1 files changed, 124 insertions, 41 deletions
diff --git a/contrib/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/contrib/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index 5fff28d..fd90fa0 100644
--- a/contrib/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/contrib/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -25,17 +25,86 @@ class TargetRegisterInfo;
 class DwarfUnit;
 class DIELoc;
 
+/// Holds a DIExpression and keeps track of how many operands have been consumed
+/// so far.
+class DIExpressionCursor {
+  DIExpression::expr_op_iterator Start, End;
+public:
+  DIExpressionCursor(const DIExpression *Expr) {
+    if (!Expr) {
+      assert(Start == End);
+      return;
+    }
+    Start = Expr->expr_op_begin();
+    End = Expr->expr_op_end();
+  }
+
+  DIExpressionCursor(ArrayRef<uint64_t> Expr)
+      : Start(Expr.begin()), End(Expr.end()) {}
+
+  /// Consume one operation.
+  Optional<DIExpression::ExprOperand> take() {
+    if (Start == End)
+      return None;
+    return *(Start++);
+  }
+
+  /// Consume N operations.
+  void consume(unsigned N) { std::advance(Start, N); }
+
+  /// Return the current operation.
+  Optional<DIExpression::ExprOperand> peek() const {
+    if (Start == End)
+      return None;
+    return *(Start);
+  }
+
+  /// Return the next operation.
+  Optional<DIExpression::ExprOperand> peekNext() const {
+    if (Start == End)
+      return None;
+
+    auto Next = Start.getNext();
+    if (Next == End)
+      return None;
+
+    return *Next;
+  }
+  /// Determine whether there are any operations left in this expression.
+  operator bool() const { return Start != End; }
+
+  /// Retrieve the fragment information, if any.
+  Optional<DIExpression::FragmentInfo> getFragmentInfo() const {
+    return DIExpression::getFragmentInfo(Start, End);
+  }
+};
+
 /// Base class containing the logic for constructing DWARF expressions
 /// independently of whether they are emitted into a DIE or into a .debug_loc
 /// entry.
 class DwarfExpression {
 protected:
-  // Various convenience accessors that extract things out of AsmPrinter.
   unsigned DwarfVersion;
+  /// Current Fragment Offset in Bits.
+  uint64_t OffsetInBits = 0;
+
+  /// Sometimes we need to add a DW_OP_bit_piece to describe a subregister. 
+  unsigned SubRegisterSizeInBits = 0;
+  unsigned SubRegisterOffsetInBits = 0;
+
+  /// Push a DW_OP_piece / DW_OP_bit_piece for emitting later, if one is needed
+  /// to represent a subregister.
+  void setSubRegisterPiece(unsigned SizeInBits, unsigned OffsetInBits) {
+    SubRegisterSizeInBits = SizeInBits;
+    SubRegisterOffsetInBits = OffsetInBits;
+  }
 
 public:
   DwarfExpression(unsigned DwarfVersion) : DwarfVersion(DwarfVersion) {}
-  virtual ~DwarfExpression() {}
+  virtual ~DwarfExpression() {};
+
+  /// This needs to be called last to commit any pending changes.
+  void finalize();
 
   /// Output a dwarf operand and an optional assembler comment.
   virtual void EmitOp(uint8_t Op, const char *Comment = nullptr) = 0;
@@ -52,24 +121,25 @@ public:
   /// Emit an (double-)indirect dwarf register operation.
   void AddRegIndirect(int DwarfReg, int Offset, bool Deref = false);
 
-  /// Emit a dwarf register operation for describing
-  /// - a small value occupying only part of a register or
-  /// - a register representing only part of a value.
+  /// Emit a DW_OP_piece or DW_OP_bit_piece operation for a variable fragment.
+  /// \param OffsetInBits    This is an optional offset into the location that
+  /// is at the top of the DWARF stack.
   void AddOpPiece(unsigned SizeInBits, unsigned OffsetInBits = 0);
+
   /// Emit a shift-right dwarf expression.
   void AddShr(unsigned ShiftBy);
+
   /// Emit a DW_OP_stack_value, if supported.
   ///
-  /// The proper way to describe a constant value is
-  /// DW_OP_constu <const>, DW_OP_stack_value.
-  /// Unfortunately, DW_OP_stack_value was not available until DWARF-4,
-  /// so we will continue to generate DW_OP_constu <const> for DWARF-2
-  /// and DWARF-3. Technically, this is incorrect since DW_OP_const <const>
-  /// actually describes a value at a constant addess, not a constant value.
-  /// However, in the past there was no better way  to describe a constant
-  /// value, so the producers and consumers started to rely on heuristics
-  /// to disambiguate the value vs. location status of the expression.
-  /// See PR21176 for more details.
+  /// The proper way to describe a constant value is DW_OP_constu <const>,
+  /// DW_OP_stack_value.  Unfortunately, DW_OP_stack_value was not available
+  /// until DWARF 4, so we will continue to generate DW_OP_constu <const> for
+  /// DWARF 2 and DWARF 3. Technically, this is incorrect since DW_OP_const
+  /// <const> actually describes a value at a constant addess, not a constant
+  /// value.  However, in the past there was no better way to describe a
+  /// constant value, so the producers and consumers started to rely on
+  /// heuristics to disambiguate the value vs. location status of the
+  /// expression.  See PR21176 for more details.
   void AddStackValue();
 
