runtime/vm/regexp/regexp-macro-assembler.h

// Copyright 2012 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef V8_REGEXP_REGEXP_MACRO_ASSEMBLER_H_
#define V8_REGEXP_REGEXP_MACRO_ASSEMBLER_H_

#include <string_view>

#include "vm/regexp/label.h"
#include "vm/regexp/regexp-ast.h"
#include "vm/regexp/regexp.h"

namespace dart {

class ByteArray;
class JSRegExp;
class V8Label;
class String;

static const base::uc32 kLeadSurrogateStart = 0xd800;
static const base::uc32 kLeadSurrogateEnd = 0xdbff;
static const base::uc32 kTrailSurrogateStart = 0xdc00;
static const base::uc32 kTrailSurrogateEnd = 0xdfff;
static const base::uc32 kNonBmpStart = 0x10000;
static const base::uc32 kNonBmpEnd = 0x10ffff;

class RegExpMacroAssembler {
 public:
  // The implementation must be able to handle at least:
  static constexpr int kMaxRegisterCount = (1 << 16);
  static constexpr int kMaxRegister = kMaxRegisterCount - 1;
  static constexpr int kMaxCaptures = (kMaxRegister - 1) / 2;
  // Note the minimum value is chosen s.t. a negated valid offset is also a
  // valid offset.
  static constexpr int kMaxCPOffset = (1 << 15) - 1;
  static constexpr int kMinCPOffset = -kMaxCPOffset;

  static constexpr int kTableSizeBits = 7;
  static constexpr int kTableSize = 1 << kTableSizeBits;
  static constexpr int kTableMask = kTableSize - 1;

  static constexpr int kUseCharactersValue = -1;

  // Type of input string to generate code for.
  enum Mode { LATIN1 = 1, UC16 = 2 };

  RegExpMacroAssembler(Isolate* isolate, Zone* zone, Mode mode);
  RegExpMacroAssembler(const RegExpMacroAssembler& other) = default;
  virtual ~RegExpMacroAssembler() = default;

  virtual ObjectPtr GetCode(const String& source, RegExpFlags flags) = 0;

  // This function is called when code generation is aborted, so that
  // the assembler could clean up internal data structures.
  virtual void AbortedCodeGeneration() {}
  // The maximal number of pushes between stack checks. Users must supply
  // kCheckStackLimit flag to push operations (instead of kNoStackLimitCheck)
  // at least once for every stack_limit() pushes that are executed.
  int stack_limit_slack_slot_count() const;
  bool CanReadUnaligned() const;

