lower L7: drop inline emit from the control-flow statements

Second slice of the inline-emit deletion: remove the QbeGen emission
from IF/WHILE/REPEAT/LOOP/FOR/CASE/CaseAlt/CaseLabel, plus RETURN and
HALT, keeping their semantic checks and AST-building actions:

- IF/WHILE/REPEAT: drop NewLabel/EmitLabel/Jmp/Jnz, keep BoolCheck.
- LOOP: drop the labels/jump, keep NewLabel(lEnd)/PushLoop/PopLoop,
  which are parser state that the EXIT validity check (TopLoop) reads.
- FOR: drop the StoreVar/LoadVar/NewTemp/Op3/IntStr/StoreVar body,
  keep the SymTab.ConstInt BY check.
- CASE/CaseAlt/CaseLabel: drop NewLabel/EmitLabel/Jmp/Jnz/Cmp/
  NewTemp/Op3/CopyOp, keep the IsImm and type checks.
- RETURN: drop EmitRet/ConvIR, keep the in-proc/result checks.
- HALT: drop HaltQ.
- CaseLabel no longer needs its lBody parameter.

Suite 204/204; FIXPOINT OK (3,539,396 bytes).

compiler/src/M2.atg

@@ -1846,78 +1846,49 @@ PRODUCTIONS
                                              END
                                            END; .) .
   IfStat                                (. VAR t: SymTab.TypeIndex;
-                                             q, lThen, lElse, lEnd:
-                                               QbeGen.QVal;
+                                             q: QbeGen.QVal;
                                              hasElse: BOOLEAN;
                                              astCond, astIf, astLast,
                                              astNode: AST.Node; .)
     = "IF" (. hasElse := FALSE; .)
       Expr<t, q> (. astCond := astCur; astStmt := AST.NoNode;
                                            IF NOT SymTab.BoolCheck(t) THEN
-                                             SemError(214) END;
-                                           QbeGen.NewLabel(lThen);
-                                           QbeGen.NewLabel(lElse);
-                                           QbeGen.NewLabel(lEnd);
-                                           QbeGen.Jnz(q, lThen, lElse);
-                                           QbeGen.EmitLabel(lThen); .)
+                                             SemError(214) END; .)
       "THEN" [ StatSeq ]                (. astNode := AST.MakeNode(AST.NkIf);
                                            AST.SetChild(astNode, 0, astCond);
                                            AST.SetChild(astNode, 1, astStmt);
                                            astIf := astNode;
-                                           astLast := astNode;
-                                           QbeGen.Jmp(lEnd); .)
-      { "ELSIF"                         (. QbeGen.EmitLabel(lElse);
-                                           QbeGen.NewLabel(lElse); .)
+                                           astLast := astNode; .)
+      { "ELSIF"
         Expr<t, q> (. astCond := astCur; astStmt := AST.NoNode;
                                            IF NOT SymTab.BoolCheck(t) THEN
-                                             SemError(214) END;
-                                           QbeGen.NewLabel(lThen);
-                                           QbeGen.Jnz(q, lThen, lElse);
-                                           QbeGen.EmitLabel(lThen); .)
+                                             SemError(214) END; .)
         "THEN" [ StatSeq ]              (. astNode := AST.MakeNode(AST.NkIf);
                                            AST.SetChild(astNode, 0, astCond);
                                            AST.SetChild(astNode, 1, astStmt);
                                            AST.SetChild(astLast, 2, astNode);
-                                           astLast := astNode;
-                                           QbeGen.Jmp(lEnd); .) }
-      [ "ELSE"                          (. QbeGen.EmitLabel(lElse);
-                                           hasElse := TRUE;
+                                           astLast := astNode; .) }
+      [ "ELSE"                          (. hasElse := TRUE;
                                            astStmt := AST.NoNode; .)
