[llvm] [NFC] Separate UnwindTable from DebugFrame into a different type (PR #142521)
Igor Kudrin via llvm-commits
llvm-commits at lists.llvm.org
Sat Jul 5 00:18:52 PDT 2025
================
@@ -0,0 +1,321 @@
+//===- DWARFUnwindTable.h ----------------------------------------*- C++-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_DEBUGINFO_DWARF_DWARFUNWINDTABLE_H
+#define LLVM_DEBUGINFO_DWARF_DWARFUNWINDTABLE_H
+
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/DebugInfo/DWARF/LowLevel/DWARFCFIProgram.h"
+#include "llvm/DebugInfo/DWARF/LowLevel/DWARFExpression.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Error.h"
+#include <map>
+#include <vector>
+
+namespace llvm {
+
+namespace dwarf {
+constexpr uint32_t InvalidRegisterNumber = UINT32_MAX;
+
+/// A class that represents a location for the Call Frame Address (CFA) or a
+/// register. This is decoded from the DWARF Call Frame Information
+/// instructions and put into an UnwindRow.
+class UnwindLocation {
+public:
+ enum Location {
+ /// Not specified.
+ Unspecified,
+ /// Register is not available and can't be recovered.
+ Undefined,
+ /// Register value is in the register, nothing needs to be done to unwind
+ /// it:
+ /// reg = reg
+ Same,
+ /// Register is in or at the CFA plus an offset:
+ /// reg = CFA + offset
+ /// reg = defef(CFA + offset)
+ CFAPlusOffset,
+ /// Register or CFA is in or at a register plus offset, optionally in
+ /// an address space:
+ /// reg = reg + offset [in addrspace]
+ /// reg = deref(reg + offset [in addrspace])
+ RegPlusOffset,
+ /// Register or CFA value is in or at a value found by evaluating a DWARF
+ /// expression:
+ /// reg = eval(dwarf_expr)
+ /// reg = deref(eval(dwarf_expr))
+ DWARFExpr,
+ /// Value is a constant value contained in "Offset":
+ /// reg = Offset
+ Constant,
+ };
+
+private:
+ Location Kind; /// The type of the location that describes how to unwind it.
+ uint32_t RegNum; /// The register number for Kind == RegPlusOffset.
+ int32_t Offset; /// The offset for Kind == CFAPlusOffset or RegPlusOffset.
+ std::optional<uint32_t> AddrSpace; /// The address space for Kind ==
+ /// RegPlusOffset for CFA.
+ std::optional<DWARFExpression> Expr; /// The DWARF expression for Kind ==
+ /// DWARFExpression.
+ bool Dereference; /// If true, the resulting location must be dereferenced
+ /// after the location value is computed.
+
+ // Constructors are private to force people to use the create static
+ // functions.
+ UnwindLocation(Location K)
+ : Kind(K), RegNum(InvalidRegisterNumber), Offset(0),
+ AddrSpace(std::nullopt), Dereference(false) {}
+
+ UnwindLocation(Location K, uint32_t Reg, int32_t Off,
+ std::optional<uint32_t> AS, bool Deref)
+ : Kind(K), RegNum(Reg), Offset(Off), AddrSpace(AS), Dereference(Deref) {}
+
+ UnwindLocation(DWARFExpression E, bool Deref)
+ : Kind(DWARFExpr), RegNum(InvalidRegisterNumber), Offset(0), Expr(E),
+ Dereference(Deref) {}
+
+public:
+ /// Create a location whose rule is set to Unspecified. This means the
+ /// register value might be in the same register but it wasn't specified in
+ /// the unwind opcodes.
+ LLVM_ABI static UnwindLocation createUnspecified();
+ /// Create a location where the value is undefined and not available. This can
+ /// happen when a register is volatile and can't be recovered.
+ LLVM_ABI static UnwindLocation createUndefined();
+ /// Create a location where the value is known to be in the register itself.
+ LLVM_ABI static UnwindLocation createSame();
+ /// Create a location that is in (Deref == false) or at (Deref == true) the
+ /// CFA plus an offset. Most registers that are spilled onto the stack use
+ /// this rule. The rule for the register will use this rule and specify a
+ /// unique offset from the CFA with \a Deref set to true. This value will be
+ /// relative to a CFA value which is typically defined using the register
+ /// plus offset location. \see createRegisterPlusOffset(...) for more
+ /// information.
+ LLVM_ABI static UnwindLocation createIsCFAPlusOffset(int32_t Off);
+ LLVM_ABI static UnwindLocation createAtCFAPlusOffset(int32_t Off);
+ /// Create a location where the saved value is in (Deref == false) or at
+ /// (Deref == true) a regiser plus an offset and, optionally, in the specified
+ /// address space (used mostly for the CFA).
