diff --git a/clang/lib/ARCMigrate/ObjCMT.cpp b/clang/lib/ARCMigrate/ObjCMT.cpp
index c8a389d1f2e5..e99c6435062f 100644
--- a/clang/lib/ARCMigrate/ObjCMT.cpp
+++ b/clang/lib/ARCMigrate/ObjCMT.cpp
@@ -487,9 +487,8 @@ static void rewriteToObjCProperty(const ObjCMethodDecl *Getter,
 
   // Short circuit 'delegate' properties that contain the name "delegate" or
   // "dataSource", or have exact name "target" to have 'assign' attribute.
-  if (PropertyName.equals("target") ||
-      (PropertyName.find("delegate") != StringRef::npos) ||
-      (PropertyName.find("dataSource") != StringRef::npos)) {
+  if (PropertyName.equals("target") || PropertyName.contains("delegate") ||
+      PropertyName.contains("dataSource")) {
     QualType QT = Getter->getReturnType();
     if (!QT->isRealType())
       append_attr(PropertyString, "assign", LParenAdded);
diff --git a/clang/lib/ARCMigrate/TransUnbridgedCasts.cpp b/clang/lib/ARCMigrate/TransUnbridgedCasts.cpp
index b14364509a0b..40220a2eef49 100644
--- a/clang/lib/ARCMigrate/TransUnbridgedCasts.cpp
+++ b/clang/lib/ARCMigrate/TransUnbridgedCasts.cpp
@@ -146,9 +146,8 @@ private:
             ento::cocoa::isRefType(E->getSubExpr()->getType(), "CF",
                                    FD->getIdentifier()->getName())) {
           StringRef fname = FD->getIdentifier()->getName();
-          if (fname.endswith("Retain") ||
-              fname.find("Create") != StringRef::npos ||
-              fname.find("Copy") != StringRef::npos) {
+          if (fname.endswith("Retain") || fname.contains("Create") ||
+              fname.contains("Copy")) {
             // Do not migrate to couple of bridge transfer casts which
             // cancel each other out. Leave it unchanged so error gets user
             // attention instead.
@@ -168,7 +167,7 @@ private:
             return;
           }
 
-          if (fname.find("Get") != StringRef::npos) {
+          if (fname.contains("Get")) {
             castToObjCObject(E, /*retained=*/false);
             return;
           }
diff --git a/clang/lib/ARCMigrate/Transforms.cpp b/clang/lib/ARCMigrate/Transforms.cpp
index e274a540e408..ca48160d9c85 100644
--- a/clang/lib/ARCMigrate/Transforms.cpp
+++ b/clang/lib/ARCMigrate/Transforms.cpp
@@ -95,11 +95,9 @@ bool trans::isPlusOne(const Expr *E) {
           ento::cocoa::isRefType(callE->getType(), "CF",
                                  FD->getIdentifier()->getName())) {
         StringRef fname = FD->getIdentifier()->getName();
-        if (fname.endswith("Retain") ||
-            fname.find("Create") != StringRef::npos ||
-            fname.find("Copy") != StringRef::npos) {
+        if (fname.endswith("Retain") || fname.contains("Create") ||
+            fname.contains("Copy"))
           return true;
-        }
       }
     }
   }
diff --git a/clang/lib/AST/Expr.cpp b/clang/lib/AST/Expr.cpp
index f0c195c08ccb..e9ee624e499d 100644
--- a/clang/lib/AST/Expr.cpp
+++ b/clang/lib/AST/Expr.cpp
@@ -4116,7 +4116,7 @@ bool ExtVectorElementExpr::containsDuplicateElements() const {
     Comp = Comp.substr(1);
 
   for (unsigned i = 0, e = Comp.size(); i != e; ++i)
-    if (Comp.substr(i + 1).find(Comp[i]) != StringRef::npos)
+    if (Comp.substr(i + 1).contains(Comp[i]))
         return true;
 
   return false;
diff --git a/clang/lib/ASTMatchers/ASTMatchersInternal.cpp b/clang/lib/ASTMatchers/ASTMatchersInternal.cpp
index 12e3c488d61a..b7622e3b51f1 100644
--- a/clang/lib/ASTMatchers/ASTMatchersInternal.cpp
+++ b/clang/lib/ASTMatchers/ASTMatchersInternal.cpp
@@ -468,8 +468,8 @@ hasAnyOverloadedOperatorNameFunc(ArrayRef<const StringRef *> NameRefs) {
 }
 
