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      1 // Copyright 2012 the V8 project authors. All rights reserved.
      2 // Redistribution and use in source and binary forms, with or without
      3 // modification, are permitted provided that the following conditions are
      4 // met:
      5 //
      6 //     * Redistributions of source code must retain the above copyright
      7 //       notice, this list of conditions and the following disclaimer.
      8 //     * Redistributions in binary form must reproduce the above
      9 //       copyright notice, this list of conditions and the following
     10 //       disclaimer in the documentation and/or other materials provided
     11 //       with the distribution.
     12 //     * Neither the name of Google Inc. nor the names of its
     13 //       contributors may be used to endorse or promote products derived
     14 //       from this software without specific prior written permission.
     15 //
     16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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     22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27 
     28 #include "v8.h"
     29 
     30 #if V8_TARGET_ARCH_MIPS
     31 
     32 #include "unicode.h"
     33 #include "log.h"
     34 #include "code-stubs.h"
     35 #include "regexp-stack.h"
     36 #include "macro-assembler.h"
     37 #include "regexp-macro-assembler.h"
     38 #include "mips/regexp-macro-assembler-mips.h"
     39 
     40 namespace v8 {
     41 namespace internal {
     42 
     43 #ifndef V8_INTERPRETED_REGEXP
     44 /*
     45  * This assembler uses the following register assignment convention
     46  * - t7 : Temporarily stores the index of capture start after a matching pass
     47  *        for a global regexp.
     48  * - t1 : Pointer to current code object (Code*) including heap object tag.
     49  * - t2 : Current position in input, as negative offset from end of string.
     50  *        Please notice that this is the byte offset, not the character offset!
     51  * - t3 : Currently loaded character. Must be loaded using
     52  *        LoadCurrentCharacter before using any of the dispatch methods.
     53  * - t4 : Points to tip of backtrack stack
     54  * - t5 : Unused.
     55  * - t6 : End of input (points to byte after last character in input).
     56  * - fp : Frame pointer. Used to access arguments, local variables and
     57  *         RegExp registers.
     58  * - sp : Points to tip of C stack.
     59  *
     60  * The remaining registers are free for computations.
     61  * Each call to a public method should retain this convention.
     62  *
     63  * The stack will have the following structure:
     64  *
     65  *  - fp[64]  Isolate* isolate   (address of the current isolate)
     66  *  - fp[60]  direct_call  (if 1, direct call from JavaScript code,
     67  *                          if 0, call through the runtime system).
     68  *  - fp[56]  stack_area_base (High end of the memory area to use as
     69  *                             backtracking stack).
     70  *  - fp[52]  capture array size (may fit multiple sets of matches)
     71  *  - fp[48]  int* capture_array (int[num_saved_registers_], for output).
     72  *  - fp[44]  secondary link/return address used by native call.
     73  *  --- sp when called ---
     74  *  - fp[40]  return address      (lr).
     75  *  - fp[36]  old frame pointer   (r11).
     76  *  - fp[0..32]  backup of registers s0..s7.
     77  *  --- frame pointer ----
     78  *  - fp[-4]  end of input       (address of end of string).
     79  *  - fp[-8]  start of input     (address of first character in string).
     80  *  - fp[-12] start index        (character index of start).
     81  *  - fp[-16] void* input_string (location of a handle containing the string).
     82  *  - fp[-20] success counter    (only for global regexps to count matches).
     83  *  - fp[-24] Offset of location before start of input (effectively character
     84  *            position -1). Used to initialize capture registers to a
     85  *            non-position.
     86  *  - fp[-28] At start (if 1, we are starting at the start of the
     87  *    string, otherwise 0)
     88  *  - fp[-32] register 0         (Only positions must be stored in the first
     89  *  -         register 1          num_saved_registers_ registers)
     90  *  -         ...
     91  *  -         register num_registers-1
     92  *  --- sp ---
     93  *
     94  * The first num_saved_registers_ registers are initialized to point to
     95  * "character -1" in the string (i.e., char_size() bytes before the first
     96  * character of the string). The remaining registers start out as garbage.
     97  *
     98  * The data up to the return address must be placed there by the calling
     99  * code and the remaining arguments are passed in registers, e.g. by calling the
    100  * code entry as cast to a function with the signature:
    101  * int (*match)(String* input_string,
    102  *              int start_index,
    103  *              Address start,
    104  *              Address end,
    105  *              Address secondary_return_address,  // Only used by native call.
    106  *              int* capture_output_array,
    107  *              byte* stack_area_base,
    108  *              bool direct_call = false)
    109  * The call is performed by NativeRegExpMacroAssembler::Execute()
    110  * (in regexp-macro-assembler.cc) via the CALL_GENERATED_REGEXP_CODE macro
    111  * in mips/simulator-mips.h.
    112  * When calling as a non-direct call (i.e., from C++ code), the return address
    113  * area is overwritten with the ra register by the RegExp code. When doing a
    114  * direct call from generated code, the return address is placed there by
    115  * the calling code, as in a normal exit frame.
    116  */
    117 
    118 #define __ ACCESS_MASM(masm_)
    119 
    120 RegExpMacroAssemblerMIPS::RegExpMacroAssemblerMIPS(
    121     Mode mode,
    122     int registers_to_save,
    123     Zone* zone)
    124     : NativeRegExpMacroAssembler(zone),
    125       masm_(new MacroAssembler(zone->isolate(), NULL, kRegExpCodeSize)),
    126       mode_(mode),
    127       num_registers_(registers_to_save),
    128       num_saved_registers_(registers_to_save),
    129       entry_label_(),
    130       start_label_(),
    131       success_label_(),
    132       backtrack_label_(),
    133       exit_label_(),
    134       internal_failure_label_() {
    135   ASSERT_EQ(0, registers_to_save % 2);
    136   __ jmp(&entry_label_);   // We'll write the entry code later.
    137   // If the code gets too big or corrupted, an internal exception will be
    138   // raised, and we will exit right away.
    139   __ bind(&internal_failure_label_);
    140   __ li(v0, Operand(FAILURE));
    141   __ Ret();
    142   __ bind(&start_label_);  // And then continue from here.
    143 }
    144 
    145 
    146 RegExpMacroAssemblerMIPS::~RegExpMacroAssemblerMIPS() {
    147   delete masm_;
    148   // Unuse labels in case we throw away the assembler without calling GetCode.
    149   entry_label_.Unuse();
    150   start_label_.Unuse();
    151   success_label_.Unuse();
    152   backtrack_label_.Unuse();
    153   exit_label_.Unuse();
    154   check_preempt_label_.Unuse();
    155   stack_overflow_label_.Unuse();
    156   internal_failure_label_.Unuse();
    157 }
    158 
    159 
    160 int RegExpMacroAssemblerMIPS::stack_limit_slack()  {
    161   return RegExpStack::kStackLimitSlack;
    162 }
    163 
    164 
    165 void RegExpMacroAssemblerMIPS::AdvanceCurrentPosition(int by) {
    166   if (by != 0) {
    167     __ Addu(current_input_offset(),
    168             current_input_offset(), Operand(by * char_size()));
    169   }
    170 }
    171 
    172 
    173 void RegExpMacroAssemblerMIPS::AdvanceRegister(int reg, int by) {
    174   ASSERT(reg >= 0);
    175   ASSERT(reg < num_registers_);
    176   if (by != 0) {
    177     __ lw(a0, register_location(reg));
    178     __ Addu(a0, a0, Operand(by));
    179     __ sw(a0, register_location(reg));
    180   }
    181 }
    182 
    183 
    184 void RegExpMacroAssemblerMIPS::Backtrack() {
    185   CheckPreemption();
    186   // Pop Code* offset from backtrack stack, add Code* and jump to location.
    187   Pop(a0);
    188   __ Addu(a0, a0, code_pointer());
    189   __ Jump(a0);
    190 }
    191 
    192 
    193 void RegExpMacroAssemblerMIPS::Bind(Label* label) {
    194   __ bind(label);
    195 }
    196 
    197 
    198 void RegExpMacroAssemblerMIPS::CheckCharacter(uint32_t c, Label* on_equal) {
    199   BranchOrBacktrack(on_equal, eq, current_character(), Operand(c));
    200 }
    201 
    202 
    203 void RegExpMacroAssemblerMIPS::CheckCharacterGT(uc16 limit, Label* on_greater) {
    204   BranchOrBacktrack(on_greater, gt, current_character(), Operand(limit));
    205 }
    206 
    207 
    208 void RegExpMacroAssemblerMIPS::CheckAtStart(Label* on_at_start) {
    209   Label not_at_start;
    210   // Did we start the match at the start of the string at all?
    211   __ lw(a0, MemOperand(frame_pointer(), kStartIndex));
    212   BranchOrBacktrack(&not_at_start, ne, a0, Operand(zero_reg));
    213 
    214   // If we did, are we still at the start of the input?
    215   __ lw(a1, MemOperand(frame_pointer(), kInputStart));
    216   __ Addu(a0, end_of_input_address(), Operand(current_input_offset()));
    217   BranchOrBacktrack(on_at_start, eq, a0, Operand(a1));
    218   __ bind(&not_at_start);
    219 }
    220 
    221 
    222 void RegExpMacroAssemblerMIPS::CheckNotAtStart(Label* on_not_at_start) {
    223   // Did we start the match at the start of the string at all?
    224   __ lw(a0, MemOperand(frame_pointer(), kStartIndex));
    225   BranchOrBacktrack(on_not_at_start, ne, a0, Operand(zero_reg));
    226   // If we did, are we still at the start of the input?
    227   __ lw(a1, MemOperand(frame_pointer(), kInputStart));
    228   __ Addu(a0, end_of_input_address(), Operand(current_input_offset()));
    229   BranchOrBacktrack(on_not_at_start, ne, a0, Operand(a1));
    230 }
    231 
    232 
    233 void RegExpMacroAssemblerMIPS::CheckCharacterLT(uc16 limit, Label* on_less) {
    234   BranchOrBacktrack(on_less, lt, current_character(), Operand(limit));
    235 }
    236 
    237 
    238 void RegExpMacroAssemblerMIPS::CheckGreedyLoop(Label* on_equal) {
    239   Label backtrack_non_equal;
    240   __ lw(a0, MemOperand(backtrack_stackpointer(), 0));
    241   __ Branch(&backtrack_non_equal, ne, current_input_offset(), Operand(a0));
    242   __ Addu(backtrack_stackpointer(),
    243           backtrack_stackpointer(),
    244           Operand(kPointerSize));
    245   __ bind(&backtrack_non_equal);
    246   BranchOrBacktrack(on_equal, eq, current_input_offset(), Operand(a0));
    247 }
    248 
    249 
    250 void RegExpMacroAssemblerMIPS::CheckNotBackReferenceIgnoreCase(
    251     int start_reg,
    252     Label* on_no_match) {
    253   Label fallthrough;
    254   __ lw(a0, register_location(start_reg));  // Index of start of capture.
    255   __ lw(a1, register_location(start_reg + 1));  // Index of end of capture.
    256   __ Subu(a1, a1, a0);  // Length of capture.
    257 
    258   // If length is zero, either the capture is empty or it is not participating.
    259   // In either case succeed immediately.
    260   __ Branch(&fallthrough, eq, a1, Operand(zero_reg));
    261 
    262   __ Addu(t5, a1, current_input_offset());
    263   // Check that there are enough characters left in the input.
    264   BranchOrBacktrack(on_no_match, gt, t5, Operand(zero_reg));
    265 
    266   if (mode_ == ASCII) {
    267     Label success;
    268     Label fail;
    269     Label loop_check;
    270 
    271     // a0 - offset of start of capture.
    272     // a1 - length of capture.
    273     __ Addu(a0, a0, Operand(end_of_input_address()));
    274     __ Addu(a2, end_of_input_address(), Operand(current_input_offset()));
    275     __ Addu(a1, a0, Operand(a1));
    276 
    277     // a0 - Address of start of capture.
    278     // a1 - Address of end of capture.
    279     // a2 - Address of current input position.
    280 
    281     Label loop;
    282     __ bind(&loop);
    283     __ lbu(a3, MemOperand(a0, 0));
    284     __ addiu(a0, a0, char_size());
    285     __ lbu(t0, MemOperand(a2, 0));
    286     __ addiu(a2, a2, char_size());
    287 
    288     __ Branch(&loop_check, eq, t0, Operand(a3));
    289 
    290     // Mismatch, try case-insensitive match (converting letters to lower-case).
    291     __ Or(a3, a3, Operand(0x20));  // Convert capture character to lower-case.
    292     __ Or(t0, t0, Operand(0x20));  // Also convert input character.
    293     __ Branch(&fail, ne, t0, Operand(a3));
    294     __ Subu(a3, a3, Operand('a'));
    295     __ Branch(&loop_check, ls, a3, Operand('z' - 'a'));
    296     // Latin-1: Check for values in range [224,254] but not 247.
    297     __ Subu(a3, a3, Operand(224 - 'a'));
    298     // Weren't Latin-1 letters.
    299     __ Branch(&fail, hi, a3, Operand(254 - 224));
    300     // Check for 247.
    301     __ Branch(&fail, eq, a3, Operand(247 - 224));
    302 
    303     __ bind(&loop_check);
    304     __ Branch(&loop, lt, a0, Operand(a1));
    305     __ jmp(&success);
    306 
    307     __ bind(&fail);
    308     GoTo(on_no_match);
    309 
    310     __ bind(&success);
    311     // Compute new value of character position after the matched part.
    312     __ Subu(current_input_offset(), a2, end_of_input_address());
    313   } else {
    314     ASSERT(mode_ == UC16);
    315     // Put regexp engine registers on stack.
    316     RegList regexp_registers_to_retain = current_input_offset().bit() |
    317         current_character().bit() | backtrack_stackpointer().bit();
    318     __ MultiPush(regexp_registers_to_retain);
    319 
    320     int argument_count = 4;
    321     __ PrepareCallCFunction(argument_count, a2);
    322 
    323     // a0 - offset of start of capture.
    324     // a1 - length of capture.
    325 
    326     // Put arguments into arguments registers.
    327     // Parameters are
    328     //   a0: Address byte_offset1 - Address captured substring's start.
    329     //   a1: Address byte_offset2 - Address of current character position.
    330     //   a2: size_t byte_length - length of capture in bytes(!).
    331     //   a3: Isolate* isolate.
    332 
    333     // Address of start of capture.
    334     __ Addu(a0, a0, Operand(end_of_input_address()));
    335     // Length of capture.
    336     __ mov(a2, a1);
    337     // Save length in callee-save register for use on return.
    338     __ mov(s3, a1);
    339     // Address of current input position.
    340     __ Addu(a1, current_input_offset(), Operand(end_of_input_address()));
    341     // Isolate.
