include/llvm/Bitcode/BitcodeReader.h

   1 //===- llvm/Bitcode/BitcodeReader.h - Bitcode reader ------------*- C++ -*-===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This header defines interfaces to read LLVM bitcode files/streams.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #ifndef LLVM_BITCODE_BITCODEREADER_H
  14 #define LLVM_BITCODE_BITCODEREADER_H
  15
  16 #include "llvm/ADT/ArrayRef.h"
  17 #include "llvm/ADT/StringRef.h"
  18 #include "llvm/Bitstream/BitCodes.h"
  19 #include "llvm/IR/ModuleSummaryIndex.h"
  20 #include "llvm/Support/Endian.h"
  21 #include "llvm/Support/Error.h"
  22 #include "llvm/Support/ErrorOr.h"
  23 #include "llvm/Support/MemoryBuffer.h"
  24 #include <cstdint>
  25 #include <memory>
  26 #include <string>
  27 #include <system_error>
  28 #include <vector>
  29 namespace llvm {
  30
  31 class LLVMContext;
  32 class Module;
  33
  34   // These functions are for converting Expected/Error values to
  35   // ErrorOr/std::error_code for compatibility with legacy clients. FIXME:
  36   // Remove these functions once no longer needed by the C and libLTO APIs.
  37
  38   std::error_code errorToErrorCodeAndEmitErrors(LLVMContext &Ctx, Error Err);
  39
  40   template <typename T>
  41   ErrorOr<T> expectedToErrorOrAndEmitErrors(LLVMContext &Ctx, Expected<T> Val) {
  42     if (!Val)
  43       return errorToErrorCodeAndEmitErrors(Ctx, Val.takeError());
  44     return std::move(*Val);
  45   }
  46
  47   struct BitcodeFileContents;
  48
  49   /// Basic information extracted from a bitcode module to be used for LTO.
  50   struct BitcodeLTOInfo {
  51     bool IsThinLTO;
  52     bool HasSummary;
  53     bool EnableSplitLTOUnit;
  54   };
  55
  56   /// Represents a module in a bitcode file.
  57   class BitcodeModule {
  58     // This covers the identification (if present) and module blocks.
  59     ArrayRef<uint8_t> Buffer;
  60     StringRef ModuleIdentifier;
  61
  62     // The string table used to interpret this module.
  63     StringRef Strtab;
  64
  65     // The bitstream location of the IDENTIFICATION_BLOCK.
  66     uint64_t IdentificationBit;
  67
  68     // The bitstream location of this module's MODULE_BLOCK.
  69     uint64_t ModuleBit;
  70
  71     BitcodeModule(ArrayRef<uint8_t> Buffer, StringRef ModuleIdentifier,
  72                   uint64_t IdentificationBit, uint64_t ModuleBit)
  73         : Buffer(Buffer), ModuleIdentifier(ModuleIdentifier),
  74           IdentificationBit(IdentificationBit), ModuleBit(ModuleBit) {}
  75
  76     // Calls the ctor.
  77     friend Expected<BitcodeFileContents>
  78     getBitcodeFileContents(MemoryBufferRef Buffer);
  79
  80     Expected<std::unique_ptr<Module>> getModuleImpl(LLVMContext &Context,
  81                                                     bool MaterializeAll,
  82                                                     bool ShouldLazyLoadMetadata,
  83                                                     bool IsImporting);
  84
  85   public:
  86     StringRef getBuffer() const {
  87       return StringRef((const char *)Buffer.begin(), Buffer.size());
  88     }
  89
  90     StringRef getStrtab() const { return Strtab; }
  91
  92     StringRef getModuleIdentifier() const { return ModuleIdentifier; }
  93
  94     /// Read the bitcode module and prepare for lazy deserialization of function
  95     /// bodies. If ShouldLazyLoadMetadata is true, lazily load metadata as well.
  96     /// If IsImporting is true, this module is being parsed for ThinLTO
  97     /// importing into another module.
  98     Expected<std::unique_ptr<Module>> getLazyModule(LLVMContext &Context,
  99                                                     bool ShouldLazyLoadMetadata,
 100                                                     bool IsImporting);
 101
 102     /// Read the entire bitcode module and return it.
 103     Expected<std::unique_ptr<Module>> parseModule(LLVMContext &Context);
 104
 105     /// Returns information about the module to be used for LTO: whether to
 106     /// compile with ThinLTO, and whether it has a summary.