  virtual void AdvanceCurrentPosition(int by) = 0;    // Signed cp change.
  virtual void AdvanceRegister(int reg, int by) = 0;  // r[reg] += by.
  // Continues execution from the position pushed on the top of the backtrack
  // stack by an earlier PushBacktrack(V8Label*).
  virtual void Backtrack() = 0;
  virtual void Bind(V8Label* label) = 0;
  // Dispatch after looking the current character up in a 2-bits-per-entry
  // map.  The destinations vector has up to 4 labels.
  virtual void CheckCharacter(unsigned c, V8Label* on_equal) = 0;
  // Bitwise and the current character with the given constant and then
  // check for a match with c.
  virtual void CheckCharacterAfterAnd(unsigned c,
                                      unsigned and_with,
                                      V8Label* on_equal) = 0;
  virtual void CheckCharacterGT(uint16_t limit, V8Label* on_greater) = 0;
  virtual void CheckCharacterLT(uint16_t limit, V8Label* on_less) = 0;
  virtual void CheckFixedLengthLoop(
      V8Label* on_tos_equals_current_position) = 0;
  virtual void CheckAtStart(int cp_offset, V8Label* on_at_start) = 0;
  virtual void CheckNotAtStart(int cp_offset, V8Label* on_not_at_start) = 0;
  virtual void CheckNotBackReference(int start_reg,
                                     bool read_backward,
                                     V8Label* on_no_match) = 0;
  virtual void CheckNotBackReferenceIgnoreCase(int start_reg,
                                               bool read_backward,
                                               bool unicode,
                                               V8Label* on_no_match) = 0;
  // Check the current character for a match with a literal character.  If we
  // fail to match then goto the on_failure label.  End of input always
  // matches.  If the label is nullptr then we should pop a backtrack address
  // off the stack and go to that.
  virtual void CheckNotCharacter(unsigned c, V8Label* on_not_equal) = 0;
  virtual void CheckNotCharacterAfterAnd(unsigned c,
                                         unsigned and_with,
                                         V8Label* on_not_equal) = 0;
  // Subtract a constant from the current character, then and with the given
  // constant and then check for a match with c.
  virtual void CheckNotCharacterAfterMinusAnd(uint16_t c,
                                              uint16_t minus,
                                              uint16_t and_with,
                                              V8Label* on_not_equal) = 0;
  virtual void CheckCharacterInRange(uint16_t from,
                                     uint16_t to,  // Both inclusive.
                                     V8Label* on_in_range) = 0;
  virtual void CheckCharacterNotInRange(uint16_t from,
                                        uint16_t to,  // Both inclusive.
                                        V8Label* on_not_in_range) = 0;
  // Returns true if the check was emitted, false otherwise.
  virtual bool CheckCharacterInRangeArray(
      const ZoneList<CharacterRange>* ranges,
      V8Label* on_in_range) = 0;
  virtual bool CheckCharacterNotInRangeArray(
      const ZoneList<CharacterRange>* ranges,
      V8Label* on_not_in_range) = 0;

  // The current character (modulus the kTableSize) is looked up in the byte
  // array, and if the found byte is non-zero, we jump to the on_bit_set label.
  virtual void CheckBitInTable(const TypedData& table, V8Label* on_bit_set) = 0;

  virtual void SkipUntilBitInTable(int cp_offset,
                                   const TypedData& table,
                                   const TypedData& nibble_table,
                                   int advance_by,
                                   V8Label* on_match,
                                   V8Label* on_no_match) = 0;
  virtual bool SkipUntilBitInTableUseSimd(int advance_by) { return false; }

  virtual void SkipUntilCharAnd(int cp_offset,
                                int advance_by,
                                unsigned character,
                                unsigned mask,
                                int eats_at_least,
                                V8Label* on_match,
                                V8Label* on_no_match);
  virtual void SkipUntilChar(int cp_offset,
                             int advance_by,
                             unsigned character,
                             V8Label* on_match,
                             V8Label* on_no_match);
  virtual void SkipUntilCharPosChecked(int cp_offset,
                                       int advance_by,
                                       unsigned character,
                                       int eats_at_least,
                                       V8Label* on_match,
                                       V8Label* on_no_match);
  virtual void SkipUntilCharOrChar(int cp_offset,
                                   int advance_by,
                                   unsigned char1,
                                   unsigned char2,
                                   V8Label* on_match,
                                   V8Label* on_no_match);
  virtual void SkipUntilGtOrNotBitInTable(int cp_offset,
                                          int advance_by,
                                          unsigned character,
                                          const TypedData& table,
                                          V8Label* on_match,
                                          V8Label* on_no_match);
  virtual void SkipUntilOneOfMasked(int cp_offset,
                                    int advance_by,
                                    unsigned both_chars,
                                    unsigned both_mask,
                                    int max_offset,
                                    unsigned chars1,
                                    unsigned mask1,
                                    unsigned chars2,
                                    unsigned mask2,
                                    V8Label* on_match1,
                                    V8Label* on_match2,
                                    V8Label* on_failure);
  struct SkipUntilOneOfMasked3Args {
    int bc0_cp_offset;
    int bc0_advance_by;
    TypedData* bc0_table;
    TypedData* bc0_nibble_table;
    int bc1_cp_offset;
    V8Label* bc1_on_failure;
    int bc2_cp_offset;
    unsigned bc3_characters;
    unsigned bc3_mask;
    int bc4_by;
    int bc5_cp_offset;
    unsigned bc6_characters;
    unsigned bc6_mask;
    V8Label* bc6_on_equal;
    unsigned bc7_characters;
    unsigned bc7_mask;
    V8Label* bc7_on_equal;
    unsigned bc8_characters;
    unsigned bc8_mask;
    V8Label* fallthrough_jump_target;
  };
  virtual bool SkipUntilOneOfMasked3UseSimd(
      const SkipUntilOneOfMasked3Args& args) {
    return false;
  }
  virtual void SkipUntilOneOfMasked3(const SkipUntilOneOfMasked3Args& args);