         [ StatSeq ] (. AST.SetChild(astLast, 2, astStmt); .) ]
-      "END" (. astStmt := astIf;
-                                           IF hasElse THEN
-                                             QbeGen.EmitLabel(lEnd)
-                                           ELSE QbeGen.EmitLabel(lElse);
-                                             QbeGen.EmitLabel(lEnd)
-                                           END; .) .
+      "END" (. astStmt := astIf; .) .
   WhileStat                             (. VAR t: SymTab.TypeIndex;
-                                             q, lTop, lBody, lEnd:
-                                               QbeGen.QVal;
+                                             q: QbeGen.QVal;
                                              astCond, astNode: AST.Node; .)
-    = "WHILE" (. astStmt := AST.NoNode;
-                                           QbeGen.NewLabel(lTop);
-                                           QbeGen.NewLabel(lBody);
-                                           QbeGen.NewLabel(lEnd);
-                                           QbeGen.EmitLabel(lTop); .)
+    = "WHILE" (. astStmt := AST.NoNode; .)
       Expr<t, q> (. astCond := astCur;
                                            IF NOT SymTab.BoolCheck(t) THEN
-                                             SemError(214) END;
-                                           QbeGen.Jnz(q, lBody, lEnd);
-                                           QbeGen.EmitLabel(lBody); .)
-      "DO" [ StatSeq ]                      (. astNode := AST.MakeNode(AST.NkWhile);
+                                             SemError(214) END; .)
+      "DO" [ StatSeq ]                  (. astNode := AST.MakeNode(AST.NkWhile);
                                            AST.SetChild(astNode, 0, astCond);
                                            AST.SetChild(astNode, 1, astStmt);
-                                           astStmt := astNode;
-                                           QbeGen.Jmp(lTop); .)
-      "END"                             (. QbeGen.EmitLabel(lEnd); .) .
+                                           astStmt := astNode; .)
+      "END" .
   RepeatStat                            (. VAR t: SymTab.TypeIndex;
-                                             q, lTop, lEnd: QbeGen.QVal;
+                                             q: QbeGen.QVal;
                                              astCond, astBody, astNode:
                                                AST.Node; .)
-    = "REPEAT" (. astStmt := AST.NoNode;
-                                           QbeGen.NewLabel(lTop);
-                                           QbeGen.NewLabel(lEnd);
-                                           QbeGen.EmitLabel(lTop); .)
+    = "REPEAT" (. astStmt := AST.NoNode; .)
       [ StatSeq ] (. astBody := astStmt; .)
       "UNTIL" Expr<t, q> (. astCond := astCur;
                                            astNode := AST.MakeNode(AST.NkRepeat);
@@ -1925,22 +1896,16 @@ PRODUCTIONS
                                            AST.SetChild(astNode, 1, astCond);
                                            astStmt := astNode;
                                            IF NOT SymTab.BoolCheck(t) THEN
-                                             SemError(214) END;
-                                           QbeGen.Jnz(q, lEnd, lTop);
-                                           QbeGen.EmitLabel(lEnd); .) .
-  LoopStat                              (. VAR lTop, lEnd: QbeGen.QVal; astNode: AST.Node; .)
-    = "LOOP"                            (. QbeGen.NewLabel(lTop);
-                                                  astStmt := AST.NoNode;
+                                             SemError(214) END; .) .
+  LoopStat                              (. VAR lEnd: QbeGen.QVal; astNode: AST.Node; .)
+    = "LOOP"                            (. astStmt := AST.NoNode;
                                            QbeGen.NewLabel(lEnd);
-                                           QbeGen.PushLoop(lEnd);
-                                           QbeGen.EmitLabel(lTop); .)
+                                           QbeGen.PushLoop(lEnd); .)
       [ StatSeq ]
       "END"                             (. astNode := AST.MakeNode(AST.NkLoop);
                                            AST.SetChild(astNode, 0, astStmt);
                                            astStmt := astNode;
-                                           QbeGen.Jmp(lTop);
-                                           QbeGen.PopLoop;
-                                           QbeGen.EmitLabel(lEnd); .) .
