[BOLT][DWARF][NFC] Add function to print DIE

[ayermolo]

Summary

This is purely to make debugging easier for developers. Now that we moved to IR
the print out of DIEs is lacking. This function will lazily parse DIE and use
DWARFDie dump function.

[Amir]

LGTM with nits

bolt/lib/Rewrite/DWARFRewriter.cpp

59–60

Remove

68

[ayermolo]

addressed comments

bolt/lib/Rewrite/DWARFRewriter.cpp

 #include <optional>
 #include <string>
 #include <unordered_map>
 #include <utility>
 #include <vector>
 
 #undef DEBUG_TYPE
 #define DEBUG_TYPE "bolt"
 
-LLVM_ATTRIBUTE_UNUSED
 static void printDie(const DWARFDie &DIE) {
   DIDumpOptions DumpOpts;
   DumpOpts.ShowForm = true;
   DumpOpts.Verbose = true;
   DumpOpts.ChildRecurseDepth = 0;
   DumpOpts.ShowChildren = false;
   DIE.dump(dbgs(), 0, DumpOpts);
 }
 
+/// Lazily parse DWARF DIE and print it out.
+LLVM_ATTRIBUTE_UNUSED
+static void printDie(DWARFUnit &DU, uint64_t DIEOffset) {
+  uint64_t OriginalOffsets = DIEOffset;
+  uint64_t NextCUOffset = DU.getNextUnitOffset();
+  DWARFDataExtractor DebugInfoData = DU.getDebugInfoExtractor();
+  DWARFDebugInfoEntry DIEEntry;
+  if (DIEEntry.extractFast(DU, &DIEOffset, DebugInfoData, NextCUOffset, 0)) {
+    if (const DWARFAbbreviationDeclaration *AbbrDecl =
+            DIEEntry.getAbbreviationDeclarationPtr()) {
+      DWARFDie DDie(&DU, &DIEEntry);
+      printDie(DDie);
+    } else {
+      dbgs() << "Failed to extract abbreviation for"
+             << Twine::utohexstr(OriginalOffsets) << "\n";
+    }
+  } else {
+    dbgs() << "Failed to extract DIE for " << Twine::utohexstr(OriginalOffsets)
+           << " \n";
+  }
+}
+
 namespace llvm {
 namespace bolt {
 /// Emits debug information into .debug_info or .debug_types section.
 class DIEStreamer : public DwarfStreamer {
   DIEBuilder *DIEBldr;
   DWARFRewriter &Rewriter;
 
 private: