Simplify control flow in the the DWARF expression compiler
by refactoring common code into a DwarfExpressionCursor wrapper.
llvm-svn: 285827
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
index 5fff28d..89768a3 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.h
@@ -25,6 +25,51 @@
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();
+ }
+
+ /// 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;
+ }
+ operator bool() const { return 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.
@@ -77,7 +122,7 @@
bool AddMachineRegIndirect(const TargetRegisterInfo &TRI, unsigned MachineReg,
int Offset = 0);
- /// \brief Emit a partial DWARF register operation.
+ /// 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
@@ -102,19 +147,19 @@
/// 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 while consuming the prefix of a
+ /// DwarfExpression.
///
- /// \param PieceOffsetInBits If this is one piece out of a fragmented
+ /// \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.
bool AddMachineRegExpression(const TargetRegisterInfo &TRI,
- const DIExpression *Expr, unsigned MachineReg,
+ DIExpressionCursor &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
+ /// Emit all remaining operations in the DIExpressionCursor.
+ /// \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,
+ void AddExpression(DIExpressionCursor &&Expr,
unsigned PieceOffsetInBits = 0);
};