+                                           QbeGen.PopLoop; .) .
   (* FOR with static-sign BY (literal, non-zero; 220 otherwise).
      Runtime direction would need a compare-select; the literal
      sign picks cslew/csegew at "DO" time. *)
@@ -1990,23 +1955,7 @@ PRODUCTIONS
                                            ELSIF by = 0 THEN
                                              SemError(220); by := 1
                                            END; .) ]
-      "DO"                              (. IF ok THEN
-                                             QbeGen.StoreVar(lv, qlo,
-                                               FALSE) END;
-                                           QbeGen.NewLabel(lTop);
-                                           QbeGen.NewLabel(lBody);
-                                           QbeGen.NewLabel(lEnd);
-                                           QbeGen.EmitLabel(lTop);
-                                           QbeGen.LoadVar(lv, FALSE, qt);
-                                           QbeGen.NewTemp(qk);
-                                           IF by > 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); .)
+      "DO"
       [ StatSeq ]
       "END" (. astNode := AST.MakeNode(AST.NkFor);
                                            AST.SetChild(astNode, 0, astVar);
@@ -2015,17 +1964,7 @@ PRODUCTIONS
                                            AST.SetChild(astNode, 3, astBy);
                                            AST.SetChild(astNode, 4, astStmt);
                                            astStmt := astNode;
-                                           IF ok THEN
-                                             QbeGen.LoadVar(lv, FALSE,
-                                               qt);
-                                             QbeGen.IntStr(by, qb);
-                                             QbeGen.NewTemp(qk);
-                                             QbeGen.Op3("add", qk,
-                                               qt, qb, FALSE);
-                                             QbeGen.StoreVar(lv, qk,
-                                               FALSE) END;
-                                           QbeGen.Jmp(lTop);
-                                           QbeGen.EmitLabel(lEnd); .) .
+                                           .) .
   CaseStat                              (. VAR tsel: SymTab.TypeIndex;
                                              qsel, lEnd: QbeGen.QVal;
                                              arm, astNode, astArms,
@@ -2034,7 +1973,7 @@ PRODUCTIONS
                                            AST.SetChild(astNode, 0, astCur);
                                            astArms := AST.NoNode;
                                            astArmsTail := AST.NoNode;
-                                           QbeGen.NewLabel(lEnd); .)
+                                           .)
       "OF" CaseAlt<tsel, qsel, lEnd, astArms, astArmsTail>
       { "|" CaseAlt<tsel, qsel, lEnd, astArms, astArmsTail> }
       [ "ELSE"                          (. astStmt := AST.NoNode; .)
@@ -2045,31 +1984,25 @@ PRODUCTIONS
                                              astArms, astArmsTail, arm); .) ]
       "END"                             (. AST.SetChild(astNode, 1, astArms);
                                            astStmt := astNode;
-                                           QbeGen.EmitLabel(lEnd); .) .
+                                           .) .
   (* Compare-chain lowering: each alternative ends its match-tests
      with "jmp lAfter", so the no-match fallthrough skips the body:
      "cmp; jnz(lBody,lF); lF: ... ; jmp lAfter; lBody: S; jmp lEnd;
      lAfter:". Falls into the next alternative, ELSE, or END. *)
   CaseAlt<tsel: SymTab.TypeIndex; qsel: QbeGen.QVal;
           lEnd: QbeGen.QVal; VAR arms, armsTail: AST.Node>
-                                        (. VAR lBody, lAfter: QbeGen.QVal;
-                                             arm: AST.Node; .)
-    =                                   (. arm := AST.MakeNode(AST.NkCaseArm);
-                                           QbeGen.NewLabel(lBody);
-                                           QbeGen.NewLabel(lAfter); .)
