[WIP] Encode WebAssembly specific locations in DBG_VALUEs and DW_AT_frame_base

llvm/include/llvm/BinaryFormat/Dwarf.def

@@ -627,6 +627,8 @@ HANDLE_DW_OP(0xa9, reinterpret, 5, DWARF)
 // Vendor extensions:
 // Extensions for GNU-style thread-local storage.
 HANDLE_DW_OP(0xe0, GNU_push_tls_address, 0, GNU)
+// Extensions for WebAssembly.
+HANDLE_DW_OP(0xed, WASM_location, 0, WASM)
 // Extensions for Fission proposal.
 HANDLE_DW_OP(0xfb, GNU_addr_index, 0, GNU)
 HANDLE_DW_OP(0xfc, GNU_const_index, 0, GNU)

llvm/include/llvm/BinaryFormat/Dwarf.h

@@ -59,7 +59,8 @@ enum LLVMConstants : uint32_t {
   DWARF_VENDOR_GNU = 3,
   DWARF_VENDOR_GOOGLE = 4,
   DWARF_VENDOR_LLVM = 5,
-  DWARF_VENDOR_MIPS = 6
+  DWARF_VENDOR_MIPS = 6,
+  DWARF_VENDOR_WASM = 7
 };
 
 /// Constants that define the DWARF format as 32 or 64 bit.

llvm/include/llvm/CodeGen/TargetRegisterInfo.h

@@ -211,6 +211,22 @@ struct RegClassWeight {
   unsigned WeightLimit;
 };
 
+struct FrameBaseLocation {
+  enum LocationKind {
+    Register,
+    CFA,
+    TargetIndex
+  } Kind;
+  struct TargetIndexInfo {
+    unsigned Index;
+    signed Offset;
+  };
+  union {
+    unsigned Reg;
+    TargetIndexInfo TI;
+  };
+};
+
 /// TargetRegisterInfo base class - We assume that the target defines a static
 /// array of TargetRegisterDesc objects that represent all of the machine
 /// registers that the target has.  As such, we simply have to track a pointer
@@ -988,6 +1004,13 @@ class TargetRegisterInfo : public MCRegisterInfo {
   /// for values allocated in the current stack frame.
   virtual unsigned getFrameRegister(const MachineFunction &MF) const = 0;
 
+  virtual FrameBaseLocation getFrameBaseLocation(const MachineFunction &MF) const {
+    FrameBaseLocation Loc;
+    Loc.Kind = FrameBaseLocation::Register;
+    Loc.Reg = getFrameRegister(MF);
+    return Loc;
+  }
+
   /// Mark a register and all its aliases as reserved in the given set.
   void markSuperRegs(BitVector &RegisterSet, unsigned Reg) const;
 

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -895,6 +895,10 @@ static bool emitDebugValueComment(const MachineInstr *MI, AsmPrinter &AP) {
     OS << MI->getOperand(0).getImm();
   } else if (MI->getOperand(0).isCImm()) {
     MI->getOperand(0).getCImm()->getValue().print(OS, false /*isSigned*/);
+  } else if (MI->getOperand(0).isTargetIndex()) {
+    auto Op = MI->getOperand(0);
+    OS << "!target-index(" << Op.getIndex() << "," << Op.getOffset() << ")";
+    return true;
   } else {
     unsigned Reg;
     if (MI->getOperand(0).isReg()) {

llvm/lib/CodeGen/AsmPrinter/DebugLocEntry.h

@@ -21,6 +21,19 @@
 namespace llvm {
 class AsmPrinter;
 
+struct TargetIndexLocation {
+  int Index;
+  int Offset;
+
+  TargetIndexLocation() = default;
+  TargetIndexLocation(unsigned Idx, int64_t Offset)
+      : Index(Idx), Offset(Offset) {}
+
+  bool operator==(const TargetIndexLocation &Other) const {
+    return Index == Other.Index && Offset == Other.Offset;
+  }
+};
+
 /// This struct describes location entries emitted in the .debug_loc
 /// section.
 class DebugLocEntry {
@@ -47,12 +60,20 @@ class DebugLocEntry {
         : Expression(Expr), EntryKind(E_Location), Loc(Loc) {
       assert(cast<DIExpression>(Expr)->isValid());
     }
+    Value(const DIExpression *Expr, TargetIndexLocation Loc)
+        : Expression(Expr), EntryKind(E_TargetIndexLocation), TIL(Loc) {}
 