 HasNameMatcher::HasNameMatcher(std::vector<std::string> N)
-    : UseUnqualifiedMatch(llvm::all_of(
-          N, [](StringRef Name) { return Name.find("::") == Name.npos; })),
+    : UseUnqualifiedMatch(
+          llvm::all_of(N, [](StringRef Name) { return !Name.contains("::"); })),
       Names(std::move(N)) {
 #ifndef NDEBUG
   for (StringRef Name : Names)
diff --git a/clang/lib/Analysis/RetainSummaryManager.cpp b/clang/lib/Analysis/RetainSummaryManager.cpp
index 7ed1e40333f4..1d7b968e994f 100644
--- a/clang/lib/Analysis/RetainSummaryManager.cpp
+++ b/clang/lib/Analysis/RetainSummaryManager.cpp
@@ -397,8 +397,7 @@ const RetainSummary *RetainSummaryManager::getSummaryForObjCOrCFObject(
                                 ArgEffect(DoNothing), ArgEffect(DoNothing));
   } else if (FName.startswith("NSLog")) {
     return getDoNothingSummary();
-  } else if (FName.startswith("NS") &&
-             (FName.find("Insert") != StringRef::npos)) {
+  } else if (FName.startswith("NS") && FName.contains("Insert")) {
     // Whitelist NSXXInsertXX, for example NSMapInsertIfAbsent, since they can
     // be deallocated by NSMapRemove. (radar://11152419)
     ScratchArgs = AF.add(ScratchArgs, 1, ArgEffect(StopTracking));
diff --git a/clang/lib/CodeGen/CodeGenFunction.cpp b/clang/lib/CodeGen/CodeGenFunction.cpp
index 0b336d410a07..fc4540f26aab 100644
--- a/clang/lib/CodeGen/CodeGenFunction.cpp
+++ b/clang/lib/CodeGen/CodeGenFunction.cpp
@@ -2500,8 +2500,7 @@ void CodeGenFunction::checkTargetFeatures(SourceLocation Loc,
     // Return if the builtin doesn't have any required features.
     if (FeatureList.empty())
       return;
-    assert(FeatureList.find(' ') == StringRef::npos &&
-           "Space in feature list");
+    assert(!FeatureList.contains(' ') && "Space in feature list");
     TargetFeatures TF(CallerFeatureMap);
     if (!TF.hasRequiredFeatures(FeatureList))
       CGM.getDiags().Report(Loc, diag::err_builtin_needs_feature)
diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 10951a01150a..c76346337dc9 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -2646,7 +2646,7 @@ static std::string qualifyWindowsLibrary(llvm::StringRef Lib) {
   // If the argument does not end in .lib, automatically add the suffix.
   // If the argument contains a space, enclose it in quotes.
   // This matches the behavior of MSVC.
-  bool Quote = (Lib.find(' ') != StringRef::npos);
+  bool Quote = Lib.contains(' ');
   std::string ArgStr = Quote ? "\"" : "";
   ArgStr += Lib;
   if (!Lib.endswith_insensitive(".lib") && !Lib.endswith_insensitive(".a"))
diff --git a/clang/lib/Lex/HeaderSearch.cpp b/clang/lib/Lex/HeaderSearch.cpp
index 866ebb193a54..150e7edb12c1 100644
--- a/clang/lib/Lex/HeaderSearch.cpp
+++ b/clang/lib/Lex/HeaderSearch.cpp
@@ -1037,7 +1037,7 @@ Optional<FileEntryRef> HeaderSearch::LookupFile(
   // resolve "foo.h" any other way, change the include to <Foo/foo.h>, where
   // "Foo" is the name of the framework in which the including header was found.
   if (!Includers.empty() && Includers.front().first && !isAngled &&
-      Filename.find('/') == StringRef::npos) {
+      !Filename.contains('/')) {
     HeaderFileInfo &IncludingHFI = getFileInfo(Includers.front().first);
     if (IncludingHFI.IndexHeaderMapHeader) {
       SmallString<128> ScratchFilename;
diff --git a/clang/lib/Lex/LiteralSupport.cpp b/clang/lib/Lex/LiteralSupport.cpp
index 64fad46323cb..a8022812a363 100644
--- a/clang/lib/Lex/LiteralSupport.cpp
+++ b/clang/lib/Lex/LiteralSupport.cpp
@@ -1242,7 +1242,7 @@ NumericLiteralParser::GetFloatValue(llvm::APFloat &Result) {
 
