Submit regexp-macro-assembler-mips.cc.

src/mips/regexp-macro-assembler-mips.cc

Index: src/mips/regexp-macro-assembler-mips.cc
diff --git a/src/mips/regexp-macro-assembler-mips.cc b/src/mips/regexp-macro-assembler-mips.cc
index fc1232c21035b4edb6eade581ad3c9fb5362e6a5..cfc8f651c7b1018b01d40095904039df26765697 100644
--- a/src/mips/regexp-macro-assembler-mips.cc
+++ b/src/mips/regexp-macro-assembler-mips.cc
@@ -56,49 +56,58 @@ namespace internal {
  * - 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:
- *       - direct_call        (if 1, direct call from JavaScript code, if 0 call
- *                             through the runtime system)
- *       - stack_area_base    (High end of the memory area to use as
- *                             backtracking stack)
- *       - int* capture_array (int[num_saved_registers_], for output).
- *       - stack frame header (16 bytes in size)
- *       --- sp when called ---
- *       - link address
- *       - backup of registers s0..s7
- *       - end of input       (Address of end of string)
- *       - start of input     (Address of first character in string)
- *       - start index        (character index of start)
- *       --- frame pointer ----
- *       - void* input_string (location of a handle containing the string)
- *       - Offset of location before start of input (effectively character
- *         position -1). Used to initialize capture registers to a non-position.
- *       - At start (if 1, we are starting at the start of the
- *         string, otherwise 0)
- *       - register 0         (Only positions must be stored in the first
- *       - register 1          num_saved_registers_ registers)
- *       - ...
- *       - register num_registers-1
- *       --- sp ---
+ *
+ *  - fp[56]  direct_call  (if 1, direct call from JavaScript code,
+ *                          if 0, call through the runtime system).
+ *  - fp[52]  stack_area_base (High end of the memory area to use as
+ *                             backtracking stack).
+ *  - fp[48]  int* capture_array (int[num_saved_registers_], for output).
+ *  - fp[44]  secondary link/return address used by native call.
+ *  --- sp when called ---
+ *  - fp[40]  return address (lr).
+ *  - fp[36]  old frame pointer (r11).
+ *  - fp[0..32]  backup of registers s0..s7.
+ *  --- 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] Offset of location before start of input (effectively character
+ *            position -1). Used to initialize capture registers to a
+ *            non-position.
+ *  - fp[-24] At start (if 1, we are starting at the start of the
+ *    string, otherwise 0)
+ *  - fp[-28] 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, by calling the code entry as cast to a function with the signature:
+ * 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,
+ *              Address secondary_return_address,  // Only used by native call.
  *              int* capture_output_array,
- *              bool at_start,
  *              byte* stack_area_base,
- *              bool direct_call)
+ *              bool direct_call = false)
  * The call is performed by NativeRegExpMacroAssembler::Execute()
- * (in regexp-macro-assembler.cc).
+ * (in regexp-macro-assembler.cc) via the CALL_GENERATED_REGEXP_CODE macro
+ * in mips/simulator-mips.h.
+ * When calling as a non-direct call (i.e., from C++ code), the return address
+ * area is overwritten with the ra register by the RegExp code. When doing a
+ * direct call from generated code, the return address is placed there by
+ * the calling code, as in a normal exit frame.
  */
 
 #define __ ACCESS_MASM(masm_)
@@ -114,9 +123,15 @@ RegExpMacroAssemblerMIPS::RegExpMacroAssemblerMIPS(
       start_label_(),
       success_label_(),
       backtrack_label_(),
-      exit_label_() {
+      exit_label_(),
+      internal_failure_label_() {
   ASSERT_EQ(0, registers_to_save % 2);
   __ jmp(&entry_label_);   // We'll write the entry code later.
+  // If the code gets too big or corrupted, an internal exception will be
+  // raised, and we will exit right away.
+  __ bind(&internal_failure_label_);
+  __ li(v0, Operand(FAILURE));
+  __ Ret();
   __ bind(&start_label_);  // And then continue from here.
 }
 
@@ -131,6 +146,7 @@ RegExpMacroAssemblerMIPS::~RegExpMacroAssemblerMIPS() {
   exit_label_.Unuse();
   check_preempt_label_.Unuse();
   stack_overflow_label_.Unuse();
+  internal_failure_label_.Unuse();
 }
 
 
@@ -140,47 +156,75 @@ int RegExpMacroAssemblerMIPS::stack_limit_slack()  {
 
 
 void RegExpMacroAssemblerMIPS::AdvanceCurrentPosition(int by) {
-  UNIMPLEMENTED_MIPS();
+  if (by != 0) {
+    __ Addu(current_input_offset(),
+           current_input_offset(), Operand(by * char_size()));
+  }
 }
 
 
 void RegExpMacroAssemblerMIPS::AdvanceRegister(int reg, int by) {
-  UNIMPLEMENTED_MIPS();
+  ASSERT(reg >= 0);
+  ASSERT(reg < num_registers_);
+  if (by != 0) {
+    __ lw(a0, register_location(reg));
+    __ Addu(a0, a0, Operand(by));
+    __ sw(a0, register_location(reg));
+  }
 }
 
 
 void RegExpMacroAssemblerMIPS::Backtrack() {
-  UNIMPLEMENTED_MIPS();
+  CheckPreemption();
+  // Pop Code* offset from backtrack stack, add Code* and jump to location.
+  Pop(a0);
+  __ Addu(a0, a0, code_pointer());
+  __ Jump(Operand(a0));
 }
 
 
 void RegExpMacroAssemblerMIPS::Bind(Label* label) {
-  UNIMPLEMENTED_MIPS();
+  __ bind(label);
 }
 
 
 void RegExpMacroAssemblerMIPS::CheckCharacter(uint32_t c, Label* on_equal) {
-  UNIMPLEMENTED_MIPS();
+  BranchOrBacktrack(on_equal, eq, current_character(), Operand(c));
 }
 
 
 void RegExpMacroAssemblerMIPS::CheckCharacterGT(uc16 limit, Label* on_greater) {
-  UNIMPLEMENTED_MIPS();
+  BranchOrBacktrack(on_greater, gt, current_character(), Operand(limit));
 }
 