     /// Any complex address location expression for this Value.
     const DIExpression *Expression;
 
     /// Type of entry that this represents.
-    enum EntryType { E_Location, E_Integer, E_ConstantFP, E_ConstantInt };
+    enum EntryType {
+      E_Location,
+      E_Integer,
+      E_ConstantFP,
+      E_ConstantInt,
+      E_TargetIndexLocation
+    };
     enum EntryType EntryKind;
 
     /// Either a constant,
@@ -62,17 +83,25 @@ class DebugLocEntry {
       const ConstantInt *CIP;
     } Constant;
 
-    // Or a location in the machine frame.
-    MachineLocation Loc;
+    union {
+      // Or a location in the machine frame.
+      MachineLocation Loc;
+      // Or a location from target specific location.
+      TargetIndexLocation TIL;
+    };
 
     bool isLocation() const { return EntryKind == E_Location; }
+    bool isTargetIndexLocation() const {
+      return EntryKind == E_TargetIndexLocation;
+    }
     bool isInt() const { return EntryKind == E_Integer; }
     bool isConstantFP() const { return EntryKind == E_ConstantFP; }
     bool isConstantInt() const { return EntryKind == E_ConstantInt; }
     int64_t getInt() const { return Constant.Int; }
     const ConstantFP *getConstantFP() const { return Constant.CFP; }
     const ConstantInt *getConstantInt() const { return Constant.CIP; }
     MachineLocation getLoc() const { return Loc; }
+    TargetIndexLocation getTargetIndexLocation() const { return TIL; }
     bool isFragment() const { return getExpression()->isFragment(); }
     const DIExpression *getExpression() const { return Expression; }
     friend bool operator==(const Value &, const Value &);
@@ -165,6 +194,8 @@ inline bool operator==(const DebugLocEntry::Value &A,
   switch (A.EntryKind) {
   case DebugLocEntry::Value::E_Location:
     return A.Loc == B.Loc;
+  case DebugLocEntry::Value::E_TargetIndexLocation:
+    return A.TIL == B.TIL;
   case DebugLocEntry::Value::E_Integer:
     return A.Constant.Int == B.Constant.Int;
   case DebugLocEntry::Value::E_ConstantFP:

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

@@ -340,13 +340,24 @@ DIE &DwarfCompileUnit::updateSubprogramScopeDIE(const DISubprogram *SP) {
 
   // Only include DW_AT_frame_base in full debug info
   if (!includeMinimalInlineScopes()) {
-    if (Asm->MF->getTarget().getTargetTriple().isNVPTX()) {
+    const TargetRegisterInfo *RI = Asm->MF->getSubtarget().getRegisterInfo();
+    auto FBL = RI->getFrameBaseLocation(*Asm->MF);
+    if (FBL.Kind == FrameBaseLocation::CFA) {
       DIELoc *Loc = new (DIEValueAllocator) DIELoc;
       addUInt(*Loc, dwarf::DW_FORM_data1, dwarf::DW_OP_call_frame_cfa);
       addBlock(*SPDie, dwarf::DW_AT_frame_base, Loc);
+    } else if (FBL.Kind == FrameBaseLocation::TargetIndex) {
+      if (FBL.TI.Offset >= 0) {
+        DIELoc *Loc = new (DIEValueAllocator) DIELoc;
+        DIEDwarfExpression DwarfExpr(*Asm, *this, *Loc);
+        DIExpressionCursor Cursor({});
+        DwarfExpr.addTargetIndexLocation(FBL.TI.Index, FBL.TI.Offset);
+        DwarfExpr.addExpression(std::move(Cursor));
+        addBlock(*SPDie, dwarf::DW_AT_frame_base, DwarfExpr.finalize());
+      }
     } else {
-      const TargetRegisterInfo *RI = Asm->MF->getSubtarget().getRegisterInfo();
-      MachineLocation Location(RI->getFrameRegister(*Asm->MF));
+      assert(FBL.Kind == FrameBaseLocation::Register);
+      MachineLocation Location(FBL.Reg);
       if (RI->isPhysicalRegister(Location.getReg()))
         addAddress(*SPDie, dwarf::DW_AT_frame_base, Location);
     }

