[clang] [Coverage] Introduce the type `CounterPair` for RegionCounterMap. NFC. (PR #112724)

[NAKAMURA Takumi via cfe-commits]

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@@ -1728,6 +1730,7 @@ bool CodeGenFunction::ConstantFoldsToSimpleInteger(const Expr *Cond,
   if (!AllowLabels && CodeGenFunction::ContainsLabel(Cond))
     return false;  // Contains a label.
 
+  PGO.markStmtMaybeUsed(Cond);
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chapuni wrote:

No. Just for checks.

https://github.com/llvm/llvm-project/pull/112724