 107     Expected<BitcodeLTOInfo> getLTOInfo();
 108
 109     /// Parse the specified bitcode buffer, returning the module summary index.
 110     Expected<std::unique_ptr<ModuleSummaryIndex>> getSummary();
 111
 112     /// Parse the specified bitcode buffer and merge its module summary index
 113     /// into CombinedIndex.
 114     Error readSummary(ModuleSummaryIndex &CombinedIndex, StringRef ModulePath,
 115                       uint64_t ModuleId);
 116   };
 117
 118   struct BitcodeFileContents {
 119     std::vector<BitcodeModule> Mods;
 120     StringRef Symtab, StrtabForSymtab;
 121   };
 122
 123   /// Returns the contents of a bitcode file. This includes the raw contents of
 124   /// the symbol table embedded in the bitcode file. Clients which require a
 125   /// symbol table should prefer to use irsymtab::read instead of this function
 126   /// because it creates a reader for the irsymtab and handles upgrading bitcode
 127   /// files without a symbol table or with an old symbol table.
 128   Expected<BitcodeFileContents> getBitcodeFileContents(MemoryBufferRef Buffer);
 129
 130   /// Returns a list of modules in the specified bitcode buffer.
 131   Expected<std::vector<BitcodeModule>>
 132   getBitcodeModuleList(MemoryBufferRef Buffer);
 133
 134   /// Read the header of the specified bitcode buffer and prepare for lazy
 135   /// deserialization of function bodies. If ShouldLazyLoadMetadata is true,
 136   /// lazily load metadata as well. If IsImporting is true, this module is
 137   /// being parsed for ThinLTO importing into another module.
 138   Expected<std::unique_ptr<Module>>
 139   getLazyBitcodeModule(MemoryBufferRef Buffer, LLVMContext &Context,
 140                        bool ShouldLazyLoadMetadata = false,
 141                        bool IsImporting = false);
 142
 143   /// Like getLazyBitcodeModule, except that the module takes ownership of
 144   /// the memory buffer if successful. If successful, this moves Buffer. On
 145   /// error, this *does not* move Buffer. If IsImporting is true, this module is
 146   /// being parsed for ThinLTO importing into another module.
 147   Expected<std::unique_ptr<Module>> getOwningLazyBitcodeModule(
 148       std::unique_ptr<MemoryBuffer> &&Buffer, LLVMContext &Context,
 149       bool ShouldLazyLoadMetadata = false, bool IsImporting = false);
 150
 151   /// Read the header of the specified bitcode buffer and extract just the
 152   /// triple information. If successful, this returns a string. On error, this
 153   /// returns "".
 154   Expected<std::string> getBitcodeTargetTriple(MemoryBufferRef Buffer);
 155
 156   /// Return true if \p Buffer contains a bitcode file with ObjC code (category
 157   /// or class) in it.
 158   Expected<bool> isBitcodeContainingObjCCategory(MemoryBufferRef Buffer);
 159
 160   /// Read the header of the specified bitcode buffer and extract just the
 161   /// producer string information. If successful, this returns a string. On
 162   /// error, this returns "".
 163   Expected<std::string> getBitcodeProducerString(MemoryBufferRef Buffer);
 164
 165   /// Read the specified bitcode file, returning the module.
 166   Expected<std::unique_ptr<Module>> parseBitcodeFile(MemoryBufferRef Buffer,
 167                                                      LLVMContext &Context);
 168
 169   /// Returns LTO information for the specified bitcode file.
 170   Expected<BitcodeLTOInfo> getBitcodeLTOInfo(MemoryBufferRef Buffer);
 171
 172   /// Parse the specified bitcode buffer, returning the module summary index.
 173   Expected<std::unique_ptr<ModuleSummaryIndex>>
 174   getModuleSummaryIndex(MemoryBufferRef Buffer);
 175
 176   /// Parse the specified bitcode buffer and merge the index into CombinedIndex.
 177   Error readModuleSummaryIndex(MemoryBufferRef Buffer,
 178                                ModuleSummaryIndex &CombinedIndex,
 179                                uint64_t ModuleId);
 180
 181   /// Parse the module summary index out of an IR file and return the module
 182   /// summary index object if found, or an empty summary if not. If Path refers
 183   /// to an empty file and IgnoreEmptyThinLTOIndexFile is true, then
 184   /// this function will return nullptr.
