Introduce CounterExpressionBuilder::subst(C, Map) (#112698)

This return a counter for each term in the expression replaced by
ReplaceMap.

At the moment, this doesn't update the Map, so Map is marked as `const`.

1 files changed, 25 insertions, 0 deletions

diff --git a/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp b/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
index e8f60d2..6d6678e 100644
--- a/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
+++ b/llvm/lib/ProfileData/Coverage/CoverageMapping.cpp
@@ -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);
+  auto NewRHS = subst(CE.RHS, Map);
+
+  // Reconstruct Expression with induced subexpressions.
+  switch (CE.Kind) {
+  case CounterExpression::Add:
+    C = add(NewLHS, NewRHS);
+    break;
+  case CounterExpression::Subtract:
+    C = subtract(NewLHS, NewRHS);
+    break;
+  }
+
+  return C;
+}
+
 void CounterMappingContext::dump(const Counter &C, raw_ostream &OS) const {
   switch (C.getKind()) {
   case Counter::Zero: