[llvm] Introduce CounterExpressionBuilder::subst(C, Map) (PR #112698)

[NAKAMURA Takumi via llvm-commits]

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@@ -135,6 +135,31 @@ Counter CounterExpressionBuilder::subtract(Counter LHS, Counter RHS,
   return Simplify ? simplify(Cnt) : Cnt;
 }
 
+Counter CounterExpressionBuilder::subst(Counter C, const SubstMap &Map) {
+  // Replace C with the value found in Map even if C is Expression.
+  if (auto I = Map.find(C); I != Map.end())
+    return I->second;
+
+  if (!C.isExpression())
+    return C;
+
+  auto CE = Expressions[C.getExpressionID()];
+  auto NewLHS = subst(CE.LHS, Map);
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chapuni wrote:

I don't want put a vaporware here.

https://github.com/llvm/llvm-project/pull/112698