text: // 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.
  
  #if V8_TARGET_ARCH_ARM
  
  #include "src/regexp/arm/regexp-macro-assembler-arm.h"
  
  #include "src/assembler-inl.h"
  #include "src/code-stubs.h"
  #include "src/heap/factory.h"
  #include "src/log.h"
  #include "src/macro-assembler.h"
  #include "src/objects-inl.h"
  #include "src/regexp/regexp-macro-assembler.h"
  #include "src/regexp/regexp-stack.h"
  #include "src/unicode.h"
  
  namespace v8 {
  namespace internal {
  
  #ifndef V8_INTERPRETED_REGEXP
  /*
   * This assembler uses the following register assignment convention
   * - r4 : Temporarily stores the index of capture start after a matching pass
   *        for a global regexp.
   * - r5 : Pointer to current code object (Code*) including heap object tag.
   * - r6 : Current position in input, as negative offset from end of string.
   *        Please notice that this is the byte offset, not the character offset!
   * - r7 : Currently loaded character. Must be loaded using
   *        LoadCurrentCharacter before using any of the dispatch methods.
   * - r8 : Points to tip of backtrack stack
   * - r9 : Unused, might be used by C code and expected unchanged.
   * - r10 : End of input (points to byte after last character in input).
   * - r11 : Frame pointer. Used to access arguments, local variables and
   *         RegExp registers.
   * - r12 : IP register, used by assembler. Very volatile.
   * - r13/sp : Points to tip of C stack.
   *
   * The remaining registers are free for computations.
   * Each call to a public method should retain this convention.
   *
   * The stack will have the following structure:
   *  - fp[52]  Isolate* isolate   (address of the current isolate)
   *  - fp[48]  direct_call        (if 1, direct call from JavaScript code,
   *                                if 0, call through the runtime system).
   *  - fp[44]  stack_area_base    (high end of the memory area to use as
   *                                backtracking stack).
   *  - fp[40]  capture array size (may fit multiple sets of matches)
   *  - fp[36]  int* capture_array (int[num_saved_registers_], for output).
   *  --- sp when called ---
   *  - fp[32]  return address     (lr).
   *  - fp[28]  old frame pointer  (r11).
   *  - fp[0..24]  backup of registers r4..r10.
   *  --- frame pointer ----
   *  - fp[-4]  end of input       (address of end of string).
   *  - fp[-8]  start of input     (address of first character in string).
   *  - fp[-12] start index        (character index of start).
   *  - fp[-16] void* input_string (location of a handle containing the string).
   *  - fp[-20] success counter    (only for global regexps to count matches).
   *  - fp[-24] Offset of location before start of input (effectively character
   *            string start - 1). Used to initialize capture registers to a
   *            non-position.
   *  - fp[-28] At start (if 1, we are starting at the start of the
   *    string, otherwise 0)
   *  - fp[-32] register 0         (Only positions must be stored in the first
   *  -         register 1          num_saved_registers_ registers)
   *  -         ...
   *  -         register num_registers-1
   *  --- sp ---
   *
   * The first num_saved_registers_ registers are initialized to point to
   * "character -1" in the string (i.e., char_size() bytes before the first
   * character of the string). The remaining registers start out as garbage.
   *
   * The data up to the return address must be placed there by the calling
   * code and the remaining arguments are passed in registers, e.g. by calling the
   * code entry as cast to a function with the signature:
   * int (*match)(String* input_string,
   *              int start_index,
   *              Address start,
   *              Address end,
   *              int* capture_output_array,
   *              int num_capture_registers,
   *              byte* stack_area_base,
   *              bool direct_call = false,
   *              Isolate* isolate);
   * The call is performed by NativeRegExpMacroAssembler::Execute()
   * (in regexp-macro-assembler.cc) via the GeneratedCode wrapper.
   */
  
  #define __ ACCESS_MASM(masm_)
  
  RegExpMacroAssemblerARM::RegExpMacroAssemblerARM(Isolate* isolate, Zone* zone,
                                                   Mode mode,
                                                   int registers_to_save)
      : NativeRegExpMacroAssembler(isolate, zone),
        masm_(new MacroAssembler(isolate, nullptr, kRegExpCodeSize,
                                 CodeObjectRequired::kYes)),
        mode_(mode),
        num_registers_(registers_to_save),
        num_saved_registers_(registers_to_save),
        entry_label_(),
        start_label_(),
        success_label_(),
        backtrack_label_(),
        exit_label_() {
    DCHECK_EQ(0, registers_to_save % 2);
    __ jmp(&entry_label_);   // We'll write the entry code later.
    __ bind(&start_label_);  // And then continue from here.
  }
  
  
  RegExpMacroAssemblerARM::~RegExpMacroAssemblerARM() {
    delete masm_;
    // Unuse labels in case we throw away the assembler without calling GetCode.
    entry_label_.Unuse();
    start_label_.Unuse();
    success_label_.Unuse();
    backtrack_label_.Unuse();
    exit_label_.Unuse();
    check_preempt_label_.Unuse();
    stack_overflow_label_.Unuse();
  }
  
  
  int RegExpMacroAssemblerARM::stack_limit_slack()  {
    return RegExpStack::kStackLimitSlack;
  }
  
  
  void RegExpMacroAssemblerARM::AdvanceCurrentPosition(int by) {
    if (by != 0) {
      __ add(current_input_offset(),
             current_input_offset(), Operand(by * char_size()));
    }
  }
  
  
  void RegExpMacroAssemblerARM::AdvanceRegister(int reg, int by) {
    DCHECK_LE(0, reg);
    DCHECK_GT(num_registers_, reg);
    if (by != 0) {
      __ ldr(r0, register_location(reg));
      __ add(r0, r0, Operand(by));
      __ str(r0, register_location(reg));
    }
  }
  
  
  void RegExpMacroAssemblerARM::Backtrack() {
    CheckPreemption();
    // Pop Code* offset from backtrack stack, add Code* and jump to location.
    Pop(r0);
    __ add(pc, r0, Operand(code_pointer()));
  }
  
