Add new llvm.dbg.declare_value intrinsic.

rastogishubham · rastogishubham · commit a1b7e1335cb9 · 2025-11-18T15:57:45.000-08:00
For swift async code, we need to use a debug intrinsic that behaves like
an llvm.dbg.declare but can take any location type rather than just a
pointer or integer.

To solve this, a new debug instrinsic called llvm.dbg.declare_value
has been created, which behaves exactly like an llvm.dbg.declare but
can take non pointer and integer location types.
diff --git a/llvm/docs/SourceLevelDebugging.rst b/llvm/docs/SourceLevelDebugging.rst
@@ -308,6 +308,27 @@ directly, not its address.  Note that the value operand of this intrinsic may
 be indirect (i.e, a pointer to the source variable), provided that interpreting
 the complex expression derives the direct value.
 
+
+``#dbg_declare_value``
+^^^^^^^^^^^^^^^^
+
+.. code-block:: llvm
+
+    #dbg_declare_value([Value|MDNode], DILocalVariable, DIExpression, DILocation)
+
+This record provides information about a local element (e.g., variable). The
+first argument is is the new value, and in the function entry block.  The 
+second argument is a :ref:`local variable <dilocalvariable>` containing a 
+description of the variable.  The third argument is a :ref:`complex expression
+<diexpression>`. The fourth argument is a :ref:`source location <dilocation>`.
+A ``#dbg_declare_value`` record describes describes the *value* of a source 
+variable directly, not its address. The difference between a ``#dbg_value``
+and a ``#dbg_declare_value`` is that, just like a ``#dbg_declare``, a frontend
+should generate exactly one ``#dbg_declare_value`` record. The idea is to have
+``#dbg_declare`` guarantees but be able to describe a value rather than the 
+address of a value.
+
+
 ``#dbg_assign``
 ^^^^^^^^^^^^^^^
 .. toctree::
diff --git a/llvm/include/llvm/Bitcode/LLVMBitCodes.h b/llvm/include/llvm/Bitcode/LLVMBitCodes.h
@@ -688,6 +688,8 @@ enum FunctionCodes {
   FUNC_CODE_DEBUG_RECORD_VALUE_SIMPLE =
       64, // [DILocation, DILocalVariable, DIExpression, Value]
   FUNC_CODE_DEBUG_RECORD_LABEL = 65, // [DILocation, DILabel]
+  FUNC_CODE_DEBUG_RECORD_DECLARE_VALUE =
+      66, // [DILocation, DILocalVariable, DIExpression, ValueAsMetadata]
 };
 
 enum UseListCodes {
diff --git a/llvm/include/llvm/IR/DIBuilder.h b/llvm/include/llvm/IR/DIBuilder.h
@@ -1156,6 +1156,18 @@ namespace llvm {
                                       DIExpression *Expr, const DILocation *DL,
                                       InsertPosition InsertPt);
 
+    /// Insert a new llvm.dbg.declare_value intrinsic call.
+    /// \param Storage      llvm::Value of the variable
+    /// \param VarInfo      Variable's debug info descriptor.
+    /// \param Expr         A complex location expression.
+    /// \param DL           Debug info location.
+    /// \param InsertPt     Location for the new intrinsic.
+    LLVM_ABI DbgInstPtr insertDeclareValue(llvm::Value *Storage,
+                                           DILocalVariable *VarInfo,
+                                           DIExpression *Expr,
+                                           const DILocation *DL,
+                                           InsertPosition InsertPt);
+
     /// Insert a new llvm.dbg.label intrinsic call.
     /// \param LabelInfo    Label's debug info descriptor.
     /// \param DL           Debug info location.
diff --git a/llvm/include/llvm/IR/DebugInfo.h b/llvm/include/llvm/IR/DebugInfo.h
@@ -44,6 +44,8 @@ class Module;
 LLVM_ABI TinyPtrVector<DbgVariableRecord *> findDVRDeclares(Value *V);
 /// As above, for DVRValues.
 LLVM_ABI TinyPtrVector<DbgVariableRecord *> findDVRValues(Value *V);
+/// As above, for DVRDeclareValues.
+LLVM_ABI TinyPtrVector<DbgVariableRecord *> findDVRDeclareValues(Value *V);
 
 /// Finds the debug info records describing a value.
 LLVM_ABI void
diff --git a/llvm/include/llvm/IR/DebugProgramInstruction.h b/llvm/include/llvm/IR/DebugProgramInstruction.h
@@ -282,6 +282,7 @@ class DbgVariableRecord : public DbgRecord, protected DebugValueUser {
     Declare,
     Value,
     Assign,
+    DeclareValue,
 
