, k) * MaxPar + i];
    CopySpan(parName, pn, VAL(CARDINAL, k) * MaxPar * 64 + i * 64, 0);
    RETURN TRUE
  END ParamInfo;

PROCEDURE WithField (nm: ARRAY OF CHAR; VAR k: INTEGER;
                     VAR t: SymTab.TypeIndex; VAR q: QbeGen.QVal): BOOLEAN;
(* Resolves a bare ident as a field of an open WITH record (innermost
   first), leaving the field address in q and k=KindField. *)
  VAR wt: CARDINAL; fo: INTEGER; qb: QbeGen.QVal;
  BEGIN
    wt := withTop;
    WHILE wt > 0 DO
      DEC(wt);
      IF SymTab.FieldExists(withRec[wt], nm) THEN
        t := SymTab.FieldType(withRec[wt], nm);
        fo := SymTab.FieldOffset(withRec[wt], nm);
        k := SymTab.KindField;
        IF QbeGen.TopWith(qb) THEN QbeGen.FieldAddr(qb, fo, q)
        ELSE QbeGen.CopyOp("0", q)
        END;
        RETURN TRUE
      END
    END;
    RETURN FALSE
  END WithField;

PROCEDURE Name (n: AST.Node; VAR s: ARRAY OF CHAR);
  BEGIN
    IF n = AST.NoNode THEN s[0] := CHR(0)
    ELSE AST.Txt(AST.Child(n, 0), s)
    END
  END Name;

(* ---------------- compile-time set constants ----------------
   A SET CONST's value must be static data.  Set literals are emitted as
   runtime temporaries, so the grammar computes the bit mask here (where
   the element expressions are already validated) and Lower re-emits it
   as a pooled descriptor (`QbeGen.PoolSet`).  Only masks up to MaxCFoldW
   words (512 bits) are folded; a wider SET CONST stays a clear 230. *)

PROCEDURE Pow2 (b: INTEGER): CARDINAL;
  VAR p: CARDINAL; k: INTEGER;
  BEGIN
    p := 1; k := 0;
    WHILE k < b DO p := p * 2; INC(k) END;
    RETURN p
  END Pow2;

PROCEDURE MaskZero (VAR mask: ARRAY OF CARDINAL; words: CARDINAL);
  VAR i: CARDINAL;
  BEGIN
    i := 0;
    WHILE (i < words) AND (i <= HIGH(mask)) DO mask[i] := 0; INC(i) END
  END MaskZero;

PROCEDURE MaskSetBit (VAR mask: ARRAY OF CARDINAL; bit: INTEGER);
  VAR w, b: INTEGER; p: CARDINAL; idx: CARDINAL;
  BEGIN
    IF (bit < 0) OR (bit >= VAL(INTEGER, MaxCFoldW) * 32) THEN RETURN END;
    w := bit DIV 32; b := bit MOD 32;
    IF w > VAL(INTEGER, HIGH(mask)) THEN RETURN END;
    idx := VAL(CARDINAL, w); p := Pow2(b);
    IF (mask[idx] DIV p) MOD 2 = 0 THEN mask[idx] := mask[idx] + p END
  END MaskSetBit;

PROCEDURE MaskGetBit (VAR mask: ARRAY OF CARDINAL; bit: INTEGER): INTEGER;
  VAR w, b: INTEGER; p: CARDINAL;
  BEGIN
    IF (bit < 0) OR (bit >= VAL(INTEGER, MaxCFoldW) * 32) THEN RETURN 0 END;
    w := bit DIV 32; b := bit MOD 32;
    IF w > VAL(INTEGER, HIGH(mask)) THEN RETURN 0 END;
    p := Pow2(b);
    IF (mask[VAL(CARDINAL, w)] DIV p) MOD 2 = 1 THEN RETURN 1 END;
    RETURN 0
  END MaskGetBit;

PROCEDURE EvalOrdConst (n: AST.Node; VAR v: INTEGER): BOOLEAN;
(* The integer value of a compile-time ordinal expression, matching the
   grammar's folding (literals, named CONSTs, unary +/-, + - * DIV MOD). *)
  VAR k: INTEGER; s, cv: QbeGen.QVal; nm, qnm, al: SymTab.Name;
      a, b: INTEGER; isCh: BOOLEAN;
  BEGIN
    IF n = AST.NoNode THEN RETURN FALSE END;
    k := AST.Kind(n);
    IF k = AST.NkIntLit THEN
      Name(n, s); QbeGen.NormInt(s, cv); RETURN SymTab.ConstInt(cv, v)
    ELSIF k = AST.NkCharLit THEN
      Name(n, s);
      IF (s[0] = "'") OR (s[0] = '"') THEN
        v := QbeGen.CharVal(s); RETURN TRUE
      END;
      QbeGen.NormLit(s, cv, isCh); RETURN SymTab.ConstInt(cv, v)
    ELSIF k = AST.NkStrLit THEN
      (* a 1-character string literal "c" is a CHAR constant *)
      Name(n, s);
      IF SymTab.StrLen(s) = 3 THEN v := QbeGen.CharVal(s); RETURN TRUE END;
      RETURN FALSE
    ELSIF k = AST.NkDesignator THEN
      IF (AST.NChild(n) = 1) AND (AST.Kind(AST.Child(n, 0)) = AST.NkIdent) THEN
        Name(AST.Child(n, 0), nm);
        IF SymTab.Equal(nm, "TRUE") THEN v := 1; RETURN TRUE END;
        IF SymTab.Equal(nm, "FALSE") THEN v := 0; RETURN TRUE END;
        IF SymTab.Lookup(nm) AND (SymTab.SymKind(nm) = SymTab.KindConst)
           AND SymTab.GetSymVal(nm, cv) AND QbeGen.IsImm(cv) THEN
          RETURN SymTab.ConstInt(cv, v)
        END;
        RETURN FALSE
      ELSIF (AST.NChild(n) = 2) AND (AST.Kind(AST.Child(n, 0)) = AST.NkIdent)
         AND (AST.Kind(AST.Child(n, 1)) = AST.NkSelector)
         AND (AST.Op(AST.Child(n, 1)) = AST.SelField) THEN
        (* M.lit: a module-qualified constant (enum literal / CONST) *)
        Name(AST.Child(n, 0), nm);
        Name(AST.Child(AST.Child(n, 1), 0), qnm);
        IF SymTab.MaterializeAlias(nm, qnm, al)
           AND SymTab.GetSymVal(al, cv) AND QbeGen.IsImm(cv) THEN
          RETURN SymTab.ConstInt(cv, v)
        END;
        RETURN FALSE
      END;
      RETURN FALSE
    ELSIF k = AST.NkUnary THEN
      IF AST.Op(n) = AST.OpSub THEN
        IF EvalOrdConst(AST.Child(n, 0), v) THEN v := -v; RETURN TRUE END
      ELSIF AST.Op(n) = AST.OpAdd THEN
        RETURN EvalOrdConst(AST.Child(n, 0), v)
      END;
      RETURN FALSE
    ELSIF k = AST.NkBinExpr THEN
      IF EvalOrdConst(AST.Child(n, 0), a)
         AND EvalOrdConst(AST.Child(n, 1), b) THEN
        IF AST.Op(n) = AST.OpAdd THEN v := a + b
        ELSIF AST.Op(n) = AST.OpSub THEN v := a - b
        ELSIF AST.Op(n) = AST.OpMul THEN v := a * b
        ELSIF AST.Op(n) = AST.OpDiv THEN
          IF b = 0 THEN RETURN FALSE END; v := a DIV b
        ELSIF AST.Op(n) = AST.OpMod THEN
          IF b = 0 THEN RETURN FALSE END; v := a MOD b
        ELSE RETURN FALSE
        END;
        RETURN TRUE
      END;
      RETURN FALSE
    END;
    RETURN FALSE
  END EvalOrdConst;

PROCEDURE EvalSetElem (el: AST.Node; VAR mask: ARRAY OF CARDINAL;
                       lo: INTEGER; span: CARDINAL): BOOLEAN;
  VAR a, b: INTEGER;
  BEGIN
    IF AST.Kind(el) = AST.NkSubrange THEN
      IF NOT EvalOrdConst(AST.Child(el, 0), a)
         OR NOT EvalOrdConst(AST.Child(el, 1), b) THEN RETURN FALSE END;
      IF (a < lo) OR (b < lo) OR (a > b)
         OR (b >= lo + VAL(INTEGER, span)) THEN RETURN FALSE END;
      WHILE a <= b DO MaskSetBit(mask, a - lo); INC(a) END;
      RETURN TRUE
    END;
    IF NOT EvalOrdConst(el, a) THEN RETURN FALSE END;
    IF (a < lo) OR (a >= lo + VAL(INTEGER, span)) THEN RETURN FALSE END;
    MaskSetBit(mask, a - lo);
    RETURN TRUE
  END EvalSetElem;

PROCEDURE NoteSetMask (name: ARRAY OF CHAR; mask: ARRAY OF CARDINAL;
                       words: CARDINAL; lo: INTEGER);
  VAR i: CARDINAL;
  BEGIN
    IF cfoldN >= MaxCFold THEN RETURN END;
    CopySpan(name, cfoldName, 0, cfoldN * 64);
    cfoldW[cfoldN] := words; cfoldLo[cfoldN] := lo;
    i := 0;
    WHILE i < MaxCFoldW DO
      IF (i < words) AND (i <= HIGH(mask)) THEN
        cfoldMask[cfoldN * MaxCFoldW + i] := mask[i]
      ELSE cfoldMask[cfoldN * MaxCFoldW + i] := 0
      END;
      INC(i)
    END;
    INC(cfoldN)
  END NoteSetMask;

PROCEDURE LookupSetMask (name: ARRAY OF CHAR; VAR mask: ARRAY OF CARDINAL;
                         VAR words: CARDINAL; VAR lo: INTEGER): BOOLEAN;
  VAR i: INTEGER; k: CARDINAL;
  BEGIN
    i := VAL(INTEGER, cfoldN) - 1;
    WHILE i >= 0 DO
      IF SpanEq(cfoldName, VAL(CARDINAL, i) * 64, name) THEN
        words := cfoldW[i]; lo := cfoldLo[i];
        k := 0;
        WHILE (k < words) AND (k <= HIGH(mask)) DO
          mask[k] := cfoldMask[VAL(CARDINAL, i) * MaxCFoldW + k]; INC(k)
        END;
        RETURN TRUE
      END;
      DEC(i)
    END;
    RETURN FALSE
  END LookupSetMask;

PROCEDURE EvalSetConst (n: AST.Node; VAR mask: ARRAY OF CARDINAL;
                        VAR words: CARDINAL; VAR lo: INTEGER): BOOLEAN;
  VAR k, i, a, b, r: INTEGER;
      t: SymTab.TypeIndex;
      span: CARDINAL;
      seq, el, next: AST.Node;
      m1, m2: ARRAY [0 .. MaxCFoldW - 1] OF CARDINAL;
      w1, w2: CARDINAL;
      l1, l2: INTEGER;
      op: INTEGER;
      nm: SymTab.Name;
  BEGIN
    IF n = AST.NoNode THEN RETURN FALSE END;
    k := AST.Kind(n);
    IF (k = AST.NkSetLit) OR (k = AST.NkBraceLit) THEN
      t := AST.Ty(n);
      IF (k = AST.NkBraceLit) AND (SymTab.ClassOf(t) # SymTab.ClSet) THEN
        RETURN FALSE
      END;
      IF t = SymTab.InvalidType THEN
        lo := 0; words := 8; span := 256
      ELSE
        lo := SymTab.SetBaseLo(t); words := SymTab.SetWords(t);
        span := SymTab.SetCount(t);
        IF words = 0 THEN words := 8; span := 256; lo := 0 END
      END;
      IF words > MaxCFoldW THEN RETURN FALSE END;
      MaskZero(mask, words);
      IF k = AST.NkSetLit THEN
        i := 0;
        WHILE i < VAL(INTEGER, AST.NChild(n)) DO
          el := AST.Child(n, VAL(CARDINAL, i));
          IF NOT EvalSetElem(el, mask, lo, span) THEN RETURN FALSE END;
          INC(i)
        END
      ELSE
        seq := n;
        WHILE seq # AST.NoNode DO
          i := 0;
          WHILE i < VAL(INTEGER, AST.NChild(seq)) DO
            el := AST.Child(seq, VAL(CARDINAL, i));
            IF AST.Kind(el) # AST.NkBlock THEN
              IF NOT EvalSetElem(el, mask, lo, span) THEN RETURN FALSE END
            END;
            INC(i)
          END;
          next := AST.NoNode;
          IF AST.NChild(seq) > 0 THEN
            next := AST.Child(seq, AST.NChild(seq) - 1);
            IF AST.Kind(next) # AST.NkBlock THEN next := AST.NoNode END
          END;
          seq := next
        END
      END;
      RETURN TRUE
    ELSIF k = AST.NkDesignator THEN
      IF (AST.NChild(n) # 1) OR (AST.Kind(AST.Child(n, 0)) # AST.NkIdent) THEN
        RETURN FALSE END;
      Name(AST.Child(n, 0), nm);
      RETURN LookupSetMask(nm, mask, words, lo)
    ELSIF k = AST.NkBinExpr THEN
      op := AST.Op(n);
      IF (op # AST.OpAdd) AND (op # AST.OpSub)
         AND (op # AST.OpMul) AND (op # AST.OpDiv) THEN
        RETURN FALSE END;
      IF NOT EvalSetConst(AST.Child(n, 0), m1, w1, l1)
         OR NOT EvalSetConst(AST.Child(n, 1), m2, w2, l2) THEN
        RETURN FALSE END;
      IF l1 # l2 THEN RETURN FALSE END;
      lo := l1;
      words := w1; IF w2 > words THEN words := w2 END;
      IF words > MaxCFoldW THEN RETURN FALSE END;
      MaskZero(mask, words);
      i := 0;
      WHILE i < VAL(INTEGER, words) * 32 DO
        a := MaskGetBit(m1, i); b := MaskGetBit(m2, i);
        IF op = AST.OpAdd THEN r := a; IF b = 1 THEN r := 1 END
        ELSIF op = AST.OpMul THEN
          IF (a = 1) AND (b = 1) THEN r := 1 ELSE r := 0 END
        ELSIF op = AST.OpSub THEN r := a; IF b = 1 THEN r := 0 END
        ELSE r := (a + b) MOD 2
        END;
        IF r # 0 THEN MaskSetBit(mask, i) END;
        INC(i)
      END;
      RETURN TRUE
    END;
    RETURN FALSE
  END EvalSetConst;

PROCEDURE SetConstMaskOf (n: AST.Node; VAR mask: ARRAY OF CARDINAL;
                          VAR words: CARDINAL; VAR lo: INTEGER): BOOLEAN;
  BEGIN
    words := 0; lo := 0;
    RETURN EvalSetConst(n, mask, words, lo)
  END SetConstMaskOf;


PROCEDURE ParamName (proc: ARRAY OF CHAR; i: CARDINAL;
                     VAR s: ARRAY OF CHAR);
  VAR t: SymTab.TypeIndex; isV: BOOLEAN;
  BEGIN
    IF NOT ParamInfo(proc, i, t, isV, s) THEN s[0] := CHR(0) END
  END ParamName;

PROCEDURE IsArith (op: INTEGER): BOOLEAN;
  BEGIN
    RETURN (op = AST.OpAdd) OR (op = AST.OpSub) OR (op = AST.OpMul)
        OR (op = AST.OpDiv) OR (op = AST.OpMod)
  END IsArith;