  
  void RegExpMacroAssemblerARM::Bind(Label* label) {
    __ bind(label);
  }
  
  
  void RegExpMacroAssemblerARM::CheckCharacter(uint32_t c, Label* on_equal) {
    __ cmp(current_character(), Operand(c));
    BranchOrBacktrack(eq, on_equal);
  }
  
  
  void RegExpMacroAssemblerARM::CheckCharacterGT(uc16 limit, Label* on_greater) {
    __ cmp(current_character(), Operand(limit));
    BranchOrBacktrack(gt, on_greater);
  }
  
  
  void RegExpMacroAssemblerARM::CheckAtStart(Label* on_at_start) {
    __ ldr(r1, MemOperand(frame_pointer(), kStringStartMinusOne));
    __ add(r0, current_input_offset(), Operand(-char_size()));
    __ cmp(r0, r1);
    BranchOrBacktrack(eq, on_at_start);
  }
  
  
  void RegExpMacroAssemblerARM::CheckNotAtStart(int cp_offset,
                                                Label* on_not_at_start) {
    __ ldr(r1, MemOperand(frame_pointer(), kStringStartMinusOne));
    __ add(r0, current_input_offset(),
           Operand(-char_size() + cp_offset * char_size()));
    __ cmp(r0, r1);
    BranchOrBacktrack(ne, on_not_at_start);
  }
  
  
  void RegExpMacroAssemblerARM::CheckCharacterLT(uc16 limit, Label* on_less) {
    __ cmp(current_character(), Operand(limit));
    BranchOrBacktrack(lt, on_less);
  }
  
  
  void RegExpMacroAssemblerARM::CheckGreedyLoop(Label* on_equal) {
    __ ldr(r0, MemOperand(backtrack_stackpointer(), 0));
    __ cmp(current_input_offset(), r0);
    __ add(backtrack_stackpointer(),
           backtrack_stackpointer(), Operand(kPointerSize), LeaveCC, eq);
    BranchOrBacktrack(eq, on_equal);
  }
  
  
  void RegExpMacroAssemblerARM::CheckNotBackReferenceIgnoreCase(
      int start_reg, bool read_backward, bool unicode, Label* on_no_match) {
    Label fallthrough;
    __ ldr(r0, register_location(start_reg));  // Index of start of capture
    __ ldr(r1, register_location(start_reg + 1));  // Index of end of capture
    __ sub(r1, r1, r0, SetCC);  // Length of capture.
  
    // At this point, the capture registers are either both set or both cleared.
    // If the capture length is zero, then the capture is either empty or cleared.
    // Fall through in both cases.
    __ b(eq, &fallthrough);
  
    // Check that there are enough characters left in the input.
    if (read_backward) {
      __ ldr(r3, MemOperand(frame_pointer(), kStringStartMinusOne));
      __ add(r3, r3, r1);
      __ cmp(current_input_offset(), r3);
      BranchOrBacktrack(le, on_no_match);
    } else {
      __ cmn(r1, Operand(current_input_offset()));
      BranchOrBacktrack(gt, on_no_match);
    }
  
    if (mode_ == LATIN1) {
      Label success;
      Label fail;
      Label loop_check;
  
      // r0 - offset of start of capture
      // r1 - length of capture
      __ add(r0, r0, end_of_input_address());
      __ add(r2, end_of_input_address(), current_input_offset());
      if (read_backward) {
        __ sub(r2, r2, r1);  // Offset by length when matching backwards.
      }
      __ add(r1, r0, r1);
  
      // r0 - Address of start of capture.
      // r1 - Address of end of capture
      // r2 - Address of current input position.
  
      Label loop;
      __ bind(&loop);
      __ ldrb(r3, MemOperand(r0, char_size(), PostIndex));
      __ ldrb(r4, MemOperand(r2, char_size(), PostIndex));
      __ cmp(r4, r3);
      __ b(eq, &loop_check);
  
      // Mismatch, try case-insensitive match (converting letters to lower-case).
      __ orr(r3, r3, Operand(0x20));  // Convert capture character to lower-case.
      __ orr(r4, r4, Operand(0x20));  // Also convert input character.
      __ cmp(r4, r3);
      __ b(ne, &fail);
      __ sub(r3, r3, Operand('a'));
      __ cmp(r3, Operand('z' - 'a'));  // Is r3 a lowercase letter?
      __ b(ls, &loop_check);  // In range 'a'-'z'.
      // Latin-1: Check for values in range [224,254] but not 247.
      __ sub(r3, r3, Operand(224 - 'a'));
      __ cmp(r3, Operand(254 - 224));
      __ b(hi, &fail);  // Weren't Latin-1 letters.
      __ cmp(r3, Operand(247 - 224));  // Check for 247.
      __ b(eq, &fail);
  
      __ bind(&loop_check);
      __ cmp(r0, r1);
      __ b(lt, &loop);
      __ jmp(&success);
  
      __ bind(&fail);
      BranchOrBacktrack(al, on_no_match);
  
      __ bind(&success);
      // Compute new value of character position after the matched part.
      __ sub(current_input_offset(), r2, end_of_input_address());
      if (read_backward) {
        __ ldr(r0, register_location(start_reg));  // Index of start of capture
        __ ldr(r1, register_location(start_reg + 1));  // Index of end of capture
        __ add(current_input_offset(), current_input_offset(), r0);
        __ sub(current_input_offset(), current_input_offset(), r1);
      }
    } else {
      DCHECK(mode_ == UC16);
      int argument_count = 4;
      __ PrepareCallCFunction(argument_count);
  
      // r0 - offset of start of capture
      // r1 - length of capture
  
      // Put arguments into arguments registers.
      // Parameters are
      //   r0: Address byte_offset1 - Address captured substring's start.
      //   r1: Address byte_offset2 - Address of current character position.
      //   r2: size_t byte_length - length of capture in bytes(!)
      //   r3: Isolate* isolate or 0 if unicode flag.
  
      // Address of start of capture.
      __ add(r0, r0, Operand(end_of_input_address()));
      // Length of capture.
      __ mov(r2, Operand(r1));
      // Save length in callee-save register for use on return.
      __ mov(r4, Operand(r1));
      // Address of current input position.
      __ add(r1, current_input_offset(), end_of_input_address());
      if (read_backward) {
        __ sub(r1, r1, r4);
      }
      // Isolate.
  #ifdef V8_INTL_SUPPORT
      if (unicode) {
        __ mov(r3, Operand(0));
      } else  // NOLINT
  #endif      // V8_INTL_SUPPORT
      {
        __ mov(r3, Operand(ExternalReference::isolate_address(isolate())));
      }
  
      {
        AllowExternalCallThatCantCauseGC scope(masm_);
        ExternalReference function =
            ExternalReference::re_case_insensitive_compare_uc16(isolate());
        __ CallCFunction(function, argument_count);
      }
  
      // Check if function returned non-zero for success or zero for failure.
      __ cmp(r0, Operand::Zero());
      BranchOrBacktrack(eq, on_no_match);
  
      // On success, advance position by length of capture.
      if (read_backward) {
        __ sub(current_input_offset(), current_input_offset(), r4);
      } else {
        __ add(current_input_offset(), current_input_offset(), r4);
      }
    }
  
    __ bind(&fallthrough);
  }
  
  
  void RegExpMacroAssemblerARM::CheckNotBackReference(int start_reg,
                                                      bool read_backward,
                                                      Label* on_no_match) {
    Label fallthrough;
    Label success;
  
    // Find length of back-referenced capture.
    __ ldr(r0, register_location(start_reg));
    __ ldr(r1, register_location(start_reg + 1));
    __ sub(r1, r1, r0, SetCC);  // Length to check.
  
    // At this point, the capture registers are either both set or both cleared.
    // If the capture length is zero, then the capture is either empty or cleared.
    // Fall through in both cases.
    __ b(eq, &fallthrough);
  
    // Check that there are enough characters left in the input.
    if (read_backward) {
      __ ldr(r3, MemOperand(frame_pointer(), kStringStartMinusOne));
      __ add(r3, r3, r1);
      __ cmp(current_input_offset(), r3);
      BranchOrBacktrack(le, on_no_match);
    } else {
      __ cmn(r1, Operand(current_input_offset()));
      BranchOrBacktrack(gt, on_no_match);
    }
  
    // r0 - offset of start of capture
    // r1 - length of capture
    __ add(r0, r0, end_of_input_address());
    __ add(r2, end_of_input_address(), current_input_offset());
    if (read_backward) {
      __ sub(r2, r2, r1);  // Offset by length when matching backwards.
    }
    __ add(r1, r0, r1);
  
    Label loop;
    __ bind(&loop);
    if (mode_ == LATIN1) {
      __ ldrb(r3, MemOperand(r0, char_size(), PostIndex));
      __ ldrb(r4, MemOperand(r2, char_size(), PostIndex));
    } else {
      DCHECK(mode_ == UC16);
      __ ldrh(r3, MemOperand(r0, char_size(), PostIndex));
      __ ldrh(r4, MemOperand(r2, char_size(), PostIndex));
    }
    __ cmp(r3, r4);
    BranchOrBacktrack(ne, on_no_match);
    __ cmp(r0, r1);
    __ b(lt, &loop);
  
    // Move current character position to position after match.
    __ sub(current_input_offset(), r2, end_of_input_address());
    if (read_backward) {
      __ ldr(r0, register_location(start_reg));      // Index of start of capture
      __ ldr(r1, register_location(start_reg + 1));  // Index of end of capture
      __ add(current_input_offset(), current_input_offset(), r0);
      __ sub(current_input_offset(), current_input_offset(), r1);
    }
  
    __ bind(&fallthrough);
  }
  
  
  void RegExpMacroAssemblerARM::CheckNotCharacter(unsigned c,
                                                  Label* on_not_equal) {
    __ cmp(current_character(), Operand(c));
    BranchOrBacktrack(ne, on_not_equal);
  }
  
  
  void RegExpMacroAssemblerARM::CheckCharacterAfterAnd(uint32_t c,
                                                       uint32_t mask,
                                                       Label* on_equal) {
    if (c == 0) {
      __ tst(current_character(), Operand(mask));
    } else {
      __ and_(r0, current_character(), Operand(mask));
      __ cmp(r0, Operand(c));
    }
    BranchOrBacktrack(eq, on_equal);
  }
  
  
  void RegExpMacroAssemblerARM::CheckNotCharacterAfterAnd(unsigned c,
                                                          unsigned mask,
                                                          Label* on_not_equal) {
    if (c == 0) {
      __ tst(current_character(), Operand(mask));
    } else {
      __ and_(r0, current_character(), Operand(mask));
      __ cmp(r0, Operand(c));
    }
    BranchOrBacktrack(ne, on_not_equal);
  }
  
  
  void RegExpMacroAssemblerARM::CheckNotCharacterAfterMinusAnd(
      uc16 c,
      uc16 minus,
      uc16 mask,
      Label* on_not_equal) {
    DCHECK_GT(String::kMaxUtf16CodeUnit, minus);
    __ sub(r0, current_character(), Operand(minus));
    __ and_(r0, r0, Operand(mask));
    __ cmp(r0, Operand(c));
    BranchOrBacktrack(ne, on_not_equal);
  }
  
  
  void RegExpMacroAssemblerARM::CheckCharacterInRange(
      uc16 from,
      uc16 to,
      Label* on_in_range) {
    __ sub(r0, current_character(), Operand(from));
    __ cmp(r0, Operand(to - from));
    BranchOrBacktrack(ls, on_in_range);  // Unsigned lower-or-same condition.
  }
  
  
  void RegExpMacroAssemblerARM::CheckCharacterNotInRange(
      uc16 from,
      uc16 to,
      Label* on_not_in_range) {
    __ sub(r0, current_character(), Operand(from));
    __ cmp(r0, Operand(to - from));
    BranchOrBacktrack(hi, on_not_in_range);  // Unsigned higher condition.
  }
  
  
  void RegExpMacroAssemblerARM::CheckBitInTable(
      Handle<ByteArray> table,
      Label* on_bit_set) {
    __ mov(r0, Operand(table));
    if (mode_ != LATIN1 || kTableMask != String::kMaxOneByteCharCode) {
      __ and_(r1, current_character(), Operand(kTableSize - 1));
      __ add(r1, r1, Operand(ByteArray::kHeaderSize - kHeapObjectTag));
    } else {
      __ add(r1,
             current_character(),
             Operand(ByteArray::kHeaderSize - kHeapObjectTag));
    }
    __ ldrb(r0, MemOperand(r0, r1));
    __ cmp(r0, Operand::Zero());
    BranchOrBacktrack(ne, on_bit_set);
  }
  
  
  bool RegExpMacroAssemblerARM::CheckSpecialCharacterClass(uc16 type,
                                                           Label* on_no_match) {
    // Range checks (c in min..max) are generally implemented by an unsigned
    // (c - min) <= (max - min) check
    switch (type) {
    case 's':
      // Match space-characters
      if (mode_ == LATIN1) {
        // One byte space characters are '\t'..'\r', ' ' and \u00a0.
        Label success;
        __ cmp(current_character(), Operand(' '));
        __ b(eq, &success);
        // Check range 0x09..0x0D
        __ sub(r0, current_character(), Operand('\t'));
        __ cmp(r0, Operand('\r' - '\t'));
        __ b(ls, &success);
        // \u00a0 (NBSP).
        __ cmp(r0, Operand(0x00A0 - '\t'));
        BranchOrBacktrack(ne, on_no_match);
        __ bind(&success);
        return true;
      }
      return false;
    case 'S':
      // The emitted code for generic character classes is good enough.
      return false;
    case 'd':
      // Match ASCII digits ('0'..'9')
      __ sub(r0, current_character(), Operand('0'));
      __ cmp(r0, Operand('9' - '0'));
      BranchOrBacktrack(hi, on_no_match);
      return true;
    case 'D':
      // Match non ASCII-digits
      __ sub(r0, current_character(), Operand('0'));
      __ cmp(r0, Operand('9' - '0'));
      BranchOrBacktrack(ls, on_no_match);
      return true;
    case '.': {
      // Match non-newlines (not 0x0A('\n'), 0x0D('\r'), 0x2028 and 0x2029)
      __ eor(r0, current_character(), Operand(0x01));
      // See if current character is '\n'^1 or '\r'^1, i.e., 0x0B or 0x0C
      __ sub(r0, r0, Operand(0x0B));
      __ cmp(r0, Operand(0x0C - 0x0B));
      BranchOrBacktrack(ls, on_no_match);
      if (mode_ == UC16) {
        // Compare original value to 0x2028 and 0x2029, using the already
        // computed (current_char ^ 0x01 - 0x0B). I.e., check for
        // 0x201D (0x2028 - 0x0B) or 0x201E.
        __ sub(r0, r0, Operand(0x2028 - 0x0B));
        __ cmp(r0, Operand(1));
        BranchOrBacktrack(ls, on_no_match);
      }
      return true;
    }
    case 'n': {
      // Match newlines (0x0A('\n'), 0x0D('\r'), 0x2028 and 0x2029)
      __ eor(r0, current_character(), Operand(0x01));
      // See if current character is '\n'^1 or '\r'^1, i.e., 0x0B or 0x0C
      __ sub(r0, r0, Operand(0x0B));
      __ cmp(r0, Operand(0x0C - 0x0B));
      if (mode_ == LATIN1) {
        BranchOrBacktrack(hi, on_no_match);
      } else {
        Label done;
        __ b(ls, &done);
        // Compare original value to 0x2028 and 0x2029, using the already
        // computed (current_char ^ 0x01 - 0x0B). I.e., check for
        // 0x201D (0x2028 - 0x0B) or 0x201E.
        __ sub(r0, r0, Operand(0x2028 - 0x0B));
        __ cmp(r0, Operand(1));
        BranchOrBacktrack(hi, on_no_match);
        __ bind(&done);
      }
      return true;
    }
    case 'w': {
      if (mode_ != LATIN1) {
        // Table is 256 entries, so all Latin1 characters can be tested.
        __ cmp(current_character(), Operand('z'));
        BranchOrBacktrack(hi, on_no_match);
      }
      ExternalReference map = ExternalReference::re_word_character_map(isolate());
      __ mov(r0, Operand(map));
      __ ldrb(r0, MemOperand(r0, current_character()));
      __ cmp(r0, Operand::Zero());
      BranchOrBacktrack(eq, on_no_match);
      return true;
    }
    case 'W': {
      Label done;
      if (mode_ != LATIN1) {
        // Table is 256 entries, so all Latin1 characters can be tested.
        __ cmp(current_character(), Operand('z'));
        __ b(hi, &done);
      }
      ExternalReference map = ExternalReference::re_word_character_map(isolate());
      __ mov(r0, Operand(map));
      __ ldrb(r0, MemOperand(r0, current_character()));
      __ cmp(r0, Operand::Zero());
      BranchOrBacktrack(ne, on_no_match);
      if (mode_ != LATIN1) {
        __ bind(&done);
      }
      return true;
    }
    case '*':
      // Match any character.
      return true;
    // No custom implementation (yet): s(UC16), S(UC16).
    default:
      return false;
    }
  }
  
  
  void RegExpMacroAssemblerARM::Fail() {
    __ mov(r0, Operand(FAILURE));
    __ jmp(&exit_label_);
  }
  
  
  Handle<HeapObject> RegExpMacroAssemblerARM::GetCode(Handle<String> source) {
    Label return_r0;
    // Finalize code - write the entry point code now we know how many
    // registers we need.
  
