[lld] Use std::tie to implement comparison operators (NFC) (llvm#143726)

std::tie facilitates lexicographical comparisons through std::tuple's
built-in operator< and operator>.

Author: kazutakahirata

lld/ELF/SyntheticSections.cpp

@@ -1939,11 +1939,8 @@ bool AndroidPackedRelocationSection<ELFT>::updateAllocSize(Ctx &ctx) {
   // For Rela, we also want to sort by r_addend when r_info is the same. This
   // enables us to group by r_addend as well.
   llvm::sort(nonRelatives, [](const Elf_Rela &a, const Elf_Rela &b) {
-    if (a.r_info != b.r_info)
-      return a.r_info < b.r_info;
-    if (a.r_addend != b.r_addend)
-      return a.r_addend < b.r_addend;
-    return a.r_offset < b.r_offset;
+    return std::tie(a.r_info, a.r_addend, a.r_offset) <
+           std::tie(b.r_info, b.r_addend, b.r_offset);
   });
 
   // Group relocations with the same r_info. Note that each group emits a group

lld/MachO/UnwindInfoSection.cpp

@@ -535,11 +535,9 @@ void UnwindInfoSectionImpl::finalize() {
   llvm::sort(commonEncodings,
              [](const std::pair<compact_unwind_encoding_t, size_t> &a,
                 const std::pair<compact_unwind_encoding_t, size_t> &b) {
-               if (a.second == b.second)
-                 // When frequencies match, secondarily sort on encoding
-                 // to maintain parity with validate-unwind-info.py
-                 return a.first > b.first;
-               return a.second > b.second;
+               // When frequencies match, secondarily sort on encoding
+               // to maintain parity with validate-unwind-info.py
+               return std::tie(a.second, a.first) > std::tie(b.second, b.first);
              });
 
   // Truncate the vector to 127 elements.