test(cfg): R5 contrast — dense ceiling fires, SSA solver converges (#2201 U6)

gitnexus/test/unit/cfg/reaching-defs.test.ts

@@ -8,6 +8,8 @@ import {
 } from '../../../src/core/ingestion/cfg/visitors/typescript.js';
 import {
   computeReachingDefs,
+  computeReachingDefsDense,
+  computeReachingDefsSparse,
   type DefUseFact,
 } from '../../../src/core/ingestion/cfg/reaching-defs.js';
 import type {
@@ -371,6 +373,33 @@ describe('computeReachingDefs — determinism and convergence', () => {
     expect(capped.facts).toEqual([]);
     expect(capped.defCount).toBe(full.defCount);
   });
+
+  it('#2201 R5: the ceiling fires on the dense oracle but not on the SSA solver', () => {
+    // Contrast the two solvers on a looping CFG under a budget below the dense
+    // worklist's convergence: the dense oracle truncates to a sound-empty result
+    // (the ceiling fires), while the SSA solver — which has no fixpoint
+    // iteration — always converges (the ceiling that fired on the dense worklist
+    // effectively never fires). The facts the SSA solver computes are identical
+    // to the dense oracle's unbounded result. This is the #2201 acceptance: the
+    // blocks×64 ceiling stops firing on deep loops.
+    const blocks: BlockSpec[] = [{}, {}, { stmts: [stmt(3, [0], [0])] }];
+    const edges: [number, number][] = [
+      [0, 2],
+      [2, 2], // self-loop → the dense fixpoint must re-visit block 2
+      [2, 1],
+    ];
+    const denseFull = computeReachingDefsDense(mkCfg(blocks, edges, ['x']));
+    const denseCeiling = computeReachingDefsDense(mkCfg(blocks, edges, ['x']), {
+      maxBlockVisits: 1,
+    });
+    const sparse = computeReachingDefsSparse(mkCfg(blocks, edges, ['x']), { maxBlockVisits: 1 });
+
+    expect(denseFull.status).toBe('computed');
+    expect(denseFull.facts.length).toBeGreaterThan(0);
+    expect(denseCeiling.status).toBe('truncated'); // ceiling fires on the dense worklist
+    expect(sparse.status).toBe('computed'); // SSA ignores the ceiling — it never fires
+    expect(render(sparse.facts)).toEqual(render(denseFull.facts)); // and the facts match
+  });
 });
 
 describe('computeReachingDefs — parser-direct acceptance (with U1/U2)', () => {