[RemoveDIs] Read/write DbgRecords directly from/to bitcode (#83251)

If --write-experimental-debuginfo-iterators-to-bitcode is true (default false)
and --expermental-debuginfo-iterators is also true then the new debug info
format (non-instruction records) is written to bitcode directly.

Added the following records:

    FUNC_CODE_DEBUG_RECORD_LABEL
    FUNC_CODE_DEBUG_RECORD_VALUE
    FUNC_CODE_DEBUG_RECORD_DECLARE
    FUNC_CODE_DEBUG_RECORD_ASSIGN
    FUNC_CODE_DEBUG_RECORD_VALUE_SIMPLE

The last one has an abbrev in FUNCTION_BLOCK BLOCK_INFO. Incidentally, this uses
the last value available without widening the code-length for FUNCTION_BLOCK
from 4 to 5 bits.

Records are formatted as follows:

    All DbgRecord start with:
      1. DILocation

      FUNC_CODE_DEBUG_RECORD_LABEL
        2. DILabel

      DPValues then share common fields:
        2. DILocalVariable
        3. DIExpression

        FUNC_CODE_DEBUG_RECORD_VALUE
          4. Location Metadata

        FUNC_CODE_DEBUG_RECORD_DECLARE
          4. Location Metadata

        FUNC_CODE_DEBUG_RECORD_VALUE_SIMPLE
	  4. Location Value (single)

        FUNC_CODE_DEBUG_RECORD_ASSIGN
	  4. Location Metadata
	  5. DIAssignID
	  6. DIExpression (address)
	  7. Location Metadata (address)

Encoding the DILocation metadata reference directly appeared to yield smaller
bitcode files than encoding the operands seperately (as is done with instruction
DILocations).

FUNC_CODE_DEBUG_RECORD_VALUE_SIMPLE is by far the most common DbgRecord record
in optimized code (order of 5x-10x over other kinds). Unoptimized code should
only contain FUNC_CODE_DEBUG_RECORD_DECLARE.

12 files changed, 500 insertions, 87 deletions

diff --git a/llvm/include/llvm/Bitcode/LLVMBitCodes.h b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
index c0a52d6..39303e6 100644
--- a/llvm/include/llvm/Bitcode/LLVMBitCodes.h
+++ b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -624,6 +624,17 @@ enum FunctionCodes {
                                   //             operation, align, vol,
                                   //             ordering, synchscope]
   FUNC_CODE_BLOCKADDR_USERS = 60, // BLOCKADDR_USERS: [value...]
+
+  FUNC_CODE_DEBUG_RECORD_VALUE =
+      61, // [DILocation, DILocalVariable, DIExpression, ValueAsMetadata]
+  FUNC_CODE_DEBUG_RECORD_DECLARE =
+      62, // [DILocation, DILocalVariable, DIExpression, ValueAsMetadata]
+  FUNC_CODE_DEBUG_RECORD_ASSIGN =
+      63, // [DILocation, DILocalVariable, DIExpression, ValueAsMetadata,
+          //  DIAssignID, DIExpression (addr), ValueAsMetadata (addr)]
+  FUNC_CODE_DEBUG_RECORD_VALUE_SIMPLE =
+      64, // [DILocation, DILocalVariable, DIExpression, Value]
+  FUNC_CODE_DEBUG_RECORD_LABEL = 65, // [DILocation, DILabel]
 };
 
 enum UseListCodes {
diff --git a/llvm/lib/Bitcode/Reader/BitcodeAnalyzer.cpp b/llvm/lib/Bitcode/Reader/BitcodeAnalyzer.cpp
index 7005011..c085c71 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeAnalyzer.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeAnalyzer.cpp
@@ -270,6 +270,11 @@ GetCodeName(unsigned CodeID, unsigned BlockID,
       STRINGIFY_CODE(FUNC_CODE, INST_CMPXCHG)
       STRINGIFY_CODE(FUNC_CODE, INST_CALLBR)
       STRINGIFY_CODE(FUNC_CODE, BLOCKADDR_USERS)
+      STRINGIFY_CODE(FUNC_CODE, DEBUG_RECORD_DECLARE)
+      STRINGIFY_CODE(FUNC_CODE, DEBUG_RECORD_VALUE)
+      STRINGIFY_CODE(FUNC_CODE, DEBUG_RECORD_ASSIGN)
+      STRINGIFY_CODE(FUNC_CODE, DEBUG_RECORD_VALUE_SIMPLE)
+      STRINGIFY_CODE(FUNC_CODE, DEBUG_RECORD_LABEL)
     }
   case bitc::VALUE_SYMTAB_BLOCK_ID:
     switch (CodeID) {
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
index 9c63116..d284c98 100644
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -100,9 +100,6 @@ static cl::opt<bool> ExpandConstantExprs(
     cl::desc(
         "Expand constant expressions to instructions for testing purposes"));
 
-// Declare external flag for whether we're using the new debug-info format.
-extern llvm::cl::opt<bool> UseNewDbgInfoFormat;
-
 namespace {
 
