[WebAssembly] Add DBG_VALUE with local operands location in WebAssemblyExplicitLocals pass

Extends DWARF expression larguage to express locals/globals locations. (via
target-index operands)

The WebAssemblyExplicitLocals can replace virtual registers to target-index()
operand type at the time when WebAssembly backend introduces local.{get,set,tee}
instead of corresponding virtual registers.

Reviewers: aprantl, dschuff

Differential Revision: https://reviews.llvm.org/D52634

Author: yurydelendik

llvm/include/llvm/BinaryFormat/Dwarf.def

@@ -633,6 +633,8 @@ 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)
 // The GNU entry value extension.
 HANDLE_DW_OP(0xf3, GNU_entry_value, 0, GNU)
 // Extensions for Fission proposal.

llvm/include/llvm/BinaryFormat/Dwarf.h

@@ -58,7 +58,8 @@ 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/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -866,6 +866,10 @@ 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

@@ -20,13 +20,32 @@
 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;
+  }
+};
+
 /// A single location or constant.
 class DbgValueLoc {
   /// Any complex address location expression for this DbgValueLoc.
   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,
@@ -36,8 +55,12 @@ class DbgValueLoc {
     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;
+  };
 
 public:
   DbgValueLoc(const DIExpression *Expr, int64_t i)
@@ -56,15 +79,21 @@ class DbgValueLoc {
       : Expression(Expr), EntryKind(E_Location), Loc(Loc) {
     assert(cast<DIExpression>(Expr)->isValid());
   }
+  DbgValueLoc(const DIExpression *Expr, TargetIndexLocation Loc)
+      : Expression(Expr), EntryKind(E_TargetIndexLocation), TIL(Loc) {}
 
   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(); }
   bool isEntryVal() const { return getExpression()->isEntryValue(); }
   const DIExpression *getExpression() const { return Expression; }
@@ -162,6 +191,8 @@ inline bool operator==(const DbgValueLoc &A,
   switch (A.EntryKind) {
   case DbgValueLoc::E_Location:
     return A.Loc == B.Loc;
+  case DbgValueLoc::E_TargetIndexLocation:
+    return A.TIL == B.TIL;
   case DbgValueLoc::E_Integer:
     return A.Constant.Int == B.Constant.Int;
   case DbgValueLoc::E_ConstantFP:

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

@@ -257,6 +257,11 @@ static DbgValueLoc getDebugLocValue(const MachineInstr *MI) {
     MachineLocation MLoc(RegOp.getReg(), Op1.isImm());
     return DbgValueLoc(Expr, MLoc);
   }
+  if (MI->getOperand(0).isTargetIndex()) {
+    auto Op = MI->getOperand(0);
+    return DbgValueLoc(Expr,
+                       TargetIndexLocation(Op.getIndex(), Op.getOffset()));
+  }
   if (MI->getOperand(0).isImm())
     return DbgValueLoc(Expr, MI->getOperand(0).getImm());
   if (MI->getOperand(0).isFPImm())
@@ -2027,6 +2032,9 @@ void DwarfDebug::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

@@ -521,3 +521,11 @@ void DwarfExpression::emitLegacyZExt(unsigned FromBits) {
   emitUnsigned((1ULL << FromBits) - 1);
   emitOp(dwarf::DW_OP_and);
 }
+
+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

@@ -295,6 +295,10 @@ class DwarfExpression {
 
   void emitLegacySExt(unsigned FromBits);
   void emitLegacyZExt(unsigned FromBits);
+
+  /// 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/WebAssembly/WebAssembly.h

@@ -79,6 +79,10 @@ 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 "WebAssemblyDebugValueManager.h"
+#include "WebAssembly.h"
 #include "WebAssemblyMachineFunctionInfo.h"
 #include "llvm/CodeGen/MachineInstr.h"
 
@@ -43,3 +44,10 @@ 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);
+  }
+}