 
 void RegExpMacroAssemblerMIPS::CheckAtStart(Label* on_at_start) {
-  UNIMPLEMENTED_MIPS();
+  Label not_at_start;
+  // Did we start the match at the start of the string at all?
+  __ lw(a0, MemOperand(frame_pointer(), kAtStart));
+  BranchOrBacktrack(&not_at_start, eq, a0, Operand(zero_reg));
+
+  // If we did, are we still at the start of the input?
+  __ lw(a1, MemOperand(frame_pointer(), kInputStart));
+  __ Addu(a0, end_of_input_address(), Operand(current_input_offset()));
+  BranchOrBacktrack(on_at_start, eq, a0, Operand(a1));
+  __ bind(&not_at_start);
 }
 
 
 void RegExpMacroAssemblerMIPS::CheckNotAtStart(Label* on_not_at_start) {
-  UNIMPLEMENTED_MIPS();
+  // Did we start the match at the start of the string at all?
+  __ lw(a0, MemOperand(frame_pointer(), kAtStart));
+  BranchOrBacktrack(on_not_at_start, eq, a0, Operand(zero_reg));
+  // If we did, are we still at the start of the input?
+  __ lw(a1, MemOperand(frame_pointer(), kInputStart));
+  __ Addu(a0, end_of_input_address(), Operand(current_input_offset()));
+  BranchOrBacktrack(on_not_at_start, ne, a0, Operand(a1));
 }
 
 
 void RegExpMacroAssemblerMIPS::CheckCharacterLT(uc16 limit, Label* on_less) {
-  UNIMPLEMENTED_MIPS();
+  BranchOrBacktrack(on_less, lt, current_character(), Operand(limit));
 }
 
 
@@ -188,26 +232,212 @@ void RegExpMacroAssemblerMIPS::CheckCharacters(Vector<const uc16> str,
                                               int cp_offset,
                                               Label* on_failure,
                                               bool check_end_of_string) {
-  UNIMPLEMENTED_MIPS();
+  if (on_failure == NULL) {
+    // Instead of inlining a backtrack for each test, (re)use the global
+    // backtrack target.
+    on_failure = &backtrack_label_;
+  }
+
+  if (check_end_of_string) {
+    // Is last character of required match inside string.
+    CheckPosition(cp_offset + str.length() - 1, on_failure);
+  }
+
+  __ Addu(a0, end_of_input_address(), Operand(current_input_offset()));
+  if (cp_offset != 0) {
+    int byte_offset = cp_offset * char_size();
+    __ Addu(a0, a0, Operand(byte_offset));
+  }
+
+  // a0 : Address of characters to match against str.
+  int stored_high_byte = 0;
+  for (int i = 0; i < str.length(); i++) {
+    if (mode_ == ASCII) {
+      __ lbu(a1, MemOperand(a0, 0));
+      __ addiu(a0, a0, char_size());
+      ASSERT(str[i] <= String::kMaxAsciiCharCode);
+      BranchOrBacktrack(on_failure, ne, a1, Operand(str[i]));
+    } else {
+      __ lhu(a1, MemOperand(a0, 0));
+      __ addiu(a0, a0, char_size());
+      uc16 match_char = str[i];
+      int match_high_byte = (match_char >> 8);
+      if (match_high_byte == 0) {
+        BranchOrBacktrack(on_failure, ne, a1, Operand(str[i]));
+      } else {
+        if (match_high_byte != stored_high_byte) {
+          __ li(a2, Operand(match_high_byte));
+          stored_high_byte = match_high_byte;
+        }
+        __ Addu(a3, a2, Operand(match_char & 0xff));
+        BranchOrBacktrack(on_failure, ne, a1, Operand(a3));
+      }
+    }
+  }
 }
 
 
 void RegExpMacroAssemblerMIPS::CheckGreedyLoop(Label* on_equal) {
-  UNIMPLEMENTED_MIPS();
+  Label backtrack_non_equal;
+  __ lw(a0, MemOperand(backtrack_stackpointer(), 0));
+  __ Branch(&backtrack_non_equal, ne, current_input_offset(), Operand(a0));
+  __ Addu(backtrack_stackpointer(),
+          backtrack_stackpointer(),
+          Operand(kPointerSize));
+  __ bind(&backtrack_non_equal);
+  BranchOrBacktrack(on_equal, eq, current_input_offset(), Operand(a0));
 }
 