    // Entry code:
    __ bind(&entry_label_);
  
    // Tell the system that we have a stack frame.  Because the type is MANUAL, no
    // is generated.
    FrameScope scope(masm_, StackFrame::MANUAL);
  
    // Actually emit code to start a new stack frame.
    // Push arguments
    // Save callee-save registers.
    // Start new stack frame.
    // Store link register in existing stack-cell.
    // Order here should correspond to order of offset constants in header file.
    RegList registers_to_retain = r4.bit() | r5.bit() | r6.bit() |
        r7.bit() | r8.bit() | r9.bit() | r10.bit() | fp.bit();
    RegList argument_registers = r0.bit() | r1.bit() | r2.bit() | r3.bit();
    __ stm(db_w, sp, argument_registers | registers_to_retain | lr.bit());
    // Set frame pointer in space for it if this is not a direct call
    // from generated code.
    __ add(frame_pointer(), sp, Operand(4 * kPointerSize));
    __ mov(r0, Operand::Zero());
    __ push(r0);  // Make room for success counter and initialize it to 0.
    __ push(r0);  // Make room for "string start - 1" constant.
    // Check if we have space on the stack for registers.
    Label stack_limit_hit;
    Label stack_ok;
  
    ExternalReference stack_limit =
        ExternalReference::address_of_stack_limit(isolate());
    __ mov(r0, Operand(stack_limit));
    __ ldr(r0, MemOperand(r0));
    __ sub(r0, sp, r0, SetCC);
    // Handle it if the stack pointer is already below the stack limit.
    __ b(ls, &stack_limit_hit);
    // Check if there is room for the variable number of registers above
    // the stack limit.
    __ cmp(r0, Operand(num_registers_ * kPointerSize));
    __ b(hs, &stack_ok);
    // Exit with OutOfMemory exception. There is not enough space on the stack
    // for our working registers.
    __ mov(r0, Operand(EXCEPTION));
    __ jmp(&return_r0);
  
    __ bind(&stack_limit_hit);
    CallCheckStackGuardState();
    __ cmp(r0, Operand::Zero());
    // If returned value is non-zero, we exit with the returned value as result.
    __ b(ne, &return_r0);
  
    __ bind(&stack_ok);
  
    // Allocate space on stack for registers.
    __ sub(sp, sp, Operand(num_registers_ * kPointerSize));
    // Load string end.
    __ ldr(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
    // Load input start.
    __ ldr(r0, MemOperand(frame_pointer(), kInputStart));
    // Find negative length (offset of start relative to end).
    __ sub(current_input_offset(), r0, end_of_input_address());
    // Set r0 to address of char before start of the input string
    // (effectively string position -1).
    __ ldr(r1, MemOperand(frame_pointer(), kStartIndex));
    __ sub(r0, current_input_offset(), Operand(char_size()));
    __ sub(r0, r0, Operand(r1, LSL, (mode_ == UC16) ? 1 : 0));
    // Store this value in a local variable, for use when clearing
    // position registers.
    __ str(r0, MemOperand(frame_pointer(), kStringStartMinusOne));
  
    // Initialize code pointer register
    __ mov(code_pointer(), Operand(masm_->CodeObject()));
  
    Label load_char_start_regexp, start_regexp;
    // Load newline if index is at start, previous character otherwise.
    __ cmp(r1, Operand::Zero());
    __ b(ne, &load_char_start_regexp);
    __ mov(current_character(), Operand('\n'), LeaveCC, eq);
    __ jmp(&start_regexp);
  
    // Global regexp restarts matching here.
    __ bind(&load_char_start_regexp);
    // Load previous char as initial value of current character register.
    LoadCurrentCharacterUnchecked(-1, 1);
    __ bind(&start_regexp);
  
    // Initialize on-stack registers.
    if (num_saved_registers_ > 0) {  // Always is, if generated from a regexp.
      // Fill saved registers with initial value = start offset - 1
      if (num_saved_registers_ > 8) {
        // Address of register 0.
        __ add(r1, frame_pointer(), Operand(kRegisterZero));
        __ mov(r2, Operand(num_saved_registers_));
        Label init_loop;
        __ bind(&init_loop);
        __ str(r0, MemOperand(r1, kPointerSize, NegPostIndex));
        __ sub(r2, r2, Operand(1), SetCC);
        __ b(ne, &init_loop);
      } else {
        for (int i = 0; i < num_saved_registers_; i++) {
          __ str(r0, register_location(i));
        }
      }
    }
  
    // Initialize backtrack stack pointer.
    __ ldr(backtrack_stackpointer(), MemOperand(frame_pointer(), kStackHighEnd));
  
    __ jmp(&start_label_);
  
    // Exit code:
    if (success_label_.is_linked()) {
      // Save captures when successful.
      __ bind(&success_label_);
      if (num_saved_registers_ > 0) {
        // copy captures to output
        __ ldr(r1, MemOperand(frame_pointer(), kInputStart));
        __ ldr(r0, MemOperand(frame_pointer(), kRegisterOutput));
        __ ldr(r2, MemOperand(frame_pointer(), kStartIndex));
        __ sub(r1, end_of_input_address(), r1);
        // r1 is length of input in bytes.
        if (mode_ == UC16) {
          __ mov(r1, Operand(r1, LSR, 1));
        }
        // r1 is length of input in characters.
        __ add(r1, r1, Operand(r2));
        // r1 is length of string in characters.
  
        DCHECK_EQ(0, num_saved_registers_ % 2);
        // Always an even number of capture registers. This allows us to
        // unroll the loop once to add an operation between a load of a register
        // and the following use of that register.
        for (int i = 0; i < num_saved_registers_; i += 2) {
          __ ldr(r2, register_location(i));
          __ ldr(r3, register_location(i + 1));
          if (i == 0 && global_with_zero_length_check()) {
            // Keep capture start in r4 for the zero-length check later.
            __ mov(r4, r2);
          }
          if (mode_ == UC16) {
            __ add(r2, r1, Operand(r2, ASR, 1));
            __ add(r3, r1, Operand(r3, ASR, 1));
          } else {
            __ add(r2, r1, Operand(r2));
            __ add(r3, r1, Operand(r3));
          }
          __ str(r2, MemOperand(r0, kPointerSize, PostIndex));
          __ str(r3, MemOperand(r0, kPointerSize, PostIndex));
        }
      }
  
      if (global()) {
        // Restart matching if the regular expression is flagged as global.
        __ ldr(r0, MemOperand(frame_pointer(), kSuccessfulCaptures));
        __ ldr(r1, MemOperand(frame_pointer(), kNumOutputRegisters));
        __ ldr(r2, MemOperand(frame_pointer(), kRegisterOutput));
        // Increment success counter.
        __ add(r0, r0, Operand(1));
        __ str(r0, MemOperand(frame_pointer(), kSuccessfulCaptures));
        // Capture results have been stored, so the number of remaining global
        // output registers is reduced by the number of stored captures.
        __ sub(r1, r1, Operand(num_saved_registers_));
        // Check whether we have enough room for another set of capture results.
        __ cmp(r1, Operand(num_saved_registers_));
        __ b(lt, &return_r0);
  
        __ str(r1, MemOperand(frame_pointer(), kNumOutputRegisters));
        // Advance the location for output.
        __ add(r2, r2, Operand(num_saved_registers_ * kPointerSize));
        __ str(r2, MemOperand(frame_pointer(), kRegisterOutput));
  
        // Prepare r0 to initialize registers with its value in the next run.
        __ ldr(r0, MemOperand(frame_pointer(), kStringStartMinusOne));
  
        if (global_with_zero_length_check()) {
          // Special case for zero-length matches.
          // r4: capture start index
          __ cmp(current_input_offset(), r4);
          // Not a zero-length match, restart.
          __ b(ne, &load_char_start_regexp);
          // Offset from the end is zero if we already reached the end.
          __ cmp(current_input_offset(), Operand::Zero());
          __ b(eq, &exit_label_);
          // Advance current position after a zero-length match.
          Label advance;
          __ bind(&advance);
          __ add(current_input_offset(),
                 current_input_offset(),
                 Operand((mode_ == UC16) ? 2 : 1));
          if (global_unicode()) CheckNotInSurrogatePair(0, &advance);
        }
  
        __ b(&load_char_start_regexp);
      } else {
        __ mov(r0, Operand(SUCCESS));
      }
    }
  
    // Exit and return r0
    __ bind(&exit_label_);
    if (global()) {
      __ ldr(r0, MemOperand(frame_pointer(), kSuccessfulCaptures));
    }
  
    __ bind(&return_r0);
    // Skip sp past regexp registers and local variables..
    __ mov(sp, frame_pointer());
    // Restore registers r4..r11 and return (restoring lr to pc).
    __ ldm(ia_w, sp, registers_to_retain | pc.bit());
  
    // Backtrack code (branch target for conditional backtracks).
    if (backtrack_label_.is_linked()) {
      __ bind(&backtrack_label_);
      Backtrack();
    }
  
    Label exit_with_exception;
  
    // Preempt-code
    if (check_preempt_label_.is_linked()) {
      SafeCallTarget(&check_preempt_label_);
  
      CallCheckStackGuardState();
      __ cmp(r0, Operand::Zero());
      // If returning non-zero, we should end execution with the given
      // result as return value.
      __ b(ne, &return_r0);
  
      // String might have moved: Reload end of string from frame.
      __ ldr(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
      SafeReturn();
    }
  
    // Backtrack stack overflow code.
    if (stack_overflow_label_.is_linked()) {
      SafeCallTarget(&stack_overflow_label_);
      // Reached if the backtrack-stack limit has been hit.
      Label grow_failed;
  
      // Call GrowStack(backtrack_stackpointer(), &stack_base)
      static const int num_arguments = 3;
      __ PrepareCallCFunction(num_arguments);
      __ mov(r0, backtrack_stackpointer());
      __ add(r1, frame_pointer(), Operand(kStackHighEnd));
      __ mov(r2, Operand(ExternalReference::isolate_address(isolate())));
      ExternalReference grow_stack =
          ExternalReference::re_grow_stack(isolate());
      __ CallCFunction(grow_stack, num_arguments);
      // If return nullptr, we have failed to grow the stack, and
      // must exit with a stack-overflow exception.
      __ cmp(r0, Operand::Zero());
      __ b(eq, &exit_with_exception);
      // Otherwise use return value as new stack pointer.
      __ mov(backtrack_stackpointer(), r0);
      // Restore saved registers and continue.
      SafeReturn();
    }
  
    if (exit_with_exception.is_linked()) {
      // If any of the code above needed to exit with an exception.
      __ bind(&exit_with_exception);
      // Exit with Result EXCEPTION(-1) to signal thrown exception.
      __ mov(r0, Operand(EXCEPTION));
      __ jmp(&return_r0);
    }
  