     End, ///< Marks the end of the concrete types.
     Any, ///< To indicate all LocationTypes in searches.
@@ -364,6 +365,13 @@ class DbgVariableRecord : public DbgRecord, protected DebugValueUser {
   createDVRDeclare(Value *Address, DILocalVariable *DV, DIExpression *Expr,
                    const DILocation *DI, DbgVariableRecord &InsertBefore);
 
+  LLVM_ABI static DbgVariableRecord *
+  createDVRDeclareValue(Value *Address, DILocalVariable *DV, DIExpression *Expr,
+                        const DILocation *DI);
+  LLVM_ABI static DbgVariableRecord *
+  createDVRDeclareValue(Value *Address, DILocalVariable *DV, DIExpression *Expr,
+                        const DILocation *DI, DbgVariableRecord &InsertBefore);
+
   /// Iterator for ValueAsMetadata that internally uses direct pointer iteration
   /// over either a ValueAsMetadata* or a ValueAsMetadata**, dereferencing to the
   /// ValueAsMetadata .
@@ -414,6 +422,7 @@ class DbgVariableRecord : public DbgRecord, protected DebugValueUser {
 
   bool isDbgDeclare() const { return Type == LocationType::Declare; }
   bool isDbgValue() const { return Type == LocationType::Value; }
+  bool isDbgDeclareValue() const { return Type == LocationType::DeclareValue; }
 
   /// Get the locations corresponding to the variable referenced by the debug
   /// info intrinsic.  Depending on the intrinsic, this could be the
@@ -439,12 +448,16 @@ class DbgVariableRecord : public DbgRecord, protected DebugValueUser {
   bool hasValidLocation() const { return getVariableLocationOp(0) != nullptr; }
 
   /// Does this describe the address of a local variable. True for dbg.addr
-  /// and dbg.declare, but not dbg.value, which describes its value.
+  /// and dbg.declare, but not dbg.value or dbg.declare_value, which describes
+  /// its value.
   bool isAddressOfVariable() const { return Type == LocationType::Declare; }
 
   /// Determine if this describes the value of a local variable. It is false for
-  /// dbg.declare, but true for dbg.value, which describes its value.
-  bool isValueOfVariable() const { return Type == LocationType::Value; }
+  /// dbg.declare, but true for dbg.value and dbg.declare_value, which describes
+  /// its value.
+  bool isValueOfVariable() const {
+    return Type == LocationType::Value || Type == LocationType::DeclareValue;
+  }
 
   LocationType getType() const { return Type; }
 
diff --git a/llvm/lib/AsmParser/LLLexer.cpp b/llvm/lib/AsmParser/LLLexer.cpp
@@ -1007,6 +1007,7 @@ lltok::Kind LLLexer::LexIdentifier() {
   DBGRECORDTYPEKEYWORD(declare);
   DBGRECORDTYPEKEYWORD(assign);
   DBGRECORDTYPEKEYWORD(label);
+  DBGRECORDTYPEKEYWORD(declare_value);
 #undef DBGRECORDTYPEKEYWORD
 
   if (Keyword.starts_with("DIFlag")) {
diff --git a/llvm/lib/AsmParser/LLParser.cpp b/llvm/lib/AsmParser/LLParser.cpp
@@ -7155,7 +7155,8 @@ bool LLParser::parseDebugRecord(DbgRecord *&DR, PerFunctionState &PFS) {
                               .Case("declare", RecordKind::ValueKind)
                               .Case("value", RecordKind::ValueKind)
                               .Case("assign", RecordKind::ValueKind)
-                              .Case("label", RecordKind::LabelKind);
+                              .Case("label", RecordKind::LabelKind)
+                              .Case("declare_value", RecordKind::ValueKind);
 
   // Parsing labels is trivial; parse here and early exit, otherwise go into the
   // full DbgVariableRecord processing stage.
@@ -7180,7 +7181,8 @@ bool LLParser::parseDebugRecord(DbgRecord *&DR, PerFunctionState &PFS) {
   LocType ValueType = StringSwitch<LocType>(Lex.getStrVal())
                           .Case("declare", LocType::Declare)
                           .Case("value", LocType::Value)
-                          .Case("assign", LocType::Assign);
+                          .Case("assign", LocType::Assign)
+                          .Case("declare_value", LocType::DeclareValue);
 