 
 void RegExpMacroAssemblerMIPS::CheckNotBackReferenceIgnoreCase(
     int start_reg,
     Label* on_no_match) {
-  UNIMPLEMENTED_MIPS();
+  Label fallthrough;
+  __ lw(a0, register_location(start_reg));  // Index of start of capture.
+  __ lw(a1, register_location(start_reg + 1));  // Index of end of capture.
+  __ Subu(a1, a1, a0);  // Length of capture.
+
+  // If length is zero, either the capture is empty or it is not participating.
+  // In either case succeed immediately.
+  __ Branch(&fallthrough, eq, a1, Operand(zero_reg));
+
+  __ Addu(t5, a1, current_input_offset());
+  // Check that there are enough characters left in the input.
+  BranchOrBacktrack(on_no_match, gt, t5, Operand(zero_reg));
+
+  if (mode_ == ASCII) {
+    Label success;
+    Label fail;
+    Label loop_check;
+
+    // a0 - offset of start of capture.
+    // a1 - length of capture.
+    __ Addu(a0, a0, Operand(end_of_input_address()));
+    __ Addu(a2, end_of_input_address(), Operand(current_input_offset()));
+    __ Addu(a1, a0, Operand(a1));
+
+    // a0 - Address of start of capture.
+    // a1 - Address of end of capture.
+    // a2 - Address of current input position.
+
+    Label loop;
+    __ bind(&loop);
+    __ lbu(a3, MemOperand(a0, 0));
+    __ addiu(a0, a0, char_size());
+    __ lbu(t0, MemOperand(a2, 0));
+    __ addiu(a2, a2, char_size());
+
+    __ Branch(&loop_check, eq, t0, Operand(a3));
+
+    // Mismatch, try case-insensitive match (converting letters to lower-case).
+    __ Or(a3, a3, Operand(0x20));  // Convert capture character to lower-case.
+    __ Or(t0, t0, Operand(0x20));  // Also convert input character.
+    __ Branch(&fail, ne, t0, Operand(a3));
+    __ Subu(a3, a3, Operand('a'));
+    __ Branch(&fail, hi, a3, Operand('z' - 'a'));  // Is a3 a lowercase letter?
+
+    __ bind(&loop_check);
+    __ Branch(&loop, lt, a0, Operand(a1));
+    __ jmp(&success);
+
+    __ bind(&fail);
+    GoTo(on_no_match);
+
+    __ bind(&success);
+    // Compute new value of character position after the matched part.
+    __ Subu(current_input_offset(), a2, end_of_input_address());
+  } else {
+    ASSERT(mode_ == UC16);
+    // Put regexp engine registers on stack.
+    RegList regexp_registers_to_retain = current_input_offset().bit() |
+        current_character().bit() | backtrack_stackpointer().bit();
+    __ MultiPush(regexp_registers_to_retain);
+
+    int argument_count = 4;
+    __ PrepareCallCFunction(argument_count, a2);
+
+    // a0 - offset of start of capture.
+    // a1 - length of capture.
+
+    // Put arguments into arguments registers.
+    // Parameters are
+    //   a0: Address byte_offset1 - Address captured substring's start.
+    //   a1: Address byte_offset2 - Address of current character position.
+    //   a2: size_t byte_length - length of capture in bytes(!).
+    //   a3: Isolate* isolate.
+
+    // Address of start of capture.
+    __ Addu(a0, a0, Operand(end_of_input_address()));
+    // Length of capture.
+    __ mov(a2, a1);
+    // Save length in callee-save register for use on return.
+    __ mov(s3, a1);
+    // Address of current input position.
+    __ Addu(a1, current_input_offset(), Operand(end_of_input_address()));
+    // Isolate.
+    __ li(a3, Operand(ExternalReference::isolate_address()));
+
+    ExternalReference function =
+        ExternalReference::re_case_insensitive_compare_uc16(masm_->isolate());
+    __ CallCFunction(function, argument_count);
+
+    // Restore regexp engine registers.
+    __ MultiPop(regexp_registers_to_retain);
+    __ li(code_pointer(), Operand(masm_->CodeObject()));
+    __ lw(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
+
+    // Check if function returned non-zero for success or zero for failure.
+    BranchOrBacktrack(on_no_match, eq, v0, Operand(zero_reg));
+    // On success, increment position by length of capture.
+    __ Addu(current_input_offset(), current_input_offset(), Operand(s3));
+  }
+
+  __ bind(&fallthrough);
 }
 
 
 void RegExpMacroAssemblerMIPS::CheckNotBackReference(
     int start_reg,
     Label* on_no_match) {
-  UNIMPLEMENTED_MIPS();
+  Label fallthrough;
+  Label success;
+
+  // Find length of back-referenced capture.
+  __ lw(a0, register_location(start_reg));
+  __ lw(a1, register_location(start_reg + 1));
+  __ Subu(a1, a1, a0);  // Length to check.
+  // Succeed on empty capture (including no capture).
+  __ Branch(&fallthrough, eq, a1, Operand(zero_reg));
+
+  __ Addu(t5, a1, current_input_offset());
+  // Check that there are enough characters left in the input.
+  BranchOrBacktrack(on_no_match, gt, t5, Operand(zero_reg));
+
+  // Compute pointers to match string and capture string.
+  __ Addu(a0, a0, Operand(end_of_input_address()));
+  __ Addu(a2, end_of_input_address(), Operand(current_input_offset()));
+  __ Addu(a1, a1, Operand(a0));
+
+  Label loop;
+  __ bind(&loop);
+  if (mode_ == ASCII) {
+    __ lbu(a3, MemOperand(a0, 0));
+    __ addiu(a0, a0, char_size());
+    __ lbu(t0, MemOperand(a2, 0));
+    __ addiu(a2, a2, char_size());
+  } else {
+    ASSERT(mode_ == UC16);
+    __ lhu(a3, MemOperand(a0, 0));
+    __ addiu(a0, a0, char_size());
+    __ lhu(t0, MemOperand(a2, 0));
+    __ addiu(a2, a2, char_size());
+  }
+  BranchOrBacktrack(on_no_match, ne, a3, Operand(t0));
+  __ Branch(&loop, lt, a0, Operand(a1));
+
+  // Move current character position to position after match.
+  __ Subu(current_input_offset(), a2, end_of_input_address());
+  __ bind(&fallthrough);
 }
 
 
@@ -220,21 +450,23 @@ void RegExpMacroAssemblerMIPS::CheckNotRegistersEqual(int reg1,
 
 void RegExpMacroAssemblerMIPS::CheckNotCharacter(uint32_t c,
                                                 Label* on_not_equal) {
-  UNIMPLEMENTED_MIPS();
+  BranchOrBacktrack(on_not_equal, ne, current_character(), Operand(c));
 }
 
 
 void RegExpMacroAssemblerMIPS::CheckCharacterAfterAnd(uint32_t c,
                                                      uint32_t mask,
                                                      Label* on_equal) {
-  UNIMPLEMENTED_MIPS();
+  __ And(a0, current_character(), Operand(mask));
+  BranchOrBacktrack(on_equal, eq, a0, Operand(c));
 }
 
 
 void RegExpMacroAssemblerMIPS::CheckNotCharacterAfterAnd(uint32_t c,
                                                         uint32_t mask,
                                                         Label* on_not_equal) {
-  UNIMPLEMENTED_MIPS();
+  __ And(a0, current_character(), Operand(mask));
+  BranchOrBacktrack(on_not_equal, ne, a0, Operand(c));
 }
 