    CodeDesc code_desc;
    masm_->GetCode(isolate(), &code_desc);
    Handle<Code> code = isolate()->factory()->NewCode(code_desc, Code::REGEXP,
                                                      masm_->CodeObject());
    PROFILE(masm_->isolate(),
            RegExpCodeCreateEvent(AbstractCode::cast(*code), *source));
    return Handle<HeapObject>::cast(code);
  }
  
  
  void RegExpMacroAssemblerARM::GoTo(Label* to) {
    BranchOrBacktrack(al, to);
  }
  
  
  void RegExpMacroAssemblerARM::IfRegisterGE(int reg,
                                             int comparand,
                                             Label* if_ge) {
    __ ldr(r0, register_location(reg));
    __ cmp(r0, Operand(comparand));
    BranchOrBacktrack(ge, if_ge);
  }
  
  
  void RegExpMacroAssemblerARM::IfRegisterLT(int reg,
                                             int comparand,
                                             Label* if_lt) {
    __ ldr(r0, register_location(reg));
    __ cmp(r0, Operand(comparand));
    BranchOrBacktrack(lt, if_lt);
  }
  
  
  void RegExpMacroAssemblerARM::IfRegisterEqPos(int reg,
                                                Label* if_eq) {
    __ ldr(r0, register_location(reg));
    __ cmp(r0, Operand(current_input_offset()));
    BranchOrBacktrack(eq, if_eq);
  }
  
  
  RegExpMacroAssembler::IrregexpImplementation
      RegExpMacroAssemblerARM::Implementation() {
    return kARMImplementation;
  }
  
  
  void RegExpMacroAssemblerARM::LoadCurrentCharacter(int cp_offset,
                                                     Label* on_end_of_input,
                                                     bool check_bounds,
                                                     int characters) {
    DCHECK(cp_offset < (1<<30));  // Be sane! (And ensure negation works)
    if (check_bounds) {
      if (cp_offset >= 0) {
        CheckPosition(cp_offset + characters - 1, on_end_of_input);
      } else {
        CheckPosition(cp_offset, on_end_of_input);
      }
    }
    LoadCurrentCharacterUnchecked(cp_offset, characters);
  }
  
  
  void RegExpMacroAssemblerARM::PopCurrentPosition() {
    Pop(current_input_offset());
  }
  
  
  void RegExpMacroAssemblerARM::PopRegister(int register_index) {
    Pop(r0);
    __ str(r0, register_location(register_index));
  }
  
  
  void RegExpMacroAssemblerARM::PushBacktrack(Label* label) {
    __ mov_label_offset(r0, label);
    Push(r0);
    CheckStackLimit();
  }
  
  
  void RegExpMacroAssemblerARM::PushCurrentPosition() {
    Push(current_input_offset());
  }
  
  
  void RegExpMacroAssemblerARM::PushRegister(int register_index,
                                             StackCheckFlag check_stack_limit) {
    __ ldr(r0, register_location(register_index));
    Push(r0);
    if (check_stack_limit) CheckStackLimit();
  }
  
  
  void RegExpMacroAssemblerARM::ReadCurrentPositionFromRegister(int reg) {
    __ ldr(current_input_offset(), register_location(reg));
  }
  
  
  void RegExpMacroAssemblerARM::ReadStackPointerFromRegister(int reg) {
    __ ldr(backtrack_stackpointer(), register_location(reg));
    __ ldr(r0, MemOperand(frame_pointer(), kStackHighEnd));
    __ add(backtrack_stackpointer(), backtrack_stackpointer(), Operand(r0));
  }
  
  
  void RegExpMacroAssemblerARM::SetCurrentPositionFromEnd(int by) {
    Label after_position;
    __ cmp(current_input_offset(), Operand(-by * char_size()));
    __ b(ge, &after_position);
    __ mov(current_input_offset(), Operand(-by * char_size()));
    // On RegExp code entry (where this operation is used), the character before
    // the current position is expected to be already loaded.
    // We have advanced the position, so it's safe to read backwards.
    LoadCurrentCharacterUnchecked(-1, 1);
    __ bind(&after_position);
  }
  
  
  void RegExpMacroAssemblerARM::SetRegister(int register_index, int to) {
    DCHECK(register_index >= num_saved_registers_);  // Reserved for positions!
    __ mov(r0, Operand(to));
    __ str(r0, register_location(register_index));
  }
  
  
  bool RegExpMacroAssemblerARM::Succeed() {
    __ jmp(&success_label_);
    return global();
  }
  
  
  void RegExpMacroAssemblerARM::WriteCurrentPositionToRegister(int reg,
                                                               int cp_offset) {
    if (cp_offset == 0) {
      __ str(current_input_offset(), register_location(reg));
    } else {
      __ add(r0, current_input_offset(), Operand(cp_offset * char_size()));
      __ str(r0, register_location(reg));
    }
  }
  
  
  void RegExpMacroAssemblerARM::ClearRegisters(int reg_from, int reg_to) {
    DCHECK(reg_from <= reg_to);
    __ ldr(r0, MemOperand(frame_pointer(), kStringStartMinusOne));
    for (int reg = reg_from; reg <= reg_to; reg++) {
      __ str(r0, register_location(reg));
    }
  }
  
  
  void RegExpMacroAssemblerARM::WriteStackPointerToRegister(int reg) {
    __ ldr(r1, MemOperand(frame_pointer(), kStackHighEnd));
    __ sub(r0, backtrack_stackpointer(), r1);
    __ str(r0, register_location(reg));
  }
  
  
  // Private methods:
  
  void RegExpMacroAssemblerARM::CallCheckStackGuardState() {
    __ PrepareCallCFunction(3);
  
    // RegExp code frame pointer.
    __ mov(r2, frame_pointer());
    // Code* of self.
    __ mov(r1, Operand(masm_->CodeObject()));
  
    // We need to make room for the return address on the stack.
    int stack_alignment = base::OS::ActivationFrameAlignment();
    DCHECK(IsAligned(stack_alignment, kPointerSize));
    __ sub(sp, sp, Operand(stack_alignment));
  
    // r0 will point to the return address, placed by DirectCEntry.
    __ mov(r0, sp);
  
    ExternalReference stack_guard_check =
        ExternalReference::re_check_stack_guard_state(isolate());
    __ mov(ip, Operand(stack_guard_check));
    DirectCEntryStub stub(isolate());
    stub.GenerateCall(masm_, ip);
  
    // Drop the return address from the stack.
    __ add(sp, sp, Operand(stack_alignment));
  
    DCHECK_NE(0, stack_alignment);
    __ ldr(sp, MemOperand(sp, 0));
  
