diff --git a/lld/COFF/COFFLinkerContext.h b/lld/COFF/COFFLinkerContext.h
--- a/lld/COFF/COFFLinkerContext.h
+++ b/lld/COFF/COFFLinkerContext.h
@@ -18,8 +18,7 @@
 #include "lld/Common/CommonLinkerContext.h"
 #include "lld/Common/Timer.h"
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 class COFFLinkerContext : public CommonLinkerContext {
 public:
@@ -80,7 +79,6 @@
   Timer diskCommitTimer;
 };
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 #endif
diff --git a/lld/COFF/COFFLinkerContext.cpp b/lld/COFF/COFFLinkerContext.cpp
--- a/lld/COFF/COFFLinkerContext.cpp
+++ b/lld/COFF/COFFLinkerContext.cpp
@@ -13,8 +13,7 @@
 #include "lld/Common/Memory.h"
 #include "llvm/DebugInfo/CodeView/TypeHashing.h"
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 COFFLinkerContext::COFFLinkerContext()
     : symtab(*this), rootTimer("Total Linking Time"),
@@ -36,5 +35,4 @@
       tpiStreamLayoutTimer("TPI Stream Layout", totalPdbLinkTimer),
       diskCommitTimer("Commit to Disk", totalPdbLinkTimer) {}
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
diff --git a/lld/COFF/CallGraphSort.h b/lld/COFF/CallGraphSort.h
--- a/lld/COFF/CallGraphSort.h
+++ b/lld/COFF/CallGraphSort.h
@@ -11,14 +11,12 @@
 
 #include "llvm/ADT/DenseMap.h"
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 class SectionChunk;
 class COFFLinkerContext;
 
 llvm::DenseMap<const SectionChunk *, int>
 computeCallGraphProfileOrder(const COFFLinkerContext &ctx);
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 #endif
diff --git a/lld/COFF/Chunks.h b/lld/COFF/Chunks.h
--- a/lld/COFF/Chunks.h
+++ b/lld/COFF/Chunks.h
@@ -21,8 +21,7 @@
 #include <utility>
 #include <vector>
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 using llvm::COFF::ImportDirectoryTableEntry;
 using llvm::object::COFFSymbolRef;
@@ -698,8 +697,7 @@
 void applyArm64Imm(uint8_t *off, uint64_t imm, uint32_t rangeLimit);
 void applyArm64Branch26(uint8_t *off, int64_t v);
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 namespace llvm {
 template <>
diff --git a/lld/COFF/Chunks.cpp b/lld/COFF/Chunks.cpp
--- a/lld/COFF/Chunks.cpp
+++ b/lld/COFF/Chunks.cpp
@@ -27,8 +27,7 @@
 using namespace llvm::COFF;
 using llvm::support::ulittle32_t;
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 SectionChunk::SectionChunk(ObjFile *f, const coff_section *h)
     : Chunk(SectionKind), file(f), header(h), repl(this) {
@@ -996,5 +995,4 @@
   }
 }
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
diff --git a/lld/COFF/Config.h b/lld/COFF/Config.h
--- a/lld/COFF/Config.h
+++ b/lld/COFF/Config.h
@@ -21,8 +21,7 @@
 #include <set>
 #include <string>
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 using llvm::COFF::IMAGE_FILE_MACHINE_UNKNOWN;
 using llvm::COFF::WindowsSubsystem;
@@ -289,7 +288,6 @@
 
 extern std::unique_ptr<Configuration> config;
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 #endif
diff --git a/lld/COFF/DLL.h b/lld/COFF/DLL.h
--- a/lld/COFF/DLL.h
+++ b/lld/COFF/DLL.h
@@ -12,8 +12,7 @@
 #include "Chunks.h"
 #include "Symbols.h"
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 // Windows-specific.
 // IdataContents creates all chunks for the DLL import table.
@@ -76,7 +75,6 @@
   }
 };
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 #endif
diff --git a/lld/COFF/DLL.cpp b/lld/COFF/DLL.cpp
--- a/lld/COFF/DLL.cpp
+++ b/lld/COFF/DLL.cpp
@@ -31,8 +31,7 @@
 using namespace llvm::support::endian;
 using namespace llvm::COFF;
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 namespace {
 