+ ///
+ /// The CFA is usually defined using this rule by using the stack pointer or
+ /// frame pointer as the register, with an offset that accounts for all
+ /// spilled registers and all local variables in a function, and Deref ==
+ /// false.
+ LLVM_ABI static UnwindLocation
+ createIsRegisterPlusOffset(uint32_t Reg, int32_t Off,
+ std::optional<uint32_t> AddrSpace = std::nullopt);
+ LLVM_ABI static UnwindLocation
+ createAtRegisterPlusOffset(uint32_t Reg, int32_t Off,
+ std::optional<uint32_t> AddrSpace = std::nullopt);
+ /// Create a location whose value is the result of evaluating a DWARF
+ /// expression. This allows complex expressions to be evaluated in order to
+ /// unwind a register or CFA value.
+ LLVM_ABI static UnwindLocation createIsDWARFExpression(DWARFExpression Expr);
+ LLVM_ABI static UnwindLocation createAtDWARFExpression(DWARFExpression Expr);
+ LLVM_ABI static UnwindLocation createIsConstant(int32_t Value);
+
+ Location getLocation() const { return Kind; }
+ uint32_t getRegister() const { return RegNum; }
+ int32_t getOffset() const { return Offset; }
+ bool hasAddressSpace() const {
+ if (AddrSpace)
+ return true;
+ return false;
+ }
+ uint32_t getAddressSpace() const {
+ assert(Kind == RegPlusOffset && AddrSpace);
+ return *AddrSpace;
+ }
+ int32_t getConstant() const { return Offset; }
+ bool getDereference() const { return Dereference; }
+
+ /// Some opcodes will modify the CFA location's register only, so we need
+ /// to be able to modify the CFA register when evaluating DWARF Call Frame
+ /// Information opcodes.
+ void setRegister(uint32_t NewRegNum) { RegNum = NewRegNum; }
+ /// Some opcodes will modify the CFA location's offset only, so we need
+ /// to be able to modify the CFA offset when evaluating DWARF Call Frame
+ /// Information opcodes.
+ void setOffset(int32_t NewOffset) { Offset = NewOffset; }
+ /// Some opcodes modify a constant value and we need to be able to update
+ /// the constant value (DW_CFA_GNU_window_save which is also known as
+ // DW_CFA_AARCH64_negate_ra_state).
+ void setConstant(int32_t Value) { Offset = Value; }
+
+ std::optional<DWARFExpression> getDWARFExpressionBytes() const {
+ return Expr;
+ }
+
+ LLVM_ABI bool operator==(const UnwindLocation &RHS) const;
+};
+
+/// A class that can track all registers with locations in a UnwindRow object.
+///
+/// Register locations use a map where the key is the register number and the
+/// the value is a UnwindLocation.
+///
+/// The register maps are put into a class so that all register locations can
+/// be copied when parsing the unwind opcodes DW_CFA_remember_state and
+/// DW_CFA_restore_state.
+class RegisterLocations {
+ std::map<uint32_t, UnwindLocation> Locations;
+
+public:
+ /// Return the location for the register in \a RegNum if there is a location.
+ ///
+ /// \param RegNum the register number to find a location for.
+ ///
+ /// \returns A location if one is available for \a RegNum, or std::nullopt
+ /// otherwise.
+ std::optional<UnwindLocation> getRegisterLocation(uint32_t RegNum) const {
+ auto Pos = Locations.find(RegNum);
+ if (Pos == Locations.end())
+ return std::nullopt;
+ return Pos->second;
+ }
+
+ SmallVector<uint32_t, 4> getRegisters() const {
+ SmallVector<uint32_t, 4> Registers;
+ for (auto &&[Register, _] : Locations)
+ Registers.push_back(Register);
+ return Registers;
+ }
+
+ /// Set the location for the register in \a RegNum to \a Location.
+ ///
+ /// \param RegNum the register number to set the location for.
+ ///
+ /// \param Location the UnwindLocation that describes how to unwind the value.
+ void setRegisterLocation(uint32_t RegNum, const UnwindLocation &Location) {
+ Locations.erase(RegNum);
+ Locations.insert(std::make_pair(RegNum, Location));
+ }
+
+ /// Removes any rule for the register in \a RegNum.
+ ///
+ /// \param RegNum the register number to remove the location for.
+ void removeRegisterLocation(uint32_t RegNum) { Locations.erase(RegNum); }
+
+ /// Returns true if we have any register locations in this object.
+ bool hasLocations() const { return !Locations.empty(); }
+
+ size_t size() const { return Locations.size(); }
+
+ bool operator==(const RegisterLocations &RHS) const {
+ return Locations == RHS.Locations;
+ }
+};
+
+/// A class that represents a single row in the unwind table that is decoded by
+/// parsing the DWARF Call Frame Information opcodes.
