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Add a LineTable class to GSYM and test it.
This patch adds the ability to create a gsym::LineTable object, populate it, encode and decode it and test all functionality. The full format of the LineTable encoding is specified in the header file LineTable.h. Differential Revision: https://reviews.llvm.org/D66602 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@371657 91177308-0d34-0410-b5e6-96231b3b80d8
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| //===- LineTable.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 | ||
| // | ||
| //===----------------------------------------------------------------------===// | ||
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| #ifndef LLVM_DEBUGINFO_GSYM_LINETABLE_H | ||
| #define LLVM_DEBUGINFO_GSYM_LINETABLE_H | ||
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| #include "llvm/DebugInfo/GSYM/LineEntry.h" | ||
| #include "llvm/Support/Error.h" | ||
| #include <cstdint> | ||
| #include <vector> | ||
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| namespace llvm { | ||
| namespace gsym { | ||
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| struct FunctionInfo; | ||
| class FileWriter; | ||
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| /// LineTable class contains deserialized versions of line tables for each | ||
| /// function's address ranges. | ||
| /// | ||
| /// When saved to disk, the line table is encoded using a modified version of | ||
| /// the DWARF line tables that only tracks address to source file and line. | ||
| /// | ||
| /// ENCODING | ||
| /// | ||
| /// The line table starts with a small prolog that contains the following | ||
| /// values: | ||
| /// | ||
| /// ENCODING NAME DESCRIPTION | ||
| /// ======== =========== ==================================================== | ||
| /// SLEB MinDelta The min line delta for special opcodes that advance | ||
| /// the address and line number. | ||
| /// SLEB MaxDelta The max line delta for single byte opcodes that | ||
| /// advance the address and line number. | ||
| /// ULEB FirstLine The value of the first source line number to | ||
| /// initialize the LineEntry with. | ||
| /// | ||
| /// Once these prolog items are read, we initialize a LineEntry struct with | ||
| /// the start address of the function from the FunctionInfo's address range, | ||
| /// a default file index of 1, and the line number set to "FirstLine" from | ||
| /// the prolog above: | ||
| /// | ||
| /// LineEntry Row(BaseAddr, 1, FirstLine); | ||
| /// | ||
| /// The line table state machine is now initialized and ready to be parsed. | ||
| /// The stream that follows this encodes the line entries in a compact | ||
| /// form. Some opcodes cause "Row" to be modified and some opcodes may also | ||
| /// push "Row" onto the end of the "LineTable.Lines" vector. The end result | ||
| /// is a vector of LineEntry structs that is sorted in ascending address | ||
| /// order. | ||
| /// | ||
| /// NORMAL OPCODES | ||
| /// | ||
| /// The opcodes 0 through 3 are normal in opcodes. Their encoding and | ||
| /// descriptions are listed below: | ||
| /// | ||
| /// ENCODING ENUMERATION VALUE DESCRIPTION | ||
| /// ======== ================ ===== ======================================== | ||
| /// LTOC_EndSequence 0x00 Parsing is done. | ||
| /// ULEB LTOC_SetFile 0x01 Row.File = ULEB | ||
| /// ULEB LTOC_AdvancePC 0x02 Row.Addr += ULEB, push "Row". | ||
| /// SLEB LTOC_AdvanceLine 0x03 Row.Line += SLEB | ||
| /// LTOC_FirstSpecial 0x04 First special opcode (see SPECIAL | ||
| /// OPCODES below). | ||
| /// | ||
| /// SPECIAL OPCODES | ||
| /// | ||
| /// Opcodes LTOC_FirstSpecial through 255 are special opcodes that always | ||
| /// increment both the Row.Addr and Row.Line and push "Row" onto the | ||
| /// LineEntry.Lines array. They do this by using some of the bits to | ||
| /// increment/decrement the source line number, and some of the bits to | ||
| /// increment the address. Line numbers can go up or down when making line | ||
| /// tables, where addresses always only increase since line tables are sorted | ||
| /// by address. | ||
| /// | ||
| /// In order to calculate the amount to increment the line and address for | ||
| /// these special opcodes, we calculate the number of values reserved for the | ||
| /// line increment/decrement using the "MinDelta" and "MaxDelta" from the | ||
| /// prolog: | ||
| /// | ||
| /// const int64_t LineRange = MaxDelta - MinDelta + 1; | ||
| /// | ||
| /// Then we can adjust the opcode to not include any of the normal opcodes: | ||
| /// | ||