    342     __ li(a3, Operand(ExternalReference::isolate_address(masm_->isolate())));
    343 
    344     {
    345       AllowExternalCallThatCantCauseGC scope(masm_);
    346       ExternalReference function =
    347           ExternalReference::re_case_insensitive_compare_uc16(masm_->isolate());
    348       __ CallCFunction(function, argument_count);
    349     }
    350 
    351     // Restore regexp engine registers.
    352     __ MultiPop(regexp_registers_to_retain);
    353     __ li(code_pointer(), Operand(masm_->CodeObject()), CONSTANT_SIZE);
    354     __ lw(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
    355 
    356     // Check if function returned non-zero for success or zero for failure.
    357     BranchOrBacktrack(on_no_match, eq, v0, Operand(zero_reg));
    358     // On success, increment position by length of capture.
    359     __ Addu(current_input_offset(), current_input_offset(), Operand(s3));
    360   }
    361 
    362   __ bind(&fallthrough);
    363 }
    364 
    365 
    366 void RegExpMacroAssemblerMIPS::CheckNotBackReference(
    367     int start_reg,
    368     Label* on_no_match) {
    369   Label fallthrough;
    370   Label success;
    371 
    372   // Find length of back-referenced capture.
    373   __ lw(a0, register_location(start_reg));
    374   __ lw(a1, register_location(start_reg + 1));
    375   __ Subu(a1, a1, a0);  // Length to check.
    376   // Succeed on empty capture (including no capture).
    377   __ Branch(&fallthrough, eq, a1, Operand(zero_reg));
    378 
    379   __ Addu(t5, a1, current_input_offset());
    380   // Check that there are enough characters left in the input.
    381   BranchOrBacktrack(on_no_match, gt, t5, Operand(zero_reg));
    382 
    383   // Compute pointers to match string and capture string.
    384   __ Addu(a0, a0, Operand(end_of_input_address()));
    385   __ Addu(a2, end_of_input_address(), Operand(current_input_offset()));
    386   __ Addu(a1, a1, Operand(a0));
    387 
    388   Label loop;
    389   __ bind(&loop);
    390   if (mode_ == ASCII) {
    391     __ lbu(a3, MemOperand(a0, 0));
    392     __ addiu(a0, a0, char_size());
    393     __ lbu(t0, MemOperand(a2, 0));
    394     __ addiu(a2, a2, char_size());
    395   } else {
    396     ASSERT(mode_ == UC16);
    397     __ lhu(a3, MemOperand(a0, 0));
    398     __ addiu(a0, a0, char_size());
    399     __ lhu(t0, MemOperand(a2, 0));
    400     __ addiu(a2, a2, char_size());
    401   }
    402   BranchOrBacktrack(on_no_match, ne, a3, Operand(t0));
    403   __ Branch(&loop, lt, a0, Operand(a1));
    404 
    405   // Move current character position to position after match.
    406   __ Subu(current_input_offset(), a2, end_of_input_address());
    407   __ bind(&fallthrough);
    408 }
    409 
    410 
    411 void RegExpMacroAssemblerMIPS::CheckNotCharacter(uint32_t c,
    412                                                  Label* on_not_equal) {
    413   BranchOrBacktrack(on_not_equal, ne, current_character(), Operand(c));
    414 }
    415 
    416 
    417 void RegExpMacroAssemblerMIPS::CheckCharacterAfterAnd(uint32_t c,
    418                                                       uint32_t mask,
    419                                                       Label* on_equal) {
    420   __ And(a0, current_character(), Operand(mask));
    421   Operand rhs = (c == 0) ? Operand(zero_reg) : Operand(c);
    422   BranchOrBacktrack(on_equal, eq, a0, rhs);
    423 }
    424 
    425 
    426 void RegExpMacroAssemblerMIPS::CheckNotCharacterAfterAnd(uint32_t c,
    427                                                          uint32_t mask,
    428                                                          Label* on_not_equal) {
    429   __ And(a0, current_character(), Operand(mask));
    430   Operand rhs = (c == 0) ? Operand(zero_reg) : Operand(c);
    431   BranchOrBacktrack(on_not_equal, ne, a0, rhs);
    432 }
    433 
    434 
    435 void RegExpMacroAssemblerMIPS::CheckNotCharacterAfterMinusAnd(
    436     uc16 c,
    437     uc16 minus,
    438     uc16 mask,
    439     Label* on_not_equal) {
    440   ASSERT(minus < String::kMaxUtf16CodeUnit);
    441   __ Subu(a0, current_character(), Operand(minus));
    442   __ And(a0, a0, Operand(mask));
    443   BranchOrBacktrack(on_not_equal, ne, a0, Operand(c));
    444 }
    445 
    446 
    447 void RegExpMacroAssemblerMIPS::CheckCharacterInRange(
    448     uc16 from,
    449     uc16 to,
    450     Label* on_in_range) {
    451   __ Subu(a0, current_character(), Operand(from));
    452   // Unsigned lower-or-same condition.
    453   BranchOrBacktrack(on_in_range, ls, a0, Operand(to - from));
    454 }
    455 
    456 
    457 void RegExpMacroAssemblerMIPS::CheckCharacterNotInRange(
    458     uc16 from,
    459     uc16 to,
    460     Label* on_not_in_range) {
    461   __ Subu(a0, current_character(), Operand(from));
    462   // Unsigned higher condition.
    463   BranchOrBacktrack(on_not_in_range, hi, a0, Operand(to - from));
    464 }
    465 
    466 
    467 void RegExpMacroAssemblerMIPS::CheckBitInTable(
    468     Handle<ByteArray> table,
    469     Label* on_bit_set) {
    470   __ li(a0, Operand(table));
    471   if (mode_ != ASCII || kTableMask != String::kMaxOneByteCharCode) {
    472     __ And(a1, current_character(), Operand(kTableSize - 1));
    473     __ Addu(a0, a0, a1);
    474   } else {
    475     __ Addu(a0, a0, current_character());
    476   }
    477 
    478   __ lbu(a0, FieldMemOperand(a0, ByteArray::kHeaderSize));
    479   BranchOrBacktrack(on_bit_set, ne, a0, Operand(zero_reg));
    480 }
    481 
    482 
    483 bool RegExpMacroAssemblerMIPS::CheckSpecialCharacterClass(uc16 type,
    484                                                           Label* on_no_match) {
    485   // Range checks (c in min..max) are generally implemented by an unsigned
    486   // (c - min) <= (max - min) check.
    487   switch (type) {
    488   case 's':
    489     // Match space-characters.
    490     if (mode_ == ASCII) {
    491       // One byte space characters are '\t'..'\r', ' ' and \u00a0.
    492       Label success;
    493       __ Branch(&success, eq, current_character(), Operand(' '));
    494       // Check range 0x09..0x0d.
    495       __ Subu(a0, current_character(), Operand('\t'));
    496       __ Branch(&success, ls, a0, Operand('\r' - '\t'));
    497       // \u00a0 (NBSP).
    498       BranchOrBacktrack(on_no_match, ne, a0, Operand(0x00a0 - '\t'));
    499       __ bind(&success);
    500       return true;
    501     }
    502     return false;
    503   case 'S':
    504     // The emitted code for generic character classes is good enough.
    505     return false;
    506   case 'd':
    507     // Match ASCII digits ('0'..'9').
    508     __ Subu(a0, current_character(), Operand('0'));
    509     BranchOrBacktrack(on_no_match, hi, a0, Operand('9' - '0'));
    510     return true;
    511   case 'D':
    512     // Match non ASCII-digits.
    513     __ Subu(a0, current_character(), Operand('0'));
    514     BranchOrBacktrack(on_no_match, ls, a0, Operand('9' - '0'));
    515     return true;
    516   case '.': {
    517     // Match non-newlines (not 0x0a('\n'), 0x0d('\r'), 0x2028 and 0x2029).
    518     __ Xor(a0, current_character(), Operand(0x01));
    519     // See if current character is '\n'^1 or '\r'^1, i.e., 0x0b or 0x0c.
    520     __ Subu(a0, a0, Operand(0x0b));
    521     BranchOrBacktrack(on_no_match, ls, a0, Operand(0x0c - 0x0b));
    522     if (mode_ == UC16) {
    523       // Compare original value to 0x2028 and 0x2029, using the already
    524       // computed (current_char ^ 0x01 - 0x0b). I.e., check for
    525       // 0x201d (0x2028 - 0x0b) or 0x201e.
    526       __ Subu(a0, a0, Operand(0x2028 - 0x0b));
    527       BranchOrBacktrack(on_no_match, ls, a0, Operand(1));
    528     }
    529     return true;
    530   }
    531   case 'n': {
    532     // Match newlines (0x0a('\n'), 0x0d('\r'), 0x2028 and 0x2029).
    533     __ Xor(a0, current_character(), Operand(0x01));
    534     // See if current character is '\n'^1 or '\r'^1, i.e., 0x0b or 0x0c.
    535     __ Subu(a0, a0, Operand(0x0b));
    536     if (mode_ == ASCII) {
    537       BranchOrBacktrack(on_no_match, hi, a0, Operand(0x0c - 0x0b));
    538     } else {
    539       Label done;
    540       BranchOrBacktrack(&done, ls, a0, Operand(0x0c - 0x0b));
    541       // Compare original value to 0x2028 and 0x2029, using the already
    542       // computed (current_char ^ 0x01 - 0x0b). I.e., check for
    543       // 0x201d (0x2028 - 0x0b) or 0x201e.
    544       __ Subu(a0, a0, Operand(0x2028 - 0x0b));
    545       BranchOrBacktrack(on_no_match, hi, a0, Operand(1));
    546       __ bind(&done);
    547     }
    548     return true;
    549   }
    550   case 'w': {
    551     if (mode_ != ASCII) {
    552       // Table is 128 entries, so all ASCII characters can be tested.
    553       BranchOrBacktrack(on_no_match, hi, current_character(), Operand('z'));
    554     }
    555     ExternalReference map = ExternalReference::re_word_character_map();
    556     __ li(a0, Operand(map));
    557     __ Addu(a0, a0, current_character());
    558     __ lbu(a0, MemOperand(a0, 0));
    559     BranchOrBacktrack(on_no_match, eq, a0, Operand(zero_reg));
    560     return true;
    561   }
    562   case 'W': {
    563     Label done;
    564     if (mode_ != ASCII) {
    565       // Table is 128 entries, so all ASCII characters can be tested.
    566       __ Branch(&done, hi, current_character(), Operand('z'));
    567     }
    568     ExternalReference map = ExternalReference::re_word_character_map();
    569     __ li(a0, Operand(map));
    570     __ Addu(a0, a0, current_character());
    571     __ lbu(a0, MemOperand(a0, 0));
    572     BranchOrBacktrack(on_no_match, ne, a0, Operand(zero_reg));
    573     if (mode_ != ASCII) {
    574       __ bind(&done);
    575     }
    576     return true;
    577   }
    578   case '*':
    579     // Match any character.
    580     return true;
    581   // No custom implementation (yet): s(UC16), S(UC16).
    582   default:
    583     return false;
    584   }
    585 }
    586 
    587 
    588 void RegExpMacroAssemblerMIPS::Fail() {
    589   __ li(v0, Operand(FAILURE));
    590   __ jmp(&exit_label_);
    591 }
    592 
    593 
    594 Handle<HeapObject> RegExpMacroAssemblerMIPS::GetCode(Handle<String> source) {
    595   Label return_v0;
    596   if (masm_->has_exception()) {
    597     // If the code gets corrupted due to long regular expressions and lack of
    598     // space on trampolines, an internal exception flag is set. If this case
    599     // is detected, we will jump into exit sequence right away.
    600     __ bind_to(&entry_label_, internal_failure_label_.pos());
    601   } else {
    602     // Finalize code - write the entry point code now we know how many
    603     // registers we need.
    604 
    605     // Entry code:
    606     __ bind(&entry_label_);
    607 
    608     // Tell the system that we have a stack frame.  Because the type is MANUAL,
    609     // no is generated.
    610     FrameScope scope(masm_, StackFrame::MANUAL);
    611 
    612     // Actually emit code to start a new stack frame.
    613     // Push arguments
    614     // Save callee-save registers.
    615     // Start new stack frame.
    616     // Store link register in existing stack-cell.
    617     // Order here should correspond to order of offset constants in header file.
    618     RegList registers_to_retain = s0.bit() | s1.bit() | s2.bit() |
    619         s3.bit() | s4.bit() | s5.bit() | s6.bit() | s7.bit() | fp.bit();
    620     RegList argument_registers = a0.bit() | a1.bit() | a2.bit() | a3.bit();
    621     __ MultiPush(argument_registers | registers_to_retain | ra.bit());
    622     // Set frame pointer in space for it if this is not a direct call
    623     // from generated code.
    624     __ Addu(frame_pointer(), sp, Operand(4 * kPointerSize));
    625     __ mov(a0, zero_reg);
    626     __ push(a0);  // Make room for success counter and initialize it to 0.
    627     __ push(a0);  // Make room for "position - 1" constant (value irrelevant).
    628 
    629     // Check if we have space on the stack for registers.
    630     Label stack_limit_hit;
    631     Label stack_ok;
    632 
    633     ExternalReference stack_limit =
    634         ExternalReference::address_of_stack_limit(masm_->isolate());
    635     __ li(a0, Operand(stack_limit));
    636     __ lw(a0, MemOperand(a0));
    637     __ Subu(a0, sp, a0);
    638     // Handle it if the stack pointer is already below the stack limit.
    639     __ Branch(&stack_limit_hit, le, a0, Operand(zero_reg));
    640     // Check if there is room for the variable number of registers above
    641     // the stack limit.
    642     __ Branch(&stack_ok, hs, a0, Operand(num_registers_ * kPointerSize));
    643     // Exit with OutOfMemory exception. There is not enough space on the stack
    644     // for our working registers.
    645     __ li(v0, Operand(EXCEPTION));
    646     __ jmp(&return_v0);
    647 
    648     __ bind(&stack_limit_hit);
    649     CallCheckStackGuardState(a0);
    650     // If returned value is non-zero, we exit with the returned value as result.
    651     __ Branch(&return_v0, ne, v0, Operand(zero_reg));
    652 
    653     __ bind(&stack_ok);
    654     // Allocate space on stack for registers.
    655     __ Subu(sp, sp, Operand(num_registers_ * kPointerSize));
    656     // Load string end.
    657     __ lw(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
    658     // Load input start.
    659     __ lw(a0, MemOperand(frame_pointer(), kInputStart));
    660     // Find negative length (offset of start relative to end).
    661     __ Subu(current_input_offset(), a0, end_of_input_address());
    662     // Set a0 to address of char before start of the input string
    663     // (effectively string position -1).