   /// Emit an indirect dwarf register operation for the given machine register.
@@ -77,23 +147,23 @@ public:
   bool AddMachineRegIndirect(const TargetRegisterInfo &TRI, unsigned MachineReg,
                              int Offset = 0);
 
-  /// \brief Emit a partial DWARF register operation.
-  /// \param MachineReg        the register
-  /// \param PieceSizeInBits   size and
-  /// \param PieceOffsetInBits offset of the piece in bits, if this is one
-  ///                          piece of an aggregate value.
+  /// Emit a partial DWARF register operation.
+  ///
+  /// \param MachineReg           The register number.
+  /// \param MaxSize              If the register must be composed from
+  ///                             sub-registers this is an upper bound
+  ///                             for how many bits the emitted DW_OP_piece
+  ///                             may cover.
   ///
-  /// If size and offset is zero an operation for the entire
-  /// register is emitted: Some targets do not provide a DWARF
-  /// register number for every register.  If this is the case, this
-  /// function will attempt to emit a DWARF register by emitting a
-  /// piece of a super-register or by piecing together multiple
-  /// subregisters that alias the register.
+  /// If size and offset is zero an operation for the entire register is
+  /// emitted: Some targets do not provide a DWARF register number for every
+  /// register.  If this is the case, this function will attempt to emit a DWARF
+  /// register by emitting a fragment of a super-register or by piecing together
+  /// multiple subregisters that alias the register.
   ///
   /// \return false if no DWARF register exists for MachineReg.
-  bool AddMachineRegPiece(const TargetRegisterInfo &TRI, unsigned MachineReg,
-                          unsigned PieceSizeInBits = 0,
-                          unsigned PieceOffsetInBits = 0);
+  bool AddMachineReg(const TargetRegisterInfo &TRI, unsigned MachineReg,
+                     unsigned MaxSize = ~1U);
 
   /// Emit a signed constant.
   void AddSignedConstant(int64_t Value);
@@ -102,20 +172,29 @@ public:
   /// Emit an unsigned constant.
   void AddUnsignedConstant(const APInt &Value);
 
-  /// \brief Emit an entire expression on top of a machine register location.
+  /// Emit a machine register location. As an optimization this may also consume
+  /// the prefix of a DwarfExpression if a more efficient representation for
+  /// combining the register location and the first operation exists.
   ///
-  /// \param PieceOffsetInBits If this is one piece out of a fragmented
-  /// location, this is the offset of the piece inside the entire variable.
-  /// \return false if no DWARF register exists for MachineReg.
+  /// \param FragmentOffsetInBits     If this is one fragment out of a fragmented
+  ///                                 location, this is the offset of the
+  ///                                 fragment inside the entire variable.
+  /// \return                         false if no DWARF register exists
+  ///                                 for MachineReg.
   bool AddMachineRegExpression(const TargetRegisterInfo &TRI,
-                               const DIExpression *Expr, unsigned MachineReg,
-                               unsigned PieceOffsetInBits = 0);
-  /// Emit a the operations remaining the DIExpressionIterator I.
-  /// \param PieceOffsetInBits If this is one piece out of a fragmented
-  /// location, this is the offset of the piece inside the entire variable.
-  void AddExpression(DIExpression::expr_op_iterator I,
-                     DIExpression::expr_op_iterator E,
-                     unsigned PieceOffsetInBits = 0);
+                               DIExpressionCursor &Expr, unsigned MachineReg,
+                               unsigned FragmentOffsetInBits = 0);
+  /// Emit all remaining operations in the DIExpressionCursor.
+  ///
+  /// \param FragmentOffsetInBits     If this is one fragment out of multiple
+  ///                                 locations, this is the offset of the
+  ///                                 fragment inside the entire variable.
+  void AddExpression(DIExpressionCursor &&Expr,
+                     unsigned FragmentOffsetInBits = 0);
+
+  /// 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);
 };
 
 /// DwarfExpression implementation for .debug_loc entries.
@@ -146,6 +225,10 @@ public:
   void EmitUnsigned(uint64_t Value) override;
   bool isFrameRegister(const TargetRegisterInfo &TRI,
                        unsigned MachineReg) override;
+  DIELoc *finalize() {
+    DwarfExpression::finalize();
+    return &DIE;
+  }
 };
 }