 enum {
@@ -4279,6 +4276,10 @@ Error BitcodeReader::parseGlobalIndirectSymbolRecord(
 Error BitcodeReader::parseModule(uint64_t ResumeBit,
                                  bool ShouldLazyLoadMetadata,
                                  ParserCallbacks Callbacks) {
+  // Force the debug-info mode into the old format for now.
+  // FIXME: Remove this once all tools support RemoveDIs.
+  TheModule->IsNewDbgInfoFormat = false;
+
   this->ValueTypeCallback = std::move(Callbacks.ValueType);
   if (ResumeBit) {
     if (Error JumpFailed = Stream.JumpToBit(ResumeBit))
@@ -6398,6 +6399,89 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
       InstructionList.push_back(I);
       break;
     }
+    case bitc::FUNC_CODE_DEBUG_RECORD_LABEL: {
+      // DPLabels are placed after the Instructions that they are attached to.
+      Instruction *Inst = getLastInstruction();
+      if (!Inst)
+        return error("Invalid dbg record: missing instruction");
+      DILocation *DIL = cast<DILocation>(getFnMetadataByID(Record[0]));
+      DILabel *Label = cast<DILabel>(getFnMetadataByID(Record[1]));
+      Inst->getParent()->insertDbgRecordBefore(
+          new DPLabel(Label, DebugLoc(DIL)), Inst->getIterator());
+      continue; // This isn't an instruction.
+    }
+    case bitc::FUNC_CODE_DEBUG_RECORD_VALUE_SIMPLE:
+    case bitc::FUNC_CODE_DEBUG_RECORD_VALUE:
+    case bitc::FUNC_CODE_DEBUG_RECORD_DECLARE:
+    case bitc::FUNC_CODE_DEBUG_RECORD_ASSIGN: {
+      // DPValues are placed after the Instructions that they are attached to.
+      Instruction *Inst = getLastInstruction();
+      if (!Inst)
+        return error("Invalid dbg record: missing instruction");
+
+      // First 3 fields are common to all kinds:
+      //   DILocation, DILocalVariable, DIExpression
+      // dbg_value (FUNC_CODE_DEBUG_RECORD_VALUE)
+      //   ..., LocationMetadata
+      // dbg_value (FUNC_CODE_DEBUG_RECORD_VALUE_SIMPLE - abbrev'd)
+      //   ..., Value
+      // dbg_declare (FUNC_CODE_DEBUG_RECORD_DECLARE)
+      //   ..., LocationMetadata
+      // dbg_assign (FUNC_CODE_DEBUG_RECORD_ASSIGN)
+      //   ..., LocationMetadata, DIAssignID, DIExpression, LocationMetadata
+      unsigned Slot = 0;
+      // Common fields (0-2).
+      DILocation *DIL = cast<DILocation>(getFnMetadataByID(Record[Slot++]));
+      DILocalVariable *Var =
+          cast<DILocalVariable>(getFnMetadataByID(Record[Slot++]));
+      DIExpression *Expr =
+          cast<DIExpression>(getFnMetadataByID(Record[Slot++]));
+
+      // Union field (3: LocationMetadata | Value).
+      Metadata *RawLocation = nullptr;
+      if (BitCode == bitc::FUNC_CODE_DEBUG_RECORD_VALUE_SIMPLE) {
+        Value *V = nullptr;
+        unsigned TyID = 0;
+        // We never expect to see a fwd reference value here because
+        // use-before-defs are encoded with the standard non-abbrev record
+        // type (they'd require encoding the type too, and they're rare). As a
+        // result, getValueTypePair only ever increments Slot by one here (once
+        // for the value, never twice for value and type).
+        unsigned SlotBefore = Slot;
+        if (getValueTypePair(Record, Slot, NextValueNo, V, TyID, CurBB))
+          return error("Invalid dbg record: invalid value");
+        (void)SlotBefore;
+        assert((SlotBefore == Slot - 1) && "unexpected fwd ref");
+        RawLocation = ValueAsMetadata::get(V);
+      } else {
+        RawLocation = getFnMetadataByID(Record[Slot++]);
+      }
+
+      DPValue *DPV = nullptr;
+      switch (BitCode) {
+      case bitc::FUNC_CODE_DEBUG_RECORD_VALUE:
+      case bitc::FUNC_CODE_DEBUG_RECORD_VALUE_SIMPLE:
+        DPV = new DPValue(RawLocation, Var, Expr, DIL,
+                          DPValue::LocationType::Value);
+        break;
+      case bitc::FUNC_CODE_DEBUG_RECORD_DECLARE:
+        DPV = new DPValue(RawLocation, Var, Expr, DIL,
+                          DPValue::LocationType::Declare);
+        break;
+      case bitc::FUNC_CODE_DEBUG_RECORD_ASSIGN: {
+        DIAssignID *ID = cast<DIAssignID>(getFnMetadataByID(Record[Slot++]));
+        DIExpression *AddrExpr =
+            cast<DIExpression>(getFnMetadataByID(Record[Slot++]));
+        Metadata *Addr = getFnMetadataByID(Record[Slot++]);
+        DPV = new DPValue(RawLocation, Var, Expr, ID, Addr, AddrExpr, DIL);
+        break;
+      }
+      default:
+        llvm_unreachable("Unknown DPValue bitcode");
+      }
+      Inst->getParent()->insertDbgRecordBefore(DPV, Inst->getIterator());
+      continue; // This isn't an instruction.
+    }
     case bitc::FUNC_CODE_INST_CALL: {
       // CALL: [paramattrs, cc, fmf, fnty, fnid, arg0, arg1...]
       if (Record.size() < 3)
@@ -6677,10 +6761,21 @@ Error BitcodeReader::materialize(GlobalValue *GV) {
   // Move the bit stream to the saved position of the deferred function body.
   if (Error JumpFailed = Stream.JumpToBit(DFII->second))
     return JumpFailed;
+
+  // Set the debug info mode to "new", forcing a mismatch between
+  // module and function debug modes. This is okay because we'll convert
+  // everything back to the old mode after parsing.
+  // FIXME: Remove this once all tools support RemoveDIs.
+  F->IsNewDbgInfoFormat = true;
+
   if (Error Err = parseFunctionBody(F))
     return Err;
   F->setIsMaterializable(false);
 
+  // Convert new debug info records into intrinsics.
+  // FIXME: Remove this once all tools support RemoveDIs.
+  F->convertFromNewDbgValues();
+
   if (StripDebugInfo)
     stripDebugInfo(*F);
 
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
index 597f493..6f0879a 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -99,6 +99,9 @@ namespace llvm {
 extern FunctionSummary::ForceSummaryHotnessType ForceSummaryEdgesCold;
 }
 
+extern bool WriteNewDbgInfoFormatToBitcode;
+extern llvm::cl::opt<bool> UseNewDbgInfoFormat;
+
 namespace {
 
 /// These are manifest constants used by the bitcode writer. They do not need to
@@ -128,6 +131,7 @@ enum {
   FUNCTION_INST_RET_VAL_ABBREV,
   FUNCTION_INST_UNREACHABLE_ABBREV,
   FUNCTION_INST_GEP_ABBREV,
+  FUNCTION_DEBUG_RECORD_VALUE_ABBREV,
 };
 
 /// Abstract class to manage the bitcode writing, subclassed for each bitcode
@@ -3512,25 +3516,95 @@ void ModuleBitcodeWriter::writeFunction(
       NeedsMetadataAttachment |= I.hasMetadataOtherThanDebugLoc();
 