PROCEDURE IsRel (op: INTEGER): BOOLEAN;
  BEGIN
    RETURN ((op >= AST.OpEq) AND (op <= AST.OpGe)) OR (op = AST.OpIn)
  END IsRel;

PROCEDURE RelSym (a: INTEGER; VAR s: INTEGER): BOOLEAN;
  BEGIN
    IF a = AST.OpEq THEN s := SymTab.OpEq
    ELSIF a = AST.OpNe THEN s := SymTab.OpNeq1
    ELSIF a = AST.OpLt THEN s := SymTab.OpLt
    ELSIF a = AST.OpLe THEN s := SymTab.OpLe
    ELSIF a = AST.OpGt THEN s := SymTab.OpGt
    ELSIF a = AST.OpGe THEN s := SymTab.OpGe
    ELSE RETURN FALSE
    END;
    RETURN TRUE
  END RelSym;

PROCEDURE IsScalarClass (cls: INTEGER): BOOLEAN;
  BEGIN
    RETURN (cls = SymTab.ClInt) OR (cls = SymTab.ClBool)
        OR (cls = SymTab.ClChar) OR (cls = SymTab.ClUChar)
        OR (cls = SymTab.ClEnum)
  END IsScalarClass;

PROCEDURE IsSimpleScalar (n: AST.Node): BOOLEAN;
  VAR nm: SymTab.Name; k: INTEGER; t: SymTab.TypeIndex;
  BEGIN
    IF (AST.Kind(n) # AST.NkDesignator) OR (AST.NChild(n) # 1) THEN
      RETURN FALSE END;
    IF AST.Kind(AST.Child(n, 0)) # AST.NkIdent THEN RETURN FALSE END;
    Name(AST.Child(n, 0), nm);
    IF NOT Resolve(nm, k, t) THEN RETURN FALSE END;
    IF (k # SymTab.KindVar) AND (k # SymTab.KindParam)
       AND (k # SymTab.KindConst) THEN
      RETURN FALSE END;
    IF SymTab.Equal(nm, "TRUE") OR SymTab.Equal(nm, "FALSE") THEN
      RETURN TRUE END;
    RETURN IsScalarClass(SymTab.ClassOf(t))
  END IsSimpleScalar;

PROCEDURE CalleeName (call: AST.Node; VAR nm: SymTab.Name);
(* The callee of NkCall: child 0 is a designator (or bare ident). *)
  VAR d: AST.Node;
  BEGIN
    nm[0] := CHR(0);
    d := AST.Child(call, 0);
    IF d = AST.NoNode THEN RETURN END;
    IF AST.Kind(d) = AST.NkDesignator THEN d := AST.Child(d, 0) END;
    IF (d # AST.NoNode) AND (AST.Kind(d) = AST.NkIdent) THEN Name(d, nm) END
  END CalleeName;

PROCEDURE CallResultType (call: AST.Node; VAR t: SymTab.TypeIndex): BOOLEAN;
(* The result type of a call used as a designator base (F().M()). *)
  VAR nm: SymTab.Name; uid, depth, np: CARDINAL; res: SymTab.TypeIndex;
      ext: BOOLEAN; pi: INTEGER;
  BEGIN
    t := SymTab.InvalidType;
    CalleeName(call, nm);
    pi := FindProc(nm);
    IF pi >= 0 THEN
      IF ProcInfoIdx(pi, uid, res, depth, ext, np) THEN t := res; RETURN TRUE END;
      RETURN FALSE
    END;
    IF SymTab.Lookup(nm) AND (SymTab.SymKind(nm) = SymTab.KindProc) THEN
      t := SymTab.ProcRes(nm); RETURN TRUE
    END;
    RETURN FALSE
  END CallResultType;

PROCEDURE IsMethodCall (n: AST.Node): BOOLEAN;
(* n is a call whose callee resolves to a class method: `obj.Method`,
   `p^.Method`, or a bare sibling name inside an implementation. *)
  VAR d, sel: AST.Node; nm, fn: SymTab.Name; k: INTEGER; t: SymTab.TypeIndex;
      i: CARDINAL;
  BEGIN
    IF (AST.Kind(n) # AST.NkCall) OR (AST.NChild(n) < 1) THEN RETURN FALSE END;
    d := AST.Child(n, 0);
    IF AST.Kind(d) # AST.NkDesignator THEN RETURN FALSE END;
    IF AST.NChild(d) = 1 THEN
      (* bare name: a sibling method inside a class implementation? *)
      Name(AST.Child(d, 0), nm);
      RETURN (curImplCls # SymTab.InvalidType)
             AND SymTab.MethodExists(curImplCls, nm)
    END;
    IF AST.Kind(AST.Child(d, 0)) = AST.NkCall THEN
      (* F().M(): the base is a call; take its result type *)
      IF NOT CallResultType(AST.Child(d, 0), t) THEN RETURN FALSE END
    ELSE
      Name(AST.Child(d, 0), nm);
      IF NOT Resolve(nm, k, t) THEN RETURN FALSE END
    END;
    i := 1;
    WHILE i < AST.NChild(d) DO
      sel := AST.Child(d, i);
      IF AST.Op(sel) = AST.SelField THEN
        Name(AST.Child(sel, 0), fn);
        IF (t # SymTab.InvalidType) AND (SymTab.ClassOf(t) = SymTab.ClClass)
           AND SymTab.MethodExists(t, fn) THEN
          RETURN i = AST.NChild(d) - 1
        END;
        IF (t = SymTab.InvalidType) OR NOT SymTab.FieldExists(t, fn) THEN
          RETURN FALSE
        END;
        t := SymTab.FieldType(t, fn)
      ELSIF AST.Op(sel) = AST.SelIndex THEN
        IF (t = SymTab.InvalidType) OR (SymTab.ClassOf(t) # SymTab.ClArray) THEN
          RETURN FALSE
        END;
        t := SymTab.ArrayElem(t)
      ELSIF AST.Op(sel) = AST.SelDeref THEN
        IF (t = SymTab.InvalidType) OR (SymTab.ClassOf(t) # SymTab.ClPtr) THEN
          RETURN FALSE
        END;
        t := SymTab.PtrBase(t)
      ELSE RETURN FALSE
      END;
      INC(i)
    END;
    RETURN FALSE
  END IsMethodCall;

PROCEDURE CalleeAlias (call: AST.Node; VAR mal: SymTab.Name): BOOLEAN;
(* Callee is `M.P` (module-qualified): materialize the export alias. *)
  VAR d, sel: AST.Node; nm, fn, al: SymTab.Name; k: INTEGER;
      t: SymTab.TypeIndex;
  BEGIN
    d := AST.Child(call, 0);
    IF (AST.Kind(d) # AST.NkDesignator) OR (AST.NChild(d) # 2) THEN
      RETURN FALSE
    END;
    sel := AST.Child(d, 1);
    IF AST.Op(sel) # AST.SelField THEN RETURN FALSE END;
    Name(AST.Child(d, 0), nm);
    IF NOT Resolve(nm, k, t) THEN RETURN FALSE END;
    IF k # SymTab.KindModule THEN RETURN FALSE END;
    Name(AST.Child(sel, 0), fn);
    IF NOT SymTab.MaterializeAlias(nm, fn, al) THEN RETURN FALSE END;
    (* Lower's proc table is keyed by the base name (the mangled symbol
       is <base>_<uid>), so return fn, not the materialized alias.  The
       uid comes from the alias, which is module-exact. *)
    qualIsVar := SymTab.SymKind(al) # SymTab.KindProc;
    qualUid := SymTab.ProcUid(al);
    CopyN(fn, mal);
    RETURN TRUE
  END CalleeAlias;
PROCEDURE FinalLoad (t: SymTab.TypeIndex; sfx: BOOLEAN; VAR q: QbeGen.QVal);
(* Fact's final load after a designator/result suffix: scalars/pointers
   are loaded from their address; aggregates keep the address. *)
  VAR cls: INTEGER; q2: QbeGen.QVal;
  BEGIN
    IF NOT sfx THEN RETURN END;
    IF t = SymTab.InvalidType THEN QbeGen.CopyOp("0", q); RETURN END;
    cls := SymTab.ClassOf(t);
    IF (cls # SymTab.ClRecord) AND (cls # SymTab.ClSet)
       AND (cls # SymTab.ClArray) AND (cls # SymTab.ClClass) THEN
      QbeGen.ElemLoad(q, t, q2); QbeGen.CopyOp(q2, q)
    END
  END FinalLoad;

PROCEDURE LowerDesign (n: AST.Node; VAR t: SymTab.TypeIndex; VAR k: INTEGER;
                       VAR q: QbeGen.QVal; VAR qn: SymTab.Name;
                       VAR sfx: BOOLEAN);
(* Base ident then selectors (mirrors the grammar's Design).  Leaves the
   address in q with sfx=TRUE for selectors; base vars/consts load. *)
  VAR nm, fn, mal: SymTab.Name; cv: QbeGen.QVal; cls, op: INTEGER;
      i: CARDINAL; sel: AST.Node; eT, it: SymTab.TypeIndex;
      iq, ql, qlo, qhi, qe: QbeGen.QVal;
      lo, hi, fo: INTEGER; isOpen: BOOLEAN;
  BEGIN
    IF AST.Kind(AST.Child(n, 0)) = AST.NkCall THEN
      (* a call result used as a designator base: P()^, P()^.field,
         A()[i].  The call yields a value (a pointer/record address);
         sfx=FALSE so a following ^ does not reload it. *)
      LowerExpr(AST.Child(n, 0), t, q);
      k := -1; qn[0] := CHR(0); sfx := FALSE
    ELSE
    Name(AST.Child(n, 0), nm);
    QbeGen.CopyOp(nm, qn);
    sfx := FALSE;
    IF NOT Resolve(nm, k, t) THEN
      IF WithField(nm, k, t, q) THEN
        sfx := TRUE
      ELSIF (curImplCls # SymTab.InvalidType)
         AND SymTab.MethodExists(curImplCls, nm) THEN
        (* bare sibling method name inside a class implementation *)
        QbeGen.ThisBase(q);
        QbeGen.ArmRecv(q);
        curMethCls := curImplCls; k := SymTab.KindProc;
        t := SymTab.InvalidType; sfx := FALSE
      ELSE
        t := SymTab.InvalidType; k := -1; QbeGen.CopyOp("0", q); RETURN
      END
    END;
    IF k = SymTab.KindConst THEN
      IF SymTab.Equal(nm, "TRUE") THEN
        t := SymTab.BoolType(); QbeGen.CopyOp("1", q)
      ELSIF SymTab.Equal(nm, "FALSE") THEN
        t := SymTab.BoolType(); QbeGen.CopyOp("0", q)
      ELSIF SymTab.Equal(nm, "NIL") THEN
        QbeGen.CopyOp("0", q)
      ELSE
        cls := SymTab.ClassOf(t);
        IF (cls = SymTab.ClArray) OR (cls = SymTab.ClRecord)
           OR (cls = SymTab.ClClass) OR (cls = SymTab.ClStr)
           OR (cls = SymTab.ClUStr) OR (cls = SymTab.ClSet) THEN
          (* aggregate/string const: its value IS the descriptor address *)
          IF GetConstVal(nm, cv) THEN QbeGen.CopyOp(cv, q)
          ELSE QbeGen.CopyOp("0", q)
          END
        ELSIF (cls = SymTab.ClInt) OR (cls = SymTab.ClChar)
           OR (cls = SymTab.ClEnum) OR (cls = SymTab.ClLong)
           OR (cls = SymTab.ClBool)
           OR (cls = SymTab.ClByte) OR (cls = SymTab.ClSByte) THEN
          IF GetConstVal(nm, cv) AND QbeGen.IsImm(cv) THEN
            QbeGen.CopyOp(cv, q)
          ELSE QbeGen.CopyOp("0", q)
          END
        ELSIF cls = SymTab.ClReal THEN
          (* a real CONST lives in its data symbol; load it *)
          QbeGen.LoadVar(nm, TRUE, q)
        ELSE QbeGen.CopyOp("0", q)
        END
      END
    ELSIF (k = SymTab.KindVar) OR (k = SymTab.KindParam) THEN
      cls := SymTab.ClassOf(t);
      IF AST.Op(n) = 1 THEN
        (* a forward module-level reference: the grammar's FwdAddrOper
           leaves an address (sfx=TRUE), not a loaded value *)
        QbeGen.AddrOf(nm, q); sfx := TRUE
      ELSIF SymTab.IsSmallInt(t) THEN
        QbeGen.LoadShortVar(nm, SymTab.IsSignedSmallInt(t),
          SymTab.SmallIntBytes(t), q)
      ELSIF (cls = SymTab.ClInt) OR (cls = SymTab.ClBool)
         OR (cls = SymTab.ClChar) OR (cls = SymTab.ClUChar)
         OR (cls = SymTab.ClEnum) OR (cls = SymTab.ClReal) THEN
        QbeGen.LoadVar(nm, cls = SymTab.ClReal, q)
      ELSIF (cls = SymTab.ClPtr) OR (cls = SymTab.ClProc) THEN
        QbeGen.LoadPtr(nm, q)
      ELSIF cls = SymTab.ClLong THEN
        QbeGen.LoadLong(nm, q)
      ELSE QbeGen.AddrOf(nm, q)
      END
    ELSIF k = SymTab.KindField THEN
      (* q already holds the field address (WithField) *)
    ELSE QbeGen.CopyOp("0", q)
    END;
    END;
    i := 1;
    WHILE i < AST.NChild(n) DO
      sel := AST.Child(n, i);
      op := AST.Op(sel);
      IF op = AST.SelField THEN
        Name(AST.Child(sel, 0), fn);
        IF k = SymTab.KindModule THEN
          (* qualified L.x: materialize the export, then load it *)
          IF SymTab.MaterializeAlias(nm, fn, mal) THEN
            QbeGen.CopyOp(mal, qn);
            t := SymTab.SymType(mal); k := SymTab.SymKind(mal); sfx := FALSE;
            IF k = SymTab.KindProc THEN QbeGen.CopyOp("0", q)
            ELSIF NOT QbeGen.LoadDesignator(mal, t, k, q) THEN
              t := SymTab.InvalidType; QbeGen.CopyOp("0", q)
            END
          ELSE t := SymTab.InvalidType; QbeGen.CopyOp("0", q)
          END
        ELSIF t = SymTab.InvalidType THEN
        ELSIF (SymTab.ClassOf(t) = SymTab.ClClass)
           AND SymTab.MethodExists(t, fn) THEN
          (* obj.Method: bind the receiver; the call supplies the value *)
          QbeGen.ArmRecv(q);
          QbeGen.CopyOp(fn, qn);
          curMethCls := t; k := SymTab.KindProc; t := SymTab.InvalidType
        ELSIF NOT SymTab.FieldExists(t, fn) THEN t := SymTab.InvalidType
        ELSE
          fo := SymTab.FieldOffset(t, fn);
          t := SymTab.FieldType(t, fn);
          QbeGen.FieldAddr(q, fo, qe);
          QbeGen.CopyOp(qe, q);
          sfx := TRUE
        END
      ELSIF op = AST.SelIndex THEN
        LowerExpr(AST.Child(sel, 0), it, iq);
        IF t = SymTab.InvalidType THEN
        ELSE
          QbeGen.WidenIndex(iq, ql);
          isOpen := SymTab.IsOpenArray(t);
          IF isOpen THEN
            QbeGen.CopyOp("0", qlo);
            IF SymTab.IsCharArray(t) OR SymTab.IsUCharArray(t) THEN
              QbeGen.OpenHiChar(q, qhi)
            ELSE QbeGen.OpenHi(q, qhi)
            END
          ELSE
            lo := SymTab.ArrayLo(t); hi := SymTab.ArrayHi(t);
            IF SymTab.IsCharArray(t) OR SymTab.IsUCharArray(t) THEN
              hi := hi + 1
            END;
            QbeGen.IntStr(lo, qlo); QbeGen.IntStr(hi, qhi)
          END;
          QbeGen.CheckRange(ql, qlo, qhi);
          eT := SymTab.ArrayElem(t);
          QbeGen.ElemAddr(q, ql, qlo, t, qe);
          IF SymTab.ClassOf(eT) = SymTab.ClArray THEN
            QbeGen.ElemLoad(qe, eT, q)
          ELSE QbeGen.CopyOp(qe, q)
          END;
          t := eT; sfx := TRUE
        END
      ELSIF op = AST.SelDeref THEN
        IF t = SymTab.InvalidType THEN
        ELSIF SymTab.ClassOf(t) # SymTab.ClPtr THEN t := SymTab.InvalidType
        ELSE
          IF sfx THEN QbeGen.ElemLoad(q, t, qe); QbeGen.CopyOp(qe, q) END;
          t := SymTab.PtrBase(t); sfx := TRUE
        END
      END;
      INC(i)
    END
  END LowerDesign;