-      CaseLabel<tsel, qsel, lBody, arm>
-      { "," CaseLabel<tsel, qsel, lBody, arm> }
-      ":"                               (. astStmt := AST.NoNode;
-                                           QbeGen.Jmp(lAfter);
-                                           QbeGen.EmitLabel(lBody); .)
+                                        (. VAR arm: AST.Node; .)
+    =                                   (. arm := AST.MakeNode(AST.NkCaseArm); .)
+      CaseLabel<tsel, qsel, arm>
+      { "," CaseLabel<tsel, qsel, arm> }
+      ":"                               (. astStmt := AST.NoNode; .)
       [ StatSeq ]                       (. AST.SetChild(arm, AST.NChild(arm),
                                            astStmt);
                                            AstAppend(AST.NkBlock,
                                              arms, armsTail, arm);
-                                           QbeGen.Jmp(lEnd);
-                                           QbeGen.EmitLabel(lAfter); .) .
+                                           .) .
   CaseLabel<tsel: SymTab.TypeIndex; qsel: QbeGen.QVal;
-            lBody: QbeGen.QVal; arm: AST.Node>
+            arm: AST.Node>
                                         (. VAR t2, t3: SymTab.TypeIndex;
                                              q2, q3, qc, qd, qe:
                                                QbeGen.QVal;
@@ -2092,15 +2025,9 @@ PRODUCTIONS
  AND NOT SymTab.EqCheck(t2,
                                                  tsel) THEN
                                              SemError(213) END;
-                                           IF NOT QbeGen.IsImm(q2) THEN
-                                             SemError(230);
-                                             QbeGen.CopyOp("0", q2)
-                                           END;
-                                           QbeGen.NewLabel(lNext);
-                                           QbeGen.Cmp(SymTab.OpEq,
-                                             qsel, q2, qc, FALSE);
-                                           QbeGen.Jnz(qc, lBody, lNext);
-                                           QbeGen.EmitLabel(lNext); .)
+                                               IF NOT QbeGen.IsImm(q2) THEN
+                                                 SemError(230)
+                                               END; .)
       [ ".." Expr<t3, q3>               (. astLab := AST.MakeBin(
                                              AST.NkSubrange, 0, astLab, astCur);
                                            IF (t3 #
@@ -2110,20 +2037,9 @@ PRODUCTIONS
  AND NOT SymTab.EqCheck(t3,
                                                  tsel) THEN
                                              SemError(213) END;
-                                           IF NOT QbeGen.IsImm(q3) THEN
-                                             SemError(230);
-                                             QbeGen.CopyOp("0", q3)
-                                           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); .) ]
+                                               IF NOT QbeGen.IsImm(q3) THEN
+                                                 SemError(230)
+                                               END; .) ]
                                         (. AST.SetChild(arm,
                                              AST.NChild(arm), astLab); .) .
   ReturnStat                            (. VAR t: SymTab.TypeIndex;
@@ -2146,8 +2062,6 @@ PRODUCTIONS
                                                IF res #
                                                   SymTab.InvalidType THEN
                                                  SemError(232)
-                                               ELSE QbeGen.EmitRet(q,
-                                                 FALSE)
                                                END
                                              ELSIF (res =
                                                     SymTab.InvalidType)
@@ -2156,16 +2070,7 @@ PRODUCTIONS
  AND NOT SymTab.Assignable(t,
                                                      res) THEN
                                                SemError(232)
-                                             ELSE
-                                               conv := (SymTab.ClassOf(
-                                                 res) = 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
                                            END; .) .
   HaltStat                              (. VAR t: SymTab.TypeIndex;
                                              q: QbeGen.QVal;
@@ -2177,7 +2082,7 @@ PRODUCTIONS
                                              AST.SetChild(astNode, 0, astVal)
                                            END;
                                            astStmt := astNode;
-                                           QbeGen.HaltQ; .) .
+                                           .) .
   (* Designator: scalar loads, array addresses, and index suffixes.
      Each index descends one level (bounds-checked, trap on breach);
      nested levels reload the inner descriptor address. q ends as the