    664     __ lw(a1, MemOperand(frame_pointer(), kStartIndex));
    665     __ Subu(a0, current_input_offset(), Operand(char_size()));
    666     __ sll(t5, a1, (mode_ == UC16) ? 1 : 0);
    667     __ Subu(a0, a0, t5);
    668     // Store this value in a local variable, for use when clearing
    669     // position registers.
    670     __ sw(a0, MemOperand(frame_pointer(), kInputStartMinusOne));
    671 
    672     // Initialize code pointer register
    673     __ li(code_pointer(), Operand(masm_->CodeObject()), CONSTANT_SIZE);
    674 
    675     Label load_char_start_regexp, start_regexp;
    676     // Load newline if index is at start, previous character otherwise.
    677     __ Branch(&load_char_start_regexp, ne, a1, Operand(zero_reg));
    678     __ li(current_character(), Operand('\n'));
    679     __ jmp(&start_regexp);
    680 
    681     // Global regexp restarts matching here.
    682     __ bind(&load_char_start_regexp);
    683     // Load previous char as initial value of current character register.
    684     LoadCurrentCharacterUnchecked(-1, 1);
    685     __ bind(&start_regexp);
    686 
    687     // Initialize on-stack registers.
    688     if (num_saved_registers_ > 0) {  // Always is, if generated from a regexp.
    689       // Fill saved registers with initial value = start offset - 1.
    690       if (num_saved_registers_ > 8) {
    691         // Address of register 0.
    692         __ Addu(a1, frame_pointer(), Operand(kRegisterZero));
    693         __ li(a2, Operand(num_saved_registers_));
    694         Label init_loop;
    695         __ bind(&init_loop);
    696         __ sw(a0, MemOperand(a1));
    697         __ Addu(a1, a1, Operand(-kPointerSize));
    698         __ Subu(a2, a2, Operand(1));
    699         __ Branch(&init_loop, ne, a2, Operand(zero_reg));
    700       } else {
    701         for (int i = 0; i < num_saved_registers_; i++) {
    702           __ sw(a0, register_location(i));
    703         }
    704       }
    705     }
    706 
    707     // Initialize backtrack stack pointer.
    708     __ lw(backtrack_stackpointer(), MemOperand(frame_pointer(), kStackHighEnd));
    709 
    710     __ jmp(&start_label_);
    711 
    712 
    713     // Exit code:
    714     if (success_label_.is_linked()) {
    715       // Save captures when successful.
    716       __ bind(&success_label_);
    717       if (num_saved_registers_ > 0) {
    718         // Copy captures to output.
    719         __ lw(a1, MemOperand(frame_pointer(), kInputStart));
    720         __ lw(a0, MemOperand(frame_pointer(), kRegisterOutput));
    721         __ lw(a2, MemOperand(frame_pointer(), kStartIndex));
    722         __ Subu(a1, end_of_input_address(), a1);
    723         // a1 is length of input in bytes.
    724         if (mode_ == UC16) {
    725           __ srl(a1, a1, 1);
    726         }
    727         // a1 is length of input in characters.
    728         __ Addu(a1, a1, Operand(a2));
    729         // a1 is length of string in characters.
    730 
    731         ASSERT_EQ(0, num_saved_registers_ % 2);
    732         // Always an even number of capture registers. This allows us to
    733         // unroll the loop once to add an operation between a load of a register
    734         // and the following use of that register.
    735         for (int i = 0; i < num_saved_registers_; i += 2) {
    736           __ lw(a2, register_location(i));
    737           __ lw(a3, register_location(i + 1));
    738           if (i == 0 && global_with_zero_length_check()) {
    739             // Keep capture start in a4 for the zero-length check later.
    740             __ mov(t7, a2);
    741           }
    742           if (mode_ == UC16) {
    743             __ sra(a2, a2, 1);
    744             __ Addu(a2, a2, a1);
    745             __ sra(a3, a3, 1);
    746             __ Addu(a3, a3, a1);
    747           } else {
    748             __ Addu(a2, a1, Operand(a2));
    749             __ Addu(a3, a1, Operand(a3));
    750           }
    751           __ sw(a2, MemOperand(a0));
    752           __ Addu(a0, a0, kPointerSize);
    753           __ sw(a3, MemOperand(a0));
    754           __ Addu(a0, a0, kPointerSize);
    755         }
    756       }
    757 
    758       if (global()) {
    759         // Restart matching if the regular expression is flagged as global.
    760         __ lw(a0, MemOperand(frame_pointer(), kSuccessfulCaptures));
    761         __ lw(a1, MemOperand(frame_pointer(), kNumOutputRegisters));
    762         __ lw(a2, MemOperand(frame_pointer(), kRegisterOutput));
    763         // Increment success counter.
    764         __ Addu(a0, a0, 1);
    765         __ sw(a0, MemOperand(frame_pointer(), kSuccessfulCaptures));
    766         // Capture results have been stored, so the number of remaining global
    767         // output registers is reduced by the number of stored captures.
    768         __ Subu(a1, a1, num_saved_registers_);
    769         // Check whether we have enough room for another set of capture results.
    770         __ mov(v0, a0);
    771         __ Branch(&return_v0, lt, a1, Operand(num_saved_registers_));
    772 
    773         __ sw(a1, MemOperand(frame_pointer(), kNumOutputRegisters));
    774         // Advance the location for output.
    775         __ Addu(a2, a2, num_saved_registers_ * kPointerSize);
    776         __ sw(a2, MemOperand(frame_pointer(), kRegisterOutput));
    777 
    778         // Prepare a0 to initialize registers with its value in the next run.
    779         __ lw(a0, MemOperand(frame_pointer(), kInputStartMinusOne));
    780 
    781         if (global_with_zero_length_check()) {
    782           // Special case for zero-length matches.
    783           // t7: capture start index
    784           // Not a zero-length match, restart.
    785           __ Branch(
    786               &load_char_start_regexp, ne, current_input_offset(), Operand(t7));
    787           // Offset from the end is zero if we already reached the end.
    788           __ Branch(&exit_label_, eq, current_input_offset(),
    789                     Operand(zero_reg));
    790           // Advance current position after a zero-length match.
    791           __ Addu(current_input_offset(),
    792                   current_input_offset(),
    793                   Operand((mode_ == UC16) ? 2 : 1));
    794         }
    795 
    796         __ Branch(&load_char_start_regexp);
    797       } else {
    798         __ li(v0, Operand(SUCCESS));
    799       }
    800     }
    801     // Exit and return v0.
    802     __ bind(&exit_label_);
    803     if (global()) {
    804       __ lw(v0, MemOperand(frame_pointer(), kSuccessfulCaptures));
    805     }
    806 
    807     __ bind(&return_v0);
    808     // Skip sp past regexp registers and local variables..
    809     __ mov(sp, frame_pointer());
    810     // Restore registers s0..s7 and return (restoring ra to pc).
    811     __ MultiPop(registers_to_retain | ra.bit());
    812     __ Ret();
    813 
    814     // Backtrack code (branch target for conditional backtracks).
    815     if (backtrack_label_.is_linked()) {
    816       __ bind(&backtrack_label_);
    817       Backtrack();
    818     }
    819 
    820     Label exit_with_exception;
    821 
    822     // Preempt-code.
    823     if (check_preempt_label_.is_linked()) {
    824       SafeCallTarget(&check_preempt_label_);
    825       // Put regexp engine registers on stack.
