[lld] [lld][macho] Support order cstrings with -order_file_cstring (PR #140307)

[Ellis Hoag via llvm-commits]

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@@ -388,3 +401,41 @@ macho::PriorityBuilder::buildInputSectionPriorities() {
 
   return sectionPriorities;
 }
+
+std::vector<StringPiecePair> macho::PriorityBuilder::buildCStringPriorities(
+    ArrayRef<CStringInputSection *> inputs) {
+  // Split the input strings into hold and cold sets.
+  // Order hot set based on -order_file_cstring for performance improvement;
+  // TODO: Order cold set of cstrings for compression via BP.
+  std::vector<std::pair<int, StringPiecePair>>
+      hotStringPrioritiesAndStringPieces;
+  std::vector<StringPiecePair> coldStringPieces;
+  std::vector<StringPiecePair> orderedStringPieces;
+
+  for (CStringInputSection *isec : inputs) {
+    for (const auto &[stringPieceIdx, piece] : llvm::enumerate(isec->pieces)) {
+      if (!piece.live)
+        continue;
+
+      std::optional<int> priority = getSymbolOrCStringPriority(
+          std::to_string(piece.hash), isec->getFile());
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ellishg wrote:

Right now we convert the string hash in the orderfile into an integer (but we don't use the result), then we also convert each hash in the object file to a string to look it up in the priority map. It would be more efficient to create a new priority map, `cstrPriorities` that maps integer hashes to priorities.

https://github.com/llvm/llvm-project/pull/140307