test(llvm_py): cover duplicate incoming per pred

src/llvm_py/tests/test_phi_wiring_selection.py

@@ -0,0 +1,80 @@
+#!/usr/bin/env python3
+"""
+Contract tests for PHI incoming selection (Phase 97.2).
+
+Goal:
+- When multiple incoming candidates map to the same predecessor, do not let a
+  failed candidate (synthesized 0) overwrite a successfully-resolved value.
+"""
+
+import unittest
+import llvmlite.ir as ir
+
+from src.llvm_py.phi_wiring.wiring import wire_incomings
+
+
+class DummyContext:
+    def get_block_snapshot(self, _block_id: int):
+        return {}
+
+
+class DummyResolver:
+    def __init__(self, i64: ir.IntType):
+        self.i64 = i64
+
+    def resolve_incoming(self, _pred_bid: int, vs: int, context=None):
+        # 100/200 are "missing" (simulate snapshot miss -> failure -> synthesized 0).
+        if int(vs) == 101:
+            return ir.Constant(self.i64, 7)
+        if int(vs) == 201:
+            return ir.Constant(self.i64, 9)
+        return None
+
+
+class DummyBuilder:
+    pass
+
+
+class TestPhiWiringSelection(unittest.TestCase):
+    def setUp(self):
+        self.mod = ir.Module(name="phi_wiring_selection_mod")
+        i64 = ir.IntType(64)
+        fn = ir.Function(self.mod, ir.FunctionType(i64, []), name="f")
+        bb1 = fn.append_basic_block(name="bb1")
+        bb2 = fn.append_basic_block(name="bb2")
+
+        b = DummyBuilder()
+        b.module = self.mod
+        b.i64 = i64
+        b.bb_map = {1: bb1, 2: bb2}
+        b.preds = {2: [1]}
+        b.vmap = {}
+        b.resolver = DummyResolver(i64)
+        b.predeclared_ret_phis = {}
+        self.builder = b
+        self.ctx = DummyContext()
+
+    def _phi_incoming_values(self, dst_vid: int):
+        phi = self.builder.vmap[dst_vid]
+        incoming = list(getattr(phi, "incomings", []))
+        return [int(getattr(v, "constant", 0)) for (v, _blk) in incoming]
+
+    def test_prefers_success_over_synthesized_zero_for_same_pred(self):
+        dst_vid = 500
+        # Two candidates map to the same predecessor:
+        # - v100 fails -> becomes 0
+        # - v101 succeeds -> becomes 7, and must replace the 0
+        wire_incomings(self.builder, 2, dst_vid, [(1, 100), (1, 101)], context=self.ctx)
+        self.assertIn(dst_vid, self.builder.vmap)
+        self.assertEqual(self._phi_incoming_values(dst_vid), [7])
+
+    def test_does_not_overwrite_success_with_failed_candidate(self):
+        dst_vid = 501
+        # Success comes first; later failure must not overwrite it.
+        wire_incomings(self.builder, 2, dst_vid, [(1, 101), (1, 100)], context=self.ctx)
+        self.assertIn(dst_vid, self.builder.vmap)
+        self.assertEqual(self._phi_incoming_values(dst_vid), [7])
+
+
+if __name__ == "__main__":
+    unittest.main()