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

[Jessica Paquette via llvm-commits]

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@@ -580,6 +583,72 @@ static unsigned getMaxBitmapSize(const CounterMappingContext &Ctx,
   return MaxBitmapID + (SizeInBits / CHAR_BIT);
 }
 
+struct DecisionRow {
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ornata wrote:

What does it represent in the MC/DC algorithm?

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