[Analysis] Avoid repeated hash lookups (NFC) (#123159)

Author: kazutakahirata

llvm/lib/Analysis/InstructionPrecedenceTracking.cpp

@@ -115,8 +115,9 @@ void InstructionPrecedenceTracking::insertInstructionTo(const Instruction *Inst,
 void InstructionPrecedenceTracking::removeInstruction(const Instruction *Inst) {
   auto *BB = Inst->getParent();
   assert(BB && "must be called before instruction is actually removed");
-  if (FirstSpecialInsts.count(BB) && FirstSpecialInsts[BB] == Inst)
-    FirstSpecialInsts.erase(BB);
+  auto It = FirstSpecialInsts.find(BB);
+  if (It != FirstSpecialInsts.end() && It->second == Inst)
+    FirstSpecialInsts.erase(It);
 }
 
 void InstructionPrecedenceTracking::removeUsersOf(const Instruction *Inst) {