  // Checks whether the given offset from the current position is is in-bounds.
  // May overwrite the current character.
  virtual void CheckPosition(int cp_offset, V8Label* on_outside_input) = 0;
  // Check whether a special character class has custom support for more
  // optimized code.
  bool CanOptimizeSpecialClassRanges(StandardCharacterSet) const;
  // Check whether a standard/default character class matches the current
  // character.
  // May clobber the current loaded character.
  virtual void CheckSpecialClassRanges(StandardCharacterSet type,
                                       V8Label* on_no_match) = 0;

  // Control-flow integrity:
  // Define a jump target and bind a label.
  virtual void BindJumpTarget(V8Label* label) { Bind(label); }

  virtual void Fail() = 0;
  virtual void GoTo(V8Label* label) = 0;
  // Check whether a register is >= a given constant and go to a label if it
  // is.  Backtracks instead if the label is nullptr.
  virtual void IfRegisterGE(int reg, int comparand, V8Label* if_ge) = 0;
  // Check whether a register is < a given constant and go to a label if it is.
  // Backtracks instead if the label is nullptr.
  virtual void IfRegisterLT(int reg, int comparand, V8Label* if_lt) = 0;
  // Check whether a register is == to the current position and go to a
  // label if it is.
  virtual void IfRegisterEqPos(int reg, V8Label* if_eq) = 0;
  void LoadCurrentCharacter(int cp_offset,
                            V8Label* on_end_of_input,
                            bool check_bounds = true,
                            int characters = 1,
                            int eats_at_least = kUseCharactersValue);
  virtual void LoadCurrentCharacterImpl(int cp_offset,
                                        V8Label* on_end_of_input,
                                        bool check_bounds,
                                        int characters,
                                        int eats_at_least) = 0;
  virtual void PopCurrentPosition() = 0;
  virtual void PopRegister(int register_index) = 0;
  // Pushes the label on the backtrack stack, so that a following Backtrack
  // will go to this label. Always checks the backtrack stack limit.
  virtual void PushBacktrack(V8Label* label) = 0;
  virtual void PushCurrentPosition() = 0;
  enum class StackCheckFlag : uint8_t {
    kNoStackLimitCheck = false,
    kCheckStackLimit = true
  };
  virtual void PushRegister(int register_index,
                            StackCheckFlag check_stack_limit) = 0;
  virtual void ReadCurrentPositionFromRegister(int reg) = 0;
  virtual void ReadStackPointerFromRegister(int reg) = 0;
  virtual void SetCurrentPositionFromEnd(int by) = 0;
  virtual void SetRegister(int register_index, int to) = 0;
  // Return whether the matching (with a global regexp) will be restarted.
  virtual bool Succeed() = 0;
  virtual void WriteCurrentPositionToRegister(int reg, int cp_offset) = 0;
  virtual void ClearRegisters(int reg_from, int reg_to) = 0;
  virtual void WriteStackPointerToRegister(int reg) = 0;
  virtual void RecordComment(std::string_view comment) = 0;
  //\virtual MacroAssembler* masm() = 0;