       // If the instruction has a debug location, emit it.
-      DILocation *DL = I.getDebugLoc();
-      if (!DL)
-        continue;
-
-      if (DL == LastDL) {
-        // Just repeat the same debug loc as last time.
-        Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC_AGAIN, Vals);
-        continue;
+      if (DILocation *DL = I.getDebugLoc()) {
+        if (DL == LastDL) {
+          // Just repeat the same debug loc as last time.
+          Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC_AGAIN, Vals);
+        } else {
+          Vals.push_back(DL->getLine());
+          Vals.push_back(DL->getColumn());
+          Vals.push_back(VE.getMetadataOrNullID(DL->getScope()));
+          Vals.push_back(VE.getMetadataOrNullID(DL->getInlinedAt()));
+          Vals.push_back(DL->isImplicitCode());
+          Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC, Vals);
+          Vals.clear();
+          LastDL = DL;
+        }
       }
 
-      Vals.push_back(DL->getLine());
-      Vals.push_back(DL->getColumn());
-      Vals.push_back(VE.getMetadataOrNullID(DL->getScope()));
-      Vals.push_back(VE.getMetadataOrNullID(DL->getInlinedAt()));
-      Vals.push_back(DL->isImplicitCode());
-      Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_LOC, Vals);
-      Vals.clear();
-
-      LastDL = DL;
+      // If the instruction has DbgRecords attached to it, emit them. Note that
+      // they come after the instruction so that it's easy to attach them again
+      // when reading the bitcode, even though conceptually the debug locations
+      // start "before" the instruction.
+      if (I.hasDbgRecords() && WriteNewDbgInfoFormatToBitcode) {
+        /// Try to push the value only (unwrapped), otherwise push the
+        /// metadata wrapped value. Returns true if the value was pushed
+        /// without the ValueAsMetadata wrapper.
+        auto PushValueOrMetadata = [&Vals, InstID,
+                                    this](Metadata *RawLocation) {
+          assert(RawLocation && "RawLocation unexpectedly null in DPValue");
+          if (ValueAsMetadata *VAM = dyn_cast<ValueAsMetadata>(RawLocation)) {
+            SmallVector<unsigned, 2> ValAndType;
+            // If the value is a fwd-ref the type is also pushed. We don't
+            // want the type, so fwd-refs are kept wrapped (pushValueAndType
+            // returns false if the value is pushed without type).
+            if (!pushValueAndType(VAM->getValue(), InstID, ValAndType)) {
+              Vals.push_back(ValAndType[0]);
+              return true;
+            }
+          }
+          // The metadata is a DIArgList, or ValueAsMetadata wrapping a
+          // fwd-ref. Push the metadata ID.
+          Vals.push_back(VE.getMetadataID(RawLocation));
+          return false;
+        };
+
+        // Write out non-instruction debug information attached to this
+        // instruction. Write it after the instruction so that it's easy to
+        // re-attach to the instruction reading the records in.
+        for (DbgRecord &DR : I.DbgMarker->getDbgRecordRange()) {
+          if (DPLabel *DPL = dyn_cast<DPLabel>(&DR)) {
+            Vals.push_back(VE.getMetadataID(&*DPL->getDebugLoc()));
+            Vals.push_back(VE.getMetadataID(DPL->getLabel()));
+            Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_RECORD_LABEL, Vals);
+            Vals.clear();
+            continue;
+          }
+
+          // First 3 fields are common to all kinds:
+          //   DILocation, DILocalVariable, DIExpression
+          // dbg_value (FUNC_CODE_DEBUG_RECORD_VALUE)
+          //   ..., LocationMetadata
+          // dbg_value (FUNC_CODE_DEBUG_RECORD_VALUE_SIMPLE - abbrev'd)
+          //   ..., Value
+          // dbg_declare (FUNC_CODE_DEBUG_RECORD_DECLARE)
+          //   ..., LocationMetadata
+          // dbg_assign (FUNC_CODE_DEBUG_RECORD_ASSIGN)
+          //   ..., LocationMetadata, DIAssignID, DIExpression, LocationMetadata
+          DPValue &DPV = cast<DPValue>(DR);
+          Vals.push_back(VE.getMetadataID(&*DPV.getDebugLoc()));
+          Vals.push_back(VE.getMetadataID(DPV.getVariable()));
+          Vals.push_back(VE.getMetadataID(DPV.getExpression()));
+          if (DPV.isDbgValue()) {
+            if (PushValueOrMetadata(DPV.getRawLocation()))
+              Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_RECORD_VALUE_SIMPLE, Vals,
+                                FUNCTION_DEBUG_RECORD_VALUE_ABBREV);
+            else
+              Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_RECORD_VALUE, Vals);
+          } else if (DPV.isDbgDeclare()) {
+            Vals.push_back(VE.getMetadataID(DPV.getRawLocation()));
+            Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_RECORD_DECLARE, Vals);
+          } else {
+            assert(DPV.isDbgAssign() && "Unexpected DbgRecord kind");
+            Vals.push_back(VE.getMetadataID(DPV.getRawLocation()));
+            Vals.push_back(VE.getMetadataID(DPV.getAssignID()));
+            Vals.push_back(VE.getMetadataID(DPV.getAddressExpression()));
+            Vals.push_back(VE.getMetadataID(DPV.getRawAddress()));
+            Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_RECORD_ASSIGN, Vals);
+          }
+          Vals.clear();
+        }
+      }
     }
 
     if (BlockAddress *BA = BlockAddress::lookup(&BB)) {
@@ -3771,7 +3845,17 @@ void ModuleBitcodeWriter::writeBlockInfo() {
         FUNCTION_INST_GEP_ABBREV)
       llvm_unreachable("Unexpected abbrev ordering!");
   }
-
+  {
+    auto Abbv = std::make_shared<BitCodeAbbrev>();
+    Abbv->Add(BitCodeAbbrevOp(bitc::FUNC_CODE_DEBUG_RECORD_VALUE_SIMPLE));
+    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 7)); // dbgloc
+    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 7)); // var
+    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 7)); // expr
+    Abbv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::VBR, 6)); // val
+    if (Stream.EmitBlockInfoAbbrev(bitc::FUNCTION_BLOCK_ID, Abbv) !=
+        FUNCTION_DEBUG_RECORD_VALUE_ABBREV)
+      llvm_unreachable("Unexpected abbrev ordering! 1");
+  }
   Stream.ExitBlock();
 }
 
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriterPass.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriterPass.cpp
index 0eb9c24..de2396f 100644
--- a/llvm/lib/Bitcode/Writer/BitcodeWriterPass.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriterPass.cpp
@@ -18,11 +18,12 @@
 #include "llvm/Pass.h"
 using namespace llvm;
 