PROCEDURE CompositeRes (t: SymTab.TypeIndex): BOOLEAN;
(* TRUE for a composite (by-value) function result: record/array/set.
   Such results use a hidden destination pointer (sret). *)
  VAR cls: INTEGER;
  BEGIN
    IF t = SymTab.InvalidType THEN RETURN FALSE END;
    cls := SymTab.ClassOf(t);
    RETURN (cls = SymTab.ClRecord) OR (cls = SymTab.ClArray)
        OR (cls = SymTab.ClSet) OR (cls = SymTab.ClClass)
  END CompositeRes;

PROCEDURE UserLabel (name: ARRAY OF CHAR; VAR q: QbeGen.QVal);
(* The QbeGen label for a user label/goto name (per procedure). *)
  VAR i: CARDINAL;
  BEGIN
    i := 0;
    WHILE i < nUserLab DO
      IF SpanEq(userLabNm, i * 64, name) THEN q := userLabQ[i]; RETURN END;
      INC(i)
    END;
    QbeGen.NewLabel(q);
    IF nUserLab <= HIGH(userLabQ) THEN
      CopySpan(name, userLabNm, 0, nUserLab * 64);
      userLabQ[nUserLab] := q;
      INC(nUserLab)
    END
  END UserLabel;

PROCEDURE LowerCall (n: AST.Node; VAR t: SymTab.TypeIndex;
                     VAR q: QbeGen.QVal; want: BOOLEAN);
  VAR nm, pn, cqn: SymTab.Name; i, ai: CARDINAL; at, ft, res: SymTab.TypeIndex;
      qa, qt, qe, mg, qres: QbeGen.QVal; conv, isV, qual, ind, isC, va: BOOLEAN;
      uid, depth, np: CARDINAL; ext: BOOLEAN; ck: INTEGER; pi: INTEGER;
      ct: SymTab.TypeIndex; csfx: BOOLEAN; cl: CHAR;
      seq, next, arg: AST.Node;
  BEGIN
    qual := CalleeAlias(n, nm);
    ind := FALSE; isC := FALSE; va := FALSE; pi := -1; ext := FALSE;
    IF qual AND qualIsVar THEN
      (* M.Error where Error is a procedure-typed variable: indirect. *)
      LowerDesign(AST.Child(n, 0), ct, ck, qa, cqn, csfx);
      IF (ct # SymTab.InvalidType)
         AND (SymTab.ClassOf(ct) = SymTab.ClProc) THEN
        ind := TRUE;
        res := SymTab.ProcTypeRes(ct);
        np := SymTab.ProcTypeNPar(ct);
        QbeGen.CallBeginInd(qa, res, FALSE)
      ELSE
        res := SymTab.InvalidType;
        QbeGen.CallBegin(nm, res, 0, FALSE)
      END
    ELSIF qual THEN
      (* M.P: the base name may be duplicated across modules, so select
         the exact proc entry by the alias's uid. *)
      pi := FindProcByUid(qualUid);
      IF ProcInfoIdx(pi, uid, res, depth, ext, np) THEN
        IF ext THEN QbeGen.CopyOp(nm, mg) ELSE QbeGen.Mangled(nm, uid, mg) END;
        QbeGen.CallBegin(mg, res, depth, ext)
      ELSE
        res := SymTab.InvalidType;
        QbeGen.CallBegin(nm, res, 0, FALSE)
      END
    ELSE
      CalleeName(n, nm);
      IF FindSym(nm, ck, ct)
         AND ((ck = SymTab.KindVar) OR (ck = SymTab.KindParam))
         AND (SymTab.ClassOf(ct) = SymTab.ClProc) THEN
        (* indirect call through a procedure-typed variable *)
        ind := TRUE;
        LowerDesign(AST.Child(n, 0), ct, ck, qa, cqn, csfx);
        res := SymTab.ProcTypeRes(ct);
        np := SymTab.ProcTypeNPar(ct);
        QbeGen.CallBeginInd(qa, res, FALSE)
      ELSIF ProcInfo(nm, uid, res, depth, ext, np) THEN
        pi := FindProc(nm);
        IF ext THEN
          (* External callee: bind to its C link name (the procedure's
             own name); SymTab.ProcLink cannot be consulted after
             EndUnit. *)
          QbeGen.CopyOp(nm, mg)
        ELSE
          QbeGen.Mangled(nm, uid, mg)
        END;
        QbeGen.CallBegin(mg, res, depth, ext)
      ELSE
        (* not in Lower's table: a predef C proc (SYSTEM.TRANSFER,
           NEWPROCESS, ...) lives in SymTab with a C link name *)
        IF SymTab.Lookup(nm) AND (SymTab.SymKind(nm) = SymTab.KindProc) THEN
          isC := TRUE;
          res := SymTab.ProcRes(nm);
          np := SymTab.ProcNPar(nm);
          IF SymTab.ProcLink(nm, pn) THEN
            QbeGen.CallBegin(pn, res, 0, TRUE)
          ELSE
            QbeGen.CallBegin(nm, res, 0, FALSE)
          END
        ELSE
          res := SymTab.InvalidType;
          QbeGen.CallBegin(nm, res, 0, FALSE)
        END
      END
    END;
    IF CompositeRes(res) THEN
      (* composite result: pass a hidden destination pointer first *)
      QbeGen.AllocLocal(res, qres);
      IF NOT QbeGen.CallArg(qres, "l") THEN END
    END;
    va := (pi >= 0) AND (pi < VAL(INTEGER, nProcs)) AND procVa[pi];
    (* actuals are a chunked sequence (AstCallNode): follow the NkBlock
       continuations so a call with >MaxChild-1 arguments is complete *)
    ai := 0;
    seq := n;
    WHILE seq # AST.NoNode DO
      i := 0;
      IF seq = n THEN i := 1 END;   (* skip the callee in the head *)
      WHILE i < AST.NChild(seq) DO
        arg := AST.Child(seq, i);
        IF AST.Kind(arg) # AST.NkBlock THEN
          LowerExpr(arg, at, qe);
          IF ind THEN
            ft := SymTab.ProcTypeParamType(ct, ai);
            isV := SymTab.ProcTypeParamIsVar(ct, ai)
          ELSIF va THEN
            ft := at; isV := FALSE
          ELSIF isC THEN
            ft := SymTab.ParamType(nm, ai);
            isV := SymTab.ParamIsVar(nm, ai)
          ELSE
            IF NOT ParamInfoIdx(pi, ai, ft, isV, pn) THEN END
          END;
          IF (NOT va) AND SymTab.IsEmptyStr(at)
             AND (ft # SymTab.InvalidType)
             AND (SymTab.ClassOf(ft) = SymTab.ClChar) THEN
            (* ISO: empty string actual for a CHAR formal is 0 *)
            QbeGen.CopyOp("0", qe); at := SymTab.CharType()
          END;
          IF va THEN
            (* permissive C variadic argument *)
            QbeGen.CArgAdd(qe, at, qa, cl)
          ELSIF isV THEN
            IF (SymTab.ClassOf(at) = SymTab.ClChar)
               AND (SymTab.ClassOf(ft) = SymTab.ClArray)
               AND (SymTab.ClassOf(SymTab.ArrayElem(ft)) = SymTab.ClChar)
               AND QbeGen.IsImm(qe) THEN
              (* 1-char string literal passed to a VAR ARRAY OF CHAR:
                 pass its static descriptor *)
              QbeGen.DeclCharStr(qe, qa);
              IF NOT QbeGen.CallArg(qa, "l") THEN END
            ELSIF SymTab.IsByteBuf(ft)
               AND (SymTab.ClassOf(at) # SymTab.ClArray)
               AND (SymTab.ClassOf(at) # SymTab.ClStr) THEN
              (* gm2 ext: wrap the scalar actual as a stack byte-buffer
                 descriptor (count = SIZE(actual), payload = a copy) *)
              QbeGen.OpenScalarDesc(qe, at, ft, qa);
              IF NOT QbeGen.CallArg(qa, "l") THEN END
            ELSIF QbeGen.AddrOfVal(qe, qa) THEN
              IF NOT QbeGen.CallArg(qa, "l") THEN END
            END
          ELSE
            IF (SymTab.ClassOf(at) = SymTab.ClChar)
               AND (SymTab.ClassOf(ft) = SymTab.ClArray)
               AND (SymTab.ClassOf(SymTab.ArrayElem(ft)) = SymTab.ClChar)
               AND QbeGen.IsImm(qe) THEN
              (* 1-char string literal passed to ARRAY OF CHAR: pass its
                 static descriptor, not the char code *)
              QbeGen.DeclCharStr(qe, qa);
              IF NOT QbeGen.CallArg(qa, "l") THEN END
            ELSIF SymTab.IsByteBuf(ft)
               AND (SymTab.ClassOf(at) # SymTab.ClArray)
               AND (SymTab.ClassOf(at) # SymTab.ClStr) THEN
              (* gm2 ext: wrap the scalar actual as a stack byte-buffer
                 descriptor (count = SIZE(actual), payload = a copy) *)
              QbeGen.OpenScalarDesc(qe, at, ft, qa);
              IF NOT QbeGen.CallArg(qa, "l") THEN END
            ELSE
              conv := (SymTab.ClassOf(ft) = SymTab.ClReal)
                      AND SymTab.IsIntFamily(at);
              IF conv THEN
                QbeGen.ConvIR(qe, qt);
                IF NOT QbeGen.CallArg(qt, "d") THEN END
              ELSE
                IF NOT QbeGen.CallArg(qe, QbeGen.ArgClass(ft)) THEN END
              END
            END
          END;
          INC(ai)
        END;
        INC(i)
      END;
      next := AST.NoNode;
      IF AST.NChild(seq) > 0 THEN
        next := AST.Child(seq, AST.NChild(seq) - 1);
        IF AST.Kind(next) # AST.NkBlock THEN next := AST.NoNode END
      END;
      seq := next
    END;
    IF want THEN
      t := res; QbeGen.CallEnd(TRUE, q);
      IF CompositeRes(res) THEN QbeGen.CopyOp(qres, q) END
    ELSE
      t := SymTab.InvalidType; QbeGen.CopyOp("0", q); QbeGen.CallEnd(FALSE, q)
    END
  END LowerCall;

PROCEDURE IsBuiltin (nm: ARRAY OF CHAR): BOOLEAN;
  BEGIN
    RETURN SymTab.Equal(nm, "ABS") OR SymTab.Equal(nm, "ODD")
        OR SymTab.Equal(nm, "CAP")
        OR SymTab.Equal(nm, "CHR") OR SymTab.Equal(nm, "ORD")
        OR SymTab.Equal(nm, "UCHR") OR SymTab.Equal(nm, "CHR8")
        OR SymTab.Equal(nm, "UORD")
        OR SymTab.Equal(nm, "SIZE") OR SymTab.Equal(nm, "TSIZE")
        OR SymTab.Equal(nm, "LEN") OR SymTab.Equal(nm, "HIGH")
        OR SymTab.Equal(nm, "VAL")
        OR SymTab.Equal(nm, "MIN") OR SymTab.Equal(nm, "MAX")
        OR SymTab.Equal(nm, "SHIFT") OR SymTab.Equal(nm, "ROTATE")
        OR SymTab.Equal(nm, "ADR")
        OR SymTab.Equal(nm, "INC") OR SymTab.Equal(nm, "DEC")
        OR SymTab.Equal(nm, "INCL") OR SymTab.Equal(nm, "EXCL")
        OR SymTab.Equal(nm, "NEW") OR SymTab.Equal(nm, "DISPOSE")
  END IsBuiltin;

PROCEDURE LowerProcAddr (nm: ARRAY OF CHAR; VAR q: QbeGen.QVal);
(* Code address of a procedure used as a value (assign to a procedure
   variable): $<base>_<uid>, or the plain C link for external procs.
   Declared before LowerBuiltinExpr, which uses it for ADR. *)
  VAR uid, depth, np: CARDINAL; res: SymTab.TypeIndex; ext: BOOLEAN;
      mg: QbeGen.QVal;
      base: SymTab.Name; ok: BOOLEAN;
  BEGIN
    ok := ProcInfo(nm, uid, res, depth, ext, np);
    IF NOT ok THEN
      (* a qualified/imported procedure appears under its base symbol
         name in the proc table *)
      IF SymTab.SymBase(nm, base) THEN
        ok := ProcInfo(base, uid, res, depth, ext, np)
      END
    END;
    IF ok THEN
      IF ext THEN QbeGen.CopyOp(nm, mg) ELSE QbeGen.Mangled(nm, uid, mg) END;
      QbeGen.ProcAddr(mg, q)
    ELSE QbeGen.CopyOp("0", q)
    END
  END LowerProcAddr;

