[Scalar] Avoid repeated hash lookups (NFC) (#129825)

Author: kazutakahirata

llvm/lib/Transforms/Scalar/LICM.cpp

@@ -766,8 +766,8 @@ class ControlFlowHoister {
     if (!ControlFlowHoisting)
       return CurLoop->getLoopPreheader();
     // If BB has already been hoisted, return that
-    if (HoistDestinationMap.count(BB))
-      return HoistDestinationMap[BB];
+    if (auto It = HoistDestinationMap.find(BB); It != HoistDestinationMap.end())
+      return It->second;
 
     // Check if this block is conditional based on a pending branch
     auto HasBBAsSuccessor =
@@ -800,11 +800,12 @@ class ControlFlowHoister {
 
     // Create hoisted versions of blocks that currently don't have them
     auto CreateHoistedBlock = [&](BasicBlock *Orig) {
-      if (HoistDestinationMap.count(Orig))
-        return HoistDestinationMap[Orig];
+      auto [It, Inserted] = HoistDestinationMap.try_emplace(Orig);
+      if (!Inserted)
+        return It->second;
       BasicBlock *New =
           BasicBlock::Create(C, Orig->getName() + ".licm", Orig->getParent());
-      HoistDestinationMap[Orig] = New;
+      It->second = New;
       DT->addNewBlock(New, HoistTarget);
       if (CurLoop->getParentLoop())
         CurLoop->getParentLoop()->addBasicBlockToLoop(New, *LI);
@@ -1531,14 +1532,11 @@ static Instruction *sinkThroughTriviallyReplaceablePHI(
   assert(isTriviallyReplaceablePHI(*TPN, *I) &&
          "Expect only trivially replaceable PHI");
   BasicBlock *ExitBlock = TPN->getParent();
-  Instruction *New;
-  auto It = SunkCopies.find(ExitBlock);
-  if (It != SunkCopies.end())
-    New = It->second;
-  else
-    New = SunkCopies[ExitBlock] = cloneInstructionInExitBlock(
-        *I, *ExitBlock, *TPN, LI, SafetyInfo, MSSAU);
-  return New;
+  auto [It, Inserted] = SunkCopies.try_emplace(ExitBlock);
+  if (Inserted)
+    It->second = cloneInstructionInExitBlock(*I, *ExitBlock, *TPN, LI,
+                                             SafetyInfo, MSSAU);
+  return It->second;
 }
 
 static bool canSplitPredecessors(PHINode *PN, LoopSafetyInfo *SafetyInfo) {