+extern bool WriteNewDbgInfoFormatToBitcode;
+
 PreservedAnalyses BitcodeWriterPass::run(Module &M, ModuleAnalysisManager &AM) {
-  // RemoveDIs: there's no bitcode representation of the DbgRecord debug-info,
-  // convert to dbg.values before writing out.
-  bool IsNewDbgInfoFormat = M.IsNewDbgInfoFormat;
-  if (IsNewDbgInfoFormat)
+  bool ConvertToOldDbgFormatForWrite =
+      M.IsNewDbgInfoFormat && !WriteNewDbgInfoFormatToBitcode;
+  if (ConvertToOldDbgFormatForWrite)
     M.convertFromNewDbgValues();
 
   const ModuleSummaryIndex *Index =
@@ -30,7 +31,7 @@ PreservedAnalyses BitcodeWriterPass::run(Module &M, ModuleAnalysisManager &AM) {
                        : nullptr;
   WriteBitcodeToFile(M, OS, ShouldPreserveUseListOrder, Index, EmitModuleHash);
 
-  if (IsNewDbgInfoFormat)
+  if (ConvertToOldDbgFormatForWrite)
     M.convertToNewDbgValues();
 
   return PreservedAnalyses::all();
@@ -56,16 +57,15 @@ namespace {
     StringRef getPassName() const override { return "Bitcode Writer"; }
 
     bool runOnModule(Module &M) override {
-      // RemoveDIs: there's no bitcode representation of the DbgRecord
-      // debug-info, convert to dbg.values before writing out.
-      bool IsNewDbgInfoFormat = M.IsNewDbgInfoFormat;
-      if (IsNewDbgInfoFormat)
+      bool ConvertToOldDbgFormatForWrite =
+          M.IsNewDbgInfoFormat && !WriteNewDbgInfoFormatToBitcode;
+      if (ConvertToOldDbgFormatForWrite)
         M.convertFromNewDbgValues();
 
       WriteBitcodeToFile(M, OS, ShouldPreserveUseListOrder, /*Index=*/nullptr,
                          /*EmitModuleHash=*/false);
 
-      if (IsNewDbgInfoFormat)
+      if (ConvertToOldDbgFormatForWrite)
         M.convertToNewDbgValues();
       return false;
     }
diff --git a/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp b/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp
index fccb2a6..1c439c9 100644
--- a/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp
+++ b/llvm/lib/Bitcode/Writer/ValueEnumerator.cpp
@@ -134,20 +134,28 @@ static OrderMap orderModule(const Module &M) {
     // Metadata used by instructions is decoded before the actual instructions,
     // so visit any constants used by it beforehand.
     for (const BasicBlock &BB : F)
-      for (const Instruction &I : BB)
-        for (const Value *V : I.operands()) {
-          if (const auto *MAV = dyn_cast<MetadataAsValue>(V)) {
-            if (const auto *VAM =
-                    dyn_cast<ValueAsMetadata>(MAV->getMetadata())) {
+      for (const Instruction &I : BB) {
+        auto OrderConstantFromMetadata = [&](Metadata *MD) {
+          if (const auto *VAM = dyn_cast<ValueAsMetadata>(MD)) {
+            orderConstantValue(VAM->getValue());
+          } else if (const auto *AL = dyn_cast<DIArgList>(MD)) {
+            for (const auto *VAM : AL->getArgs())
               orderConstantValue(VAM->getValue());
-            } else if (const auto *AL =
-                           dyn_cast<DIArgList>(MAV->getMetadata())) {
-              for (const auto *VAM : AL->getArgs())
-                orderConstantValue(VAM->getValue());
-            }
           }
+        };
+
+        for (DPValue &DPV : filterDbgVars(I.getDbgRecordRange())) {
+          OrderConstantFromMetadata(DPV.getRawLocation());
+          if (DPV.isDbgAssign())
+            OrderConstantFromMetadata(DPV.getRawAddress());
         }
 
+        for (const Value *V : I.operands()) {
+          if (const auto *MAV = dyn_cast<MetadataAsValue>(V))
+            OrderConstantFromMetadata(MAV->getMetadata());
+        }
+      }
+
     for (const Argument &A : F.args())
       orderValue(&A, OM);
     for (const BasicBlock &BB : F)
@@ -261,33 +269,39 @@ static UseListOrderStack predictUseListOrder(const Module &M) {
   // constants in the last Function they're used in.  Module-level constants
   // have already been visited above.
   for (const Function &F : llvm::reverse(M)) {
+    auto PredictValueOrderFromMetadata = [&](Metadata *MD) {
+      if (const auto *VAM = dyn_cast<ValueAsMetadata>(MD)) {
+        predictValueUseListOrder(VAM->getValue(), &F, OM, Stack);
+      } else if (const auto *AL = dyn_cast<DIArgList>(MD)) {
+        for (const auto *VAM : AL->getArgs())
+          predictValueUseListOrder(VAM->getValue(), &F, OM, Stack);
+      }
+    };
     if (F.isDeclaration())
       continue;
     for (const BasicBlock &BB : F)
       predictValueUseListOrder(&BB, &F, OM, Stack);
     for (const Argument &A : F.args())
       predictValueUseListOrder(&A, &F, OM, Stack);
-    for (const BasicBlock &BB : F)
+    for (const BasicBlock &BB : F) {
       for (const Instruction &I : BB) {
+        for (DPValue &DPV : filterDbgVars(I.getDbgRecordRange())) {
+          PredictValueOrderFromMetadata(DPV.getRawLocation());
+          if (DPV.isDbgAssign())
+            PredictValueOrderFromMetadata(DPV.getRawAddress());
+        }
         for (const Value *Op : I.operands()) {
           if (isa<Constant>(*Op) || isa<InlineAsm>(*Op)) // Visit GlobalValues.
             predictValueUseListOrder(Op, &F, OM, Stack);
-          if (const auto *MAV = dyn_cast<MetadataAsValue>(Op)) {
-            if (const auto *VAM =
-                    dyn_cast<ValueAsMetadata>(MAV->getMetadata())) {
-              predictValueUseListOrder(VAM->getValue(), &F, OM, Stack);
-            } else if (const auto *AL =
-                           dyn_cast<DIArgList>(MAV->getMetadata())) {
-              for (const auto *VAM : AL->getArgs())
-                predictValueUseListOrder(VAM->getValue(), &F, OM, Stack);
-            }
-          }
+          if (const auto *MAV = dyn_cast<MetadataAsValue>(Op))
+            PredictValueOrderFromMetadata(MAV->getMetadata());
         }
         if (auto *SVI = dyn_cast<ShuffleVectorInst>(&I))
           predictValueUseListOrder(SVI->getShuffleMaskForBitcode(), &F, OM,
                                    Stack);
         predictValueUseListOrder(&I, &F, OM, Stack);
       }
+    }
   }
 
