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

[NAKAMURA Takumi via llvm-commits]

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@@ -580,6 +583,72 @@ static unsigned getMaxBitmapSize(const CounterMappingContext &Ctx,
   return MaxBitmapID + (SizeInBits / CHAR_BIT);
 }
 
+struct DecisionRow {
+  const CounterMappingRegion *DecisionRegion;
+  LineColPair DecisionStartLoc;
+  LineColPair DecisionEndLoc;
+
+  SmallVector<const CounterMappingRegion *, 6> Branches;
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chapuni wrote:

I didn't mention `6` since it will be enhanced in the future. I will remove `6` for now rather than adding explanations.

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