diff --git a/clang/lib/AST/TypePrinter.cpp b/clang/lib/AST/TypePrinter.cpp
index 63e56a8296db3..4363280757714 100644
--- a/clang/lib/AST/TypePrinter.cpp
+++ b/clang/lib/AST/TypePrinter.cpp
@@ -2264,7 +2264,7 @@ printTo(raw_ostream &OS, ArrayRef<TA> Args, const PrintingPolicy &Policy,
     // If this is the first argument and its string representation
     // begins with the global scope specifier ('::foo'), add a space
     // to avoid printing the diagraph '<:'.
-    if (FirstArg && !ArgString.empty() && ArgString[0] == ':')
+    if (FirstArg && ArgString.starts_with(":"))
       OS << ' ';
 
     OS << ArgString;
diff --git a/clang/lib/Basic/Targets/X86.cpp b/clang/lib/Basic/Targets/X86.cpp
index a68b662d9401a..c6fc17fcc1b70 100644
--- a/clang/lib/Basic/Targets/X86.cpp
+++ b/clang/lib/Basic/Targets/X86.cpp
@@ -151,7 +151,7 @@ bool X86TargetInfo::initFeatureMap(
       // Postpone AVX10 features handling after AVX512 settled.
       UpdatedAVX10FeaturesVec.push_back(Feature);
       continue;
-    } else if (!HasAVX512F && Feature.substr(0, 7) == "+avx512") {
+    } else if (!HasAVX512F && StringRef(Feature).starts_with("+avx512")) {
       HasAVX512F = true;
       LastAVX512 = Feature;
     } else if (HasAVX512F && Feature == "-avx512f") {
diff --git a/clang/lib/CodeGen/CGObjCMac.cpp b/clang/lib/CodeGen/CGObjCMac.cpp
index 517f7cddebc1a..27d77e9a8a551 100644
--- a/clang/lib/CodeGen/CGObjCMac.cpp
+++ b/clang/lib/CodeGen/CGObjCMac.cpp
@@ -5038,12 +5038,10 @@ std::string CGObjCCommonMac::GetSectionName(StringRef Section,
     return ("__DATA," + Section + "," + MachOAttributes).str();
   }
   case llvm::Triple::ELF:
-    assert(Section.substr(0, 2) == "__" &&
-           "expected the name to begin with __");
+    assert(Section.starts_with("__") && "expected the name to begin with __");
     return Section.substr(2).str();
   case llvm::Triple::COFF:
-    assert(Section.substr(0, 2) == "__" &&
-           "expected the name to begin with __");
+    assert(Section.starts_with("__") && "expected the name to begin with __");
     return ("." + Section.substr(2) + "$B").str();
   case llvm::Triple::Wasm:
   case llvm::Triple::GOFF:
diff --git a/clang/lib/Format/FormatTokenLexer.cpp b/clang/lib/Format/FormatTokenLexer.cpp
index d7de09ef0e12a..a87d0ba3dbbf9 100644
--- a/clang/lib/Format/FormatTokenLexer.cpp
+++ b/clang/lib/Format/FormatTokenLexer.cpp
@@ -1420,7 +1420,7 @@ void FormatTokenLexer::readRawToken(FormatToken &Tok) {
   // For formatting, treat unterminated string literals like normal string
   // literals.
   if (Tok.is(tok::unknown)) {
-    if (!Tok.TokenText.empty() && Tok.TokenText[0] == '"') {
+    if (Tok.TokenText.starts_with("\"")) {
       Tok.Tok.setKind(tok::string_literal);
       Tok.IsUnterminatedLiteral = true;
     } else if (Style.isJavaScript() && Tok.TokenText == "''") {
diff --git a/clang/lib/Frontend/FrontendActions.cpp b/clang/lib/Frontend/FrontendActions.cpp
index c1d6e71455365..b9ed5dedfa422 100644
--- a/clang/lib/Frontend/FrontendActions.cpp
+++ b/clang/lib/Frontend/FrontendActions.cpp
@@ -826,8 +826,7 @@ void DumpModuleInfoAction::ExecuteAction() {
   auto &FileMgr = CI.getFileManager();
   auto Buffer = FileMgr.getBufferForFile(getCurrentFile());
   StringRef Magic = (*Buffer)->getMemBufferRef().getBuffer();
-  bool IsRaw = (Magic.size() >= 4 && Magic[0] == 'C' && Magic[1] == 'P' &&
-                Magic[2] == 'C' && Magic[3] == 'H');
+  bool IsRaw = Magic.starts_with("CPCH");
   Out << "  Module format: " << (IsRaw ? "raw" : "obj") << "\n";
 
   Preprocessor &PP = CI.getPreprocessor();