  // Check that we are not in the middle of a surrogate pair.
  void CheckNotInSurrogatePair(int cp_offset, V8Label* on_failure);

#define IMPLEMENTATIONS_LIST(V)                                                \
  V(IA32)                                                                      \
  V(ARM)                                                                       \
  V(ARM64)                                                                     \
  V(MIPS)                                                                      \
  V(LOONG64)                                                                   \
  V(RISCV)                                                                     \
  V(RISCV32)                                                                   \
  V(S390)                                                                      \
  V(PPC)                                                                       \
  V(X64)                                                                       \
  V(Bytecode)

  enum IrregexpImplementation {
#define V(Name) k##Name##Implementation,
    IMPLEMENTATIONS_LIST(V)
#undef V
  };

  inline const char* ImplementationToString(IrregexpImplementation impl) {
    static const char* const kNames[] = {
#define V(Name) #Name,
        IMPLEMENTATIONS_LIST(V)
#undef V
    };
    return kNames[impl];
  }
#undef IMPLEMENTATIONS_LIST
  virtual IrregexpImplementation Implementation() = 0;

  // Compare two-byte strings case insensitively.
  //
  // Called from generated code.
  static int CaseInsensitiveCompareNonUnicode(uword byte_offset1,
                                              uword byte_offset2,
                                              size_t byte_length,
                                              Isolate* isolate);
  static int CaseInsensitiveCompareUnicode(uword byte_offset1,
                                           uword byte_offset2,
                                           size_t byte_length,
                                           Isolate* isolate);

  // `raw_byte_array` is a ByteArray containing a set of character ranges,
  // where ranges are encoded as uint16_t elements:
  //
  //  [from0, to0, from1, to1, ..., fromN, toN], or
  //  [from0, to0, from1, to1, ..., fromN]  (open-ended last interval).
  //
  // fromN is inclusive, toN is exclusive. Returns zero if not in a range,
  // non-zero otherwise.
  //
  // Called from generated code.
  static uint32_t IsCharacterInRangeArray(uint32_t current_char,
                                          uword raw_byte_array);

  // Controls the generation of large inlined constants in the code.
  virtual void set_slow_safe(bool ssc) { slow_safe_compiler_ = ssc; }
  bool slow_safe() const { return slow_safe_compiler_; }

  // Controls after how many backtracks irregexp should abort execution.  If it
  // can fall back to the experimental engine (see `set_can_fallback`), it will
  // return the appropriate error code, otherwise it will return the number of
  // matches found so far (perhaps none).
  virtual void set_backtrack_limit(uint32_t backtrack_limit) {
    backtrack_limit_ = backtrack_limit;
  }

  // Set whether or not irregexp can fall back to the experimental engine on
  // excessive backtracking.  The number of backtracks considered excessive can
  // be controlled with set_backtrack_limit.
  virtual void set_can_fallback(bool val) { can_fallback_ = val; }

  enum GlobalMode {
    NOT_GLOBAL,
    GLOBAL_NO_ZERO_LENGTH_CHECK,
    GLOBAL,
    GLOBAL_UNICODE
  };
  // Set whether the regular expression has the global flag.  Exiting due to
  // a failure in a global regexp may still mean success overall.
  inline virtual void set_global_mode(GlobalMode mode) { global_mode_ = mode; }
  inline bool global() const { return global_mode_ != NOT_GLOBAL; }
  inline bool global_with_zero_length_check() const {
    return global_mode_ == GLOBAL || global_mode_ == GLOBAL_UNICODE;
  }
  inline bool global_unicode() const { return global_mode_ == GLOBAL_UNICODE; }

  static const base::Vector<const uint8_t> word_character_map() {
    return base::ArrayVector(word_character_map_);
  }

