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

[NAKAMURA Takumi via llvm-commits]

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@@ -557,6 +558,35 @@ struct MCDCRecord {
   }
 };
 
+/// Compute Conds[].Idx from Branch-like structure
+class MCDCTVIdxBuilder {
+public:
+  struct MCDCNode {
+    int InCount = 0; /// Reference count; temporary use
+    int Width;       /// Number of paths (>= 1)
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chapuni wrote:

Which is better for me to rename to easy `N` or to define `Width` here.
I haven't learnt the graph theory though, looks like I have introduced similar concept, as far as I read introductions of the theory.

Let me think more.

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