 185   Expected<std::unique_ptr<ModuleSummaryIndex>>
 186   getModuleSummaryIndexForFile(StringRef Path,
 187                                bool IgnoreEmptyThinLTOIndexFile = false);
 188
 189   /// isBitcodeWrapper - Return true if the given bytes are the magic bytes
 190   /// for an LLVM IR bitcode wrapper.
 191   inline bool isBitcodeWrapper(const unsigned char *BufPtr,
 192                                const unsigned char *BufEnd) {
 193     // See if you can find the hidden message in the magic bytes :-).
 194     // (Hint: it's a little-endian encoding.)
 195     return BufPtr != BufEnd &&
 196            BufPtr[0] == 0xDE &&
 197            BufPtr[1] == 0xC0 &&
 198            BufPtr[2] == 0x17 &&
 199            BufPtr[3] == 0x0B;
 200   }
 201
 202   /// isRawBitcode - Return true if the given bytes are the magic bytes for
 203   /// raw LLVM IR bitcode (without a wrapper).
 204   inline bool isRawBitcode(const unsigned char *BufPtr,
 205                            const unsigned char *BufEnd) {
 206     // These bytes sort of have a hidden message, but it's not in
 207     // little-endian this time, and it's a little redundant.
 208     return BufPtr != BufEnd &&
 209            BufPtr[0] == 'B' &&
 210            BufPtr[1] == 'C' &&
 211            BufPtr[2] == 0xc0 &&
 212            BufPtr[3] == 0xde;
 213   }
 214
 215   /// isBitcode - Return true if the given bytes are the magic bytes for
 216   /// LLVM IR bitcode, either with or without a wrapper.
 217   inline bool isBitcode(const unsigned char *BufPtr,
 218                         const unsigned char *BufEnd) {
 219     return isBitcodeWrapper(BufPtr, BufEnd) ||
 220            isRawBitcode(BufPtr, BufEnd);
 221   }
 222
 223   /// SkipBitcodeWrapperHeader - Some systems wrap bc files with a special
 224   /// header for padding or other reasons.  The format of this header is:
 225   ///
 226   /// struct bc_header {
 227   ///   uint32_t Magic;         // 0x0B17C0DE
 228   ///   uint32_t Version;       // Version, currently always 0.
 229   ///   uint32_t BitcodeOffset; // Offset to traditional bitcode file.
 230   ///   uint32_t BitcodeSize;   // Size of traditional bitcode file.
 231   ///   ... potentially other gunk ...
 232   /// };
 233   ///
 234   /// This function is called when we find a file with a matching magic number.
 235   /// In this case, skip down to the subsection of the file that is actually a
 236   /// BC file.
 237   /// If 'VerifyBufferSize' is true, check that the buffer is large enough to
 238   /// contain the whole bitcode file.
 239   inline bool SkipBitcodeWrapperHeader(const unsigned char *&BufPtr,
 240                                        const unsigned char *&BufEnd,
 241                                        bool VerifyBufferSize) {
 242     // Must contain the offset and size field!
 243     if (unsigned(BufEnd - BufPtr) < BWH_SizeField + 4)
 244       return true;
 245
 246     unsigned Offset = support::endian::read32le(&BufPtr[BWH_OffsetField]);
 247     unsigned Size = support::endian::read32le(&BufPtr[BWH_SizeField]);
 248     uint64_t BitcodeOffsetEnd = (uint64_t)Offset + (uint64_t)Size;
 249
 250     // Verify that Offset+Size fits in the file.
 251     if (VerifyBufferSize && BitcodeOffsetEnd > uint64_t(BufEnd-BufPtr))
 252       return true;
 253     BufPtr += Offset;
 254     BufEnd = BufPtr+Size;
 255     return false;
 256   }
 257
 258   const std::error_category &BitcodeErrorCategory();
 259   enum class BitcodeError { CorruptedBitcode = 1 };
 260   inline std::error_code make_error_code(BitcodeError E) {
 261     return std::error_code(static_cast<int>(E), BitcodeErrorCategory());
 262   }
 263
 264 } // end namespace llvm
 265
 266 namespace std {
 267
 268 template <> struct is_error_code_enum<llvm::BitcodeError> : std::true_type {};
 269
 270 } // end namespace std
 271
 272 #endif // LLVM_BITCODE_BITCODEREADER_H