  Isolate* isolate() const { return isolate_; }
  Zone* zone() const { return zone_; }

 protected:
  // Byte size of chars in the string to match (decided by the Mode argument).
  inline int char_size() const {
    static_assert(static_cast<int>(Mode::LATIN1) == sizeof(uint8_t));
    static_assert(static_cast<int>(Mode::UC16) == sizeof(uint16_t));
    return static_cast<int>(mode());
  }

  bool has_backtrack_limit() const;
  uint32_t backtrack_limit() const { return backtrack_limit_; }

  bool can_fallback() const { return can_fallback_; }

  // Which mode to generate code for (LATIN1 or UC16).
  Mode mode() const { return mode_; }

  static constexpr size_t kWordCharacterMapSize = 256;
  // Byte map of one byte characters with a 0xff if the character is a word
  // character (digit, letter or underscore) and 0x00 otherwise.
  // Used by generated RegExp code.
  static const uint8_t word_character_map_[kWordCharacterMapSize];

 private:
  bool slow_safe_compiler_;
  uint32_t backtrack_limit_;
  bool can_fallback_ = false;
  GlobalMode global_mode_;
  Isolate* const isolate_;
  Zone* const zone_;
  const Mode mode_;
};

class NativeRegExpMacroAssembler : public RegExpMacroAssembler {
 public:
  // Result of calling generated native RegExp code.
  // RETRY: Something significant changed during execution, and the matching
  //        should be retried from scratch.
  // EXCEPTION: Something failed during execution. If no exception has been
  //            thrown, it's an internal out-of-memory, and the caller should
  //            throw the exception.
  // FAILURE: Matching failed.
  // SUCCESS: Matching succeeded, and the output array has been filled with
  //          capture positions.
  // FALLBACK_TO_EXPERIMENTAL: Execute the regexp on this subject using the
  //                           experimental engine instead.
  enum Result {
    FAILURE = RegExpStatics::kInternalRegExpFailure,
    SUCCESS = RegExpStatics::kInternalRegExpSuccess,
    EXCEPTION = RegExpStatics::kInternalRegExpException,
    RETRY = RegExpStatics::kInternalRegExpRetry,
    FALLBACK_TO_EXPERIMENTAL =
        RegExpStatics::kInternalRegExpFallbackToExperimental,
    SMALLEST_REGEXP_RESULT = RegExpStatics::kInternalRegExpSmallestResult,
  };

  NativeRegExpMacroAssembler(Isolate* isolate, Zone* zone, Mode mode)
      : RegExpMacroAssembler(isolate, zone, mode), range_array_cache_(zone) {}
  ~NativeRegExpMacroAssembler() override = default;

  // Returns a {Result} sentinel, or the number of successful matches.
  static int Match(const Object& regexp_data,
                   const String& subject,
                   int* offsets_vector,
                   int offsets_vector_length,
                   int previous_index,
                   Isolate* isolate);

  static int ExecuteForTesting(const String& input,
                               int start_offset,
                               const uint8_t* input_start,
                               const uint8_t* input_end,
                               int* output,
                               int output_size,
                               Isolate* isolate,
                               const RegExp& regexp);

  void LoadCurrentCharacterImpl(int cp_offset,
                                V8Label* on_end_of_input,
                                bool check_bounds,
                                int characters,
                                int eats_at_least) override;
  // Load a number of characters at the given offset from the
  // current position, into the current-character register.
  virtual void LoadCurrentCharacterUnchecked(int cp_offset,
                                             int character_count) = 0;

 protected:
  TypedDataPtr GetOrAddRangeArray(const ZoneList<CharacterRange>* ranges);

 private:
  // Returns a {Result} sentinel, or the number of successful matches.
  static int Execute(const String& input,
                     int start_offset,
                     const uint8_t* input_start,
                     const uint8_t* input_end,
                     int* output,
                     int output_size,
                     Isolate* isolate,
                     const Object& regexp_data);

  ZoneUnorderedMap<uint32_t, TypedData*> range_array_cache_;
};

}  // namespace dart

#endif  // V8_REGEXP_REGEXP_MACRO_ASSEMBLER_H_