[BOLT] Avoid repeated map lookups (NFC) (#112118)

Author: kazutakahirata

bolt/lib/Core/BinaryFunction.cpp

@@ -3684,9 +3684,8 @@ BinaryFunction::BasicBlockListType BinaryFunction::dfs() const {
     BinaryBasicBlock *BB = Stack.top();
     Stack.pop();
 
-    if (Visited.find(BB) != Visited.end())
+    if (!Visited.insert(BB).second)
       continue;
-    Visited.insert(BB);
     DFS.push_back(BB);
 
     for (BinaryBasicBlock *SuccBB : BB->landing_pads()) {
@@ -3879,11 +3878,8 @@ void BinaryFunction::disambiguateJumpTables(
       JumpTable *JT = getJumpTable(Inst);
       if (!JT)
         continue;
-      auto Iter = JumpTables.find(JT);
-      if (Iter == JumpTables.end()) {
-        JumpTables.insert(JT);
+      if (JumpTables.insert(JT).second)
         continue;
-      }
       // This instruction is an indirect jump using a jump table, but it is
       // using the same jump table of another jump. Try all our tricks to
       // extract the jump table symbol and make it point to a new, duplicated JT