[llvm] Replace LLVM_ATTRIBUTE_UNUSED with [[maybe_unused]] (NFC) (#163507)

This patch replaces LLVM_ATTRIBUTE_UNUSED with [[maybe_unused]].  Note
that this patch adjusts the placement of [[maybe_unused]] to comply
with the C++17 language.

Author: kazutakahirata

llvm/include/llvm/Analysis/TargetLibraryInfo.h

@@ -373,12 +373,10 @@ class TargetLibraryInfo {
   /// Disables all builtins.
   ///
   /// This can be used for options like -fno-builtin.
-  void disableAllFunctions() LLVM_ATTRIBUTE_UNUSED {
-    OverrideAsUnavailable.set();
-  }
+  [[maybe_unused]] void disableAllFunctions() { OverrideAsUnavailable.set(); }
 
   /// Forces a function to be marked as unavailable.
-  void setUnavailable(LibFunc F) LLVM_ATTRIBUTE_UNUSED {
+  [[maybe_unused]] void setUnavailable(LibFunc F) {
     assert(F < OverrideAsUnavailable.size() && "out-of-bounds LibFunc");
     OverrideAsUnavailable.set(F);
   }

llvm/include/llvm/CodeGen/LiveRangeCalc.h

@@ -259,7 +259,7 @@ class LiveRangeCalc {
   /// jointly dominated by the blocks corresponding to the slot indices
   /// in @p Defs. This function is mainly for use in self-verification
   /// checks.
-  LLVM_ABI LLVM_ATTRIBUTE_UNUSED static bool
+  [[maybe_unused]] LLVM_ABI static bool
   isJointlyDominated(const MachineBasicBlock *MBB, ArrayRef<SlotIndex> Defs,
                      const SlotIndexes &Indexes);
 };

llvm/include/llvm/Support/DebugLog.h

@@ -221,12 +221,10 @@ constexpr ::llvm::StringRef strip_quotes(const char *Str) {
 #define LDBG_GET_DEBUG_TYPE_STR() LDBG_GET_DEBUG_TYPE_STR_(DEBUG_TYPE)
 
 /// Helper to call isCurrentDebugType with a StringRef.
-static LLVM_ATTRIBUTE_UNUSED bool ldbgIsCurrentDebugType(StringRef Type,
-                                                         int Level) {
+[[maybe_unused]] static bool ldbgIsCurrentDebugType(StringRef Type, int Level) {
   return ::llvm::isCurrentDebugType(Type.str().c_str(), Level);
 }
-static LLVM_ATTRIBUTE_UNUSED bool ldbgIsCurrentDebugType(int Level,
-                                                         StringRef Type) {
+[[maybe_unused]] static bool ldbgIsCurrentDebugType(int Level, StringRef Type) {
   return ::llvm::isCurrentDebugType(Type.str().c_str(), Level);
 }
 
@@ -302,7 +300,7 @@ class RAIINewLineStream final : public raw_ostream {
 };
 
 /// Remove the path prefix from the file name.
-static LLVM_ATTRIBUTE_UNUSED constexpr const char *
+[[maybe_unused]] static constexpr const char *
 getShortFileName(const char *path) {
   const char *filename = path;
   for (const char *p = path; *p != '\0'; ++p) {
@@ -315,7 +313,7 @@ getShortFileName(const char *path) {
 /// Compute the prefix for the debug log in the form of:
 /// "[DebugType] File:Line "
 /// Where the File is the file name without the path prefix.
-static LLVM_ATTRIBUTE_UNUSED std::string
+[[maybe_unused]] static std::string
 computePrefix(StringRef DebugType, const char *File, int Line, int Level) {
   std::string Prefix;
   raw_string_ostream OsPrefix(Prefix);
@@ -326,7 +324,7 @@ computePrefix(StringRef DebugType, const char *File, int Line, int Level) {
   return OsPrefix.str();
 }
 /// Overload allowing to swap the order of the DebugType and Level arguments.
-static LLVM_ATTRIBUTE_UNUSED std::string
+[[maybe_unused]] static std::string
 computePrefix(int Level, const char *File, int Line, StringRef DebugType) {
   return computePrefix(DebugType, File, Line, Level);
 }

llvm/lib/CodeGen/CodeGenPrepare.cpp

@@ -819,7 +819,7 @@ void CodeGenPrepare::removeAllAssertingVHReferences(Value *V) {
 }
 
