[llvm] [Coverage] Rework Decision/Expansion/Branch (PR #78969)

[Jessica Paquette via llvm-commits]

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@@ -638,18 +720,12 @@ Error CoverageMapping::loadFunctionRecord(
       Record.MappingRegions[0].Count.isZero() && Counts[0] > 0)
     return Error::success();
 
-  unsigned NumConds = 0;
-  const CounterMappingRegion *MCDCDecision;
-  std::vector<const CounterMappingRegion *> MCDCBranches;
-
+  SmallVector<DecisionRow> Decisions;
   FunctionRecord Function(OrigFuncName, Record.Filenames);
   for (const auto &Region : Record.MappingRegions) {
-    // If an MCDCDecisionRegion is seen, track the BranchRegions that follow
-    // it according to Region.NumConditions.
     if (Region.Kind == CounterMappingRegion::MCDCDecisionRegion) {
-      assert(NumConds == 0);
-      MCDCDecision = &Region;
-      NumConds = Region.MCDCParams.NumConditions;
+      // Start recording `Region` as the `Decision`
+      Decisions.emplace_back(Region);
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ornata wrote:

why `emplace_back` instead of `push_back`?

https://github.com/llvm/llvm-project/pull/78969