PROCEDURE LowerBuiltinExpr (n: AST.Node; nm: SymTab.Name;
                            VAR t: SymTab.TypeIndex; VAR q: QbeGen.QVal);
(* Value builtins (Fact). *)
  VAR et, et2, dt, vt: SymTab.TypeIndex; qa, qt, q2, qd, qr: QbeGen.QVal;
      k, lo, hi, c1, c2, ucp: INTEGER; qn, vn: SymTab.Name; sfx: BOOLEAN;
      isMax, isU, uok: BOOLEAN;
  BEGIN
    IF SymTab.Equal(nm, "ODD") THEN
      LowerExpr(AST.Child(n, 1), et, q);
      QbeGen.NewTemp(qt);
      QbeGen.Op3("and", qt, q, "1", FALSE);       (* x & 1 *)
      QbeGen.NewTemp(qa);
      QbeGen.Cmp(SymTab.OpNeq1, qt, "0", qa, FALSE);   (* <> 0 *)
      QbeGen.CopyOp(qa, q); t := SymTab.BoolType()
    ELSIF SymTab.Equal(nm, "ABS") THEN
      LowerExpr(AST.Child(n, 1), et, q);
      QbeGen.AbsQ(q, qa, SymTab.ClassOf(et) = SymTab.ClReal);
      QbeGen.CopyOp(qa, q); t := et
    ELSIF SymTab.Equal(nm, "CAP") THEN
      LowerExpr(AST.Child(n, 1), et, q);
      QbeGen.CapQ(q, qa); QbeGen.CopyOp(qa, q); t := SymTab.CharType()
    ELSIF SymTab.Equal(nm, "CHR") THEN
      LowerExpr(AST.Child(n, 1), et, q); t := SymTab.CharType()
    ELSIF SymTab.Equal(nm, "ORD") THEN
      LowerExpr(AST.Child(n, 1), et, q); t := SymTab.IntType()
    ELSIF SymTab.Equal(nm, "UCHR") THEN
      LowerExpr(AST.Child(n, 1), et, q); t := SymTab.UCharType()
    ELSIF SymTab.Equal(nm, "CHR8") THEN
      LowerExpr(AST.Child(n, 1), et, q);
      QbeGen.WidenLong(q, qa); QbeGen.CheckRange(qa, "0", "255");
      t := SymTab.CharType()
    ELSIF SymTab.Equal(nm, "UORD") THEN
      LowerExpr(AST.Child(n, 1), et, q); t := SymTab.IntType()
    ELSIF SymTab.Equal(nm, "SIZE") OR SymTab.Equal(nm, "TSIZE") THEN
      LowerDesign(AST.Child(n, 1), dt, k, qd, qn, sfx);
      QbeGen.IntStr(VAL(INTEGER, SymTab.ObjectSize(dt)), q);
      t := SymTab.IntType()
    ELSIF SymTab.Equal(nm, "MIN") OR SymTab.Equal(nm, "MAX") THEN
      isMax := SymTab.Equal(nm, "MAX");
      LowerDesign(AST.Child(n, 1), dt, k, qd, qn, sfx);
      IF SymTab.ClassOf(dt) = SymTab.ClReal THEN
        IF isMax THEN QbeGen.NormReal("3.402823e38", q)
        ELSE QbeGen.NormReal("-3.402823e38", q) END;
        t := SymTab.RealType()
      ELSIF SymTab.ClassOf(dt) = SymTab.ClLong THEN
        IF isMax THEN QbeGen.CopyOp("9223372036854775807", q)
        ELSE QbeGen.CopyOp("-9223372036854775808", q) END;
        t := SymTab.LongType()
      ELSIF SymTab.TypeBounds(dt, lo, hi) THEN
        IF isMax THEN QbeGen.IntStr(hi, q) ELSE QbeGen.IntStr(lo, q) END;
        t := SymTab.IntType()
      ELSE t := SymTab.InvalidType; QbeGen.CopyOp("0", q)
      END
    ELSIF SymTab.Equal(nm, "LEN") OR SymTab.Equal(nm, "HIGH") THEN
      IF AST.Kind(AST.Child(n, 1)) = AST.NkStrLit THEN
        (* LEN("literal"): the content length of the literal; a real
           string literal is still declared, as the grammar does *)
        Name(AST.Child(n, 1), qn);
        IF (qn[0] = "U") OR (qn[0] = "u") THEN
          QbeGen.DeclUStr(qn, qd, isU, ucp, uok);
          IF NOT uok THEN t := SymTab.InvalidType; QbeGen.CopyOp("0", q)
          ELSIF isU THEN
            IF SymTab.Equal(nm, "HIGH") THEN QbeGen.CopyOp("0", q)
            ELSE QbeGen.CopyOp("1", q)
            END;
            t := SymTab.IntType()
          ELSE
            QbeGen.UStrLen(qd, qr);
            IF SymTab.Equal(nm, "HIGH") THEN QbeGen.DecQ(qr) END;
            QbeGen.CopyOp(qr, q); t := SymTab.IntType()
          END
        ELSE
        IF SymTab.StrLen(qn) = 3 THEN c1 := 1
        ELSE QbeGen.DeclStr(qn, qd); c1 := SymTab.StrLen(qn) - 2
        END;
        IF SymTab.Equal(nm, "HIGH") THEN DEC(c1) END;
        QbeGen.IntStr(c1, q); t := SymTab.IntType()
        END
      ELSE
      LowerDesign(AST.Child(n, 1), dt, k, qd, qn, sfx);
      IF dt = SymTab.InvalidType THEN
        t := SymTab.InvalidType; QbeGen.CopyOp("0", q)
      ELSIF SymTab.ClassOf(dt) = SymTab.ClArray THEN
        IF SymTab.Equal(nm, "HIGH") THEN
          IF SymTab.IsOpenArray(dt) THEN QbeGen.OpenHi(qd, q)
          ELSE QbeGen.IntStr(SymTab.ArrayHi(dt), q) END
        ELSE
          IF SymTab.IsOpenArray(dt) THEN QbeGen.LoadCount(qd, q)
          ELSE QbeGen.IntStr(VAL(INTEGER, SymTab.ArrayLen(dt)), q) END
        END;
        t := SymTab.IntType()
      ELSE
        t := SymTab.InvalidType; QbeGen.CopyOp("0", q)
      END
      END;
    ELSIF SymTab.Equal(nm, "VAL") THEN
      Name(AST.Child(n, 1), vn);
      IF NOT SymTab.Lookup(vn) THEN
        t := SymTab.InvalidType; QbeGen.CopyOp("0", q)
      ELSE
        vt := SymTab.SymType(vn);
        LowerExpr(AST.Child(n, 2), et, q);
        c1 := SymTab.ClassOf(et); c2 := SymTab.ClassOf(vt);
        IF ((c1 = SymTab.ClInt) OR (c1 = SymTab.ClByte)
            OR (c1 = SymTab.ClSByte) OR (c1 = SymTab.ClWord16)
            OR (c1 = SymTab.ClSWord16))
           AND (c2 = SymTab.ClLong) THEN
          QbeGen.WidenLong(q, qa); QbeGen.CopyOp(qa, q); t := vt
        ELSIF (c1 = SymTab.ClLong) AND ((c2 = SymTab.ClInt)
            OR (c2 = SymTab.ClByte) OR (c2 = SymTab.ClSByte)
            OR (c2 = SymTab.ClWord16) OR (c2 = SymTab.ClSWord16)) THEN
          QbeGen.NarrowLong(q, qa); QbeGen.CopyOp(qa, q); t := vt
        ELSIF ((c1 = SymTab.ClInt) OR (c1 = SymTab.ClByte)
            OR (c1 = SymTab.ClSByte) OR (c1 = SymTab.ClWord16)
            OR (c1 = SymTab.ClSWord16))
           AND (c2 = SymTab.ClReal) THEN
          QbeGen.ConvIR(q, qa); QbeGen.CopyOp(qa, q); t := vt
        ELSIF (c1 = SymTab.ClLong) AND (c2 = SymTab.ClReal) THEN
          QbeGen.ConvLR(q, qa); QbeGen.CopyOp(qa, q); t := vt
        ELSIF (c1 = SymTab.ClReal) AND ((c2 = SymTab.ClInt)
            OR (c2 = SymTab.ClByte) OR (c2 = SymTab.ClSByte)
            OR (c2 = SymTab.ClWord16) OR (c2 = SymTab.ClSWord16)) THEN
          QbeGen.ConvRI(q, qa); QbeGen.CopyOp(qa, q); t := vt
        ELSIF (c1 = SymTab.ClReal) AND (c2 = SymTab.ClLong) THEN
          QbeGen.ConvRL(q, qa); QbeGen.CopyOp(qa, q); t := vt
        ELSIF (c1 = SymTab.ClSet) AND (c2 = SymTab.ClInt) THEN
          (* a set as its (first) machine word *)
          QbeGen.LoadW(q, qa); QbeGen.CopyOp(qa, q); t := vt
        ELSIF (c1 = SymTab.ClInt) AND (c2 = SymTab.ClSet) THEN
          (* a word as a set value: zero-filled one-word temp *)
          c2 := SymTab.SetWords(vt);
          IF c2 = 0 THEN c2 := 1 END;
          QbeGen.NewSetTemp(VAL(CARDINAL, c2), qa);
          QbeGen.SetZero(qa, VAL(CARDINAL, c2));
          QbeGen.StoreW(qa, q); QbeGen.CopyOp(qa, q); t := vt
        ELSE t := vt   (* same representation: no-op *)
        END
      END
    ELSIF SymTab.Equal(nm, "SHIFT") OR SymTab.Equal(nm, "ROTATE") THEN
      LowerExpr(AST.Child(n, 1), et, q);
      LowerExpr(AST.Child(n, 2), et2, q2);
      QbeGen.SetShift(q, q2, SymTab.SetWords(et), SymTab.SetCount(et),
                      SymTab.Equal(nm, "ROTATE"), qt);
      t := et; QbeGen.CopyOp(qt, q)
    ELSIF SymTab.Equal(nm, "ADR") THEN
      LowerDesign(AST.Child(n, 1), dt, k, qd, qn, sfx);
      IF k = SymTab.KindProc THEN
        (* ADR of a procedure is its code address *)
        LowerProcAddr(qn, q)
      ELSIF sfx THEN QbeGen.CopyOp(qd, q)
      ELSIF (k = SymTab.KindVar) OR (k = SymTab.KindParam) THEN
        QbeGen.AddrOf(qn, q)
      ELSE QbeGen.CopyOp("0", q)
      END;
      t := SymTab.AddrType()
    ELSE t := SymTab.InvalidType; QbeGen.CopyOp("0", q)
    END
  END LowerBuiltinExpr;

PROCEDURE LowerBuiltinStmt (n: AST.Node; nm: SymTab.Name);
(* Statement builtins (AssOrCall): INC/DEC, INCL/EXCL, NEW/DISPOSE. *)
  VAR dt, at, et2, bt: SymTab.TypeIndex; dk: INTEGER;
      qd, qv, qe, qn2, qstep, qm: QbeGen.QVal;
      qn: SymTab.Name; sfx, isInc: BOOLEAN;
  BEGIN
    IF SymTab.Equal(nm, "INC") OR SymTab.Equal(nm, "DEC") THEN
      isInc := SymTab.Equal(nm, "INC");
      QbeGen.CopyOp("1", qstep);
      LowerDesign(AST.Child(n, 1), dt, dk, qd, qn, sfx);
      IF AST.NChild(n) > 2 THEN LowerExpr(AST.Child(n, 2), et2, qstep) END;
      IF dt = SymTab.InvalidType THEN
      ELSE
        IF sfx OR (dk = SymTab.KindField) THEN QbeGen.ElemLoad(qd, dt, qv)
        ELSIF SymTab.IsSmallInt(dt) THEN
          QbeGen.LoadShortVar(qn, SymTab.IsSignedSmallInt(dt),
            SymTab.SmallIntBytes(dt), qv)
        ELSE QbeGen.LoadVar(qn, FALSE, qv)
        END;
        QbeGen.NewTemp(qn2);
        IF isInc THEN QbeGen.Op3("add", qn2, qv, qstep, FALSE)
        ELSE QbeGen.Op3("sub", qn2, qv, qstep, FALSE)
        END;
        IF sfx OR (dk = SymTab.KindField) THEN QbeGen.ElemStore(qd, qn2, dt)
        ELSIF SymTab.IsSmallInt(dt) THEN
          QbeGen.StoreShortVar(qn, SymTab.SmallIntBytes(dt), qn2)
        ELSE QbeGen.StoreVar(qn, qn2, FALSE)
        END
      END
    ELSIF SymTab.Equal(nm, "INCL") OR SymTab.Equal(nm, "EXCL") THEN
      isInc := SymTab.Equal(nm, "INCL");
      LowerDesign(AST.Child(n, 1), at, dk, qd, qn, sfx);
      LowerExpr(AST.Child(n, 2), et2, qe);
      IF at = SymTab.InvalidType THEN
      ELSIF SymTab.ClassOf(at) # SymTab.ClSet THEN
      ELSE
        IF isInc THEN QbeGen.SetBit(qd, qe, SymTab.SetBaseLo(at), SymTab.SetCount(at))
        ELSE QbeGen.SetClearBit(qd, qe, SymTab.SetBaseLo(at), SymTab.SetCount(at))
        END
      END
    ELSIF SymTab.Equal(nm, "NEW") THEN
      LowerDesign(AST.Child(n, 1), dt, dk, qd, qn, sfx);
      IF dt = SymTab.InvalidType THEN
      ELSIF SymTab.ClassOf(dt) # SymTab.ClPtr THEN
      ELSE
        bt := SymTab.PtrBase(dt);
        IF bt # SymTab.InvalidType THEN
          QbeGen.NewHeap(bt, qm); QbeGen.InitHeap(qm, bt);
          IF sfx OR (dk = SymTab.KindField) THEN QbeGen.ElemStore(qd, qm, dt)
          ELSE QbeGen.StorePtr(qn, qm)
          END
        END
      END
    ELSIF SymTab.Equal(nm, "DISPOSE") THEN
      LowerDesign(AST.Child(n, 1), dt, dk, qd, qn, sfx);
      IF dt = SymTab.InvalidType THEN
      ELSIF SymTab.ClassOf(dt) # SymTab.ClPtr THEN
      ELSE
        IF sfx OR (dk = SymTab.KindField) THEN QbeGen.ElemLoad(qd, dt, qv)
        ELSE QbeGen.LoadPtr(qn, qv)
        END;
        QbeGen.FreeHeap(qv);
        IF sfx OR (dk = SymTab.KindField) THEN QbeGen.ElemStore(qd, "0", dt)
        ELSE QbeGen.StorePtr(qn, "0")
        END
      END
    END
  END LowerBuiltinStmt;

PROCEDURE LowerMethod (m: AST.Node; ct: SymTab.TypeIndex);
(* A class method: hidden THIS receiver, then declared formals; the body
   runs with THIS pushed as the WITH base (bare field names resolve). *)
  VAR nm, txt: SymTab.Name; mg, thisQ: QbeGen.QVal;
      uid, depth, np: CARDINAL; res, pt: SymTab.TypeIndex;
      pv, ext: BOOLEAN; j: CARDINAL; saveCls: SymTab.TypeIndex;
      savedProc: INTEGER;
  BEGIN
    IF (AST.Op(m) # 0) AND (AST.Op(m) # 3) THEN RETURN END;
    Name(AST.Child(m, 0), nm);
    IF NOT ProcInfo(nm, uid, res, depth, ext, np) THEN RETURN END;
    QbeGen.Mangled(nm, SymTab.ClassMethodUid(ct, nm), mg);
    QbeGen.BeginFunc(mg);
    IF NOT QbeGen.FuncParam("THIS", TRUE, ct) THEN END;
    IF CompositeRes(res) THEN
      IF NOT QbeGen.FuncParam("__res", TRUE, res) THEN END
    END;
    j := 0;
    WHILE j < np DO
      IF NOT ParamInfo(nm, j, pt, pv, txt) THEN END;
      IF NOT QbeGen.FuncParam(txt, pv OR SymTab.IsOpenArray(pt), pt) THEN END;
      INC(j)
    END;
    QbeGen.SetFuncRes(res);
    QbeGen.EndFuncHeader;
    QbeGen.ThisBase(thisQ);
    saveCls := curImplCls;
    curImplCls := ct;
    QbeGen.PushWith(thisQ);
    IF withTop <= HIGH(withRec) THEN withRec[withTop] := ct; INC(withTop) END;
    savedProc := emitProc;
    emitProc := FindProc(nm);
    LowerDecls(AST.Child(m, 2));
    nUserLab := 0;
    LowerStmt(AST.Child(m, 1));
    emitProc := savedProc;
    IF withTop > 0 THEN DEC(withTop) END;
    curImplCls := saveCls;
    QbeGen.PopWith;
    QbeGen.EndFunc(res)
  END LowerMethod;

PROCEDURE LowerMethods (seq: AST.Node; ct: SymTab.TypeIndex);
  VAR i: CARDINAL; m: AST.Node;
  BEGIN
    IF seq = AST.NoNode THEN RETURN END;
    i := 0;
    WHILE i < AST.NChild(seq) DO
      m := AST.Child(seq, i);
      IF i = AST.MaxChild - 1 THEN LowerMethods(m, ct)
      ELSIF AST.Kind(m) = AST.NkFieldDecl THEN LowerMethods(m, ct)
      ELSIF AST.Kind(m) = AST.NkProcDecl THEN LowerMethod(m, ct)
      END;
      INC(i)
    END
  END LowerMethods;

PROCEDURE LowerMethodHeadings (seq: AST.Node; ct: SymTab.TypeIndex);
(* Class-declaration method headings: emit+discard a function header per
   method so the backend temp counters advance exactly as the legacy
   parse did (the implementation's temps then line up). *)
  VAR i, j: CARDINAL; m: AST.Node; nm, txt: SymTab.Name;
      mg: QbeGen.QVal; uid, depth, np: CARDINAL; res, pt: SymTab.TypeIndex;
      pv, ext: BOOLEAN;
  BEGIN
    IF seq = AST.NoNode THEN RETURN END;
    i := 0;
    WHILE i < AST.NChild(seq) DO
      m := AST.Child(seq, i);
      IF i = AST.MaxChild - 1 THEN LowerMethodHeadings(m, ct)
      ELSIF AST.Kind(m) = AST.NkFieldDecl THEN LowerMethodHeadings(m, ct)
      ELSIF AST.Kind(m) = AST.NkProcDecl THEN
        Name(AST.Child(m, 0), nm);
        IF ProcInfo(nm, uid, res, depth, ext, np) THEN
          QbeGen.Mangled(nm, SymTab.ClassMethodUid(ct, nm), mg);
          QbeGen.BeginFunc(mg);
          j := 0;
          WHILE j < np DO
            IF NOT ParamInfo(nm, j, pt, pv, txt) THEN END;
            IF NOT QbeGen.FuncParam(txt, pv OR SymTab.IsOpenArray(pt), pt) THEN END;
            INC(j)
          END;
          QbeGen.SetFuncRes(res);
          QbeGen.AbortFunc
        END
      END;
      INC(i)
    END
  END LowerMethodHeadings;

PROCEDURE LowerMethodCall (n: AST.Node; VAR t: SymTab.TypeIndex;
                           VAR q: QbeGen.QVal; want: BOOLEAN);
  VAR d: AST.Node; ct, res, ft, at: SymTab.TypeIndex;
      cq, mg, qa, qt, qe, qres: QbeGen.QVal; fn, pn: SymTab.Name;
      k, vs: INTEGER; i: CARDINAL; sfx, isV, conv: BOOLEAN;
  BEGIN
    d := AST.Child(n, 0);
    curMethCls := SymTab.InvalidType;
    LowerDesign(d, ct, k, cq, pn, sfx);
    ct := curMethCls;
    IF ct = SymTab.InvalidType THEN
      t := SymTab.InvalidType; QbeGen.CopyOp("0", q); RETURN
    END;
    IF AST.NChild(d) = 1 THEN
      Name(AST.Child(d, 0), fn)
    ELSE
      Name(AST.Child(AST.Child(d, AST.NChild(d) - 1), 0), fn)
    END;
    res := SymTab.ClassMethodRes(ct, fn);
    vs := SymTab.VirtSlot(ct, fn);
    IF vs >= 0 THEN QbeGen.VirtCallBegin(cq, vs, res)
    ELSE
      QbeGen.Mangled(fn, SymTab.ClassMethodUid(ct, fn), mg);
      QbeGen.CallBegin(mg, res, 0, FALSE)
    END;
    IF CompositeRes(res) THEN
      QbeGen.AllocLocal(res, qres);
      IF NOT QbeGen.CallArg(qres, "l") THEN END
    END;
    i := 1;
    WHILE i < AST.NChild(n) DO
      LowerExpr(AST.Child(n, i), at, qe);
      ft := SymTab.ClassMethodParamType(ct, fn, i - 1);
      isV := SymTab.ClassMethodParamIsVar(ct, fn, i - 1);
      IF isV THEN
        IF QbeGen.AddrOfVal(qe, qa) THEN
          IF NOT QbeGen.CallArg(qa, "l") THEN END
        END
      ELSE
        conv := (SymTab.ClassOf(ft) = SymTab.ClReal) AND SymTab.IsIntFamily(at);
        IF conv THEN
          QbeGen.ConvIR(qe, qt);
          IF NOT QbeGen.CallArg(qt, "d") THEN END
        ELSE
          IF NOT QbeGen.CallArg(qe, QbeGen.ArgClass(ft)) THEN END
        END
      END;
      INC(i)
    END;
    IF want THEN t := res; QbeGen.CallEnd(TRUE, q);
      IF CompositeRes(res) THEN QbeGen.CopyOp(qres, q) END
    ELSE t := SymTab.InvalidType; QbeGen.CopyOp("0", q); QbeGen.CallEnd(FALSE, q)
    END
  END LowerMethodCall;

PROCEDURE LowerCase (n: AST.Node);
(* CASE as a compare-chain (mirrors CaseStat/CaseAlt/CaseLabel).  The
   arm list is chunked (AstAppend) so a CASE with more than MaxChild
   alternatives is not truncated. *)
  VAR i, j: CARDINAL; arm, lab, seq, next: AST.Node;
      tsel, t2, t3: SymTab.TypeIndex;
      qsel, q2, q3, qc, qd, qe, lEnd, lBody, lAfter, lNext: QbeGen.QVal;
  BEGIN
    LowerExpr(AST.Child(n, 0), tsel, qsel);
    QbeGen.NewLabel(lEnd);
    (* pass 1: alternatives (ELSE arms come after) *)
    seq := AST.Child(n, 1);
    WHILE seq # AST.NoNode DO
      i := 0;
      WHILE i < AST.NChild(seq) DO
        arm := AST.Child(seq, i);
        IF AST.Kind(arm) = AST.NkBlock THEN
          (* continuation chunk *)
        ELSIF AST.Op(arm) = 1 THEN
          (* ELSE arm: emitted in pass 2 *)
        ELSE
          QbeGen.NewLabel(lBody); QbeGen.NewLabel(lAfter);
          j := 0;
          WHILE j + 1 < AST.NChild(arm) DO
            lab := AST.Child(arm, j);
            IF AST.Kind(lab) = AST.NkSubrange THEN
              LowerExpr(AST.Child(lab, 0), t2, q2);
              IF SymTab.IsEmptyStr(t2)
                 AND (SymTab.ClassOf(tsel) = SymTab.ClChar) THEN
                QbeGen.CopyOp("0", q2); t2 := SymTab.CharType()
              END;
              QbeGen.NewLabel(lNext);
              QbeGen.Cmp(SymTab.OpEq, qsel, q2, qc, FALSE);
              QbeGen.Jnz(qc, lBody, lNext);
              QbeGen.EmitLabel(lNext);
              LowerExpr(AST.Child(lab, 1), t3, q3);
              IF SymTab.IsEmptyStr(t3)
                 AND (SymTab.ClassOf(tsel) = SymTab.ClChar) THEN
                QbeGen.CopyOp("0", q3); t3 := SymTab.CharType()
              END;
              QbeGen.Cmp(SymTab.OpGe, qsel, q2, qc, FALSE);
              QbeGen.Cmp(SymTab.OpLe, qsel, q3, qd, FALSE);
              QbeGen.NewTemp(qe);
              QbeGen.Op3("and", qe, qc, qd, FALSE);
              QbeGen.NewLabel(lNext);
              QbeGen.Jnz(qe, lBody, lNext);
              QbeGen.EmitLabel(lNext)
            ELSE
              LowerExpr(lab, t2, q2);
              IF SymTab.IsEmptyStr(t2)
                 AND (SymTab.ClassOf(tsel) = SymTab.ClChar) THEN
                QbeGen.CopyOp("0", q2); t2 := SymTab.CharType()
              END;
              QbeGen.NewLabel(lNext);
              IF (SymTab.ClassOf(tsel) = SymTab.ClSet)
                 AND (SymTab.ClassOf(t2) = SymTab.ClSet) THEN
                QbeGen.CmpSet(SymTab.OpEq, qsel, q2,
                  SymTab.SetWords(tsel), SymTab.SetWords(t2), qc)
              ELSE
                QbeGen.Cmp(SymTab.OpEq, qsel, q2, qc, FALSE)
              END;
              QbeGen.Jnz(qc, lBody, lNext);
              QbeGen.EmitLabel(lNext)
            END;
            INC(j)
          END;
          QbeGen.Jmp(lAfter);
          QbeGen.EmitLabel(lBody);
          LowerStmt(AST.Child(arm, AST.NChild(arm) - 1));
          QbeGen.Jmp(lEnd);
          QbeGen.EmitLabel(lAfter)
        END;
        INC(i)
      END;
      next := AST.NoNode;
      IF AST.NChild(seq) > 0 THEN
        next := AST.Child(seq, AST.NChild(seq) - 1);
        IF AST.Kind(next) # AST.NkBlock THEN next := AST.NoNode END
      END;
      seq := next
    END;
    (* pass 2: ELSE arms *)
    seq := AST.Child(n, 1);
    WHILE seq # AST.NoNode DO
      i := 0;
      WHILE i < AST.NChild(seq) DO
        arm := AST.Child(seq, i);
        IF (AST.Kind(arm) # AST.NkBlock) AND (AST.Op(arm) = 1) THEN
          LowerStmt(AST.Child(arm, 0))
        END;
        INC(i)
      END;
      next := AST.NoNode;
      IF AST.NChild(seq) > 0 THEN
        next := AST.Child(seq, AST.NChild(seq) - 1);
        IF AST.Kind(next) # AST.NkBlock THEN next := AST.NoNode END
      END;
      seq := next
    END;
    QbeGen.EmitLabel(lEnd)
  END LowerCase;

PROCEDURE LowerWith (n: AST.Node);
(* WITH: push each record's base address, lower the body, pop only the
   levels this WITH pushed (a nested WITH must restore the outer one). *)
  VAR i, base: CARDINAL; dt: SymTab.TypeIndex; dk: INTEGER;
      qd: QbeGen.QVal; qn: SymTab.Name; sfx: BOOLEAN;
  BEGIN
    base := withTop;
    i := 0;
    WHILE i + 1 < AST.NChild(n) DO
      LowerDesign(AST.Child(n, i), dt, dk, qd, qn, sfx);
      QbeGen.PushWith(qd);
      IF withTop <= HIGH(withRec) THEN
        withRec[withTop] := dt; INC(withTop)
      END;
      INC(i)
    END;
    LowerStmt(AST.Child(n, AST.NChild(n) - 1));
    WHILE withTop > base DO DEC(withTop); QbeGen.PopWith END
  END LowerWith;