    __ mov(code_pointer(), Operand(masm_->CodeObject()));
  }
  
  
  // Helper function for reading a value out of a stack frame.
  template <typename T>
  static T& frame_entry(Address re_frame, int frame_offset) {
    return reinterpret_cast<T&>(Memory::int32_at(re_frame + frame_offset));
  }
  
  
  template <typename T>
  static T* frame_entry_address(Address re_frame, int frame_offset) {
    return reinterpret_cast<T*>(re_frame + frame_offset);
  }
  
  
  int RegExpMacroAssemblerARM::CheckStackGuardState(Address* return_address,
                                                    Code* re_code,
                                                    Address re_frame) {
    return NativeRegExpMacroAssembler::CheckStackGuardState(
        frame_entry<Isolate*>(re_frame, kIsolate),
        frame_entry<int>(re_frame, kStartIndex),
        frame_entry<int>(re_frame, kDirectCall) == 1, return_address, re_code,
        frame_entry_address<String*>(re_frame, kInputString),
        frame_entry_address<const byte*>(re_frame, kInputStart),
        frame_entry_address<const byte*>(re_frame, kInputEnd));
  }
  
  
  MemOperand RegExpMacroAssemblerARM::register_location(int register_index) {
    DCHECK(register_index < (1<<30));
    if (num_registers_ <= register_index) {
      num_registers_ = register_index + 1;
    }
    return MemOperand(frame_pointer(),
                      kRegisterZero - register_index * kPointerSize);
  }
  
  
  void RegExpMacroAssemblerARM::CheckPosition(int cp_offset,
                                              Label* on_outside_input) {
    if (cp_offset >= 0) {
      __ cmp(current_input_offset(), Operand(-cp_offset * char_size()));
      BranchOrBacktrack(ge, on_outside_input);
    } else {
      __ ldr(r1, MemOperand(frame_pointer(), kStringStartMinusOne));
      __ add(r0, current_input_offset(), Operand(cp_offset * char_size()));
      __ cmp(r0, r1);
      BranchOrBacktrack(le, on_outside_input);
    }
  }
  
  
  void RegExpMacroAssemblerARM::BranchOrBacktrack(Condition condition,
                                                  Label* to) {
    if (condition == al) {  // Unconditional.
      if (to == nullptr) {
        Backtrack();
        return;
      }
      __ jmp(to);
      return;
    }
    if (to == nullptr) {
      __ b(condition, &backtrack_label_);
      return;
    }
    __ b(condition, to);
  }
  
  
  void RegExpMacroAssemblerARM::SafeCall(Label* to, Condition cond) {
    __ bl(to, cond);
  }
  
  
  void RegExpMacroAssemblerARM::SafeReturn() {
    __ pop(lr);
    __ add(pc, lr, Operand(masm_->CodeObject()));
  }
  
  
  void RegExpMacroAssemblerARM::SafeCallTarget(Label* name) {
    __ bind(name);
    __ sub(lr, lr, Operand(masm_->CodeObject()));
    __ push(lr);
  }
  
  
  void RegExpMacroAssemblerARM::Push(Register source) {
    DCHECK(source != backtrack_stackpointer());
    __ str(source,
           MemOperand(backtrack_stackpointer(), kPointerSize, NegPreIndex));
  }
  
  
  void RegExpMacroAssemblerARM::Pop(Register target) {
    DCHECK(target != backtrack_stackpointer());
    __ ldr(target,
           MemOperand(backtrack_stackpointer(), kPointerSize, PostIndex));
  }
  
  
  void RegExpMacroAssemblerARM::CheckPreemption() {
    // Check for preemption.
    ExternalReference stack_limit =
        ExternalReference::address_of_stack_limit(isolate());
    __ mov(r0, Operand(stack_limit));
    __ ldr(r0, MemOperand(r0));
    __ cmp(sp, r0);
    SafeCall(&check_preempt_label_, ls);
  }
  
  
  void RegExpMacroAssemblerARM::CheckStackLimit() {
    ExternalReference stack_limit =
        ExternalReference::address_of_regexp_stack_limit(isolate());
    __ mov(r0, Operand(stack_limit));
    __ ldr(r0, MemOperand(r0));
    __ cmp(backtrack_stackpointer(), Operand(r0));
    SafeCall(&stack_overflow_label_, ls);
  }
  
  
  void RegExpMacroAssemblerARM::LoadCurrentCharacterUnchecked(int cp_offset,
                                                              int characters) {
    Register offset = current_input_offset();
    if (cp_offset != 0) {
      // r4 is not being used to store the capture start index at this point.
      __ add(r4, current_input_offset(), Operand(cp_offset * char_size()));
      offset = r4;
    }
    // The ldr, str, ldrh, strh instructions can do unaligned accesses, if the CPU
    // and the operating system running on the target allow it.
    // If unaligned load/stores are not supported then this function must only
    // be used to load a single character at a time.
    if (!CanReadUnaligned()) {
      DCHECK_EQ(1, characters);
    }
  
    if (mode_ == LATIN1) {
      if (characters == 4) {
        __ ldr(current_character(), MemOperand(end_of_input_address(), offset));
      } else if (characters == 2) {
        __ ldrh(current_character(), MemOperand(end_of_input_address(), offset));
      } else {
        DCHECK_EQ(1, characters);
        __ ldrb(current_character(), MemOperand(end_of_input_address(), offset));
      }
    } else {
      DCHECK(mode_ == UC16);
      if (characters == 2) {
        __ ldr(current_character(), MemOperand(end_of_input_address(), offset));
      } else {
        DCHECK_EQ(1, characters);
        __ ldrh(current_character(), MemOperand(end_of_input_address(), offset));
      }
    }
  }
  
  
  #undef __
  
  #endif  // V8_INTERPRETED_REGEXP
  
  }  // namespace internal
  }  // namespace v8
  
  #endif  // V8_TARGET_ARCH_ARM
  