 
@@ -249,24 +481,360 @@ void RegExpMacroAssemblerMIPS::CheckNotCharacterAfterMinusAnd(
 
 bool RegExpMacroAssemblerMIPS::CheckSpecialCharacterClass(uc16 type,
                                                          Label* on_no_match) {
-  UNIMPLEMENTED_MIPS();
-  return false;
+  // 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_ == ASCII) {
+      // ASCII space characters are '\t'..'\r' and ' '.
+      Label success;
+      __ Branch(&success, eq, current_character(), Operand(' '));
+      // Check range 0x09..0x0d.
+      __ Subu(a0, current_character(), Operand('\t'));
+      BranchOrBacktrack(on_no_match, hi, a0, Operand('\r' - '\t'));
+      __ bind(&success);
+      return true;
+    }
+    return false;
+  case 'S':
+    // Match non-space characters.
+    if (mode_ == ASCII) {
+      // ASCII space characters are '\t'..'\r' and ' '.
+      BranchOrBacktrack(on_no_match, eq, current_character(), Operand(' '));
+      __ Subu(a0, current_character(), Operand('\t'));
+      BranchOrBacktrack(on_no_match, ls, a0, Operand('\r' - '\t'));
+      return true;
+    }
+    return false;
+  case 'd':
+    // Match ASCII digits ('0'..'9').
+    __ Subu(a0, current_character(), Operand('0'));
+    BranchOrBacktrack(on_no_match, hi, a0, Operand('9' - '0'));
+    return true;
+  case 'D':
+    // Match non ASCII-digits.
+    __ Subu(a0, current_character(), Operand('0'));
+    BranchOrBacktrack(on_no_match, ls, a0, Operand('9' - '0'));
+    return true;
+  case '.': {
+    // Match non-newlines (not 0x0a('\n'), 0x0d('\r'), 0x2028 and 0x2029).
+    __ Xor(a0, current_character(), Operand(0x01));
+    // See if current character is '\n'^1 or '\r'^1, i.e., 0x0b or 0x0c.
+    __ Subu(a0, a0, Operand(0x0b));
+    BranchOrBacktrack(on_no_match, ls, a0, Operand(0x0c - 0x0b));
+    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.
+      __ Subu(a0, a0, Operand(0x2028 - 0x0b));
+      BranchOrBacktrack(on_no_match, ls, a0, Operand(1));
+    }
+    return true;
+  }
+  case 'n': {
+    // Match newlines (0x0a('\n'), 0x0d('\r'), 0x2028 and 0x2029).
+    __ Xor(a0, current_character(), Operand(0x01));
+    // See if current character is '\n'^1 or '\r'^1, i.e., 0x0b or 0x0c.
+    __ Subu(a0, a0, Operand(0x0b));
+    if (mode_ == ASCII) {
+      BranchOrBacktrack(on_no_match, hi, a0, Operand(0x0c - 0x0b));
+    } else {
+      Label done;
+      BranchOrBacktrack(&done, ls, a0, Operand(0x0c - 0x0b));
+      // Compare original value to 0x2028 and 0x2029, using the already
+      // computed (current_char ^ 0x01 - 0x0b). I.e., check for
+      // 0x201d (0x2028 - 0x0b) or 0x201e.
+      __ Subu(a0, a0, Operand(0x2028 - 0x0b));
+      BranchOrBacktrack(on_no_match, hi, a0, Operand(1));
+      __ bind(&done);
+    }
+    return true;
+  }
+  case 'w': {
+    if (mode_ != ASCII) {
+      // Table is 128 entries, so all ASCII characters can be tested.
+      BranchOrBacktrack(on_no_match, hi, current_character(), Operand('z'));
+    }
+    ExternalReference map = ExternalReference::re_word_character_map();
+    __ li(a0, Operand(map));
+    __ Addu(a0, a0, current_character());
+    __ lbu(a0, MemOperand(a0, 0));
+    BranchOrBacktrack(on_no_match, eq, a0, Operand(zero_reg));
+    return true;
+  }
+  case 'W': {
+    Label done;
+    if (mode_ != ASCII) {
+      // Table is 128 entries, so all ASCII characters can be tested.
+      __ Branch(&done, hi, current_character(), Operand('z'));
+    }
+    ExternalReference map = ExternalReference::re_word_character_map();
+    __ li(a0, Operand(map));
+    __ Addu(a0, a0, current_character());
+    __ lbu(a0, MemOperand(a0, 0));
+    BranchOrBacktrack(on_no_match, ne, a0, Operand(zero_reg));
+    if (mode_ != ASCII) {
+      __ bind(&done);
+    }
+    return true;
+  }
+  case '*':
+    // Match any character.
+    return true;
+  // No custom implementation (yet): s(UC16), S(UC16).
+  default:
+    return false;
+  }
 }
 
 
 void RegExpMacroAssemblerMIPS::Fail() {
-  UNIMPLEMENTED_MIPS();
+  __ li(v0, Operand(FAILURE));
+  __ jmp(&exit_label_);
 }
 
 
 Handle<HeapObject> RegExpMacroAssemblerMIPS::GetCode(Handle<String> source) {
-  UNIMPLEMENTED_MIPS();
-  return Handle<HeapObject>::null();
+  if (masm_->has_exception()) {
+    // If the code gets corrupted due to long regular expressions and lack of
+    // space on trampolines, an internal exception flag is set. If this case
+    // is detected, we will jump into exit sequence right away.
+    __ bind_to(&entry_label_, internal_failure_label_.pos());
+  } else {
+    // Finalize code - write the entry point code now we know how many
+    // registers we need.
+
+    // Entry code:
+    __ bind(&entry_label_);
+    // 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 = s0.bit() | s1.bit() | s2.bit() |
+        s3.bit() | s4.bit() | s5.bit() | s6.bit() | s7.bit() | fp.bit();
+    RegList argument_registers = a0.bit() | a1.bit() | a2.bit() | a3.bit();
+    __ MultiPush(argument_registers | registers_to_retain | ra.bit());
+    // Set frame pointer in space for it if this is not a direct call
+    // from generated code.
+    __ Addu(frame_pointer(), sp, Operand(4 * kPointerSize));
+    __ push(a0);  // Make room for "position - 1" constant (value irrelevant).
+    __ push(a0);  // Make room for "at start" constant (value irrelevant).
+
+    // 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(masm_->isolate());
+    __ li(a0, Operand(stack_limit));
+    __ lw(a0, MemOperand(a0));
+    __ Subu(a0, sp, a0);
+    // Handle it if the stack pointer is already below the stack limit.
+    __ Branch(&stack_limit_hit, le, a0, Operand(zero_reg));
+    // Check if there is room for the variable number of registers above
+    // the stack limit.
+    __ Branch(&stack_ok, hs, a0, Operand(num_registers_ * kPointerSize));
+    // Exit with OutOfMemory exception. There is not enough space on the stack
+    // for our working registers.
+    __ li(v0, Operand(EXCEPTION));
+    __ jmp(&exit_label_);
+
+    __ bind(&stack_limit_hit);
+    CallCheckStackGuardState(a0);
+    // If returned value is non-zero, we exit with the returned value as result.
+    __ Branch(&exit_label_, ne, v0, Operand(zero_reg));
+
+    __ bind(&stack_ok);
+    // Allocate space on stack for registers.
+    __ Subu(sp, sp, Operand(num_registers_ * kPointerSize));
+    // Load string end.
+    __ lw(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
+    // Load input start.
+    __ lw(a0, MemOperand(frame_pointer(), kInputStart));
+    // Find negative length (offset of start relative to end).
+    __ Subu(current_input_offset(), a0, end_of_input_address());
+    // Set a0 to address of char before start of the input string
+    // (effectively string position -1).
+    __ lw(a1, MemOperand(frame_pointer(), kStartIndex));
+    __ Subu(a0, current_input_offset(), Operand(char_size()));
+    __ sll(t5, a1, (mode_ == UC16) ? 1 : 0);
+    __ Subu(a0, a0, t5);
+    // Store this value in a local variable, for use when clearing
+    // position registers.
+    __ sw(a0, MemOperand(frame_pointer(), kInputStartMinusOne));
+
+    // Determine whether the start index is zero, that is at the start of the
+    // string, and store that value in a local variable.
+    __ mov(t5, a1);
+    __ li(a1, Operand(1));
+    __ movn(a1, zero_reg, t5);
+    __ sw(a1, MemOperand(frame_pointer(), kAtStart));
+
+    if (num_saved_registers_ > 0) {  // Always is, if generated from a regexp.
+      // Fill saved registers with initial value = start offset - 1.
+
+      // Address of register 0.
+      __ Addu(a1, frame_pointer(), Operand(kRegisterZero));
+      __ li(a2, Operand(num_saved_registers_));
+      Label init_loop;
+      __ bind(&init_loop);
+      __ sw(a0, MemOperand(a1));
+      __ Addu(a1, a1, Operand(-kPointerSize));
+      __ Subu(a2, a2, Operand(1));
+      __ Branch(&init_loop, ne, a2, Operand(zero_reg));
+    }
+
+    // Initialize backtrack stack pointer.
+    __ lw(backtrack_stackpointer(), MemOperand(frame_pointer(), kStackHighEnd));
+    // Initialize code pointer register
+    __ li(code_pointer(), Operand(masm_->CodeObject()));
+    // Load previous char as initial value of current character register.
+    Label at_start;
+    __ lw(a0, MemOperand(frame_pointer(), kAtStart));
+    __ Branch(&at_start, ne, a0, Operand(zero_reg));
+    LoadCurrentCharacterUnchecked(-1, 1);  // Load previous char.
+    __ jmp(&start_label_);
+    __ bind(&at_start);
+    __ li(current_character(), Operand('\n'));
+    __ 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.
+        __ lw(a1, MemOperand(frame_pointer(), kInputStart));
+        __ lw(a0, MemOperand(frame_pointer(), kRegisterOutput));
+        __ lw(a2, MemOperand(frame_pointer(), kStartIndex));
+        __ Subu(a1, end_of_input_address(), a1);
+        // a1 is length of input in bytes.
+        if (mode_ == UC16) {
+          __ srl(a1, a1, 1);
+        }
+        // a1 is length of input in characters.
+        __ Addu(a1, a1, Operand(a2));
+        // a1 is length of string in characters.
+
+        ASSERT_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) {
+          __ lw(a2, register_location(i));
+          __ lw(a3, register_location(i + 1));
+          if (mode_ == UC16) {
+            __ sra(a2, a2, 1);
+            __ Addu(a2, a2, a1);
+            __ sra(a3, a3, 1);
+            __ Addu(a3, a3, a1);
+          } else {
+            __ Addu(a2, a1, Operand(a2));
+            __ Addu(a3, a1, Operand(a3));
+          }
+          __ sw(a2, MemOperand(a0));
+          __ Addu(a0, a0, kPointerSize);
+          __ sw(a3, MemOperand(a0));
+          __ Addu(a0, a0, kPointerSize);
+        }
+      }
+      __ li(v0, Operand(SUCCESS));
+    }
+    // Exit and return v0.
+    __ bind(&exit_label_);
+    // Skip sp past regexp registers and local variables..
+    __ mov(sp, frame_pointer());
+    // Restore registers s0..s7 and return (restoring ra to pc).
+    __ MultiPop(registers_to_retain | ra.bit());
+    __ Ret();
+
+    // 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_);
+      // Put regexp engine registers on stack.
+      RegList regexp_registers_to_retain = current_input_offset().bit() |
+          current_character().bit() | backtrack_stackpointer().bit();
+      __ MultiPush(regexp_registers_to_retain);
+      CallCheckStackGuardState(a0);
+      __ MultiPop(regexp_registers_to_retain);
+      // If returning non-zero, we should end execution with the given
+      // result as return value.
+      __ Branch(&exit_label_, ne, v0, Operand(zero_reg));
+
+      // String might have moved: Reload end of string from frame.
+      __ lw(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
+      __ li(code_pointer(), Operand(masm_->CodeObject()));
+      SafeReturn();
+    }
+
+    // Backtrack stack overflow code.
+    if (stack_overflow_label_.is_linked()) {
+      SafeCallTarget(&stack_overflow_label_);
+      // Reached if the backtrack-stack limit has been hit.
+      // Put regexp engine registers on stack first.
+      RegList regexp_registers = current_input_offset().bit() |
+          current_character().bit();
+      __ MultiPush(regexp_registers);
+      Label grow_failed;
+      // Call GrowStack(backtrack_stackpointer(), &stack_base)
+      static const int num_arguments = 3;
+      __ PrepareCallCFunction(num_arguments, a0);
+      __ mov(a0, backtrack_stackpointer());
+      __ Addu(a1, frame_pointer(), Operand(kStackHighEnd));
+      __ li(a2, Operand(ExternalReference::isolate_address()));
+      ExternalReference grow_stack =
+          ExternalReference::re_grow_stack(masm_->isolate());
+      __ CallCFunction(grow_stack, num_arguments);
+      // Restore regexp registers.
+      __ MultiPop(regexp_registers);
+      // If return NULL, we have failed to grow the stack, and
+      // must exit with a stack-overflow exception.
+      __ Branch(&exit_with_exception, eq, v0, Operand(zero_reg));
+      // Otherwise use return value as new stack pointer.
+      __ mov(backtrack_stackpointer(), v0);
+      // Restore saved registers and continue.
+      __ li(code_pointer(), Operand(masm_->CodeObject()));
+      __ lw(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
+      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.
+      __ li(v0, Operand(EXCEPTION));
+      __ jmp(&exit_label_);
+    }
+  }
+
+  CodeDesc code_desc;
+  masm_->GetCode(&code_desc);
+  Handle<Code> code = FACTORY->NewCode(code_desc,
+                                       Code::ComputeFlags(Code::REGEXP),
+                                       masm_->CodeObject());
+  LOG(Isolate::Current(), RegExpCodeCreateEvent(*code, *source));
+  return Handle<HeapObject>::cast(code);
 }
 
 
 void RegExpMacroAssemblerMIPS::GoTo(Label* to) {
-  UNIMPLEMENTED_MIPS();
+  if (to == NULL) {
+    Backtrack();
+    return;
+  }
+  __ jmp(to);
+  return;
 }
 
 
@@ -281,13 +849,15 @@ void RegExpMacroAssemblerMIPS::IfRegisterGE(int reg,
 void RegExpMacroAssemblerMIPS::IfRegisterLT(int reg,
                                            int comparand,
                                            Label* if_lt) {
-  UNIMPLEMENTED_MIPS();
+  __ lw(a0, register_location(reg));
+  BranchOrBacktrack(if_lt, lt, a0, Operand(comparand));
 }
 
 
 void RegExpMacroAssemblerMIPS::IfRegisterEqPos(int reg,
                                               Label* if_eq) {
-  UNIMPLEMENTED_MIPS();
+  __ lw(a0, register_location(reg));
+  BranchOrBacktrack(if_eq, eq, a0, Operand(current_input_offset()));
 }
 
 
@@ -301,23 +871,47 @@ void RegExpMacroAssemblerMIPS::LoadCurrentCharacter(int cp_offset,
                                                    Label* on_end_of_input,
                                                    bool check_bounds,
                                                    int characters) {
-  UNIMPLEMENTED_MIPS();
+  ASSERT(cp_offset >= -1);      // ^ and \b can look behind one character.
+  ASSERT(cp_offset < (1<<30));  // Be sane! (And ensure negation works).
+  if (check_bounds) {
+    CheckPosition(cp_offset + characters - 1, on_end_of_input);
+  }
+  LoadCurrentCharacterUnchecked(cp_offset, characters);
 }
 
 
 void RegExpMacroAssemblerMIPS::PopCurrentPosition() {
-  UNIMPLEMENTED_MIPS();
+  Pop(current_input_offset());
 }
 
 
 void RegExpMacroAssemblerMIPS::PopRegister(int register_index) {
-  UNIMPLEMENTED_MIPS();
+  Pop(a0);
+  __ sw(a0, register_location(register_index));
 }
 
 
-
 void RegExpMacroAssemblerMIPS::PushBacktrack(Label* label) {
-  UNIMPLEMENTED_MIPS();
+  if (label->is_bound()) {
+    int target = label->pos();
+    __ li(a0, Operand(target + Code::kHeaderSize - kHeapObjectTag));
+  } else {
+    Label after_constant;
+    __ Branch(&after_constant);
+    int offset = masm_->pc_offset();
+    int cp_offset = offset + Code::kHeaderSize - kHeapObjectTag;
+    __ emit(0);
+    masm_->label_at_put(label, offset);
+    __ bind(&after_constant);
+    if (is_int16(cp_offset)) {
+      __ lw(a0, MemOperand(code_pointer(), cp_offset));
+    } else {
+      __ Addu(a0, code_pointer(), cp_offset);
+      __ lw(a0, MemOperand(a0, 0));
+    }
+  }
+  Push(a0);
+  CheckStackLimit();
 }
 
 
@@ -328,55 +922,90 @@ void RegExpMacroAssemblerMIPS::PushCurrentPosition() {
 
 void RegExpMacroAssemblerMIPS::PushRegister(int register_index,
                                            StackCheckFlag check_stack_limit) {
-  UNIMPLEMENTED_MIPS();
+  __ lw(a0, register_location(register_index));
+  Push(a0);
+  if (check_stack_limit) CheckStackLimit();
 }
 
 
 void RegExpMacroAssemblerMIPS::ReadCurrentPositionFromRegister(int reg) {
-  UNIMPLEMENTED_MIPS();
+  __ lw(current_input_offset(), register_location(reg));
 }
 
 
 void RegExpMacroAssemblerMIPS::ReadStackPointerFromRegister(int reg) {
-  UNIMPLEMENTED_MIPS();
+  __ lw(backtrack_stackpointer(), register_location(reg));
+  __ lw(a0, MemOperand(frame_pointer(), kStackHighEnd));
+  __ Addu(backtrack_stackpointer(), backtrack_stackpointer(), Operand(a0));
 }
 
 
 void RegExpMacroAssemblerMIPS::SetCurrentPositionFromEnd(int by) {
-  UNIMPLEMENTED_MIPS();
+  Label after_position;
+  __ Branch(&after_position,
+            ge,
+            current_input_offset(),
+            Operand(-by * char_size()));
+  __ li(current_input_offset(), -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 RegExpMacroAssemblerMIPS::SetRegister(int register_index, int to) {
-  UNIMPLEMENTED_MIPS();
+  ASSERT(register_index >= num_saved_registers_);  // Reserved for positions!
+  __ li(a0, Operand(to));
+  __ sw(a0, register_location(register_index));
 }
 
 
 void RegExpMacroAssemblerMIPS::Succeed() {
-  UNIMPLEMENTED_MIPS();
+  __ jmp(&success_label_);
 }
 
 
 void RegExpMacroAssemblerMIPS::WriteCurrentPositionToRegister(int reg,
                                                              int cp_offset) {
-  UNIMPLEMENTED_MIPS();
+  if (cp_offset == 0) {
+    __ sw(current_input_offset(), register_location(reg));
+  } else {
+    __ Addu(a0, current_input_offset(), Operand(cp_offset * char_size()));
+    __ sw(a0, register_location(reg));
+  }
 }
 
 
 void RegExpMacroAssemblerMIPS::ClearRegisters(int reg_from, int reg_to) {
-  UNIMPLEMENTED_MIPS();
+  ASSERT(reg_from <= reg_to);
+  __ lw(a0, MemOperand(frame_pointer(), kInputStartMinusOne));
+  for (int reg = reg_from; reg <= reg_to; reg++) {
+    __ sw(a0, register_location(reg));
+  }
 }
 
 
 void RegExpMacroAssemblerMIPS::WriteStackPointerToRegister(int reg) {
-  UNIMPLEMENTED_MIPS();
+  __ lw(a1, MemOperand(frame_pointer(), kStackHighEnd));
+  __ Subu(a0, backtrack_stackpointer(), a1);
+  __ sw(a0, register_location(reg));
 }
 
 
 // Private methods:
 
 void RegExpMacroAssemblerMIPS::CallCheckStackGuardState(Register scratch) {
-  UNIMPLEMENTED_MIPS();
+  static const int num_arguments = 3;
+  __ PrepareCallCFunction(num_arguments, scratch);
+  __ mov(a2, frame_pointer());
+  // Code* of self.
+  __ li(a1, Operand(masm_->CodeObject()));
+  // a0 becomes return address pointer.
+  ExternalReference stack_guard_check =
+      ExternalReference::re_check_stack_guard_state(masm_->isolate());
+  CallCFunctionUsingStub(stack_guard_check, num_arguments);
 }
 
 
@@ -388,22 +1017,101 @@ static T& frame_entry(Address re_frame, int frame_offset) {
 
 
 int RegExpMacroAssemblerMIPS::CheckStackGuardState(Address* return_address,
-                                                  Code* re_code,
-                                                  Address re_frame) {
-  UNIMPLEMENTED_MIPS();
+                                                   Code* re_code,
+                                                   Address re_frame) {
+  Isolate* isolate = frame_entry<Isolate*>(re_frame, kIsolate);
+  ASSERT(isolate == Isolate::Current());
+  if (isolate->stack_guard()->IsStackOverflow()) {
+    isolate->StackOverflow();
+    return EXCEPTION;
+  }
+
+  // If not real stack overflow the stack guard was used to interrupt
+  // execution for another purpose.
+
+  // If this is a direct call from JavaScript retry the RegExp forcing the call
+  // through the runtime system. Currently the direct call cannot handle a GC.
+  if (frame_entry<int>(re_frame, kDirectCall) == 1) {
+    return RETRY;
+  }
+
+  // Prepare for possible GC.
+  HandleScope handles;
+  Handle<Code> code_handle(re_code);
+
+  Handle<String> subject(frame_entry<String*>(re_frame, kInputString));
+  // Current string.
+  bool is_ascii = subject->IsAsciiRepresentation();
+
+  ASSERT(re_code->instruction_start() <= *return_address);
+  ASSERT(*return_address <=
+      re_code->instruction_start() + re_code->instruction_size());
+
+  MaybeObject* result = Execution::HandleStackGuardInterrupt();
+
+  if (*code_handle != re_code) {  // Return address no longer valid.
+    int delta = *code_handle - re_code;
+    // Overwrite the return address on the stack.
+    *return_address += delta;
+  }
+
+  if (result->IsException()) {
+    return EXCEPTION;
+  }
+
+  // String might have changed.
+  if (subject->IsAsciiRepresentation() != is_ascii) {
+    // If we changed between an ASCII and an UC16 string, the specialized
+    // code cannot be used, and we need to restart regexp matching from
+    // scratch (including, potentially, compiling a new version of the code).
+    return RETRY;
+  }
+
+  // Otherwise, the content of the string might have moved. It must still
+  // be a sequential or external string with the same content.
+  // Update the start and end pointers in the stack frame to the current
+  // location (whether it has actually moved or not).
+  ASSERT(StringShape(*subject).IsSequential() ||
+      StringShape(*subject).IsExternal());
+
+  // The original start address of the characters to match.
+  const byte* start_address = frame_entry<const byte*>(re_frame, kInputStart);
+
+  // Find the current start address of the same character at the current string
+  // position.
+  int start_index = frame_entry<int>(re_frame, kStartIndex);
+  const byte* new_address = StringCharacterPosition(*subject, start_index);
+
+  if (start_address != new_address) {
+    // If there is a difference, update the object pointer and start and end
+    // addresses in the RegExp stack frame to match the new value.
+    const byte* end_address = frame_entry<const byte* >(re_frame, kInputEnd);
+    int byte_length = end_address - start_address;
+    frame_entry<const String*>(re_frame, kInputString) = *subject;
+    frame_entry<const byte*>(re_frame, kInputStart) = new_address;
+    frame_entry<const byte*>(re_frame, kInputEnd) = new_address + byte_length;
+  }
+
   return 0;
 }
 
 
 MemOperand RegExpMacroAssemblerMIPS::register_location(int register_index) {
-  UNIMPLEMENTED_MIPS();
-  return MemOperand(zero_reg, 0);
+  ASSERT(register_index < (1<<30));
+  if (num_registers_ <= register_index) {
+    num_registers_ = register_index + 1;
+  }
+  return MemOperand(frame_pointer(),
+                    kRegisterZero - register_index * kPointerSize);
 }
 
 
 void RegExpMacroAssemblerMIPS::CheckPosition(int cp_offset,
                                             Label* on_outside_input) {
-  UNIMPLEMENTED_MIPS();
+  BranchOrBacktrack(on_outside_input,
+                    ge,
+                    current_input_offset(),
+                    Operand(-cp_offset * char_size()));
 }
 
 
@@ -411,61 +1119,126 @@ void RegExpMacroAssemblerMIPS::BranchOrBacktrack(Label* to,
                                                  Condition condition,
                                                  Register rs,
                                                  const Operand& rt) {
-  UNIMPLEMENTED_MIPS();
+  if (condition == al) {  // Unconditional.
+    if (to == NULL) {
+      Backtrack();
+      return;
+    }
+    __ jmp(to);
+    return;
+  }
+  if (to == NULL) {
+    __ Branch(&backtrack_label_, condition, rs, rt);
+    return;
+  }
+  __ Branch(to, condition, rs, rt);
 }
 
 
 void RegExpMacroAssemblerMIPS::SafeCall(Label* to, Condition cond, Register rs,
                                            const Operand& rt) {
-  UNIMPLEMENTED_MIPS();
+  __ BranchAndLink(to, cond, rs, rt);
 }
 
 
 void RegExpMacroAssemblerMIPS::SafeReturn() {
-  UNIMPLEMENTED_MIPS();
+  __ pop(ra);
+  __ Addu(t5, ra, Operand(masm_->CodeObject()));
+  __ Jump(t5);
 }
 
 
 void RegExpMacroAssemblerMIPS::SafeCallTarget(Label* name) {
-  UNIMPLEMENTED_MIPS();
+  __ bind(name);
+  __ Subu(ra, ra, Operand(masm_->CodeObject()));
+  __ push(ra);
 }
 
 
 void RegExpMacroAssemblerMIPS::Push(Register source) {
-  UNIMPLEMENTED_MIPS();
+  ASSERT(!source.is(backtrack_stackpointer()));
+  __ Addu(backtrack_stackpointer(),
+          backtrack_stackpointer(),
+          Operand(-kPointerSize));
+  __ sw(source, MemOperand(backtrack_stackpointer()));
 }
 
 
 void RegExpMacroAssemblerMIPS::Pop(Register target) {
-  UNIMPLEMENTED_MIPS();
+  ASSERT(!target.is(backtrack_stackpointer()));
+  __ lw(target, MemOperand(backtrack_stackpointer()));
+  __ Addu(backtrack_stackpointer(), backtrack_stackpointer(), kPointerSize);
 }
 
 
 void RegExpMacroAssemblerMIPS::CheckPreemption() {
-  UNIMPLEMENTED_MIPS();
+  // Check for preemption.
+  ExternalReference stack_limit =
+      ExternalReference::address_of_stack_limit(masm_->isolate());
+  __ li(a0, Operand(stack_limit));
+  __ lw(a0, MemOperand(a0));
+  SafeCall(&check_preempt_label_, ls, sp, Operand(a0));
 }
 
 
 void RegExpMacroAssemblerMIPS::CheckStackLimit() {
-  UNIMPLEMENTED_MIPS();
+  ExternalReference stack_limit =
+      ExternalReference::address_of_regexp_stack_limit(masm_->isolate());
+
+  __ li(a0, Operand(stack_limit));
+  __ lw(a0, MemOperand(a0));
+  SafeCall(&stack_overflow_label_, ls, backtrack_stackpointer(), Operand(a0));
 }
 
 
 void RegExpMacroAssemblerMIPS::CallCFunctionUsingStub(
     ExternalReference function,
     int num_arguments) {
-  UNIMPLEMENTED_MIPS();
+  // Must pass all arguments in registers. The stub pushes on the stack.
+  ASSERT(num_arguments <= 4);
+  __ li(code_pointer(), Operand(function));
+  RegExpCEntryStub stub;
+  __ CallStub(&stub);
+  if (OS::ActivationFrameAlignment() != 0) {
+    __ lw(sp, MemOperand(sp, 16));
+  }
+  __ li(code_pointer(), Operand(masm_->CodeObject()));
 }
 
 
 void RegExpMacroAssemblerMIPS::LoadCurrentCharacterUnchecked(int cp_offset,
-                                                             int characters) {
-  UNIMPLEMENTED_MIPS();
+                                                            int characters) {
+  Register offset = current_input_offset();
+  if (cp_offset != 0) {
+    __ Addu(a0, current_input_offset(), Operand(cp_offset * char_size()));
+    offset = a0;
+  }
+  // We assume that we cannot do unaligned loads on MIPS, so this function
+  // must only be used to load a single character at a time.
+  ASSERT(characters == 1);
+  __ Addu(t5, end_of_input_address(), Operand(offset));
+  if (mode_ == ASCII) {
+    __ lbu(current_character(), MemOperand(t5, 0));
+  } else {
+    ASSERT(mode_ == UC16);
+    __ lhu(current_character(), MemOperand(t5, 0));
+  }
 }
 
 
 void RegExpCEntryStub::Generate(MacroAssembler* masm_) {
-  UNIMPLEMENTED_MIPS();
+  int stack_alignment = OS::ActivationFrameAlignment();
+  if (stack_alignment < kPointerSize) stack_alignment = kPointerSize;
+  // Stack is already aligned for call, so decrement by alignment
+  // to make room for storing the return address.
+  __ Subu(sp, sp, Operand(stack_alignment));
+  __ sw(ra, MemOperand(sp, 0));
+  __ mov(a0, sp);
+  __ mov(t9, t1);
+  __ Call(t9);
+  __ lw(ra, MemOperand(sp, 0));
+  __ Addu(sp, sp, Operand(stack_alignment));
+  __ Jump(Operand(ra));
 }