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -1072,6 +1072,11 @@ static DebugLocEntry::Value getDebugLocValue(const MachineInstr *MI) {
     MachineLocation MLoc(RegOp.getReg(), Op1.isImm());
     return DebugLocEntry::Value(Expr, MLoc);
   }
+  if (MI->getOperand(0).isTargetIndex()) {
+    auto Op = MI->getOperand(0);
+    return DebugLocEntry::Value(
+        Expr, TargetIndexLocation(Op.getIndex(), Op.getOffset()));
+  }
   if (MI->getOperand(0).isImm())
     return DebugLocEntry::Value(Expr, MI->getOperand(0).getImm());
   if (MI->getOperand(0).isFPImm())
@@ -1920,6 +1925,9 @@ static void emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
     if (!DwarfExpr.addMachineRegExpression(TRI, Cursor, Location.getReg()))
       return;
     return DwarfExpr.addExpression(std::move(Cursor));
+  } else if (Value.isTargetIndexLocation()) {
+    TargetIndexLocation Loc = Value.getTargetIndexLocation();
+    DwarfExpr.addTargetIndexLocation(Loc.Index, Loc.Offset);
   } else if (Value.isConstantFP()) {
     APInt RawBytes = Value.getConstantFP()->getValueAPF().bitcastToAPInt();
     DwarfExpr.addUnsignedConstant(RawBytes);

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp

@@ -437,3 +437,11 @@ void DwarfExpression::addFragmentOffset(const DIExpression *Expr) {
     addOpPiece(FragmentOffset - OffsetInBits);
   OffsetInBits = FragmentOffset;
 }
+
+void DwarfExpression::addTargetIndexLocation(unsigned Index, int64_t Offset) {
+  assert(LocationKind == Implicit || LocationKind == Unknown);
+  LocationKind = Implicit;
+  emitOp(dwarf::DW_OP_WASM_location);
+  emitUnsigned(Index);
+  emitSigned(Offset);
+}

llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h

@@ -248,6 +248,10 @@ class DwarfExpression {
   /// If applicable, emit an empty DW_OP_piece / DW_OP_bit_piece to advance to
   /// the fragment described by \c Expr.
   void addFragmentOffset(const DIExpression *Expr);
+
+  /// Emit location information expressed via target's index + offset
+  /// It is an extension for WebAssembly locals, globals and operand stack.
+  void addTargetIndexLocation(unsigned Index, int64_t Offset);
 };
 
 /// DwarfExpression implementation for .debug_loc entries.

llvm/lib/DebugInfo/DWARF/DWARFExpression.cpp

@@ -93,6 +93,8 @@ static DescVector getDescriptions() {
   Descriptions[DW_OP_implicit_value] =
       Desc(Op::Dwarf3, Op::SizeLEB, Op::SizeBlock);
   Descriptions[DW_OP_stack_value] = Desc(Op::Dwarf3);
+  Descriptions[DW_OP_WASM_location] =
+      Desc(Op::Dwarf4, Op::SizeLEB, Op::SignedSizeLEB);
   Descriptions[DW_OP_GNU_push_tls_address] = Desc(Op::Dwarf3);
   Descriptions[DW_OP_addrx] = Desc(Op::Dwarf4, Op::SizeLEB);
   Descriptions[DW_OP_GNU_addr_index] = Desc(Op::Dwarf4, Op::SizeLEB);

llvm/lib/Target/NVPTX/NVPTXRegisterInfo.h

@@ -45,6 +45,12 @@ class NVPTXRegisterInfo : public NVPTXGenRegisterInfo {
 
   unsigned getFrameRegister(const MachineFunction &MF) const override;
 
+  FrameBaseLocation getFrameBaseLocation(const MachineFunction &MF) const override {
+    FrameBaseLocation Loc;
+    Loc.Kind = FrameBaseLocation::CFA;
+    return Loc;
+  }
+
   ManagedStringPool *getStrPool() const {
     return const_cast<ManagedStringPool *>(&ManagedStrPool);
   }

llvm/lib/Target/WebAssembly/WebAssembly.h

@@ -82,6 +82,10 @@ void initializeWebAssemblyRegNumberingPass(PassRegistry &);
 void initializeWebAssemblyPeepholePass(PassRegistry &);
 void initializeWebAssemblyCallIndirectFixupPass(PassRegistry &);
 
+namespace WebAssembly {
+enum TargetIndex { TI_LOCAL_START, TI_GLOBAL_START, TI_OPERAND_STACK_START };
+} // end namespace WebAssembly
+
 } // end namespace llvm
 
 #endif

llvm/lib/Target/WebAssembly/WebAssemblyDebugValueManager.cpp

@@ -12,6 +12,7 @@
 ///
 //===----------------------------------------------------------------------===//
 
+#include "WebAssembly.h"
 #include "WebAssemblyDebugValueManager.h"
 #include "WebAssemblyMachineFunctionInfo.h"
 #include "llvm/CodeGen/MachineInstr.h"
@@ -44,3 +45,10 @@ void WebAssemblyDebugValueManager::clone(MachineInstr *Insert,
     MBB->insert(Insert, Clone);
   }
 }
+
+void WebAssemblyDebugValueManager::replaceWithLocal(unsigned LocalId) {
+  for (auto *DBI : DbgValues) {
+    MachineOperand &Op = DBI->getOperand(0);
+    Op.ChangeToTargetIndex(llvm::WebAssembly::TI_LOCAL_START, LocalId);
+  }
+}

llvm/lib/Target/WebAssembly/WebAssemblyDebugValueManager.h

@@ -31,6 +31,7 @@ class WebAssemblyDebugValueManager {
   void move(MachineInstr *Insert);
   void updateReg(unsigned Reg);
   void clone(MachineInstr *Insert, unsigned NewReg);
+  void replaceWithLocal(unsigned LocalId);
 };
 
 } // end namespace llvm

llvm/lib/Target/WebAssembly/WebAssemblyExplicitLocals.cpp

@@ -18,6 +18,7 @@
 
 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
 #include "WebAssembly.h"
+#include "WebAssemblyDebugValueManager.h"
 #include "WebAssemblyMachineFunctionInfo.h"
 #include "WebAssemblySubtarget.h"
 #include "WebAssemblyUtilities.h"
@@ -262,6 +263,8 @@ bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
             .addImm(LocalId)
             .addReg(MI.getOperand(2).getReg());
 
+        WebAssemblyDebugValueManager(&MI).replaceWithLocal(LocalId);
+
         MI.eraseFromParent();
         Changed = true;
         continue;
@@ -291,6 +294,9 @@ bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
           } else {
             unsigned LocalId = getLocalId(Reg2Local, CurLocal, OldReg);
             unsigned Opc = getSetLocalOpcode(RC);
+
+            WebAssemblyDebugValueManager(&MI).replaceWithLocal(LocalId);
+
             BuildMI(MBB, InsertPt, MI.getDebugLoc(), TII->get(Opc))
                 .addImm(LocalId)
                 .addReg(NewReg);
@@ -380,6 +386,13 @@ bool WebAssemblyExplicitLocals::runOnMachineFunction(MachineFunction &MF) {
     Changed = true;
   }
 