    826       RegList regexp_registers_to_retain = current_input_offset().bit() |
    827           current_character().bit() | backtrack_stackpointer().bit();
    828       __ MultiPush(regexp_registers_to_retain);
    829       CallCheckStackGuardState(a0);
    830       __ MultiPop(regexp_registers_to_retain);
    831       // If returning non-zero, we should end execution with the given
    832       // result as return value.
    833       __ Branch(&return_v0, ne, v0, Operand(zero_reg));
    834 
    835       // String might have moved: Reload end of string from frame.
    836       __ lw(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
    837       __ li(code_pointer(), Operand(masm_->CodeObject()), CONSTANT_SIZE);
    838       SafeReturn();
    839     }
    840 
    841     // Backtrack stack overflow code.
    842     if (stack_overflow_label_.is_linked()) {
    843       SafeCallTarget(&stack_overflow_label_);
    844       // Reached if the backtrack-stack limit has been hit.
    845       // Put regexp engine registers on stack first.
    846       RegList regexp_registers = current_input_offset().bit() |
    847           current_character().bit();
    848       __ MultiPush(regexp_registers);
    849       Label grow_failed;
    850       // Call GrowStack(backtrack_stackpointer(), &stack_base)
    851       static const int num_arguments = 3;
    852       __ PrepareCallCFunction(num_arguments, a0);
    853       __ mov(a0, backtrack_stackpointer());
    854       __ Addu(a1, frame_pointer(), Operand(kStackHighEnd));
    855       __ li(a2, Operand(ExternalReference::isolate_address(masm_->isolate())));
    856       ExternalReference grow_stack =
    857           ExternalReference::re_grow_stack(masm_->isolate());
    858       __ CallCFunction(grow_stack, num_arguments);
    859       // Restore regexp registers.
    860       __ MultiPop(regexp_registers);
    861       // If return NULL, we have failed to grow the stack, and
    862       // must exit with a stack-overflow exception.
    863       __ Branch(&exit_with_exception, eq, v0, Operand(zero_reg));
    864       // Otherwise use return value as new stack pointer.
    865       __ mov(backtrack_stackpointer(), v0);
    866       // Restore saved registers and continue.
    867       __ li(code_pointer(), Operand(masm_->CodeObject()), CONSTANT_SIZE);
    868       __ lw(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
    869       SafeReturn();
    870     }
    871 
    872     if (exit_with_exception.is_linked()) {
    873       // If any of the code above needed to exit with an exception.
    874       __ bind(&exit_with_exception);
    875       // Exit with Result EXCEPTION(-1) to signal thrown exception.
    876       __ li(v0, Operand(EXCEPTION));
    877       __ jmp(&return_v0);
    878     }
    879   }
    880 
    881   CodeDesc code_desc;
    882   masm_->GetCode(&code_desc);
    883   Handle<Code> code = isolate()->factory()->NewCode(
    884       code_desc, Code::ComputeFlags(Code::REGEXP), masm_->CodeObject());
    885   LOG(Isolate::Current(), RegExpCodeCreateEvent(*code, *source));
    886   return Handle<HeapObject>::cast(code);
    887 }
    888 
    889 
    890 void RegExpMacroAssemblerMIPS::GoTo(Label* to) {
    891   if (to == NULL) {
    892     Backtrack();
    893     return;
    894   }
    895   __ jmp(to);
    896   return;
    897 }
    898 
    899 
    900 void RegExpMacroAssemblerMIPS::IfRegisterGE(int reg,
    901                                             int comparand,
    902                                             Label* if_ge) {
    903   __ lw(a0, register_location(reg));
    904     BranchOrBacktrack(if_ge, ge, a0, Operand(comparand));
    905 }
    906 
    907 
    908 void RegExpMacroAssemblerMIPS::IfRegisterLT(int reg,
    909                                             int comparand,
    910                                             Label* if_lt) {
    911   __ lw(a0, register_location(reg));
    912   BranchOrBacktrack(if_lt, lt, a0, Operand(comparand));
    913 }
    914 
    915 
    916 void RegExpMacroAssemblerMIPS::IfRegisterEqPos(int reg,
    917                                                Label* if_eq) {
    918   __ lw(a0, register_location(reg));
    919   BranchOrBacktrack(if_eq, eq, a0, Operand(current_input_offset()));
    920 }
    921 
    922 
    923 RegExpMacroAssembler::IrregexpImplementation
    924     RegExpMacroAssemblerMIPS::Implementation() {
    925   return kMIPSImplementation;
    926 }
    927 
    928 
    929 void RegExpMacroAssemblerMIPS::LoadCurrentCharacter(int cp_offset,
    930                                                     Label* on_end_of_input,
    931                                                     bool check_bounds,
    932                                                     int characters) {
    933   ASSERT(cp_offset >= -1);      // ^ and \b can look behind one character.
    934   ASSERT(cp_offset < (1<<30));  // Be sane! (And ensure negation works).
    935   if (check_bounds) {
    936     CheckPosition(cp_offset + characters - 1, on_end_of_input);
    937   }
    938   LoadCurrentCharacterUnchecked(cp_offset, characters);
    939 }
    940 
    941 
    942 void RegExpMacroAssemblerMIPS::PopCurrentPosition() {
    943   Pop(current_input_offset());
    944 }
    945 
    946 
    947 void RegExpMacroAssemblerMIPS::PopRegister(int register_index) {
    948   Pop(a0);
    949   __ sw(a0, register_location(register_index));
    950 }
    951 
    952 
    953 void RegExpMacroAssemblerMIPS::PushBacktrack(Label* label) {
    954   if (label->is_bound()) {
    955     int target = label->pos();
    956     __ li(a0, Operand(target + Code::kHeaderSize - kHeapObjectTag));
    957   } else {
    958     Assembler::BlockTrampolinePoolScope block_trampoline_pool(masm_);
    959     Label after_constant;
    960     __ Branch(&after_constant);
    961     int offset = masm_->pc_offset();
    962     int cp_offset = offset + Code::kHeaderSize - kHeapObjectTag;
    963     __ emit(0);
    964     masm_->label_at_put(label, offset);
    965     __ bind(&after_constant);
    966     if (is_int16(cp_offset)) {
    967       __ lw(a0, MemOperand(code_pointer(), cp_offset));
    968     } else {
    969       __ Addu(a0, code_pointer(), cp_offset);
    970       __ lw(a0, MemOperand(a0, 0));
    971     }
    972   }
    973   Push(a0);
    974   CheckStackLimit();
    975 }
    976 
    977 
    978 void RegExpMacroAssemblerMIPS::PushCurrentPosition() {
    979   Push(current_input_offset());
    980 }
    981 
    982 
    983 void RegExpMacroAssemblerMIPS::PushRegister(int register_index,
    984                                             StackCheckFlag check_stack_limit) {
    985   __ lw(a0, register_location(register_index));
    986   Push(a0);
    987   if (check_stack_limit) CheckStackLimit();
    988 }
    989 
    990 
    991 void RegExpMacroAssemblerMIPS::ReadCurrentPositionFromRegister(int reg) {
    992   __ lw(current_input_offset(), register_location(reg));
    993 }
    994 
    995 
    996 void RegExpMacroAssemblerMIPS::ReadStackPointerFromRegister(int reg) {
    997   __ lw(backtrack_stackpointer(), register_location(reg));
    998   __ lw(a0, MemOperand(frame_pointer(), kStackHighEnd));
    999   __ Addu(backtrack_stackpointer(), backtrack_stackpointer(), Operand(a0));
   1000 }
   1001 
   1002 
   1003 void RegExpMacroAssemblerMIPS::SetCurrentPositionFromEnd(int by) {
   1004   Label after_position;
   1005   __ Branch(&after_position,
   1006             ge,
   1007             current_input_offset(),
   1008             Operand(-by * char_size()));
   1009   __ li(current_input_offset(), -by * char_size());
   1010   // On RegExp code entry (where this operation is used), the character before
   1011   // the current position is expected to be already loaded.
