[BOLT] Replace LLVM_ATTRIBUTE_UNUSED with [[maybe_unused]] (NFC)

[kazutakahirata]

This patch replaces LLVM_ATTRIBUTE_UNUSED with [[maybe_unused]],
introduced as part of C++17.

[llvmbot]

@llvm/pr-subscribers-bolt

Author: Kazu Hirata (kazutakahirata)

Changes

This patch replaces LLVM_ATTRIBUTE_UNUSED with [[maybe_unused]],
introduced as part of C++17.

---

Full diff: https://github.com/llvm/llvm-project/pull/163700.diff

3 Files Affected:

• (modified) bolt/lib/Core/CallGraph.cpp (+2-2)
• (modified) bolt/lib/Core/DebugData.cpp (+1-1)
• (modified) bolt/lib/Rewrite/DWARFRewriter.cpp (+1-1)

diff --git a/bolt/lib/Core/CallGraph.cpp b/bolt/lib/Core/CallGraph.cpp
index f1d52737bf556..f07add3a88112 100644
--- a/bolt/lib/Core/CallGraph.cpp
+++ b/bolt/lib/Core/CallGraph.cpp
@@ -22,7 +22,7 @@
 #undef USE_SSECRC
 #endif
 
-static LLVM_ATTRIBUTE_UNUSED inline size_t hash_int64_fallback(int64_t k) {
+[[maybe_unused]] static inline size_t hash_int64_fallback(int64_t k) {
   uint64_t key = (unsigned long long)k;
   // "64 bit Mix Functions", from Thomas Wang's "Integer Hash Function."
   // http://www.concentric.net/~ttwang/tech/inthash.htm
@@ -35,7 +35,7 @@ static LLVM_ATTRIBUTE_UNUSED inline size_t hash_int64_fallback(int64_t k) {
   return static_cast<size_t>(static_cast<uint32_t>(key));
 }
 
-static LLVM_ATTRIBUTE_UNUSED inline size_t hash_int64(int64_t k) {
+[[maybe_unused]] static inline size_t hash_int64(int64_t k) {
 #if defined(USE_SSECRC) && defined(__SSE4_2__)
   size_t h = 0;
   __asm("crc32q %1, %0\n" : "+r"(h) : "rm"(k));
diff --git a/bolt/lib/Core/DebugData.cpp b/bolt/lib/Core/DebugData.cpp
index 24a4c852e9d7e..2687788167a8a 100644
--- a/bolt/lib/Core/DebugData.cpp
+++ b/bolt/lib/Core/DebugData.cpp
@@ -101,7 +101,7 @@ std::optional<AttrInfo> findAttributeInfo(const DWARFDie DIE,
   return findAttributeInfo(DIE, AbbrevDecl, *Index);
 }
 
-LLVM_ATTRIBUTE_UNUSED
+[[maybe_unused]]
 static void printLE64(const std::string &S) {
   for (uint32_t I = 0, Size = S.size(); I < Size; ++I) {
     errs() << Twine::utohexstr(S[I]);
diff --git a/bolt/lib/Rewrite/DWARFRewriter.cpp b/bolt/lib/Rewrite/DWARFRewriter.cpp
index a7a4b664693fc..5e3fa931e826f 100644
--- a/bolt/lib/Rewrite/DWARFRewriter.cpp
+++ b/bolt/lib/Rewrite/DWARFRewriter.cpp
@@ -69,7 +69,7 @@ static void printDie(const DWARFDie &DIE) {
 }
 
 /// Lazily parse DWARF DIE and print it out.
-LLVM_ATTRIBUTE_UNUSED
+[[maybe_unused]]
 static void printDie(DWARFUnit &DU, uint64_t DIEOffset) {
   uint64_t OriginalOffsets = DIEOffset;
   uint64_t NextCUOffset = DU.getNextUnitOffset();