   Lex.Lex();
   if (parseToken(lltok::lparen, "Expected '(' here"))
diff --git a/llvm/lib/Bitcode/Reader/BitcodeAnalyzer.cpp b/llvm/lib/Bitcode/Reader/BitcodeAnalyzer.cpp
@@ -272,6 +272,7 @@ GetCodeName(unsigned CodeID, unsigned BlockID,
       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_DECLARE_VALUE)
       STRINGIFY_CODE(FUNC_CODE, DEBUG_RECORD_VALUE)
       STRINGIFY_CODE(FUNC_CODE, DEBUG_RECORD_ASSIGN)
       STRINGIFY_CODE(FUNC_CODE, DEBUG_RECORD_VALUE_SIMPLE)
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -6655,6 +6655,7 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
     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_DECLARE_VALUE:
     case bitc::FUNC_CODE_DEBUG_RECORD_ASSIGN: {
       // DbgVariableRecords are placed after the Instructions that they are
       // attached to.
@@ -6671,6 +6672,8 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
       //   ..., Value
       // dbg_declare (FUNC_CODE_DEBUG_RECORD_DECLARE)
       //   ..., LocationMetadata
+      // dbg_declare_value (FUNC_CODE_DEBUG_RECORD_DECLARE_VALUE)
+      //   ..., LocationMetadata
       // dbg_assign (FUNC_CODE_DEBUG_RECORD_ASSIGN)
       //   ..., LocationMetadata, DIAssignID, DIExpression, LocationMetadata
       unsigned Slot = 0;
@@ -6712,6 +6715,11 @@ Error BitcodeReader::parseFunctionBody(Function *F) {
         DVR = new DbgVariableRecord(RawLocation, Var, Expr, DIL,
                                     DbgVariableRecord::LocationType::Declare);
         break;
+      case bitc::FUNC_CODE_DEBUG_RECORD_DECLARE_VALUE:
+        DVR = new DbgVariableRecord(
+            RawLocation, Var, Expr, DIL,
+            DbgVariableRecord::LocationType::DeclareValue);
+        break;
       case bitc::FUNC_CODE_DEBUG_RECORD_ASSIGN: {
         DIAssignID *ID = cast<DIAssignID>(getFnMetadataByID(Record[Slot++]));
         DIExpression *AddrExpr =
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -3844,6 +3844,9 @@ void ModuleBitcodeWriter::writeFunction(
           } else if (DVR.isDbgDeclare()) {
             Vals.push_back(VE.getMetadataID(DVR.getRawLocation()));
             Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_RECORD_DECLARE, Vals);
+          } else if (DVR.isDbgDeclareValue()) {
+            Vals.push_back(VE.getMetadataID(DVR.getRawLocation()));
+            Stream.EmitRecord(bitc::FUNC_CODE_DEBUG_RECORD_DECLARE_VALUE, Vals);
           } else {
             assert(DVR.isDbgAssign() && "Unexpected DbgRecord kind");
             Vals.push_back(VE.getMetadataID(DVR.getRawLocation()));
diff --git a/llvm/lib/IR/AsmWriter.cpp b/llvm/lib/IR/AsmWriter.cpp
@@ -4864,6 +4864,9 @@ void AssemblyWriter::printDbgVariableRecord(const DbgVariableRecord &DVR) {
   case DbgVariableRecord::LocationType::Declare:
     Out << "declare";
     break;
+  case DbgVariableRecord::LocationType::DeclareValue:
+    Out << "declare_value";
+    break;
   case DbgVariableRecord::LocationType::Assign:
     Out << "assign";
     break;
diff --git a/llvm/lib/IR/DIBuilder.cpp b/llvm/lib/IR/DIBuilder.cpp
@@ -1147,6 +1147,24 @@ DbgInstPtr DIBuilder::insertDeclare(Value *Storage, DILocalVariable *VarInfo,
   return DVR;
 }
 
+DbgInstPtr DIBuilder::insertDeclareValue(Value *Storage,
+                                         DILocalVariable *VarInfo,
+                                         DIExpression *Expr,
+                                         const DILocation *DL,
+                                         InsertPosition InsertPt) {
+  assert(VarInfo &&
+         "empty or invalid DILocalVariable* passed to dbg.declare_value");
+  assert(DL && "Expected debug loc");
+  assert(DL->getScope()->getSubprogram() ==
+             VarInfo->getScope()->getSubprogram() &&
+         "Expected matching subprograms");
+
+  DbgVariableRecord *DVR =
+      DbgVariableRecord::createDVRDeclareValue(Storage, VarInfo, Expr, DL);
+  insertDbgVariableRecord(DVR, InsertPt);
+  return DVR;
+}
+
 void DIBuilder::insertDbgVariableRecord(DbgVariableRecord *DVR,
                                         InsertPosition InsertPt) {
   assert(InsertPt.isValid());
diff --git a/llvm/lib/IR/DebugInfo.cpp b/llvm/lib/IR/DebugInfo.cpp
@@ -62,6 +62,23 @@ TinyPtrVector<DbgVariableRecord *> llvm::findDVRDeclares(Value *V) {
   return Declares;
 }
 