   1012   // We have advanced the position, so it's safe to read backwards.
   1013   LoadCurrentCharacterUnchecked(-1, 1);
   1014   __ bind(&after_position);
   1015 }
   1016 
   1017 
   1018 void RegExpMacroAssemblerMIPS::SetRegister(int register_index, int to) {
   1019   ASSERT(register_index >= num_saved_registers_);  // Reserved for positions!
   1020   __ li(a0, Operand(to));
   1021   __ sw(a0, register_location(register_index));
   1022 }
   1023 
   1024 
   1025 bool RegExpMacroAssemblerMIPS::Succeed() {
   1026   __ jmp(&success_label_);
   1027   return global();
   1028 }
   1029 
   1030 
   1031 void RegExpMacroAssemblerMIPS::WriteCurrentPositionToRegister(int reg,
   1032                                                               int cp_offset) {
   1033   if (cp_offset == 0) {
   1034     __ sw(current_input_offset(), register_location(reg));
   1035   } else {
   1036     __ Addu(a0, current_input_offset(), Operand(cp_offset * char_size()));
   1037     __ sw(a0, register_location(reg));
   1038   }
   1039 }
   1040 
   1041 
   1042 void RegExpMacroAssemblerMIPS::ClearRegisters(int reg_from, int reg_to) {
   1043   ASSERT(reg_from <= reg_to);
   1044   __ lw(a0, MemOperand(frame_pointer(), kInputStartMinusOne));
   1045   for (int reg = reg_from; reg <= reg_to; reg++) {
   1046     __ sw(a0, register_location(reg));
   1047   }
   1048 }
   1049 
   1050 
   1051 void RegExpMacroAssemblerMIPS::WriteStackPointerToRegister(int reg) {
   1052   __ lw(a1, MemOperand(frame_pointer(), kStackHighEnd));
   1053   __ Subu(a0, backtrack_stackpointer(), a1);
   1054   __ sw(a0, register_location(reg));
   1055 }
   1056 
   1057 
   1058 bool RegExpMacroAssemblerMIPS::CanReadUnaligned() {
   1059   return false;
   1060 }
   1061 
   1062 
   1063 // Private methods:
   1064 
   1065 void RegExpMacroAssemblerMIPS::CallCheckStackGuardState(Register scratch) {
   1066   static const int num_arguments = 3;
   1067   __ PrepareCallCFunction(num_arguments, scratch);
   1068   __ mov(a2, frame_pointer());
   1069   // Code* of self.
   1070   __ li(a1, Operand(masm_->CodeObject()), CONSTANT_SIZE);
   1071   // a0 becomes return address pointer.
   1072   ExternalReference stack_guard_check =
   1073       ExternalReference::re_check_stack_guard_state(masm_->isolate());
   1074   CallCFunctionUsingStub(stack_guard_check, num_arguments);
   1075 }
   1076 
   1077 
   1078 // Helper function for reading a value out of a stack frame.
   1079 template <typename T>
   1080 static T& frame_entry(Address re_frame, int frame_offset) {
   1081   return reinterpret_cast<T&>(Memory::int32_at(re_frame + frame_offset));
   1082 }
   1083 
   1084 
   1085 int RegExpMacroAssemblerMIPS::CheckStackGuardState(Address* return_address,
   1086                                                    Code* re_code,
   1087                                                    Address re_frame) {
   1088   Isolate* isolate = frame_entry<Isolate*>(re_frame, kIsolate);
   1089   ASSERT(isolate == Isolate::Current());
   1090   if (isolate->stack_guard()->IsStackOverflow()) {
   1091     isolate->StackOverflow();
   1092     return EXCEPTION;
   1093   }
   1094 
   1095   // If not real stack overflow the stack guard was used to interrupt
   1096   // execution for another purpose.
   1097 
   1098   // If this is a direct call from JavaScript retry the RegExp forcing the call
   1099   // through the runtime system. Currently the direct call cannot handle a GC.
   1100   if (frame_entry<int>(re_frame, kDirectCall) == 1) {
   1101     return RETRY;
   1102   }
   1103 
   1104   // Prepare for possible GC.
   1105   HandleScope handles(isolate);
   1106   Handle<Code> code_handle(re_code);
   1107 
   1108   Handle<String> subject(frame_entry<String*>(re_frame, kInputString));
   1109   // Current string.
   1110   bool is_ascii = subject->IsOneByteRepresentationUnderneath();
   1111 
   1112   ASSERT(re_code->instruction_start() <= *return_address);
   1113   ASSERT(*return_address <=
   1114       re_code->instruction_start() + re_code->instruction_size());
   1115 
   1116   MaybeObject* result = Execution::HandleStackGuardInterrupt(isolate);
   1117 
   1118   if (*code_handle != re_code) {  // Return address no longer valid.
   1119     int delta = code_handle->address() - re_code->address();
   1120     // Overwrite the return address on the stack.
   1121     *return_address += delta;
   1122   }
   1123 
   1124   if (result->IsException()) {
   1125     return EXCEPTION;
   1126   }
   1127 
   1128   Handle<String> subject_tmp = subject;
   1129   int slice_offset = 0;
   1130 
   1131   // Extract the underlying string and the slice offset.
   1132   if (StringShape(*subject_tmp).IsCons()) {
   1133     subject_tmp = Handle<String>(ConsString::cast(*subject_tmp)->first());
   1134   } else if (StringShape(*subject_tmp).IsSliced()) {
   1135     SlicedString* slice = SlicedString::cast(*subject_tmp);
   1136     subject_tmp = Handle<String>(slice->parent());
   1137     slice_offset = slice->offset();
   1138   }
   1139 
   1140   // String might have changed.
   1141   if (subject_tmp->IsOneByteRepresentation() != is_ascii) {
   1142     // If we changed between an ASCII and an UC16 string, the specialized
   1143     // code cannot be used, and we need to restart regexp matching from
   1144     // scratch (including, potentially, compiling a new version of the code).
   1145     return RETRY;
   1146   }
   1147 
   1148   // Otherwise, the content of the string might have moved. It must still
   1149   // be a sequential or external string with the same content.
   1150   // Update the start and end pointers in the stack frame to the current
   1151   // location (whether it has actually moved or not).
   1152   ASSERT(StringShape(*subject_tmp).IsSequential() ||
   1153       StringShape(*subject_tmp).IsExternal());
   1154 
   1155   // The original start address of the characters to match.
   1156   const byte* start_address = frame_entry<const byte*>(re_frame, kInputStart);
   1157 
   1158   // Find the current start address of the same character at the current string
   1159   // position.
   1160   int start_index = frame_entry<int>(re_frame, kStartIndex);
   1161   const byte* new_address = StringCharacterPosition(*subject_tmp,
   1162                                                     start_index + slice_offset);
   1163 
   1164   if (start_address != new_address) {
   1165     // If there is a difference, update the object pointer and start and end
   1166     // addresses in the RegExp stack frame to match the new value.