 // Import table
@@ -752,5 +751,4 @@
   chunks.insert(chunks.end(), forwards.begin(), forwards.end());
 }
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
diff --git a/lld/COFF/DebugTypes.h b/lld/COFF/DebugTypes.h
--- a/lld/COFF/DebugTypes.h
+++ b/lld/COFF/DebugTypes.h
@@ -17,18 +17,15 @@
 #include "llvm/Support/Error.h"
 #include "llvm/Support/MemoryBuffer.h"
 
-namespace llvm {
-namespace codeview {
+namespace llvm::codeview {
 struct GloballyHashedType;
-} // namespace codeview
-namespace pdb {
+}
+namespace llvm::pdb {
 class NativeSession;
 class TpiStream;
 }
-} // namespace llvm
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 using llvm::codeview::GloballyHashedType;
 using llvm::codeview::TypeIndex;
@@ -175,7 +172,6 @@
 TpiSource *makeUsePrecompSource(COFFLinkerContext &ctx, ObjFile *file,
                                 llvm::codeview::PrecompRecord ts);
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 #endif
diff --git a/lld/COFF/DebugTypes.cpp b/lld/COFF/DebugTypes.cpp
--- a/lld/COFF/DebugTypes.cpp
+++ b/lld/COFF/DebugTypes.cpp
@@ -953,15 +953,13 @@
 };
 } // namespace
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 /// This type is just a wrapper around GHashTable with external linkage so it
 /// can be used from a header.
 struct GHashState {
   GHashTable table;
 };
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 GHashTable::~GHashTable() { delete[] table; }
 
diff --git a/lld/COFF/Driver.h b/lld/COFF/Driver.h
--- a/lld/COFF/Driver.h
+++ b/lld/COFF/Driver.h
@@ -28,8 +28,7 @@
 #include <set>
 #include <vector>
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 extern std::unique_ptr<class LinkerDriver> driver;
 
@@ -234,7 +233,6 @@
 #undef OPTION
 };
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 #endif
diff --git a/lld/COFF/Driver.cpp b/lld/COFF/Driver.cpp
--- a/lld/COFF/Driver.cpp
+++ b/lld/COFF/Driver.cpp
@@ -58,8 +58,7 @@
 using namespace llvm::COFF;
 using namespace llvm::sys;
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 std::unique_ptr<Configuration> config;
 std::unique_ptr<LinkerDriver> driver;
@@ -2418,5 +2417,4 @@
     ctx.rootTimer.print();
 }
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
diff --git a/lld/COFF/ICF.h b/lld/COFF/ICF.h
--- a/lld/COFF/ICF.h
+++ b/lld/COFF/ICF.h
@@ -13,15 +13,13 @@
 #include "lld/Common/LLVM.h"
 #include "llvm/ADT/ArrayRef.h"
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 class Chunk;
 class COFFLinkerContext;
 
 void doICF(COFFLinkerContext &ctx, ICFLevel);
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 #endif
diff --git a/lld/COFF/ICF.cpp b/lld/COFF/ICF.cpp
--- a/lld/COFF/ICF.cpp
+++ b/lld/COFF/ICF.cpp
@@ -34,8 +34,7 @@
 
 using namespace llvm;
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 class ICF {
 public:
@@ -322,5 +321,4 @@
   ICF(ctx, icfLevel).run();
 }
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
diff --git a/lld/COFF/LLDMapFile.h b/lld/COFF/LLDMapFile.h
--- a/lld/COFF/LLDMapFile.h
+++ b/lld/COFF/LLDMapFile.h
@@ -9,11 +9,9 @@
 #ifndef LLD_COFF_LLDMAPFILE_H
 #define LLD_COFF_LLDMAPFILE_H
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 class COFFLinkerContext;
 void writeLLDMapFile(const COFFLinkerContext &ctx);
 }
-}
 
 #endif
diff --git a/lld/COFF/LTO.h b/lld/COFF/LTO.h
--- a/lld/COFF/LTO.h
+++ b/lld/COFF/LTO.h
@@ -27,14 +27,11 @@
 #include <memory>
 #include <vector>
 
-namespace llvm {
-namespace lto {
+namespace llvm::lto {
 class LTO;
 }
-}
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 class BitcodeFile;
 class InputFile;
@@ -56,6 +53,5 @@
   llvm::DenseSet<StringRef> thinIndices;
 };
 }
-}
 