+///
+/// The row consists of an optional address, the rule to unwind the CFA and all
+/// rules to unwind any registers. If the address doesn't have a value, this
+/// row represents the initial instructions for a CIE. If the address has a
+/// value the UnwindRow represents a row in the UnwindTable for a FDE. The
+/// address is the first address for which the CFA location and register rules
+/// are valid within a function.
+///
+/// UnwindRow objects are created by parsing opcodes in the DWARF Call Frame
+/// Information and UnwindRow objects are lazily populated and pushed onto a
+/// stack in the UnwindTable when evaluating this state machine. Accessors are
+/// needed for the address, CFA value, and register locations as the opcodes
+/// encode a state machine that produces a sorted array of UnwindRow objects
+/// \see UnwindTable.
+class UnwindRow {
+ /// The address will be valid when parsing the instructions in a FDE. If
+ /// invalid, this object represents the initial instructions of a CIE.
+ std::optional<uint64_t> Address; ///< Address for row in FDE, invalid for CIE.
+ UnwindLocation CFAValue; ///< How to unwind the Call Frame Address (CFA).
+ RegisterLocations RegLocs; ///< How to unwind all registers in this list.
+
+public:
+ UnwindRow() : CFAValue(UnwindLocation::createUnspecified()) {}
+
+ /// Returns true if the address is valid in this object.
+ bool hasAddress() const { return Address.has_value(); }
+
+ /// Get the address for this row.
+ ///
+ /// Clients should only call this function after verifying it has a valid
+ /// address with a call to \see hasAddress().
+ uint64_t getAddress() const { return *Address; }
+
+ /// Set the address for this UnwindRow.
+ ///
+ /// The address represents the first address for which the CFAValue and
+ /// RegLocs are valid within a function.
+ void setAddress(uint64_t Addr) { Address = Addr; }
+
+ /// Offset the address for this UnwindRow.
+ ///
+ /// The address represents the first address for which the CFAValue and
+ /// RegLocs are valid within a function. Clients must ensure that this object
+ /// already has an address (\see hasAddress()) prior to calling this
+ /// function.
+ void slideAddress(uint64_t Offset) { *Address += Offset; }
+ UnwindLocation &getCFAValue() { return CFAValue; }
+ const UnwindLocation &getCFAValue() const { return CFAValue; }
+ RegisterLocations &getRegisterLocations() { return RegLocs; }
+ const RegisterLocations &getRegisterLocations() const { return RegLocs; }
+};
+
+/// A class that contains all UnwindRow objects for an FDE or a single unwind
+/// row for a CIE. To unwind an address the rows, which are sorted by start
+/// address, can be searched to find the UnwindRow with the lowest starting
+/// address that is greater than or equal to the address that is being looked
+/// up.
+class UnwindTable {
+public:
+ using RowContainer = std::vector<UnwindRow>;
+ using iterator = RowContainer::iterator;
+ using const_iterator = RowContainer::const_iterator;
+
+ UnwindTable(RowContainer &&Rows) : Rows(std::move(Rows)) {}
+
+ size_t size() const { return Rows.size(); }
+ iterator begin() { return Rows.begin(); }
+ const_iterator begin() const { return Rows.begin(); }
+ iterator end() { return Rows.end(); }
+ const_iterator end() const { return Rows.end(); }
+ const UnwindRow &operator[](size_t Index) const {
+ assert(Index < size());
+ return Rows[Index];
+ }
+
+private:
+ RowContainer Rows;
+};
+
+/// Parse the information in the CFIProgram and update the CurrRow object
+/// that the state machine describes.
+///
+/// This function emulates the state machine described in the DWARF Call Frame
+/// Information opcodes and will push CurrRow onto a RowContainer when needed.
+///
+/// \param CFIP the CFI program that contains the opcodes from a CIE or FDE.
+///
+/// \param CurrRow the current row to modify while parsing the state machine.
+///
+/// \param InitialLocs If non-NULL, we are parsing a FDE and this contains
+/// the initial register locations from the CIE. If NULL, then a CIE's
+/// opcodes are being parsed and this is not needed. This is used for the
+/// DW_CFA_restore and DW_CFA_restore_extended opcodes.
+///
+/// \returns An error if the DWARF Call Frame Information opcodes have state
+/// machine errors, or the accumulated rows otherwise.
+LLVM_ABI Expected<UnwindTable::RowContainer>
+parseRows(const CFIProgram &CFIP, UnwindRow &CurrRow,
+ const RegisterLocations *InitialLocs);
+
+} // end namespace dwarf
+
+} // end namespace llvm
+
+#endif
----------------
igorkudrin wrote:
Add a comment with the header guard after `#endif`
https://github.com/llvm/llvm-project/pull/142521
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