   llvm::SmallString<16> Buffer;
   StringRef Str(ThisTokBegin, n);
-  if (Str.find('\'') != StringRef::npos) {
+  if (Str.contains('\'')) {
     Buffer.reserve(n);
     std::remove_copy_if(Str.begin(), Str.end(), std::back_inserter(Buffer),
                         &isDigitSeparator);
diff --git a/clang/lib/Rewrite/Rewriter.cpp b/clang/lib/Rewrite/Rewriter.cpp
index 040e1c284253..3b06afc76e16 100644
--- a/clang/lib/Rewrite/Rewriter.cpp
+++ b/clang/lib/Rewrite/Rewriter.cpp
@@ -259,7 +259,7 @@ bool Rewriter::InsertText(SourceLocation Loc, StringRef Str,
   unsigned StartOffs = getLocationOffsetAndFileID(Loc, FID);
 
   SmallString<128> indentedStr;
-  if (indentNewLines && Str.find('\n') != StringRef::npos) {
+  if (indentNewLines && Str.contains('\n')) {
     StringRef MB = SourceMgr->getBufferData(FID);
 
     unsigned lineNo = SourceMgr->getLineNumber(FID, StartOffs) - 1;
diff --git a/clang/utils/TableGen/ClangASTPropertiesEmitter.cpp b/clang/utils/TableGen/ClangASTPropertiesEmitter.cpp
index caced02e1e11..c3735f70136d 100644
--- a/clang/utils/TableGen/ClangASTPropertiesEmitter.cpp
+++ b/clang/utils/TableGen/ClangASTPropertiesEmitter.cpp
@@ -455,7 +455,7 @@ void ASTPropsEmitter::emitPropertiedReaderWriterBody(HasProperties node,
   // Emit code to read all the properties.
   visitAllProperties(node, nodeInfo, [&](Property prop) {
     // Verify that the creation code refers to this property.
-    if (info.IsReader && creationCode.find(prop.getName()) == StringRef::npos)
+    if (info.IsReader && !creationCode.contains(prop.getName()))
       PrintFatalError(nodeInfo.Creator.getLoc(),
                       "creation code for " + node.getName()
                         + " doesn't refer to property \""
diff --git a/clang/utils/TableGen/NeonEmitter.cpp b/clang/utils/TableGen/NeonEmitter.cpp
index f0da1a7d2f4e..294584938295 100644
--- a/clang/utils/TableGen/NeonEmitter.cpp
+++ b/clang/utils/TableGen/NeonEmitter.cpp
@@ -382,7 +382,7 @@ public:
     StringRef Mods = getNextModifiers(Proto, Pos);
     while (!Mods.empty()) {
       Types.emplace_back(InTS, Mods);
-      if (Mods.find('!') != StringRef::npos)
+      if (Mods.contains('!'))
         PolymorphicKeyType = Types.size() - 1;
 
       Mods = getNextModifiers(Proto, Pos);
diff --git a/clang/utils/TableGen/RISCVVEmitter.cpp b/clang/utils/TableGen/RISCVVEmitter.cpp
index b4fa0e288470..26aecb6fd961 100644
--- a/clang/utils/TableGen/RISCVVEmitter.cpp
+++ b/clang/utils/TableGen/RISCVVEmitter.cpp
@@ -652,7 +652,7 @@ void RVVType::applyModifier(StringRef Transformer) {
     assert(Idx != StringRef::npos);
     StringRef ComplexType = Transformer.slice(1, Idx);
     Transformer = Transformer.drop_front(Idx + 1);
-    assert(Transformer.find('(') == StringRef::npos &&
+    assert(!Transformer.contains('(') &&
            "Only allow one complex type transformer");
 
     auto UpdateAndCheckComplexProto = [&]() {