 #endif
diff --git a/lld/COFF/MapFile.h b/lld/COFF/MapFile.h
--- a/lld/COFF/MapFile.h
+++ b/lld/COFF/MapFile.h
@@ -9,11 +9,9 @@
 #ifndef LLD_COFF_MAPFILE_H
 #define LLD_COFF_MAPFILE_H
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 class COFFLinkerContext;
 void writeMapFile(COFFLinkerContext &ctx);
 }
-}
 
 #endif
diff --git a/lld/COFF/MarkLive.h b/lld/COFF/MarkLive.h
--- a/lld/COFF/MarkLive.h
+++ b/lld/COFF/MarkLive.h
@@ -11,14 +11,12 @@
 
 #include "lld/Common/LLVM.h"
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 class COFFLinkerContext;
 
 void markLive(COFFLinkerContext &ctx);
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 #endif // LLD_COFF_MARKLIVE_H
diff --git a/lld/COFF/MarkLive.cpp b/lld/COFF/MarkLive.cpp
--- a/lld/COFF/MarkLive.cpp
+++ b/lld/COFF/MarkLive.cpp
@@ -13,8 +13,7 @@
 #include "llvm/ADT/STLExtras.h"
 #include <vector>
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 // Set live bit on for each reachable chunk. Unmarked (unreachable)
 // COMDAT chunks will be ignored by Writer, so they will be excluded
@@ -70,4 +69,3 @@
   }
 }
 }
-}
diff --git a/lld/COFF/MinGW.h b/lld/COFF/MinGW.h
--- a/lld/COFF/MinGW.h
+++ b/lld/COFF/MinGW.h
@@ -17,8 +17,7 @@
 #include "llvm/Option/ArgList.h"
 #include <vector>
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 class COFFLinkerContext;
 
 // Logic for deciding what symbols to export, when exporting all
@@ -59,7 +58,6 @@
 
 void wrapSymbols(COFFLinkerContext &ctx, ArrayRef<WrappedSymbol> wrapped);
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 #endif
diff --git a/lld/COFF/PDB.h b/lld/COFF/PDB.h
--- a/lld/COFF/PDB.h
+++ b/lld/COFF/PDB.h
@@ -13,11 +13,9 @@
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/StringRef.h"
 
-namespace llvm {
-namespace codeview {
+namespace llvm::codeview {
 union DebugInfo;
 }
-}
 
 namespace lld {
 class Timer;
diff --git a/lld/COFF/SymbolTable.h b/lld/COFF/SymbolTable.h
--- a/lld/COFF/SymbolTable.h
+++ b/lld/COFF/SymbolTable.h
@@ -20,8 +20,7 @@
 struct LTOCodeGenerator;
 }
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 class Chunk;
 class CommonChunk;
@@ -142,7 +141,6 @@
 
 StringRef ltrim1(StringRef s, const char *chars);
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 #endif
diff --git a/lld/COFF/SymbolTable.cpp b/lld/COFF/SymbolTable.cpp
--- a/lld/COFF/SymbolTable.cpp
+++ b/lld/COFF/SymbolTable.cpp
@@ -26,8 +26,7 @@
 
 using namespace llvm;
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 StringRef ltrim1(StringRef s, const char *chars) {
   if (!s.empty() && strchr(chars, s[0]))
@@ -891,5 +890,4 @@
   }
 }
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
diff --git a/lld/COFF/TypeMerger.h b/lld/COFF/TypeMerger.h
--- a/lld/COFF/TypeMerger.h
+++ b/lld/COFF/TypeMerger.h
@@ -17,8 +17,7 @@
 #include "llvm/Support/Allocator.h"
 #include <atomic>
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 
 using llvm::codeview::GloballyHashedType;
 using llvm::codeview::TypeIndex;
@@ -79,7 +78,6 @@
   COFFLinkerContext &ctx;
 };
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 #endif
diff --git a/lld/COFF/Writer.h b/lld/COFF/Writer.h
--- a/lld/COFF/Writer.h
+++ b/lld/COFF/Writer.h
@@ -16,8 +16,7 @@
 #include <cstdint>
 #include <vector>
 
-namespace lld {
-namespace coff {
+namespace lld::coff {
 static const int pageSize = 4096;
 class COFFLinkerContext;
 
@@ -80,7 +79,6 @@
   uint32_t stringTableOff = 0;
 };
 
-} // namespace coff
-} // namespace lld
+} // namespace lld::coff
 
 #endif