+  {
+    auto RL = Reg2Local.find(MFI.SPVReg);
+    if (RL != Reg2Local.end()) {
+      MFI.SPLocal = RL->second;
+    }
+  }
+
 #ifndef NDEBUG
   // Assert that all registers have been stackified at this point.
   for (const MachineBasicBlock &MBB : MF) {

llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.cpp

@@ -15,6 +15,7 @@
 
 #include "WebAssemblyInstrInfo.h"
 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
+#include "WebAssembly.h"
 #include "WebAssemblyMachineFunctionInfo.h"
 #include "WebAssemblySubtarget.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
@@ -198,3 +199,12 @@ bool WebAssemblyInstrInfo::reverseBranchCondition(
   Cond.front() = MachineOperand::CreateImm(!Cond.front().getImm());
   return false;
 }
+
+ArrayRef<std::pair<int, const char *>>
+WebAssemblyInstrInfo::getSerializableTargetIndices() const {
+  static const std::pair<int, const char *> TargetIndices[] = {
+      {WebAssembly::TI_LOCAL_START, "wasm-local-start"},
+      {WebAssembly::TI_GLOBAL_START, "wasm-global-start"},
+      {WebAssembly::TI_OPERAND_STACK_START, "wasm-operator-stack-start"}};
+  return makeArrayRef(TargetIndices);
+}

llvm/lib/Target/WebAssembly/WebAssemblyInstrInfo.h

@@ -17,6 +17,7 @@
 #define LLVM_LIB_TARGET_WEBASSEMBLY_WEBASSEMBLYINSTRINFO_H
 
 #include "WebAssemblyRegisterInfo.h"
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/CodeGen/TargetInstrInfo.h"
 
 #define GET_INSTRINFO_HEADER
@@ -56,6 +57,9 @@ class WebAssemblyInstrInfo final : public WebAssemblyGenInstrInfo {
                         int *BytesAdded = nullptr) const override;
   bool
   reverseBranchCondition(SmallVectorImpl<MachineOperand> &Cond) const override;
+
+  ArrayRef<std::pair<int, const char *>>
+  getSerializableTargetIndices() const override;
 };
 
 } // end namespace llvm

llvm/lib/Target/WebAssembly/WebAssemblyMachineFunctionInfo.h

@@ -53,7 +53,7 @@ class WebAssemblyFunctionInfo final : public MachineFunctionInfo {
   unsigned BasePtrVreg = -1U;
 
 public:
-  explicit WebAssemblyFunctionInfo(MachineFunction &MF) : MF(MF) {}
+  explicit WebAssemblyFunctionInfo(MachineFunction &MF) : MF(MF), SPVReg(WebAssembly::NoRegister) {}
   ~WebAssemblyFunctionInfo() override;
 
   void addParam(MVT VT) { Params.push_back(VT); }
@@ -118,6 +118,9 @@ class WebAssemblyFunctionInfo final : public MachineFunctionInfo {
     assert(Reg & INT32_MIN);
     return Reg & INT32_MAX;
   }
+
+  unsigned SPVReg;
+  unsigned SPLocal;
 };
 
 void ComputeLegalValueVTs(const Function &F, const TargetMachine &TM, Type *Ty,

llvm/lib/Target/WebAssembly/WebAssemblyRegisterInfo.cpp

@@ -138,6 +138,16 @@ WebAssemblyRegisterInfo::getFrameRegister(const MachineFunction &MF) const {
   return Regs[TFI->hasFP(MF)][TT.isArch64Bit()];
 }
 
+FrameBaseLocation
+WebAssemblyRegisterInfo::getFrameBaseLocation(const MachineFunction &MF) const {
+  const WebAssemblyFunctionInfo &MFI = *MF.getInfo<WebAssemblyFunctionInfo>();
+  FrameBaseLocation Loc;
+  Loc.Kind = FrameBaseLocation::TargetIndex;
+  signed Local = MFI.SPVReg != WebAssembly::NoRegister ? MFI.SPLocal : -1;
+  Loc.TI = {0, Local};
+  return Loc;
+}
+
 const TargetRegisterClass *
 WebAssemblyRegisterInfo::getPointerRegClass(const MachineFunction &MF,
                                             unsigned Kind) const {