+TinyPtrVector<DbgVariableRecord *> llvm::findDVRDeclareValues(Value *V) {
+  // This function is hot. Check whether the value has any metadata to avoid a
+  // DenseMap lookup. This check is a bitfield datamember lookup.
+  if (!V->isUsedByMetadata())
+    return {};
+  auto *L = ValueAsMetadata::getIfExists(V);
+  if (!L)
+    return {};
+
+  TinyPtrVector<DbgVariableRecord *> DEclareValues;
+  for (DbgVariableRecord *DVR : L->getAllDbgVariableRecordUsers())
+    if (DVR->getType() == DbgVariableRecord::LocationType::DeclareValue)
+      DEclareValues.push_back(DVR);
+
+  return DEclareValues;
+}
+
 TinyPtrVector<DbgVariableRecord *> llvm::findDVRValues(Value *V) {
   // This function is hot. Check whether the value has any metadata to avoid a
   // DenseMap lookup. This check is a bitfield datamember lookup.
diff --git a/llvm/lib/IR/DebugProgramInstruction.cpp b/llvm/lib/IR/DebugProgramInstruction.cpp
@@ -211,6 +211,22 @@ DbgVariableRecord::createDVRDeclare(Value *Address, DILocalVariable *DV,
   return NewDVRDeclare;
 }
 
+DbgVariableRecord *
+DbgVariableRecord::createDVRDeclareValue(Value *Address, DILocalVariable *DV,
+                                         DIExpression *Expr,
+                                         const DILocation *DI) {
+  return new DbgVariableRecord(ValueAsMetadata::get(Address), DV, Expr, DI,
+                               LocationType::DeclareValue);
+}
+
+DbgVariableRecord *DbgVariableRecord::createDVRDeclareValue(
+    Value *Address, DILocalVariable *DV, DIExpression *Expr,
+    const DILocation *DI, DbgVariableRecord &InsertBefore) {
+  auto *NewDVRCoro = createDVRDeclareValue(Address, DV, Expr, DI);
+  NewDVRCoro->insertBefore(&InsertBefore);
+  return NewDVRCoro;
+}
+
 DbgVariableRecord *DbgVariableRecord::createDVRAssign(
     Value *Val, DILocalVariable *Variable, DIExpression *Expression,
     DIAssignID *AssignID, Value *Address, DIExpression *AddressExpression,
@@ -427,6 +443,10 @@ DbgVariableRecord::createDebugIntrinsic(Module *M,
   case DbgVariableRecord::LocationType::End:
   case DbgVariableRecord::LocationType::Any:
     llvm_unreachable("Invalid LocationType");
+    break;
+  case DbgVariableRecord::LocationType::DeclareValue:
+    llvm_unreachable(
+        "#dbg_declare_value should never be converted to an intrinsic");
   }
 
   // Create the intrinsic from this DbgVariableRecord's information, optionally
diff --git a/llvm/lib/IR/Verifier.cpp b/llvm/lib/IR/Verifier.cpp
@@ -190,6 +190,9 @@ struct llvm::VerifierSupport {
     case DbgVariableRecord::LocationType::Declare:
       *OS << "declare";
       break;
+    case DbgVariableRecord::LocationType::DeclareValue:
+      *OS << "declare_value";
+      break;
     case DbgVariableRecord::LocationType::Assign:
       *OS << "assign";
       break;
@@ -7058,6 +7061,7 @@ void Verifier::visit(DbgVariableRecord &DVR) {
 
   CheckDI(DVR.getType() == DbgVariableRecord::LocationType::Value ||
               DVR.getType() == DbgVariableRecord::LocationType::Declare ||
+              DVR.getType() == DbgVariableRecord::LocationType::DeclareValue ||
               DVR.getType() == DbgVariableRecord::LocationType::Assign,
           "invalid #dbg record type", &DVR, DVR.getType(), BB, F);
 
diff --git a/llvm/test/Assembler/dbg_declare_value.ll b/llvm/test/Assembler/dbg_declare_value.ll
@@ -0,0 +1,19 @@
+; RUN: llvm-as < %s | llvm-dis | llvm-as | llvm-dis
+
+; CHECK: #dbg_declare_value(double %0, !{{[0-9]+}}, !DIExpression(), ![0-9]+)
+
+; ModuleID = '/tmp/test.c'
+source_filename = "/tmp/test.c"
+target datalayout = "e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-n32:64-S128-Fn32"
+target triple = "arm64-apple-macosx26.0.0"
+
+; Function Attrs: noinline nounwind optnone ssp uwtable(sync)
+define void @foo(double noundef %0) #0 !dbg !9 {
+    #dbg_declare_value(double %0, !15, !DIExpression(), !16)
+    ret void, !dbg !21
+}
+
+!9 = distinct !DISubprogram(name: "foo")
+!15 = !DILocalVariable(name: "x", arg: 1, scope: !9)
+!16 = !DILocation(line: 1, column: 17, scope: !9)
+!21 = !DILocation(line: 3, column: 1, scope: !9)