PROCEDURE LowerExprFull (n: AST.Node; VAR t: SymTab.TypeIndex;
                         VAR q: QbeGen.QVal; VAR k: INTEGER;
                         VAR qn: SymTab.Name; VAR sfx: BOOLEAN;
                         asAddr: BOOLEAN);
  VAR t2: SymTab.TypeIndex; q2, qt, qf, qs, qr, qaddr, qa, qb: QbeGen.QVal;
      lNext, lFalse, lTrue, lDone: QbeGen.QVal;
      kind, op, rop, ucp: INTEGER;
      folded, isR, isCh, isU, uok: BOOLEAN;
      i: CARDINAL; el, seq, next: AST.Node;
      lw, rw, mw: CARDINAL; idx: INTEGER; fok, isL: BOOLEAN;
      lt, rt: SymTab.TypeIndex; qw: QbeGen.QVal;
  BEGIN
    IF AST.Kind(n) = AST.NkDesignator THEN
      LowerDesign(n, t, k, q, qn, sfx);
      IF k = SymTab.KindProc THEN
        (* bare procedure used as a value: its code address *)
        LowerProcAddr(qn, q);
        RETURN
      END;
      (* Record value->address for VAR actuals, mirroring the grammar's
         Design.  AddrOfVal cannot rely on the grammar's notes: its ring
         (256) wraps long before a whole-session emit finishes. *)
      IF sfx THEN QbeGen.CopyOp(q, qaddr) ELSE QbeGen.AddrOf(qn, qaddr) END;
      IF NOT asAddr THEN FinalLoad(t, sfx, q) END;
      IF (k = SymTab.KindVar) OR (k = SymTab.KindParam)
         OR (k = SymTab.KindField) THEN
        QbeGen.NoteAddr(q, qaddr)
      ELSIF sfx AND (t # SymTab.InvalidType)
         AND ((SymTab.ClassOf(t) = SymTab.ClArray)
              OR (SymTab.ClassOf(t) = SymTab.ClSet)
              OR (SymTab.ClassOf(t) = SymTab.ClRecord)) THEN
        QbeGen.NoteAddr(q, qaddr)
      END;
      RETURN
    END;
    k := -1; qn[0] := CHR(0); sfx := FALSE;
    IF AST.Kind(n) = AST.NkIntLit THEN
      Name(n, qn); QbeGen.NormInt(qn, q); t := SymTab.IntType()
    ELSIF AST.Kind(n) = AST.NkCharLit THEN
      Name(n, qn); QbeGen.NormLit(qn, q, isCh); t := SymTab.CharType()
    ELSIF AST.Kind(n) = AST.NkRealLit THEN
      Name(n, qn); QbeGen.NormReal(qn, q); t := SymTab.RealType()
    ELSIF AST.Kind(n) = AST.NkStrLit THEN
      Name(n, qn);
      IF (qn[0] = "U") OR (qn[0] = "u") THEN
        (* U"..." / U'...': one codepoint -> UCHAR, else a ustring *)
        QbeGen.DeclUStr(qn, q, isU, ucp, uok);
        IF NOT uok THEN
          t := SymTab.InvalidType; QbeGen.CopyOp("0", q)
        ELSIF isU THEN
          t := SymTab.UCharType(); QbeGen.IntStr(ucp, q)
        ELSE
          t := AST.Ty(n); IF t = -1 THEN t := SymTab.NewUStr() END; QbeGen.NoteAddr(q, q)
        END
      ELSIF SymTab.StrLen(qn) = 3 THEN
        t := SymTab.CharType(); QbeGen.IntStr(QbeGen.CharVal(qn), q)
      ELSE
        t := AST.Ty(n); IF t = -1 THEN t := SymTab.NewStr() END; QbeGen.DeclStr(qn, q); QbeGen.NoteAddr(q, q)
      END
    ELSIF AST.Kind(n) = AST.NkSetLit THEN
      t := AST.Ty(n); IF t = -1 THEN t := SymTab.NewSet(SymTab.NewSubR(0, 255)) END;
      QbeGen.NewSetTemp(8, q); QbeGen.SetZero(q, 8);
      i := 0;
      WHILE i < AST.NChild(n) DO
        el := AST.Child(n, i);
        IF AST.Kind(el) = AST.NkSubrange THEN
          LowerExpr(AST.Child(el, 0), t2, q2);
          LowerExpr(AST.Child(el, 1), t2, qt);
          QbeGen.SetRange(q, q2, qt, SymTab.SetBaseLo(t), SymTab.SetCount(t))
        ELSE
          LowerExpr(el, t2, q2);
          QbeGen.SetBit(q, q2, SymTab.SetBaseLo(t), SymTab.SetCount(t))
        END;
        INC(i)
      END
    ELSIF AST.Kind(n) = AST.NkBraceLit THEN
      (* T{...} typed brace literal: a set here (the type was recorded by
         the grammar in the node's ty field).  Array/record/class
         constructors are not lowered here yet. *)
      t := AST.Ty(n);
      IF (t # SymTab.InvalidType) AND (SymTab.ClassOf(t) = SymTab.ClSet) THEN
        IF SymTab.SetWords(t) = 0 THEN
          QbeGen.NewSetTemp(8, q); QbeGen.SetZero(q, 8)
        ELSE
          QbeGen.NewSetTemp(SymTab.SetWords(t), q);
          QbeGen.SetZero(q, SymTab.SetWords(t))
        END;
        seq := n;
        WHILE seq # AST.NoNode DO
          i := 0;
          WHILE i < AST.NChild(seq) DO
            el := AST.Child(seq, i);
            IF AST.Kind(el) # AST.NkBlock THEN
              IF AST.Kind(el) = AST.NkSubrange THEN
                LowerExpr(AST.Child(el, 0), t2, q2);
                LowerExpr(AST.Child(el, 1), t2, qt);
                QbeGen.SetRange(q, q2, qt, SymTab.SetBaseLo(t),
                  SymTab.SetCount(t))
              ELSE
                LowerExpr(el, t2, q2);
                QbeGen.SetBit(q, q2, SymTab.SetBaseLo(t), SymTab.SetCount(t))
              END
            END;
            INC(i)
          END;
          next := AST.NoNode;
          IF AST.NChild(seq) > 0 THEN
            next := AST.Child(seq, AST.NChild(seq) - 1);
            IF AST.Kind(next) # AST.NkBlock THEN next := AST.NoNode END
          END;
          seq := next
        END
      ELSIF (t # SymTab.InvalidType)
         AND ((SymTab.ClassOf(t) = SymTab.ClArray)
              OR (SymTab.ClassOf(t) = SymTab.ClRecord)
              OR (SymTab.ClassOf(t) = SymTab.ClClass)) THEN
        (* T{...} aggregate constructor *)
        QbeGen.CtorBegin(t);
        seq := n;
        WHILE seq # AST.NoNode DO
          i := 0;
          WHILE i < AST.NChild(seq) DO
            el := AST.Child(seq, i);
            IF AST.Kind(el) # AST.NkBlock THEN
              LowerExpr(el, t2, q2);
              QbeGen.CtorElem(q2)
            END;
            INC(i)
          END;
          next := AST.NoNode;
          IF AST.NChild(seq) > 0 THEN
            next := AST.Child(seq, AST.NChild(seq) - 1);
            IF AST.Kind(next) # AST.NkBlock THEN next := AST.NoNode END
          END;
          seq := next
        END;
        QbeGen.CtorEnd(q)
      ELSE
        t := SymTab.InvalidType; QbeGen.CopyOp("0", q)
      END
    ELSIF AST.Kind(n) = AST.NkDesignator THEN
      LowerDesign(n, t, k, q, qn, sfx)
    ELSIF AST.Kind(n) = AST.NkCall THEN
      IF IsMethodCall(n) THEN LowerMethodCall(n, t, q, TRUE)
      ELSE
        CalleeName(n, qn);
        IF IsBuiltin(qn) THEN LowerBuiltinExpr(n, qn, t, q)
        ELSE LowerCall(n, t, q, TRUE)
        END
      END
    ELSIF AST.Kind(n) = AST.NkUnary THEN
      LowerExpr(AST.Child(n, 0), t, q);
      IF AST.Op(n) = AST.OpSub THEN
        IF QbeGen.IsImm(q) THEN QbeGen.NegFold(q, q)
        ELSE QbeGen.NewTemp(qt);
          QbeGen.NegQ(q, qt, SymTab.ClassOf(t) = SymTab.ClReal);
          QbeGen.CopyOp(qt, q)
        END
      ELSE
        QbeGen.NotQ(q, qt); QbeGen.CopyOp(qt, q); t := SymTab.BoolType()
      END
    ELSIF AST.Kind(n) = AST.NkBinExpr THEN
      op := AST.Op(n);
      IF IsRel(op) THEN
        LowerExpr(AST.Child(n, 0), t, q);
        LowerExpr(AST.Child(n, 1), t2, q2);
        (* ISO: an empty string compared with CHAR is the terminator;
           against a CHAR array it stays a string (StrEq below). *)
        IF (t # SymTab.InvalidType) AND SymTab.IsEmptyStr(t)
           AND (t2 # SymTab.InvalidType)
           AND (SymTab.ClassOf(t2) = SymTab.ClChar) THEN
          QbeGen.CopyOp("0", q); t := SymTab.CharType()
        ELSIF (t2 # SymTab.InvalidType) AND SymTab.IsEmptyStr(t2)
           AND (t # SymTab.InvalidType)
           AND (SymTab.ClassOf(t) = SymTab.ClChar) THEN
          QbeGen.CopyOp("0", q2); t2 := SymTab.CharType()
        END;
        rop := SymTab.OpEq; folded := RelSym(op, rop);
        IF op = AST.OpIn THEN
          QbeGen.InSet(q, q2, SymTab.SetBaseLo(t2), SymTab.SetCount(t2), qt);
          t := SymTab.BoolType(); QbeGen.CopyOp(qt, q)
        ELSIF (SymTab.ClassOf(t) = SymTab.ClPtr)
           OR (SymTab.ClassOf(t2) = SymTab.ClPtr) THEN
          QbeGen.CmpL(rop, q, q2, qt);
          t := SymTab.BoolType(); QbeGen.CopyOp(qt, q)
        ELSIF (SymTab.ClassOf(t) = SymTab.ClSet)
           OR (SymTab.ClassOf(t2) = SymTab.ClSet) THEN
          QbeGen.CmpSet(rop, q, q2, SymTab.SetWords(t), SymTab.SetWords(t2), qt);
          t := SymTab.BoolType(); QbeGen.CopyOp(qt, q)
        ELSIF SymTab.StrCompat(t, t2) THEN
          QbeGen.StrEq(rop, q, q2, qt);
          t := SymTab.BoolType(); QbeGen.CopyOp(qt, q)
        ELSIF SymTab.IsLongFamily(t) OR SymTab.IsLongFamily(t2) THEN
          IF SymTab.IsIntFamily(t) THEN QbeGen.WidenLong(q, qf); QbeGen.CopyOp(qf, q) END;
          IF SymTab.IsIntFamily(t2) THEN QbeGen.WidenLong(q2, qf); QbeGen.CopyOp(qf, q2) END;
          QbeGen.CmpLong(rop, q, q2, qt);
          t := SymTab.BoolType(); QbeGen.CopyOp(qt, q)
        ELSE
          isR := (t # SymTab.InvalidType) AND (SymTab.ClassOf(t) = SymTab.ClReal);
          t := SymTab.BoolType();
          QbeGen.Cmp(rop, q, q2, qt, isR);
          QbeGen.CopyOp(qt, q)
        END
      ELSIF op = AST.OpAnd THEN
        LowerExpr(AST.Child(n, 0), t, q);
        QbeGen.DelayBegin;
        LowerExpr(AST.Child(n, 1), t2, q2);
        QbeGen.DelayEnd;
        QbeGen.Slot4(qs);
        QbeGen.NewLabel(lNext); QbeGen.NewLabel(lFalse); QbeGen.NewLabel(lDone);
        QbeGen.Jnz(q, lNext, lFalse);
        QbeGen.EmitLabel(lNext);
        QbeGen.DelayFlush;
        QbeGen.StoreW(qs, q2);
        QbeGen.Jmp(lDone);
        QbeGen.EmitLabel(lFalse);
        QbeGen.StoreW(qs, "0");
        QbeGen.Jmp(lDone);
        QbeGen.EmitLabel(lDone);
        QbeGen.LoadW(qs, qr);
        QbeGen.CopyOp(qr, q);
        t := SymTab.BoolType()
      ELSIF op = AST.OpOr THEN
        LowerExpr(AST.Child(n, 0), t, q);
        QbeGen.DelayBegin;
        LowerExpr(AST.Child(n, 1), t2, q2);
        QbeGen.DelayEnd;
        QbeGen.Slot4(qs);
        QbeGen.NewLabel(lTrue); QbeGen.NewLabel(lNext); QbeGen.NewLabel(lDone);
        QbeGen.Jnz(q, lTrue, lNext);
        QbeGen.EmitLabel(lTrue);
        QbeGen.StoreW(qs, "1");
        QbeGen.Jmp(lDone);
        QbeGen.EmitLabel(lNext);
        QbeGen.DelayFlush;
        QbeGen.StoreW(qs, q2);
        QbeGen.Jmp(lDone);
        QbeGen.EmitLabel(lDone);
        QbeGen.LoadW(qs, qr);
        QbeGen.CopyOp(qr, q);
        t := SymTab.BoolType()
      ELSE
        LowerExpr(AST.Child(n, 0), t, q);
        LowerExpr(AST.Child(n, 1), t2, q2);
        IF (t # SymTab.InvalidType) AND (t2 # SymTab.InvalidType)
           AND (SymTab.ClassOf(t) = SymTab.ClSet)
           AND (SymTab.ClassOf(t2) = SymTab.ClSet) THEN
          (* set union/diff (Add/Sub) or intersection/symdiff (Mul/Div) *)
          lw := SymTab.SetWords(t); rw := SymTab.SetWords(t2);
          mw := lw; IF rw > mw THEN mw := rw END;
          IF op = AST.OpAdd THEN idx := 0
          ELSIF op = AST.OpSub THEN idx := 2
          ELSIF op = AST.OpMul THEN idx := 1
          ELSE idx := 3
          END;
          QbeGen.SetBinOp(idx, q, q2, lw, rw, qt);
          t := SymTab.NewSet(SymTab.NewSubR(0, VAL(INTEGER, mw) * 32 - 1));
          QbeGen.CopyOp(qt, q)
        ELSIF (op = AST.OpAdd)
           AND (SymTab.StrCompat(t, t2)
                OR (SymTab.IsStrType(t) AND (SymTab.ClassOf(t2) = SymTab.ClChar))
                OR ((SymTab.ClassOf(t) = SymTab.ClChar) AND SymTab.IsStrType(t2))) THEN
          QbeGen.StrFold(q, q2, SymTab.ClassOf(t), SymTab.ClassOf(t2), qt, fok);
          IF NOT fok THEN
            IF SymTab.StrCompat(t, t2) THEN QbeGen.StrCat(q, q2, qt)
            ELSIF SymTab.IsStrType(t) THEN
              QbeGen.DeclCharStr(q2, qs); QbeGen.StrCat(q, qs, qt)
            ELSE
              QbeGen.DeclCharStr(q, qs); QbeGen.StrCat(qs, q2, qt)
            END
          END;
          t := SymTab.NewStr(); QbeGen.CopyOp(qt, q)
        ELSIF (op = AST.OpAdd)
           AND (SymTab.UStrCompat(t, t2)
                OR ((SymTab.ClassOf(t) = SymTab.ClUChar)
                    AND (SymTab.ClassOf(t2) = SymTab.ClUStr))
                OR ((SymTab.ClassOf(t) = SymTab.ClUStr)
                    AND (SymTab.ClassOf(t2) = SymTab.ClUChar))
                OR ((SymTab.ClassOf(t) = SymTab.ClUChar)
                    AND (SymTab.ClassOf(t2) = SymTab.ClUChar))) THEN
          (* UString concatenation: a UCHAR operand becomes a
             1-codepoint UString; the result is a descriptor *)
          IF SymTab.ClassOf(t) = SymTab.ClUStr THEN QbeGen.CopyOp(q, qa)
          ELSE QbeGen.UStrFrom(q, qa)
          END;
          IF SymTab.ClassOf(t2) = SymTab.ClUStr THEN QbeGen.UStrCat(qa, q2, qt)
          ELSE QbeGen.UStrFrom(q2, qb); QbeGen.UStrCat(qa, qb, qt)
          END;
          t := SymTab.NewUStr(); QbeGen.CopyOp(qt, q)
        ELSE
          lt := t; rt := t2;
          IF (SymTab.ClassOf(lt) = SymTab.ClReal)
             OR (SymTab.ClassOf(rt) = SymTab.ClReal) THEN
            t := SymTab.RealType()
          ELSIF SymTab.IsLongFamily(lt) OR SymTab.IsLongFamily(rt) THEN
            t := SymTab.LongType()
          ELSE t := SymTab.IntType()
          END;
          isL := SymTab.IsLongFamily(t);
          isR := SymTab.ClassOf(t) = SymTab.ClReal;
          kind := 0;
          IF op = AST.OpSub THEN kind := 1
          ELSIF op = AST.OpMul THEN kind := 2
          ELSIF op = AST.OpDiv THEN kind := 3
          ELSIF op = AST.OpMod THEN kind := 4
          END;
          folded := FALSE;
          IF (NOT isL) AND (NOT isR) AND QbeGen.IsImm(q) AND QbeGen.IsImm(q2) THEN
            folded := QbeGen.Fold2(kind, q, q2, qf)
          END;
          IF folded THEN QbeGen.CopyOp(qf, q)
          ELSE
            IF isL THEN
              IF SymTab.IsIntFamily(lt) THEN
                QbeGen.WidenLong(q, qw); QbeGen.CopyOp(qw, q)
              END;
              IF SymTab.IsIntFamily(rt) THEN
                QbeGen.WidenLong(q2, qw); QbeGen.CopyOp(qw, q2)
              END;
              QbeGen.NewTemp(qt);
              IF op = AST.OpAdd THEN QbeGen.Op3L("add", qt, q, q2)
              ELSIF op = AST.OpSub THEN QbeGen.Op3L("sub", qt, q, q2)
              ELSIF op = AST.OpMul THEN QbeGen.Op3L("mul", qt, q, q2)
              ELSE QbeGen.Op3L("div", qt, q, q2)
              END
            ELSE
              QbeGen.NewTemp(qt);
              IF op = AST.OpAdd THEN QbeGen.Op3("add", qt, q, q2, isR)
              ELSIF op = AST.OpSub THEN QbeGen.Op3("sub", qt, q, q2, isR)
              ELSIF op = AST.OpMul THEN QbeGen.Op3("mul", qt, q, q2, isR)
              ELSIF op = AST.OpDiv THEN QbeGen.Op3("div", qt, q, q2, isR)
              ELSE QbeGen.Op3("rem", qt, q, q2, isR)
              END
            END;
            QbeGen.CopyOp(qt, q)
          END
        END
      END
    END
  END LowerExprFull;

PROCEDURE LowerExpr (n: AST.Node; VAR t: SymTab.TypeIndex;
                     VAR q: QbeGen.QVal);
  VAR k: INTEGER; qn: SymTab.Name; sfx: BOOLEAN;
  BEGIN
    LowerExprFull(n, t, q, k, qn, sfx, FALSE)
  END LowerExpr;