   // Visit globals last, since the module-level use-list block will be seen
@@ -409,6 +423,41 @@ ValueEnumerator::ValueEnumerator(const Module &M,
 
     for (const BasicBlock &BB : F)
       for (const Instruction &I : BB) {
+        // Local metadata is enumerated during function-incorporation, but
+        // any ConstantAsMetadata arguments in a DIArgList should be examined
+        // now.
+        auto EnumerateNonLocalValuesFromMetadata = [&](Metadata *MD) {
+          assert(MD && "Metadata unexpectedly null");
+          if (const auto *AL = dyn_cast<DIArgList>(MD)) {
+            for (const auto *VAM : AL->getArgs()) {
+              if (isa<ConstantAsMetadata>(VAM))
+                EnumerateMetadata(&F, VAM);
+            }
+            return;
+          }
+
+          if (!isa<LocalAsMetadata>(MD))
+            EnumerateMetadata(&F, MD);
+        };
+
+        for (DbgRecord &DR : I.getDbgRecordRange()) {
+          if (DPLabel *DPL = dyn_cast<DPLabel>(&DR)) {
+            EnumerateMetadata(&F, DPL->getLabel());
+            EnumerateMetadata(&F, &*DPL->getDebugLoc());
+            continue;
+          }
+          // Enumerate non-local location metadata.
+          DPValue &DPV = cast<DPValue>(DR);
+          EnumerateNonLocalValuesFromMetadata(DPV.getRawLocation());
+          EnumerateMetadata(&F, DPV.getExpression());
+          EnumerateMetadata(&F, DPV.getVariable());
+          EnumerateMetadata(&F, &*DPV.getDebugLoc());
+          if (DPV.isDbgAssign()) {
+            EnumerateNonLocalValuesFromMetadata(DPV.getRawAddress());
+            EnumerateMetadata(&F, DPV.getAssignID());
+            EnumerateMetadata(&F, DPV.getAddressExpression());
+          }
+        }
         for (const Use &Op : I.operands()) {
           auto *MD = dyn_cast<MetadataAsValue>(&Op);
           if (!MD) {
@@ -416,19 +465,7 @@ ValueEnumerator::ValueEnumerator(const Module &M,
             continue;
           }
 
-          // Local metadata is enumerated during function-incorporation, but
-          // any ConstantAsMetadata arguments in a DIArgList should be examined
-          // now.
-          if (isa<LocalAsMetadata>(MD->getMetadata()))
-            continue;
-          if (auto *AL = dyn_cast<DIArgList>(MD->getMetadata())) {
-            for (auto *VAM : AL->getArgs())
-              if (isa<ConstantAsMetadata>(VAM))
-                EnumerateMetadata(&F, VAM);
-            continue;
-          }
-
-          EnumerateMetadata(&F, MD->getMetadata());
+          EnumerateNonLocalValuesFromMetadata(MD->getMetadata());
         }
         if (auto *SVI = dyn_cast<ShuffleVectorInst>(&I))
           EnumerateType(SVI->getShuffleMaskForBitcode()->getType());
@@ -1064,27 +1101,41 @@ void ValueEnumerator::incorporateFunction(const Function &F) {
 
   SmallVector<LocalAsMetadata *, 8> FnLocalMDVector;
   SmallVector<DIArgList *, 8> ArgListMDVector;
+
+  auto AddFnLocalMetadata = [&](Metadata *MD) {
+    if (!MD)
+      return;
+    if (auto *Local = dyn_cast<LocalAsMetadata>(MD)) {
+      // Enumerate metadata after the instructions they might refer to.
+      FnLocalMDVector.push_back(Local);
+    } else if (auto *ArgList = dyn_cast<DIArgList>(MD)) {
+      ArgListMDVector.push_back(ArgList);
+      for (ValueAsMetadata *VMD : ArgList->getArgs()) {
+        if (auto *Local = dyn_cast<LocalAsMetadata>(VMD)) {
+          // Enumerate metadata after the instructions they might refer
+          // to.
+          FnLocalMDVector.push_back(Local);
+        }
+      }
+    }
+  };
+
   // Add all of the instructions.
   for (const BasicBlock &BB : F) {
     for (const Instruction &I : BB) {
       for (const Use &OI : I.operands()) {
-        if (auto *MD = dyn_cast<MetadataAsValue>(&OI)) {
-          if (auto *Local = dyn_cast<LocalAsMetadata>(MD->getMetadata())) {
-            // Enumerate metadata after the instructions they might refer to.
-            FnLocalMDVector.push_back(Local);
-          } else if (auto *ArgList = dyn_cast<DIArgList>(MD->getMetadata())) {
-            ArgListMDVector.push_back(ArgList);
-            for (ValueAsMetadata *VMD : ArgList->getArgs()) {
-              if (auto *Local = dyn_cast<LocalAsMetadata>(VMD)) {
-                // Enumerate metadata after the instructions they might refer
-                // to.
-                FnLocalMDVector.push_back(Local);
-              }
-            }
-          }
+        if (auto *MD = dyn_cast<MetadataAsValue>(&OI))
+          AddFnLocalMetadata(MD->getMetadata());
+      }
+      /// RemoveDIs: Add non-instruction function-local metadata uses.
+      for (DPValue &DPV : filterDbgVars(I.getDbgRecordRange())) {
+        assert(DPV.getRawLocation() && "DPValue location unexpectedly null");
+        AddFnLocalMetadata(DPV.getRawLocation());
+        if (DPV.isDbgAssign()) {
+          assert(DPV.getRawAddress() && "DPValue location unexpectedly null");
+          AddFnLocalMetadata(DPV.getRawAddress());
         }
       }
-
       if (!I.getType()->isVoidTy())
         EnumerateValue(&I);
     }
diff --git a/llvm/lib/IR/BasicBlock.cpp b/llvm/lib/IR/BasicBlock.cpp
index 4dd1bdd..5f07808 100644
--- a/llvm/lib/IR/BasicBlock.cpp
+++ b/llvm/lib/IR/BasicBlock.cpp
@@ -36,6 +36,11 @@ cl::opt<bool>
                                  "through iterators, eliminating intrinsics"),
                         cl::init(true));
 
