[llvm] Implement MCDCTVIdxBuilder (LLVM side) (PR #80676)

[Alan Phipps via llvm-commits]

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@@ -283,35 +408,38 @@ class MCDCRecordProcessor {
   // Walk the binary decision diagram and try assigning both false and true to
   // each node. When a terminal node (ID == 0) is reached, fill in the value in
   // the truth table.
-  void buildTestVector(MCDCRecord::TestVector &TV, unsigned ID,
+  void buildTestVector(MCDCRecord::TestVector &TV, int ID, int TVIdx,
                        unsigned Index) {
-    const CounterMappingRegion *Branch = Map[ID];
-
-    TV[ID - 1] = MCDCRecord::MCDC_False;
-    if (Branch->MCDCParams.FalseID > 0)
-      buildTestVector(TV, Branch->MCDCParams.FalseID, Index);
-    else
-      recordTestVector(TV, Index, MCDCRecord::MCDC_False);
-
-    Index |= 1 << (ID - 1);
-    TV[ID - 1] = MCDCRecord::MCDC_True;
-    if (Branch->MCDCParams.TrueID > 0)
-      buildTestVector(TV, Branch->MCDCParams.TrueID, Index);
-    else
-      recordTestVector(TV, Index, MCDCRecord::MCDC_True);
+    const auto &Node = Nodes[ID];
+
+    for (unsigned I = 0; I < 2; ++I) {
+      auto MCDCCond = (I ? MCDCRecord::MCDC_True : MCDCRecord::MCDC_False);
+      const auto &Cond = Node.Conds[I];
+      auto NextID = Cond.ID;
+      Index |= I << ID;
+      TV[ID] = MCDCCond;
+      if (NextID >= 0) {
+        buildTestVector(TV, NextID, TVIdx + Cond.Idx, Index);
+      } else {
+        assert(TVIdx < Node.Width);
+        recordTestVector(TV, Cond.Idx + TVIdx, Index, MCDCCond);
+      }
+    }
 
     // Reset back to DontCare.
-    TV[ID - 1] = MCDCRecord::MCDC_DontCare;
+    TV[ID] = MCDCRecord::MCDC_DontCare;
   }
 
   /// Walk the bits in the bitmap.  A bit set to '1' indicates that the test
   /// vector at the corresponding index was executed during a test run.
   void findExecutedTestVectors() {
     // Walk the binary decision diagram to enumerate all possible test vectors.
-    // We start at the root node (ID == 1) with all values being DontCare.
+    // We start at the root node (ID == 0) with all values being DontCare.
+    // `TVIdx` starts with 0 and is in the traversal.
     // `Index` encodes the bitmask of true values and is initially 0.
     MCDCRecord::TestVector TV(NumConditions, MCDCRecord::MCDC_DontCare);
-    buildTestVector(TV, 1, 0);
+    buildTestVector(TV, 0, 0, 0);
+    assert(TVIdxs.size() == NumTestVectors && "TVIdxs wasn't fulfilled");
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evodius96 wrote:

Good assert

https://github.com/llvm/llvm-project/pull/80676