| /// const uint8_t AdjustedOp = Opcode - LTOC_FirstSpecial; | ||
| /// | ||
| /// And we can calculate the line offset, and address offset: | ||
| /// | ||
| /// const int64_t LineDelta = MinDelta + (AdjustedOp % LineRange); | ||
| /// const uint64_t AddrDelta = (AdjustedOp / LineRange); | ||
| /// | ||
| /// And use these to modify our "Row": | ||
| /// | ||
| /// Row.Line += LineDelta; | ||
| /// Row.Addr += AddrDelta; | ||
| /// | ||
| /// And push a row onto the line table: | ||
| /// | ||
| /// Lines.push_back(Row); | ||
| /// | ||
| /// This is verify similar to the way that DWARF encodes its line tables. The | ||
| /// only difference is the DWARF line tables have more normal opcodes and the | ||
| /// "Row" contains more members, like source column number, bools for end of | ||
| /// prologue, beginnging of epilogue, is statement and many others. There are | ||
| /// also more complex rules that happen for the extra normal opcodes. By | ||
| /// leaving these extra opcodes out, we leave more bits for the special | ||
| /// opcodes that allows us to encode line tables in fewer bytes than standard | ||
| /// DWARF encodings. | ||
| /// | ||
| /// Opcodes that will push "Row" onto the LineEntry.Lines include the | ||
| /// LTOC_AdvancePC opcode and all special opcodes. All other opcodes | ||
| /// only modify the current "Row", or cause the line table to end. | ||
| class LineTable { | ||
| typedef std::vector<gsym::LineEntry> Collection; | ||
| Collection Lines; ///< All line entries in the line table. | ||
| public: | ||
| static LineEntry lookup(DataExtractor &Data, uint64_t BaseAddr, | ||
| uint64_t Addr); | ||
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| /// Decode an LineTable object from a binary data stream. | ||
| /// | ||
| /// \param Data The binary stream to read the data from. This object must | ||
| /// have the data for the LineTable object starting at offset zero. The data | ||
| /// can contain more data than needed. | ||
| /// | ||
| /// \param BaseAddr The base address to use when decoding the line table. | ||
| /// This will be the FunctionInfo's start address and will be used to | ||
| /// initialize the line table row prior to parsing any opcodes. | ||
| /// | ||
| /// \returns An LineTable or an error describing the issue that was | ||
| /// encountered during decoding. | ||
| static llvm::Expected<LineTable> decode(DataExtractor &Data, | ||
| uint64_t BaseAddr); | ||
| /// Encode this LineTable object into FileWriter stream. | ||
| /// | ||
| /// \param O The binary stream to write the data to at the current file | ||
| /// position. | ||
| /// | ||
| /// \param BaseAddr The base address to use when decoding the line table. | ||
| /// This will be the FunctionInfo's start address. | ||
| /// | ||
| /// \returns An error object that indicates success or failure or the | ||
| /// encoding process. | ||
| llvm::Error encode(FileWriter &O, uint64_t BaseAddr) const; | ||
| bool empty() const { return Lines.empty(); } | ||
| void clear() { Lines.clear(); } | ||
| void push(const LineEntry &LE) { | ||
| Lines.push_back(LE); | ||
| } | ||
| size_t isValid() const { | ||
| return !Lines.empty(); | ||
| } | ||
| size_t size() const { | ||
| return Lines.size(); | ||
| } | ||
| LineEntry &get(size_t i) { | ||
| assert(i < Lines.size()); | ||
| return Lines[i]; | ||
| } | ||
| const LineEntry &get(size_t i) const { | ||
| assert(i < Lines.size()); | ||
| return Lines[i]; | ||
| } | ||
| LineEntry &operator[](size_t i) { | ||
| return get(i); | ||
| } | ||
| const LineEntry &operator[](size_t i) const { | ||
| return get(i); | ||
| } | ||
| bool operator==(const LineTable &RHS) const { | ||
| return Lines == RHS.Lines; | ||
| } | ||
| bool operator!=(const LineTable &RHS) const { | ||
| return Lines != RHS.Lines; | ||
| } | ||
| bool operator<(const LineTable &RHS) const { | ||
| const auto LHSSize = Lines.size(); | ||
| const auto RHSSize = RHS.Lines.size(); | ||
| if (LHSSize == RHSSize) | ||
| return Lines < RHS.Lines; | ||
| return LHSSize < RHSSize; | ||
| } | ||
| Collection::const_iterator begin() const { return Lines.begin(); } | ||
| Collection::const_iterator end() const { return Lines.end(); } | ||
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| }; | ||
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| raw_ostream &operator<<(raw_ostream &OS, const gsym::LineTable <); | ||
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| } // namespace gsym | ||
| } // namespace llvm | ||
|
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| #endif // #ifndef LLVM_DEBUGINFO_GSYM_LINETABLE_H |
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