+bool WriteNewDbgInfoFormatToBitcode /*set default value in cl::init() below*/;
+cl::opt<bool, true> WriteNewDbgInfoFormatToBitcode2(
+    "write-experimental-debuginfo-iterators-to-bitcode", cl::Hidden,
+    cl::location(WriteNewDbgInfoFormatToBitcode), cl::init(false));
+
 DPMarker *BasicBlock::createMarker(Instruction *I) {
   assert(IsNewDbgInfoFormat &&
          "Tried to create a marker in a non new debug-info block!");
diff --git a/llvm/lib/Linker/IRMover.cpp b/llvm/lib/Linker/IRMover.cpp
index 37d2111..a7e6db8 100644
--- a/llvm/lib/Linker/IRMover.cpp
+++ b/llvm/lib/Linker/IRMover.cpp
@@ -8,6 +8,7 @@
 
 #include "llvm/Linker/IRMover.h"
 #include "LinkDiagnosticInfo.h"
+#include "llvm/ADT/ScopeExit.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallString.h"
@@ -1546,7 +1547,23 @@ Error IRLinker::run() {
     if (Error Err = SrcM->getMaterializer()->materializeMetadata())
       return Err;
 
-  DstM.IsNewDbgInfoFormat = SrcM->IsNewDbgInfoFormat;
+  // Convert source module to match dest for the duration of the link.
+  bool SrcModuleNewDbgFormat = SrcM->IsNewDbgInfoFormat;
+  if (DstM.IsNewDbgInfoFormat != SrcM->IsNewDbgInfoFormat) {
+    if (DstM.IsNewDbgInfoFormat)
+      SrcM->convertToNewDbgValues();
+    else
+      SrcM->convertFromNewDbgValues();
+  }
+  // Undo debug mode conversion afterwards.
+  auto Cleanup = make_scope_exit([&]() {
+    if (SrcModuleNewDbgFormat != SrcM->IsNewDbgInfoFormat) {
+      if (SrcModuleNewDbgFormat)
+        SrcM->convertToNewDbgValues();
+      else
+        SrcM->convertFromNewDbgValues();
+    }
+  });
 
   // Inherit the target data from the source module if the destination module
   // doesn't have one already.
@@ -1775,8 +1792,6 @@ IRMover::IRMover(Module &M) : Composite(M) {
 Error IRMover::move(std::unique_ptr<Module> Src,
                     ArrayRef<GlobalValue *> ValuesToLink,
                     LazyCallback AddLazyFor, bool IsPerformingImport) {
-  if (getModule().IsNewDbgInfoFormat)
-    Src->convertToNewDbgValues();
   IRLinker TheIRLinker(Composite, SharedMDs, IdentifiedStructTypes,
                        std::move(Src), ValuesToLink, std::move(AddLazyFor),
                        IsPerformingImport);
diff --git a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
index dd6062d..6b9a1f6 100644
--- a/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
+++ b/llvm/lib/Transforms/IPO/ThinLTOBitcodeWriter.cpp
@@ -575,7 +575,7 @@ bool writeThinLTOBitcode(raw_ostream &OS, raw_ostream *ThinLinkOS,
 }
 
 } // anonymous namespace
-
+extern bool WriteNewDbgInfoFormatToBitcode;
 PreservedAnalyses
 llvm::ThinLTOBitcodeWriterPass::run(Module &M, ModuleAnalysisManager &AM) {
   FunctionAnalysisManager &FAM =
@@ -583,8 +583,9 @@ llvm::ThinLTOBitcodeWriterPass::run(Module &M, ModuleAnalysisManager &AM) {
 
   // RemoveDIs: there's no bitcode representation of the DPValue debug-info,
   // convert to dbg.values before writing out.
-  bool IsNewDbgInfoFormat = M.IsNewDbgInfoFormat;
-  if (IsNewDbgInfoFormat)
+  bool ConvertToOldDbgFormatForWrite =
+      M.IsNewDbgInfoFormat && !WriteNewDbgInfoFormatToBitcode;
+  if (ConvertToOldDbgFormatForWrite)
     M.convertFromNewDbgValues();
 
   bool Changed = writeThinLTOBitcode(
@@ -594,7 +595,7 @@ llvm::ThinLTOBitcodeWriterPass::run(Module &M, ModuleAnalysisManager &AM) {
       },
       M, &AM.getResult<ModuleSummaryIndexAnalysis>(M));
 
-  if (IsNewDbgInfoFormat)
+  if (ConvertToOldDbgFormatForWrite)
     M.convertToNewDbgValues();
 