   1167     const byte* end_address = frame_entry<const byte* >(re_frame, kInputEnd);
   1168     int byte_length = static_cast<int>(end_address - start_address);
   1169     frame_entry<const String*>(re_frame, kInputString) = *subject;
   1170     frame_entry<const byte*>(re_frame, kInputStart) = new_address;
   1171     frame_entry<const byte*>(re_frame, kInputEnd) = new_address + byte_length;
   1172   } else if (frame_entry<const String*>(re_frame, kInputString) != *subject) {
   1173     // Subject string might have been a ConsString that underwent
   1174     // short-circuiting during GC. That will not change start_address but
   1175     // will change pointer inside the subject handle.
   1176     frame_entry<const String*>(re_frame, kInputString) = *subject;
   1177   }
   1178 
   1179   return 0;
   1180 }
   1181 
   1182 
   1183 MemOperand RegExpMacroAssemblerMIPS::register_location(int register_index) {
   1184   ASSERT(register_index < (1<<30));
   1185   if (num_registers_ <= register_index) {
   1186     num_registers_ = register_index + 1;
   1187   }
   1188   return MemOperand(frame_pointer(),
   1189                     kRegisterZero - register_index * kPointerSize);
   1190 }
   1191 
   1192 
   1193 void RegExpMacroAssemblerMIPS::CheckPosition(int cp_offset,
   1194                                              Label* on_outside_input) {
   1195   BranchOrBacktrack(on_outside_input,
   1196                     ge,
   1197                     current_input_offset(),
   1198                     Operand(-cp_offset * char_size()));
   1199 }
   1200 
   1201 
   1202 void RegExpMacroAssemblerMIPS::BranchOrBacktrack(Label* to,
   1203                                                  Condition condition,
   1204                                                  Register rs,
   1205                                                  const Operand& rt) {
   1206   if (condition == al) {  // Unconditional.
   1207     if (to == NULL) {
   1208       Backtrack();
   1209       return;
   1210     }
   1211     __ jmp(to);
   1212     return;
   1213   }
   1214   if (to == NULL) {
   1215     __ Branch(&backtrack_label_, condition, rs, rt);
   1216     return;
   1217   }
   1218   __ Branch(to, condition, rs, rt);
   1219 }
   1220 
   1221 
   1222 void RegExpMacroAssemblerMIPS::SafeCall(Label* to,
   1223                                         Condition cond,
   1224                                         Register rs,
   1225                                         const Operand& rt) {
   1226   __ BranchAndLink(to, cond, rs, rt);
   1227 }
   1228 
   1229 
   1230 void RegExpMacroAssemblerMIPS::SafeReturn() {
   1231   __ pop(ra);
   1232   __ Addu(t5, ra, Operand(masm_->CodeObject()));
   1233   __ Jump(t5);
   1234 }
   1235 
   1236 
   1237 void RegExpMacroAssemblerMIPS::SafeCallTarget(Label* name) {
   1238   __ bind(name);
   1239   __ Subu(ra, ra, Operand(masm_->CodeObject()));
   1240   __ push(ra);
   1241 }
   1242 
   1243 
   1244 void RegExpMacroAssemblerMIPS::Push(Register source) {
   1245   ASSERT(!source.is(backtrack_stackpointer()));
   1246   __ Addu(backtrack_stackpointer(),
   1247           backtrack_stackpointer(),
   1248           Operand(-kPointerSize));
   1249   __ sw(source, MemOperand(backtrack_stackpointer()));
   1250 }
   1251 
   1252 
   1253 void RegExpMacroAssemblerMIPS::Pop(Register target) {
   1254   ASSERT(!target.is(backtrack_stackpointer()));
   1255   __ lw(target, MemOperand(backtrack_stackpointer()));
   1256   __ Addu(backtrack_stackpointer(), backtrack_stackpointer(), kPointerSize);
   1257 }
   1258 
   1259 
   1260 void RegExpMacroAssemblerMIPS::CheckPreemption() {
   1261   // Check for preemption.
   1262   ExternalReference stack_limit =
   1263       ExternalReference::address_of_stack_limit(masm_->isolate());
   1264   __ li(a0, Operand(stack_limit));
   1265   __ lw(a0, MemOperand(a0));
   1266   SafeCall(&check_preempt_label_, ls, sp, Operand(a0));
   1267 }
   1268 
   1269 
   1270 void RegExpMacroAssemblerMIPS::CheckStackLimit() {
   1271   ExternalReference stack_limit =
   1272       ExternalReference::address_of_regexp_stack_limit(masm_->isolate());
   1273 
   1274   __ li(a0, Operand(stack_limit));
   1275   __ lw(a0, MemOperand(a0));
   1276   SafeCall(&stack_overflow_label_, ls, backtrack_stackpointer(), Operand(a0));
   1277 }
   1278 
   1279 
   1280 void RegExpMacroAssemblerMIPS::CallCFunctionUsingStub(
   1281     ExternalReference function,
   1282     int num_arguments) {
   1283   // Must pass all arguments in registers. The stub pushes on the stack.
   1284   ASSERT(num_arguments <= 4);
   1285   __ li(code_pointer(), Operand(function));
   1286   RegExpCEntryStub stub;
   1287   __ CallStub(&stub);
   1288   if (OS::ActivationFrameAlignment() != 0) {
   1289     __ lw(sp, MemOperand(sp, 16));
   1290   }
   1291   __ li(code_pointer(), Operand(masm_->CodeObject()), CONSTANT_SIZE);
   1292 }
   1293 
   1294 
   1295 void RegExpMacroAssemblerMIPS::LoadCurrentCharacterUnchecked(int cp_offset,
   1296                                                              int characters) {
   1297   Register offset = current_input_offset();
   1298   if (cp_offset != 0) {
   1299     // t7 is not being used to store the capture start index at this point.
   1300     __ Addu(t7, current_input_offset(), Operand(cp_offset * char_size()));
   1301     offset = t7;
   1302   }
   1303   // We assume that we cannot do unaligned loads on MIPS, so this function
   1304   // must only be used to load a single character at a time.
   1305   ASSERT(characters == 1);
   1306   __ Addu(t5, end_of_input_address(), Operand(offset));
   1307   if (mode_ == ASCII) {
   1308     __ lbu(current_character(), MemOperand(t5, 0));
   1309   } else {
   1310     ASSERT(mode_ == UC16);
   1311     __ lhu(current_character(), MemOperand(t5, 0));
   1312   }
   1313 }
   1314 
   1315 
   1316 void RegExpCEntryStub::Generate(MacroAssembler* masm_) {
   1317   int stack_alignment = OS::ActivationFrameAlignment();
   1318   if (stack_alignment < kPointerSize) stack_alignment = kPointerSize;
   1319   // Stack is already aligned for call, so decrement by alignment
   1320   // to make room for storing the return address.
   1321   __ Subu(sp, sp, Operand(stack_alignment + kCArgsSlotsSize));
   1322   const int return_address_offset = kCArgsSlotsSize;
   1323   __ Addu(a0, sp, return_address_offset);
   1324   __ sw(ra, MemOperand(a0, 0));
   1325   __ mov(t9, t1);
   1326   __ Call(t9);
   1327   __ lw(ra, MemOperand(sp, return_address_offset));
   1328   __ Addu(sp, sp, Operand(stack_alignment + kCArgsSlotsSize));
   1329   __ Jump(ra);
   1330 }
   1331 
   1332 
   1333 #undef __
   1334 
   1335 #endif  // V8_INTERPRETED_REGEXP
   1336 
   1337 }}  // namespace v8::internal
   1338 
   1339 #endif  // V8_TARGET_ARCH_MIPS
   1340