 // Verify BFI has been updated correctly by recomputing BFI and comparing them.
-void LLVM_ATTRIBUTE_UNUSED CodeGenPrepare::verifyBFIUpdates(Function &F) {
+[[maybe_unused]] void CodeGenPrepare::verifyBFIUpdates(Function &F) {
   DominatorTree NewDT(F);
   LoopInfo NewLI(NewDT);
   BranchProbabilityInfo NewBPI(F, NewLI, TLInfo);

llvm/lib/CodeGen/MachineCopyPropagation.cpp

@@ -1257,7 +1257,7 @@ void MachineCopyPropagation::BackwardCopyPropagateBlock(
   Tracker.clear();
 }
 
-static void LLVM_ATTRIBUTE_UNUSED printSpillReloadChain(
+[[maybe_unused]] static void printSpillReloadChain(
     DenseMap<MachineInstr *, SmallVector<MachineInstr *>> &SpillChain,
     DenseMap<MachineInstr *, SmallVector<MachineInstr *>> &ReloadChain,
     MachineInstr *Leader) {

llvm/lib/DebugInfo/DWARF/DWARFDebugFrame.cpp

@@ -181,8 +181,8 @@ DWARFDebugFrame::DWARFDebugFrame(Triple::ArchType Arch,
 
 DWARFDebugFrame::~DWARFDebugFrame() = default;
 
-static void LLVM_ATTRIBUTE_UNUSED dumpDataAux(DataExtractor Data,
-                                              uint64_t Offset, int Length) {
+[[maybe_unused]] static void dumpDataAux(DataExtractor Data, uint64_t Offset,
+                                         int Length) {
   errs() << "DUMP: ";
   for (int i = 0; i < Length; ++i) {
     uint8_t c = Data.getU8(&Offset);

llvm/lib/ProfileData/InstrProf.cpp

@@ -302,7 +302,7 @@ void ProfOStream::patch(ArrayRef<PatchItem> P) {
 
 std::string getPGOFuncName(StringRef Name, GlobalValue::LinkageTypes Linkage,
                            StringRef FileName,
-                           uint64_t Version LLVM_ATTRIBUTE_UNUSED) {
+                           [[maybe_unused]] uint64_t Version) {
   // Value names may be prefixed with a binary '1' to indicate
   // that the backend should not modify the symbols due to any platform
   // naming convention. Do not include that '1' in the PGO profile name.

llvm/lib/Support/PrettyStackTrace.cpp

@@ -141,7 +141,7 @@ extern "C" const char *__crashreporter_info__
 asm(".desc ___crashreporter_info__, 0x10");
 #endif
 
-static void setCrashLogMessage(const char *msg) LLVM_ATTRIBUTE_UNUSED;
+[[maybe_unused]] static void setCrashLogMessage(const char *msg);
 static void setCrashLogMessage(const char *msg) {
 #ifdef HAVE_CRASHREPORTERCLIENT_H
   (void)CRSetCrashLogMessage(msg);

llvm/lib/Target/ARM/ARMExpandPseudoInsts.cpp

@@ -161,8 +161,8 @@ namespace {
     friend bool operator<(const NEONLdStTableEntry &TE, unsigned PseudoOpc) {
       return TE.PseudoOpc < PseudoOpc;
     }
-    friend bool LLVM_ATTRIBUTE_UNUSED operator<(unsigned PseudoOpc,
-                                                const NEONLdStTableEntry &TE) {
+    [[maybe_unused]] friend bool operator<(unsigned PseudoOpc,
+                                           const NEONLdStTableEntry &TE) {
       return PseudoOpc < TE.PseudoOpc;
     }
   };

llvm/lib/Target/Hexagon/HexagonBitSimplify.cpp

@@ -174,8 +174,8 @@ namespace {
     const TargetRegisterInfo *TRI;
   };
 
-  raw_ostream &operator<< (raw_ostream &OS, const PrintRegSet &P)
-    LLVM_ATTRIBUTE_UNUSED;
+  [[maybe_unused]] raw_ostream &operator<<(raw_ostream &OS,
+                                           const PrintRegSet &P);
   raw_ostream &operator<< (raw_ostream &OS, const PrintRegSet &P) {
     OS << '{';
     for (unsigned R = P.RS.find_first(); R; R = P.RS.find_next(R))