   return Changed ? PreservedAnalyses::none() : PreservedAnalyses::all();
diff --git a/llvm/test/Bitcode/dbg-record-roundtrip.ll b/llvm/test/Bitcode/dbg-record-roundtrip.ll
new file mode 100644
index 0000000..be6f65c
--- /dev/null
+++ b/llvm/test/Bitcode/dbg-record-roundtrip.ll
@@ -0,0 +1,128 @@
+;; Roundtrip tests.
+; RUN: llvm-as --write-experimental-debuginfo-iterators-to-bitcode=true %s -o - | llvm-dis | FileCheck %s
+;; Check that verify-uselistorder passes regardless of input format.
+; RUN: llvm-as %s -o - --write-experimental-debuginfo-iterators-to-bitcode=true | verify-uselistorder
+; RUN: verify-uselistorder %s
+
+;; Confirm we're producing RemoveDI records from various tools.
+; RUN: opt %s -o - --write-experimental-debuginfo-iterators-to-bitcode=true | llvm-bcanalyzer - | FileCheck %s --check-prefix=BITCODE
+; RUN: llvm-as %s -o - --write-experimental-debuginfo-iterators-to-bitcode=true | llvm-bcanalyzer - | FileCheck %s --check-prefix=BITCODE
+; BITCODE-DAG: DEBUG_RECORD_LABEL
+; BITCODE-DAG: DEBUG_RECORD_VALUE
+; BITCODE-DAG: DEBUG_RECORD_ASSIGN
+; BITCODE-DAG: DEBUG_RECORD_DECLARE
+
+;; Check that llvm-link doesn't explode if we give it different formats to
+;; link.
+; RUN: llvm-as %s --experimental-debuginfo-iterators=true --write-experimental-debuginfo-iterators-to-bitcode=true -o - | llvm-link %s --experimental-debuginfo-iterators=false
+; RUN: llvm-as %s --experimental-debuginfo-iterators=false -o - | llvm-link %s --experimental-debuginfo-iterators=true
+
+;; Checks inline.
+
+@g = internal dso_local global i32 0, align 4, !dbg !0
+
+define internal dso_local noundef i32 @_Z3funv(i32 %p, ptr %storage) !dbg !13 {
+entry:
+;; Dbg record at top of block, check dbg.value configurations.
+; CHECK: entry:
+; CHECK-NEXT: dbg.value(metadata i32 %p, metadata ![[e:[0-9]+]], metadata !DIExpression()), !dbg ![[dbg:[0-9]+]]
+; CHECK-NEXT: dbg.value(metadata ![[empty:[0-9]+]], metadata ![[e]], metadata !DIExpression()), !dbg ![[dbg]]
+; CHECK-NEXT: dbg.value(metadata i32 poison, metadata ![[e]], metadata !DIExpression()), !dbg ![[dbg]]
+; CHECK-NEXT: dbg.value(metadata i32 1, metadata ![[f:[0-9]+]], metadata !DIExpression()), !dbg ![[dbg]]
+  tail call void @llvm.dbg.value(metadata i32 %p, metadata !32, metadata !DIExpression()), !dbg !19
+  tail call void @llvm.dbg.value(metadata !29, metadata !32, metadata !DIExpression()), !dbg !19
+  tail call void @llvm.dbg.value(metadata i32 poison, metadata !32, metadata !DIExpression()), !dbg !19
+  tail call void @llvm.dbg.value(metadata i32 1, metadata !33, metadata !DIExpression()), !dbg !19
+;; Arglist with an argument, constant, local use before def, poison.
+; CHECK-NEXT: dbg.value(metadata !DIArgList(i32 %p, i32 0, i32 %0, i32 poison), metadata ![[f]], metadata !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_plus, DW_OP_LLVM_arg, 2, DW_OP_LLVM_arg, 3, DW_OP_plus, DW_OP_minus)), !dbg ![[dbg]]
+  tail call void @llvm.dbg.value(metadata !DIArgList(i32 %p, i32 0, i32 %0, i32 poison), metadata !33, metadata !DIExpression(DW_OP_LLVM_arg, 0, DW_OP_LLVM_arg, 1, DW_OP_plus, DW_OP_LLVM_arg, 2, DW_OP_LLVM_arg, 3, DW_OP_plus, DW_OP_minus)), !dbg !19
+;; Check dbg.assign use before def (value, addr and ID). Check expression order too.
+; CHECK: dbg.assign(metadata i32 %0, metadata ![[i:[0-9]+]], metadata !DIExpression(DW_OP_plus_uconst, 0),
+; CHECK-SAME:       metadata ![[ID:[0-9]+]], metadata ptr %a, metadata !DIExpression(DW_OP_plus_uconst, 1)), !dbg ![[dbg]]
+  tail call void @llvm.dbg.assign(metadata i32 %0, metadata !36, metadata !DIExpression(DW_OP_plus_uconst, 0), metadata !37, metadata ptr %a, metadata !DIExpression(DW_OP_plus_uconst, 1)), !dbg !19
+  %a = alloca i32, align 4, !DIAssignID !37
+; CHECK: %a = alloca i32, align 4, !DIAssignID ![[ID]]
+;; Check dbg.declare configurations.
+; CHECK-NEXT: dbg.declare(metadata ptr %a, metadata ![[a:[0-9]+]], metadata !DIExpression()), !dbg ![[dbg]]
+; CHECK-NEXT: dbg.declare(metadata ![[empty:[0-9]+]], metadata ![[b:[0-9]+]], metadata !DIExpression()), !dbg ![[dbg]]
+; CHECK-NEXT: dbg.declare(metadata ptr poison, metadata ![[c:[0-9]+]], metadata !DIExpression()), !dbg ![[dbg]]
+; CHECK-NEXT: dbg.declare(metadata ptr null, metadata ![[d:[0-9]+]], metadata !DIExpression()), !dbg ![[dbg]]
+; CHECK-NEXT: dbg.declare(metadata ptr @g, metadata ![[h:[0-9]+]], metadata !DIExpression()), !dbg ![[dbg]]
+  tail call void @llvm.dbg.declare(metadata ptr %a, metadata !17, metadata !DIExpression()), !dbg !19
+  tail call void @llvm.dbg.declare(metadata !29, metadata !28, metadata !DIExpression()), !dbg !19
+  tail call void @llvm.dbg.declare(metadata ptr poison, metadata !30, metadata !DIExpression()), !dbg !19
+  tail call void @llvm.dbg.declare(metadata ptr null, metadata !31, metadata !DIExpression()), !dbg !19
+  tail call void @llvm.dbg.declare(metadata ptr @g, metadata !35, metadata !DIExpression()), !dbg !19
+;; Argument value dbg.declare.
+; CHECK: dbg.declare(metadata ptr %storage, metadata ![[g:[0-9]+]], metadata !DIExpression()), !dbg ![[dbg]]
+  tail call void @llvm.dbg.declare(metadata ptr %storage, metadata !34, metadata !DIExpression()), !dbg !19
+;; Use before def dbg.value.
+; CHECK: dbg.value(metadata i32 %0, metadata ![[e]], metadata !DIExpression()), !dbg ![[dbg]]
+  tail call void @llvm.dbg.value(metadata i32 %0, metadata !32, metadata !DIExpression()), !dbg !19
+  %0 = load i32, ptr @g, align 4, !dbg !20
+;; Non-argument local value dbg.value.
+; CHECK: dbg.value(metadata i32 %0, metadata ![[e]], metadata !DIExpression()), !dbg ![[dbg]]
+  tail call void @llvm.dbg.value(metadata i32 %0, metadata !32, metadata !DIExpression()), !dbg !19
+  store i32 %0, ptr %a, align 4, !dbg !19
+  %1 = load i32, ptr %a, align 4, !dbg !25
+; CHECK: dbg.label(metadata ![[label:[0-9]+]]), !dbg ![[dbg]]
+  tail call void @llvm.dbg.label(metadata !38), !dbg !19
+  ret i32 %1, !dbg !27
+}
+
+; CHECK-DAG: ![[a]] = !DILocalVariable(name: "a",
+; CHECK-DAG: ![[b]] = !DILocalVariable(name: "b",
+; CHECK-DAG: ![[c]] = !DILocalVariable(name: "c",
+; CHECK-DAG: ![[d]] = !DILocalVariable(name: "d",
+; CHECK-DAG: ![[e]] = !DILocalVariable(name: "e",
+; CHECK-DAG: ![[f]] = !DILocalVariable(name: "f",
+; CHECK-DAG: ![[g]] = !DILocalVariable(name: "g",
+; CHECK-DAG: ![[h]] = !DILocalVariable(name: "h",
+; CHECK-DAG: ![[i]] = !DILocalVariable(name: "i",
+; CHECK-DAG: ![[empty]] = !{}
+; CHECK-DAG: ![[label]] = !DILabel
+
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+declare void @llvm.dbg.value(metadata, metadata, metadata)
+declare void @llvm.dbg.assign(metadata, metadata, metadata, metadata, metadata, metadata)
+declare void @llvm.dbg.label(metadata)
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!6, !7, !8, !9, !10, !11}
+!llvm.ident = !{!12}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "g", scope: !2, file: !3, line: 1, type: !5, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !3, producer: "clang version 19.0.0", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, globals: !4, splitDebugInlining: false, nameTableKind: None)
+!3 = !DIFile(filename: "test.cpp", directory: "/")
+!4 = !{!0}
+!5 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!6 = !{i32 7, !"Dwarf Version", i32 5}
+!7 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = !{i32 1, !"wchar_size", i32 4}
+!9 = !{i32 8, !"PIC Level", i32 2}
+!10 = !{i32 7, !"PIE Level", i32 2}
+!11 = !{i32 7, !"uwtable", i32 2}
+!12 = !{!"clang version 19.0.0"}
+!13 = distinct !DISubprogram(name: "fun", linkageName: "_Z3funv", scope: !3, file: !3, line: 2, type: !14, scopeLine: 2, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !16)
+!14 = !DISubroutineType(types: !15)
+!15 = !{!5}
+!16 = !{!17}
+!17 = !DILocalVariable(name: "a", scope: !13, file: !3, line: 3, type: !5)
+!18 = !DILocation(line: 3, column: 3, scope: !13)
+!19 = !DILocation(line: 3, column: 7, scope: !13)
+!20 = !DILocation(line: 3, column: 11, scope: !13)
+!25 = !DILocation(line: 4, column: 12, scope: !13)
+!26 = !DILocation(line: 5, column: 1, scope: !13)
+!27 = !DILocation(line: 4, column: 5, scope: !13)
+!28 = !DILocalVariable(name: "b", scope: !13, file: !3, line: 3, type: !5)
+!29 = !{}
+!30 = !DILocalVariable(name: "c", scope: !13, file: !3, line: 3, type: !5)
+!31 = !DILocalVariable(name: "d", scope: !13, file: !3, line: 3, type: !5)
+!32 = !DILocalVariable(name: "e", scope: !13, file: !3, line: 3, type: !5)
+!33 = !DILocalVariable(name: "f", scope: !13, file: !3, line: 3, type: !5)
+!34 = !DILocalVariable(name: "g", scope: !13, file: !3, line: 3, type: !5)
+!35 = !DILocalVariable(name: "h", scope: !13, file: !3, line: 3, type: !5)
+!36 = !DILocalVariable(name: "i", scope: !13, file: !3, line: 3, type: !5)
+!37 = distinct !DIAssignID()
+!38 = !DILabel(scope: !13, name: "label", file: !3, line: 1)
diff --git a/llvm/tools/llvm-as/llvm-as.cpp b/llvm/tools/llvm-as/llvm-as.cpp
index 1c869e1..fd85256 100644
--- a/llvm/tools/llvm-as/llvm-as.cpp
+++ b/llvm/tools/llvm-as/llvm-as.cpp
@@ -67,6 +67,7 @@ static cl::opt<std::string> ClDataLayout("data-layout",
                                          cl::desc("data layout string to use"),
                                          cl::value_desc("layout-string"),
                                          cl::init(""), cl::cat(AsCat));
+extern bool WriteNewDbgInfoFormatToBitcode;
 
