[lld/mac] Add a few TimeTraceScopes

[thakis]

Summary

Identical literal folding takes ~1.4% of the time, and was missing
from the trace.

Signature computation still needs ~2.2% of the time, so probably worth
explicitly marking its contribution to "Write output file" (9.1%)

[int3]

lgtm

lld/MachO/Driver.cpp

for (const Section *section : file->sections) {
         }
       }
     }
   }
   assert(inputOrder <= UnspecifiedInputOrder);
 }
 
 static void foldIdenticalLiterals() {
+  TimeTraceScope timeScope("Fold identical literals");
   // We always create a cStringSection, regardless of whether dedupLiterals is
   // true. If it isn't, we simply create a non-deduplicating CStringSection.
   // Either way, we must unconditionally finalize it here.
   in.cStringSection->finalizeContents();
   if (in.wordLiteralSection)
     in.wordLiteralSection->finalizeContents();
 }
 

lld/MachO/ICF.cpp

 
 void macho::markSymAsAddrSig(Symbol *s) {
   if (auto *d = dyn_cast_or_null<Defined>(s))
     if (d->isec)
       d->isec->keepUnique = true;
 }
 
 void macho::markAddrSigSymbols() {
+  TimeTraceScope timeScope("Mark addrsig symbols");
   for (InputFile *file : inputFiles) {
     ObjFile *obj = dyn_cast<ObjFile>(file);
     if (!obj)
       continue;
 
     Section *addrSigSection = obj->addrSigSection;
     if (!addrSigSection)
       continue;

lld/MachO/Writer.cpp

void Writer::writeUuid() {
   // don't get the same UUID.
   hashes[chunks.size()] = xxHash64(sys::path::filename(config->finalOutput));
   uint64_t digest = xxHash64({reinterpret_cast<uint8_t *>(hashes.data()),
                               hashes.size() * sizeof(uint64_t)});
   uuidCommand->writeUuid(digest);
 }
 
 void Writer::writeCodeSignature() {
-  if (codeSignatureSection)
+  if (codeSignatureSection) {
+    TimeTraceScope timeScope("Write code signature");
     codeSignatureSection->writeHashes(buffer->getBufferStart());
   }
+}
 
 void Writer::writeOutputFile() {
   TimeTraceScope timeScope("Write output file");
   openFile();
   reportPendingUndefinedSymbols();
   if (errorCount())
     return;
   writeSections();