[RemoveDIs] Load into new debug info format by default in llvm-dis (#86276)

Directly load all bitcode into the new debug info format in llvm-dis.
This means that new-mode bitcode no longer round-trips back to old-mode
after parsing, and that old-mode bitcode gets auto-upgraded to new-mode
debug info (which is the current in-memory default in LLVM).

Author: OCHyams

llvm/tools/llvm-dis/llvm-dis.cpp

@@ -82,6 +82,8 @@ static cl::opt<bool> PrintThinLTOIndexOnly(
 
 extern cl::opt<bool> WriteNewDbgInfoFormat;
 
+extern cl::opt<cl::boolOrDefault> LoadBitcodeIntoNewDbgInfoFormat;
+
 namespace {
 
 static void printDebugLoc(const DebugLoc &DL, formatted_raw_ostream &OS) {
@@ -169,6 +171,10 @@ int main(int argc, char **argv) {
   cl::HideUnrelatedOptions({&DisCategory, &getColorCategory()});
   cl::ParseCommandLineOptions(argc, argv, "llvm .bc -> .ll disassembler\n");
 
+  // Load bitcode into the new debug info format by default.
+  if (LoadBitcodeIntoNewDbgInfoFormat == cl::boolOrDefault::BOU_UNSET)
+    LoadBitcodeIntoNewDbgInfoFormat = cl::boolOrDefault::BOU_TRUE;
+
   LLVMContext Context;
   Context.setDiagnosticHandler(
       std::make_unique<LLVMDisDiagnosticHandler>(argv[0]));