[Analysis, IR] Use *Map::lookup (NFC)

llvm/include/llvm/Analysis/RegionInfoImpl.h

@@ -815,8 +815,7 @@ void RegionInfoBase<Tr>::verifyAnalysis() const {
 // Region pass manager support.
 template <class Tr>
 typename Tr::RegionT *RegionInfoBase<Tr>::getRegionFor(BlockT *BB) const {
-  typename BBtoRegionMap::const_iterator I = BBtoRegion.find(BB);
-  return I != BBtoRegion.end() ? I->second : nullptr;
+  return BBtoRegion.lookup(BB);
 }
 
 template <class Tr>

llvm/include/llvm/Analysis/VectorUtils.h

@@ -655,11 +655,7 @@ public:
   /// \returns nullptr if contains no such member.
   InstTy *getMember(uint32_t Index) const {
     int32_t Key = SmallestKey + Index;
-    auto Member = Members.find(Key);
-    if (Member == Members.end())
-      return nullptr;
-
-    return Member->second;
+    return Members.lookup(Key);
   }
 
   /// Get the index for the given member. Unlike the key in the member
@@ -777,9 +773,7 @@ public:
   /// \returns nullptr if doesn't have such group.
   InterleaveGroup<Instruction> *
   getInterleaveGroup(const Instruction *Instr) const {
-    if (InterleaveGroupMap.count(Instr))
-      return InterleaveGroupMap.find(Instr)->second;
-    return nullptr;
+    return InterleaveGroupMap.lookup(Instr);
   }
 
   iterator_range<SmallPtrSetIterator<llvm::InterleaveGroup<Instruction> *>>

llvm/lib/IR/PassRegistry.cpp

@@ -40,14 +40,12 @@ PassRegistry::~PassRegistry() = default;
 
 const PassInfo *PassRegistry::getPassInfo(const void *TI) const {
   sys::SmartScopedReader<true> Guard(Lock);
-  MapType::const_iterator I = PassInfoMap.find(TI);
-  return I != PassInfoMap.end() ? I->second : nullptr;
+  return PassInfoMap.lookup(TI);
 }
 
 const PassInfo *PassRegistry::getPassInfo(StringRef Arg) const {
   sys::SmartScopedReader<true> Guard(Lock);
-  StringMapType::const_iterator I = PassInfoStringMap.find(Arg);
-  return I != PassInfoStringMap.end() ? I->second : nullptr;
+  return PassInfoStringMap.lookup(Arg);
 }
 
 //===----------------------------------------------------------------------===//

llvm/lib/IR/SafepointIRVerifier.cpp

@@ -561,8 +561,7 @@ GCPtrTracker::GCPtrTracker(const Function &F, const DominatorTree &DT,
 }
 
 BasicBlockState *GCPtrTracker::getBasicBlockState(const BasicBlock *BB) {
-  auto it = BlockMap.find(BB);
-  return it != BlockMap.end() ? it->second : nullptr;
+  return BlockMap.lookup(BB);
 }
 
 const BasicBlockState *GCPtrTracker::getBasicBlockState(