[llvm-profgen] Avoid repeated hash lookups (NFC) (#127028)

Author: kazutakahirata

llvm/tools/llvm-profgen/MissingFrameInferrer.cpp

@@ -238,12 +238,13 @@ bool MissingFrameInferrer::inferMissingFrames(
     return false;
 
   // Bail out if caller has no known outgoing call edges.
-  if (!CallEdgesF.count(From))
+  auto It = CallEdgesF.find(From);
+  if (It == CallEdgesF.end())
     return false;
 
   // Done with the inference if the calle is reachable via a single callsite.
   // This may not be accurate but it improves the search throughput.
-  if (llvm::is_contained(CallEdgesF[From], ToFRange->Func))
+  if (llvm::is_contained(It->second, ToFRange->Func))
     return true;
 
   // Bail out if callee is not tailcall reachable at all.
@@ -253,7 +254,7 @@ bool MissingFrameInferrer::inferMissingFrames(
   Visiting.clear();
   CurSearchingDepth = 0;
   uint64_t NumPaths = 0;
-  for (auto Target : CallEdgesF[From]) {
+  for (auto Target : It->second) {
     NumPaths +=
         computeUniqueTailCallPath(Target, ToFRange->Func, UniquePath);
     // Stop analyzing the remaining if we are already seeing more than one