PROCEDURE LowerStmt (seq: AST.Node);
  VAR i: CARDINAL; c, els, by: AST.Node; k: INTEGER;
      t, t2, t3, dt, et: SymTab.TypeIndex;
      q, q2, qt, qf, qd, qe: QbeGen.QVal;
      qlo, qhi, qk, qb, ql, qby: QbeGen.QVal; step: INTEGER;
      lTop, lBody, lEnd, lThen, lElse, lNext, lFalse, lDone, lx: QbeGen.QVal;
      qn, lv: SymTab.Name;
      kind, op, rop, cls: INTEGER;
      sfx, folded, isR, conv, wconv, hasElse: BOOLEAN;
  BEGIN
    IF seq = AST.NoNode THEN RETURN END;
    k := AST.Kind(seq);

    IF k = AST.NkBlock THEN
      i := 0;
      WHILE i < AST.NChild(seq) DO
        LowerStmt(AST.Child(seq, i)); INC(i)
      END
    ELSIF k = AST.NkAssign THEN
      LowerDesign(AST.Child(seq, 0), dt, cls, qd, qn, sfx);
      LowerExpr(AST.Child(seq, 1), et, qe);
      IF (dt # SymTab.InvalidType) AND (et # SymTab.InvalidType)
         AND SymTab.IsEmptyStr(et)
         AND (SymTab.ClassOf(dt) = SymTab.ClChar) THEN
        (* ISO: the empty string assigned to CHAR is the terminator *)
        QbeGen.CopyOp("0", qe); et := SymTab.CharType()
      END;
      isR := (dt # SymTab.InvalidType) AND (SymTab.ClassOf(dt) = SymTab.ClReal);
      conv := isR AND SymTab.IsIntFamily(et);
      wconv := (dt # SymTab.InvalidType) AND SymTab.IsLongFamily(dt)
               AND SymTab.IsIntFamily(et);
      IF sfx OR (cls = SymTab.KindField) THEN
        IF SymTab.ClassOf(dt) = SymTab.ClArray THEN
          IF (et # SymTab.InvalidType) AND (SymTab.ClassOf(et) = SymTab.ClUStr)
             AND SymTab.IsUCharArray(dt) THEN QbeGen.UAssign(qd, qe)
          ELSIF SymTab.StrCompat(dt, et) THEN QbeGen.StrAssign(qd, qe)
          ELSE QbeGen.CopyArray(qd, qe, dt)
          END
        ELSIF SymTab.ClassOf(dt) = SymTab.ClSet THEN
          QbeGen.CopySet(qd, qe, SymTab.SetWords(dt), SymTab.SetWords(et))
        ELSIF SymTab.ClassOf(dt) = SymTab.ClRecord THEN
          QbeGen.CopyRecord(qd, qe, dt)
        ELSIF SymTab.IsLongFamily(dt) THEN
          IF wconv THEN QbeGen.WidenLong(qe, ql); QbeGen.ElemStore(qd, ql, dt)
          ELSE QbeGen.ElemStore(qd, qe, dt)
          END
        ELSIF conv THEN QbeGen.ConvIR(qe, qt); QbeGen.ElemStore(qd, qt, dt)
        ELSE QbeGen.ElemStore(qd, qe, dt)
        END
      ELSE
        IF SymTab.ClassOf(dt) = SymTab.ClArray THEN
          IF (et # SymTab.InvalidType) AND (SymTab.ClassOf(et) = SymTab.ClUStr)
             AND SymTab.IsUCharArray(dt) THEN QbeGen.UAssign(qd, qe)
          ELSIF SymTab.StrCompat(dt, et) THEN QbeGen.StrAssign(qd, qe)
          ELSE QbeGen.CopyArray(qd, qe, dt)
          END
        ELSIF SymTab.ClassOf(dt) = SymTab.ClSet THEN
          QbeGen.CopySet(qd, qe, SymTab.SetWords(dt), SymTab.SetWords(et))
        ELSIF SymTab.ClassOf(dt) = SymTab.ClRecord THEN
          QbeGen.CopyRecord(qd, qe, dt)
        ELSIF SymTab.IsSmallInt(dt) THEN
          QbeGen.StoreShortVar(qn, SymTab.SmallIntBytes(dt), qe)
        ELSIF (SymTab.ClassOf(dt) = SymTab.ClPtr)
           OR (SymTab.ClassOf(dt) = SymTab.ClProc) THEN
          QbeGen.StorePtr(qn, qe)
        ELSIF SymTab.IsLongFamily(dt) THEN
          IF wconv THEN QbeGen.WidenLong(qe, ql); QbeGen.StoreLong(qn, ql)
          ELSE QbeGen.StoreLong(qn, qe)
          END
        ELSIF conv THEN QbeGen.ConvIR(qe, qt); QbeGen.StoreVar(qn, qt, TRUE)
        ELSE QbeGen.StoreVar(qn, qe, isR)
        END
      END
    ELSIF k = AST.NkIf THEN
      LowerExpr(AST.Child(seq, 0), t, q);
      QbeGen.NewLabel(lThen); QbeGen.NewLabel(lElse); QbeGen.NewLabel(lEnd);
      QbeGen.Jnz(q, lThen, lElse); QbeGen.EmitLabel(lThen);
      LowerStmt(AST.Child(seq, 1));
      QbeGen.Jmp(lEnd);
      els := AST.Child(seq, 2); hasElse := FALSE;
      WHILE (els # AST.NoNode) AND (AST.Kind(els) = AST.NkIf) DO
        QbeGen.EmitLabel(lElse); QbeGen.NewLabel(lElse);
        LowerExpr(AST.Child(els, 0), t, q);
        QbeGen.NewLabel(lThen); QbeGen.Jnz(q, lThen, lElse);
        QbeGen.EmitLabel(lThen);
        LowerStmt(AST.Child(els, 1));
        QbeGen.Jmp(lEnd);
        els := AST.Child(els, 2)
      END;
      IF els # AST.NoNode THEN
        QbeGen.EmitLabel(lElse); hasElse := TRUE; LowerStmt(els)
      END;
      IF hasElse THEN QbeGen.EmitLabel(lEnd)
      ELSE QbeGen.EmitLabel(lElse); QbeGen.EmitLabel(lEnd)
      END
    ELSIF k = AST.NkWhile THEN
      QbeGen.NewLabel(lTop); QbeGen.NewLabel(lBody); QbeGen.NewLabel(lEnd);
      QbeGen.EmitLabel(lTop);
      LowerExpr(AST.Child(seq, 0), t, q);
      QbeGen.Jnz(q, lBody, lEnd); QbeGen.EmitLabel(lBody);
      LowerStmt(AST.Child(seq, 1));
      QbeGen.Jmp(lTop); QbeGen.EmitLabel(lEnd)
    ELSIF k = AST.NkRepeat THEN
      QbeGen.NewLabel(lTop); QbeGen.NewLabel(lEnd); QbeGen.EmitLabel(lTop);
      LowerStmt(AST.Child(seq, 0));
      LowerExpr(AST.Child(seq, 1), t, q);
      QbeGen.Jnz(q, lEnd, lTop); QbeGen.EmitLabel(lEnd)
    ELSIF k = AST.NkLoop THEN
      QbeGen.NewLabel(lTop); QbeGen.NewLabel(lEnd);
      QbeGen.PushLoop(lEnd); QbeGen.EmitLabel(lTop);
      LowerStmt(AST.Child(seq, 0));
      QbeGen.Jmp(lTop); QbeGen.PopLoop; QbeGen.EmitLabel(lEnd)
    ELSIF k = AST.NkExit THEN
      IF QbeGen.TopLoop(lx) THEN QbeGen.Jmp(lx) END
    ELSIF k = AST.NkFor THEN
      Name(AST.Child(seq, 0), lv);
      LowerExpr(AST.Child(seq, 1), t, qlo);
      LowerExpr(AST.Child(seq, 2), t2, qhi);
      IF SymTab.IsEmptyStr(t) THEN
        QbeGen.CopyOp("0", qlo); t := SymTab.CharType()
      END;
      IF SymTab.IsEmptyStr(t2) THEN
        QbeGen.CopyOp("0", qhi); t2 := SymTab.CharType()
      END;
      (* optional BY step: a constant, default +1; its sign also
         selects the termination comparison *)
      step := 1;
      IF AST.Child(seq, 3) # AST.NoNode THEN
        LowerExpr(AST.Child(seq, 3), t3, qby);
        IF NOT SymTab.ConstInt(qby, step) THEN step := 1
        ELSIF step = 0 THEN step := 1
        END
      END;
      IF SymTab.IsSmallInt(SymTab.SymType(lv)) THEN
        QbeGen.StoreShortVar(lv,
          SymTab.SmallIntBytes(SymTab.SymType(lv)), qlo)
      ELSE QbeGen.StoreVar(lv, qlo, FALSE)
      END;
      QbeGen.NewLabel(lTop); QbeGen.NewLabel(lBody); QbeGen.NewLabel(lEnd);
      QbeGen.EmitLabel(lTop);
      IF SymTab.IsSmallInt(SymTab.SymType(lv)) THEN
        QbeGen.LoadShortVar(lv,
          SymTab.IsSignedSmallInt(SymTab.SymType(lv)),
          SymTab.SmallIntBytes(SymTab.SymType(lv)), qt)
      ELSE QbeGen.LoadVar(lv, FALSE, qt)
      END;
      QbeGen.NewTemp(qk);
      IF step > 0 THEN QbeGen.Op3("cslew", qk, qt, qhi, FALSE)
      ELSE QbeGen.Op3("csgew", qk, qt, qhi, FALSE)
      END;
      QbeGen.Jnz(qk, lBody, lEnd);
      QbeGen.EmitLabel(lBody);
      LowerStmt(AST.Child(seq, 4));
      IF SymTab.IsSmallInt(SymTab.SymType(lv)) THEN
        QbeGen.LoadShortVar(lv,
          SymTab.IsSignedSmallInt(SymTab.SymType(lv)),
          SymTab.SmallIntBytes(SymTab.SymType(lv)), qt)
      ELSE QbeGen.LoadVar(lv, FALSE, qt)
      END;
      QbeGen.IntStr(step, qb);
      QbeGen.NewTemp(qk);
      QbeGen.Op3("add", qk, qt, qb, FALSE);
      IF SymTab.IsSmallInt(SymTab.SymType(lv)) THEN
        QbeGen.StoreShortVar(lv,
          SymTab.SmallIntBytes(SymTab.SymType(lv)), qk)
      ELSE QbeGen.StoreVar(lv, qk, FALSE)
      END;
      QbeGen.Jmp(lTop); QbeGen.EmitLabel(lEnd)
    ELSIF k = AST.NkHalt THEN
      IF AST.Child(seq, 0) # AST.NoNode THEN
        LowerExpr(AST.Child(seq, 0), t, q) END;
      QbeGen.HaltQ
    ELSIF k = AST.NkGoto THEN
      Name(AST.Child(seq, 0), qn);
      UserLabel(qn, q);
      QbeGen.Jmp(q)
    ELSIF k = AST.NkLabel THEN
      Name(AST.Child(seq, 0), qn);
      UserLabel(qn, q);
      QbeGen.EmitLabel(q)
    ELSIF k = AST.NkReturn THEN
      IF AST.Child(seq, 0) = AST.NoNode THEN
        QbeGen.EmitRet(q, FALSE)
      ELSE
        LowerExpr(AST.Child(seq, 0), t, q);
        IF SymTab.IsEmptyStr(t)
           AND (emitProc >= 0) AND (emitProc < VAL(INTEGER, nProcs))
           AND (SymTab.ClassOf(procRes[emitProc]) = SymTab.ClChar) THEN
          QbeGen.CopyOp("0", q); t := SymTab.CharType()
        END;
        IF (emitProc >= 0) AND (emitProc < VAL(INTEGER, nProcs))
           AND CompositeRes(procRes[emitProc]) THEN
          (* composite result: copy into the hidden destination *)
          QbeGen.AddrOf("__res", qt);
          IF SymTab.ClassOf(procRes[emitProc]) = SymTab.ClArray THEN
            QbeGen.CopyArray(qt, q, procRes[emitProc])
          ELSIF SymTab.ClassOf(procRes[emitProc]) = SymTab.ClSet THEN
            QbeGen.CopySet(qt, q, SymTab.SetWords(procRes[emitProc]),
                                    SymTab.SetWords(procRes[emitProc]))
          ELSE QbeGen.CopyRecord(qt, q, procRes[emitProc])
          END;
          QbeGen.EmitRet("0", FALSE)
        ELSE
          conv := (SymTab.ClassOf(SymTab.CurRes()) = SymTab.ClReal)
                  AND SymTab.IsIntFamily(t);
          IF conv THEN QbeGen.ConvIR(q, qt); QbeGen.EmitRet(qt, TRUE)
          ELSE QbeGen.EmitRet(q, TRUE)
          END
        END
      END
    ELSIF k = AST.NkCase THEN LowerCase(seq)
    ELSIF k = AST.NkWith THEN LowerWith(seq)
    ELSIF k = AST.NkCall THEN
      IF IsMethodCall(seq) THEN LowerMethodCall(seq, t, q, FALSE)
      ELSE
        CalleeName(seq, qn);
        IF IsBuiltin(qn) THEN LowerBuiltinStmt(seq, qn)
        ELSE LowerCall(seq, t, q, FALSE)
        END
      END
    END
  END LowerStmt;

PROCEDURE ReenterGlobals (seq: AST.Node);
(* Re-registers a nested module's non-exported globals in the enclosing
   (still-open) module scope, so QbeGen.GlobalRef can resolve their
   "<outer>_<name>" symbols after the nested scope has been popped. *)
  VAR i, j: CARDINAL; c: AST.Node; nm: SymTab.Name; chunk, vn: AST.Node;
  BEGIN
    IF seq = AST.NoNode THEN RETURN END;
    i := 0;
    WHILE i < AST.NChild(seq) DO
      c := AST.Child(seq, i);
      IF i = AST.MaxChild - 1 THEN ReenterGlobals(c)
      ELSIF AST.Kind(c) = AST.NkDeclSeq THEN ReenterGlobals(c)
      ELSIF AST.Kind(c) = AST.NkVarDecl THEN
        chunk := c;
        WHILE chunk # AST.NoNode DO
          j := 0;
          WHILE j < AST.NChild(chunk) DO
            vn := AST.Child(chunk, j);
            IF AST.Kind(vn) = AST.NkIdent THEN
              Name(vn, nm);
              IF SymTab.ReenterModGlobal(nm, SymTab.KindVar, curUnitName) THEN
                SymTab.SetSymType(nm, AST.Ty(c))
              END
            END;
            INC(j)
          END;
          IF AST.NChild(chunk) > 0 THEN
            vn := AST.Child(chunk, AST.NChild(chunk) - 1);
            IF AST.Kind(vn) = AST.NkBlock THEN chunk := vn
            ELSE chunk := AST.NoNode END
          ELSE chunk := AST.NoNode END
        END
      ELSIF (AST.Kind(c) = AST.NkTypeDecl)
         OR (AST.Kind(c) = AST.NkClassDecl) THEN
        (* a nested module's TYPE/CLASS: re-register it so ObjectSize and
           GlobalRef can resolve it after the nested scope is popped *)
        IF AST.NChild(c) >= 1 THEN
          Name(AST.Child(c, 0), nm);
          IF SymTab.ReenterModGlobal(nm, SymTab.KindType, curUnitName) THEN
            SymTab.SetSymType(nm, AST.Ty(c))
          END
        END
      END;
      INC(i)
    END
  END ReenterGlobals;

PROCEDURE ReenterImports (seq: AST.Node);
(* A nested module's FROM-imports live in its (now popped) scope.  Copy
   them into the enclosing scope so lowering the nested module's
   declarations and body can still resolve the imported names. *)
  VAR i, j: CARDINAL;
    c, cn: AST.Node;
    mod, nm: SymTab.Name;
  BEGIN
    IF seq = AST.NoNode THEN RETURN END;
    i := 0;
    WHILE i < AST.NChild(seq) DO
      c := AST.Child(seq, i);
      IF i = AST.MaxChild - 1 THEN ReenterImports(c)
      ELSIF AST.Kind(c) = AST.NkDeclSeq THEN ReenterImports(c)
      ELSIF (AST.Kind(c) = AST.NkImport) AND (AST.NChild(c) >= 1) THEN
        Name(AST.Child(c, 0), mod);
        IF SymTab.Equal(mod, "libc") THEN
          j := 1;
          WHILE j < AST.NChild(c) DO
            cn := AST.Child(c, j);
            IF AST.Kind(cn) = AST.NkIdent THEN
              Name(cn, nm);
              IF SymTab.DeclareCProc(nm) THEN NoteCProc(nm) END
            END;
            INC(j)
          END
        ELSIF SymTab.ModKnown(mod)
           AND NOT SymTab.Equal(mod, "SYSTEM") THEN
          j := 1;
          WHILE j < AST.NChild(c) DO
            cn := AST.Child(c, j);
            IF AST.Kind(cn) = AST.NkIdent THEN
              Name(cn, nm);
              (* plain IMPORT lists modules; only FROM adds names *)
              IF SymTab.SymKind(nm) # SymTab.KindModule THEN
                IF NOT SymTab.ImportFrom(mod, nm) THEN END
              END
            END;
            INC(j)
          END
        END
      END;
      INC(i)
    END
  END ReenterImports;

PROCEDURE EmitVarNames (c: AST.Node);
(* Emit DeclVar for each name of an NkVarDecl; the names are a chunked
   sequence (AstAppend), so follow NkBlock continuations. *)
  VAR j: CARDINAL; chunk, vn: AST.Node; nm: SymTab.Name;
  BEGIN
    chunk := c;
    WHILE chunk # AST.NoNode DO
      j := 0;
      WHILE j < AST.NChild(chunk) DO
        vn := AST.Child(chunk, j);
        IF AST.Kind(vn) = AST.NkIdent THEN
          Name(vn, nm);
          QbeGen.DeclVar(nm, AST.Ty(c));
          IF (NOT QbeGen.InFunction())
             AND (SymTab.ClassOf(AST.Ty(c)) = SymTab.ClArray)
             AND QbeGen.RecArrayNeedsInit(SymTab.ArrayLen(AST.Ty(c)),
                                          AST.Ty(c))
             AND (nCountInit <= HIGH(countArr)) THEN
            QbeGen.DeclRecTemplate(nm, SymTab.ArrayElem(AST.Ty(c)));
            countArr[nCountInit] := nm;
            countTyp[nCountInit] := AST.Ty(c);
            INC(nCountInit)
          END
        END;
        INC(j)
      END;
      IF AST.NChild(chunk) > 0 THEN
        vn := AST.Child(chunk, AST.NChild(chunk) - 1);
        IF AST.Kind(vn) = AST.NkBlock THEN chunk := vn
        ELSE chunk := AST.NoNode END
      ELSE chunk := AST.NoNode END
    END
  END EmitVarNames;

PROCEDURE EmitCountInits;
(* Initialise the length words of record-array globals that were emitted
   compactly (recorded by EmitVarNames). *)
  VAR k: CARDINAL;
  BEGIN
    k := 0;
    WHILE k < nCountInit DO
      QbeGen.InitRecArray(countArr[k], countTyp[k]);
      INC(k)
    END
  END EmitCountInits;

PROCEDURE LowerDecls (seq: AST.Node);
  VAR i, j: CARDINAL; c: AST.Node; nm, txt, gn: SymTab.Name; qv: QbeGen.QVal;
      mg: QbeGen.QVal; uid, depth, np: CARDINAL; res, pt: SymTab.TypeIndex;
      ext, pv: BOOLEAN; kk: INTEGER; ct: SymTab.TypeIndex; savedProc: INTEGER;
      chunk, vn: AST.Node; pi: INTEGER;
      mk: ARRAY [0 .. MaxCFoldW - 1] OF CARDINAL; mw: CARDINAL; mlo: INTEGER;
  BEGIN
    IF seq = AST.NoNode THEN RETURN END;
    i := 0;
    WHILE i < AST.NChild(seq) DO
      c := AST.Child(seq, i);
      IF i = AST.MaxChild - 1 THEN LowerDecls(c)
      ELSIF AST.Kind(c) = AST.NkDeclSeq THEN LowerDecls(c)
      ELSIF AST.Kind(c) = AST.NkClassDecl THEN
        Name(AST.Child(c, 0), nm);
        IF Resolve(nm, kk, ct) THEN
          IF SymTab.ClassOf(ct) = SymTab.ClClass THEN
            IF AST.Op(c) = 1 THEN
              LowerMethods(AST.Child(c, 3), ct);
              IF AST.Child(c, 2) # AST.NoNode THEN
                QbeGen.BeginInit(nm);
                LowerStmt(AST.Child(c, 2));
                QbeGen.EndInit
              END
            ELSE
              LowerMethodHeadings(AST.Child(c, 3), ct)
            END
          END
        END
      ELSIF AST.Kind(c) = AST.NkUnit THEN
        Name(AST.Child(c, 0), nm);
        ReenterImports(AST.Child(c, 3));
        ReenterGlobals(AST.Child(c, 1));
        LowerDecls(AST.Child(c, 1));
        IF AST.Child(c, 2) # AST.NoNode THEN
          QbeGen.BeginInit(nm);
          LowerStmt(AST.Child(c, 2));
          QbeGen.EndInit
        END
      ELSIF AST.Kind(c) = AST.NkVarDecl THEN
        (* op=1 marks a forward-typed global: emit it after the rest,
           as the grammar's FlushPend does *)
        IF AST.Op(c) # 1 THEN EmitVarNames(c) END
      ELSIF AST.Kind(c) = AST.NkConstDecl THEN
        Name(AST.Child(c, 0), nm);
        kk := SymTab.ClassOf(AST.Ty(c));
        IF kk = SymTab.ClSet THEN
          (* SET CONST: static data from the mask the grammar computed.
             A module-level const is emitted under its global name
             (<unit>_<name>) so a client's qualified reference binds. *)
          IF LookupSetMask(nm, mk, mw, mlo) THEN
            IF SymTab.GlobalRef(nm, gn) THEN
              QbeGen.PoolSetNamed(gn, mk, mw, qv)
            ELSE QbeGen.PoolSet(mk, mw, qv)
            END;
            SetConstVal(nm, qv)
          ELSE SetConstVal(nm, "0")
          END
        ELSIF (kk = SymTab.ClArray) OR (kk = SymTab.ClRecord)
           OR (kk = SymTab.ClClass) OR (kk = SymTab.ClStr)
           OR (kk = SymTab.ClUStr) THEN
          (* aggregate/string CONST: re-emit the constructor/string so
             its static data is produced (the grammar's CtorEnd/DeclStr
             are suppressed under NoEmit), then refresh the value *)
          LowerExpr(AST.Child(c, 1), ct, qv);
          SetConstVal(nm, qv)
        ELSIF GetConstVal(nm, qv) AND QbeGen.IsImm(qv) THEN
          (* scalar: use the evaluated value recorded by NoteConstVal *)
          QbeGen.DeclConst(nm, qv, AST.Ty(c))
        END
      ELSIF AST.Kind(c) = AST.NkProcDecl THEN
        Name(AST.Child(c, 0), nm);
        pi := AST.Ty(c);   (* proc-table index recorded by NoteProcNode *)
        IF (pi < 0) OR (pi >= VAL(INTEGER, nProcs)) THEN pi := FindProc(nm) END;
        IF ProcInfoIdx(pi, uid, res, depth, ext, np) THEN
          QbeGen.Mangled(nm, uid, mg);
          QbeGen.BeginFunc(mg);
          IF CompositeRes(res) THEN
            IF NOT QbeGen.FuncParam("__res", TRUE, res) THEN END
          END;
          j := 0;
          WHILE j < np DO
            IF ParamInfoIdx(pi, j, pt, pv, txt) THEN
              IF NOT QbeGen.FuncParam(txt, pv OR SymTab.IsOpenArray(pt), pt) THEN END
            END;
            INC(j)
          END;
          QbeGen.SetFuncRes(res);
          IF AST.Child(c, 1) = AST.NoNode THEN
            (* declaration-only (definition module): replay the heading *)
            QbeGen.AbortFunc
          ELSE
            QbeGen.EndFuncHeader;
            savedProc := emitProc;
            emitProc := pi;
            LowerDecls(AST.Child(c, 2));
            nUserLab := 0;
            LowerStmt(AST.Child(c, 1));
            emitProc := savedProc;
            QbeGen.EndFunc(res)
          END
        END
      END;
      INC(i)
    END
  END LowerDecls;

PROCEDURE MaterializeGlobals (unitName: ARRAY OF CHAR; decls: AST.Node);
(* Make a unit's module-level VAR/CONST visible in the (global) scope
   Lower runs in at session end, so GlobalRef resolves "<unit>_<name>". *)
  VAR i, j: CARDINAL; c: AST.Node; nm: SymTab.Name; chunk, vn: AST.Node;
  BEGIN
    IF decls = AST.NoNode THEN RETURN END;
    i := 0;
    WHILE i < AST.NChild(decls) DO
      c := AST.Child(decls, i);
      IF i = AST.MaxChild - 1 THEN MaterializeGlobals(unitName, c)
      ELSIF AST.Kind(c) = AST.NkDeclSeq THEN MaterializeGlobals(unitName, c)
      ELSIF (AST.Kind(c) = AST.NkVarDecl) OR (AST.Kind(c) = AST.NkConstDecl) THEN
        chunk := c;
        WHILE chunk # AST.NoNode DO
          j := 0;
          WHILE j < AST.NChild(chunk) DO
            vn := AST.Child(chunk, j);
            IF AST.Kind(vn) = AST.NkIdent THEN
              Name(vn, nm);
              IF NOT SymTab.MaterializeReplace(unitName, nm) THEN END
            END;
            INC(j)
          END;
          IF AST.NChild(chunk) > 0 THEN
            vn := AST.Child(chunk, AST.NChild(chunk) - 1);
            IF AST.Kind(vn) = AST.NkBlock THEN chunk := vn
            ELSE chunk := AST.NoNode END
          ELSE chunk := AST.NoNode END
        END
      ELSIF (AST.Kind(c) = AST.NkTypeDecl) OR (AST.Kind(c) = AST.NkClassDecl) THEN
        IF AST.NChild(c) >= 1 THEN
          Name(AST.Child(c, 0), nm);
          IF NOT SymTab.MaterializeReplace(unitName, nm) THEN END
        END
      END;
      INC(i)
    END
  END MaterializeGlobals;

PROCEDURE LowerDeferredVars (seq: AST.Node);
(* Emit the forward-typed globals (NkVarDecl op=1) after the rest of the
   unit's declarations, matching the grammar's FlushPend ordering. *)
  VAR i: CARDINAL; c: AST.Node;
  BEGIN
    IF seq = AST.NoNode THEN RETURN END;
    i := 0;
    WHILE i < AST.NChild(seq) DO
      c := AST.Child(seq, i);
      IF i = AST.MaxChild - 1 THEN LowerDeferredVars(c)
      ELSIF AST.Kind(c) = AST.NkDeclSeq THEN LowerDeferredVars(c)
      ELSIF (AST.Kind(c) = AST.NkVarDecl) AND (AST.Op(c) = 1) THEN
        EmitVarNames(c)
      END;
      INC(i)
    END
  END LowerDeferredVars;

PROCEDURE LowerOneUnit (u: AST.Node; isProg: BOOLEAN);
  VAR nm: SymTab.Name;
  BEGIN
    nCountInit := 0;
    Name(AST.Child(u, 0), nm);
    CopySpan(nm, curUnitName, 0, 0);
    QbeGen.SetModule(nm);
    MaterializeGlobals(nm, AST.Child(u, 1));
    LowerDecls(AST.Child(u, 1));
    LowerDeferredVars(AST.Child(u, 1));
    IF isProg THEN
      QbeGen.BeginBody;
      EmitCountInits;
      nUserLab := 0;
      LowerStmt(AST.Child(u, 2))
    ELSIF AST.Child(u, 2) # AST.NoNode THEN
      QbeGen.BeginInit(nm);
      EmitCountInits;
      nUserLab := 0;
      LowerStmt(AST.Child(u, 2));
      QbeGen.EndInit
    ELSIF nCountInit > 0 THEN
      QbeGen.BeginInit(nm);
      EmitCountInits;
      QbeGen.EndInit
    END
  END LowerOneUnit;

PROCEDURE BeginSession (progName: ARRAY OF CHAR);
(* Per-unit Lower emission.  The grammar still runs its inline emit while
   parsing, but under NoEmit it only mutates QbeGen's counters (nothing
   reaches the buffer).  For each unit: BeginUnit snapshots the state
   *before* parsing; after parsing, LowerUnitNow restores that snapshot
   and lets Lower re-emit the unit from the same counter values the
   legacy inline path would have used, so the image stays byte-identical.
   EndSession writes the accumulated session image. *)
  BEGIN
    withTop := 0;
    curImplCls := SymTab.InvalidType;
    scopeTop := 0; curScopeProc := -1; emitProc := -1;
    QbeGen.OpenModule(progName);
    QbeGen.SetNoEmit(TRUE)
  END BeginSession;

PROCEDURE BeginUnit;
(* Snapshot the pre-parse state so Lower can discard the grammar's
   suppressed inline mutations for this unit. *)
  BEGIN
    nImps := 0;
    QbeGen.SaveSession
  END BeginUnit;

PROCEDURE LowerUnitNow (unit: AST.Node; isProg: BOOLEAN);
  VAR nm: SymTab.Name; scoped: BOOLEAN;
  BEGIN
    IF unit = AST.NoNode THEN RETURN END;
    QbeGen.RestoreSession;
    QbeGen.SetNoEmit(FALSE);
    (* Lower the unit in its own module scope, so type lookups resolve
       locally and nothing needs to be copied into globScope. *)
    Name(AST.Child(unit, 0), nm);
    scoped := SymTab.EnterLowerScope(nm);
    LowerOneUnit(unit, isProg);
    IF scoped THEN SymTab.LeaveLowerScope END;
    QbeGen.SetNoEmit(TRUE)
  END LowerUnitNow;

PROCEDURE EndSession;
  VAR scoped: BOOLEAN;
  BEGIN
    QbeGen.SetNoEmit(FALSE);
    (* EndModule probes the program module's ExitCode symbol. *)
    scoped := SymTab.EnterLowerScope(curUnitName);
    QbeGen.EndModule(curUnitName);
    IF scoped THEN SymTab.LeaveLowerScope END
  END EndSession;

BEGIN
  scopeTop := 0; curScopeProc := -1; emitProc := -1
END Lower.