 static void WriteOutputFile(const Module *M, const ModuleSummaryIndex *Index) {
   // Infer the output filename if needed.
@@ -139,6 +140,12 @@ int main(int argc, char **argv) {
     Err.print(argv[0], errs());
     return 1;
   }
+
+  // Convert to new debug format if requested.
+  assert(!M->IsNewDbgInfoFormat && "Unexpectedly in new debug mode");
+  if (UseNewDbgInfoFormat && WriteNewDbgInfoFormatToBitcode)
+    M->convertToNewDbgValues();
+
   std::unique_ptr<ModuleSummaryIndex> Index = std::move(ModuleAndIndex.Index);
 
   if (!DisableVerify) {
diff --git a/llvm/tools/verify-uselistorder/verify-uselistorder.cpp b/llvm/tools/verify-uselistorder/verify-uselistorder.cpp
index 9afe681..d929ae0 100644
--- a/llvm/tools/verify-uselistorder/verify-uselistorder.cpp
+++ b/llvm/tools/verify-uselistorder/verify-uselistorder.cpp
@@ -166,6 +166,11 @@ std::unique_ptr<Module> TempFile::readBitcode(LLVMContext &Context) const {
                           "verify-uselistorder: error: ");
     return nullptr;
   }
+
+  // verify-uselistoder currently only supports old-style debug info mode.
+  // FIXME: Update mapping code for RemoveDIs.
+  assert(!ModuleOr.get()->IsNewDbgInfoFormat &&
+         "Unexpectedly in new debug info mode");
   return std::move(ModuleOr.get());
 }
 
@@ -175,6 +180,9 @@ std::unique_ptr<Module> TempFile::readAssembly(LLVMContext &Context) const {
   std::unique_ptr<Module> M = parseAssemblyFile(Filename, Err, Context);
   if (!M.get())
     Err.print("verify-uselistorder", errs());
+  // verify-uselistoder currently only supports old-style debug info mode.
+  // FIXME: Update mapping code for RemoveDIs.
+  assert(!M->IsNewDbgInfoFormat && "Unexpectedly in new debug info mode");
   return M;
 }
 
@@ -541,6 +549,9 @@ int main(int argc, char **argv) {
 
   // Load the input module...
   std::unique_ptr<Module> M = parseIRFile(InputFilename, Err, Context);
+  // verify-uselistoder currently only supports old-style debug info mode.
+  // FIXME: Update mapping code for RemoveDIs.
+  assert(!M->IsNewDbgInfoFormat && "Unexpectedly in new debug info mode");
 
   if (!M.get()) {
     Err.print(argv[0], errs());