* Move irregexp backtrack stack to external memory area, instead of the system stack.

src/regexp-macro-assembler.h

 // Copyright 2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 12 matching lines @@
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #ifndef V8_REGEXP_MACRO_ASSEMBLER_H_
 #define V8_REGEXP_MACRO_ASSEMBLER_H_
 
 namespace v8 { namespace internal {
 
-
 struct DisjunctDecisionRow {
   RegExpCharacterClass cc;
   Label* on_match;
 };
 
 
 class RegExpMacroAssembler {
  public:
   enum IrregexpImplementation {
     kIA32Implementation,
     kARMImplementation,
-    kBytecodeImplementation};
+    kBytecodeImplementation
+  };
+
+  enum StackCheckFlag {
+    kNoStackLimitCheck = false,
+    kCheckStackLimit = true
+  };
 
   RegExpMacroAssembler();
   virtual ~RegExpMacroAssembler();
+  // The maximal number of pushes between stack checks. Users must supply
+  // kCheckStackLimit flag to push operations (instead of kNoStackLimitCheck)
+  // at least once for every stack_limit() pushes that are executed. More
+  // often is allowed (and encouraged)

[Erik Corry, 2009/01/12 11:50:13]

Missing full stop, and I see no need to encourage inefficiency.  Also the name
is not descriptive.  Something including the word 'slack' seems more
appropriate.

[Lasse Reichstein, 2009/01/12 13:03:59]

Done.

+  virtual int stack_limit() = 0;
   virtual void AdvanceCurrentPosition(int by) = 0;  // Signed cp change.
   virtual void AdvanceRegister(int reg, int by) = 0;  // r[reg] += by.
   virtual void Backtrack() = 0;
   virtual void Bind(Label* label) = 0;
   // Check the current character against a bitmap.  The range of the current
   // character must be from start to start + length_of_bitmap_in_bits.
   virtual void CheckBitmap(
       uc16 start,           // The bitmap is indexed from this character.
       Label* bitmap,        // Where the bitmap is emitted.
       Label* on_zero) = 0;  // Where to go if the bit is 0.  Fall through on 1.
@@ skipping 79 matching lines @@
   // Check whether a register is == to the current position and go to a
   // label if it is.
   virtual void IfRegisterEqPos(int reg, Label* if_eq) = 0;
   virtual IrregexpImplementation Implementation() = 0;
   virtual void LoadCurrentCharacter(int cp_offset,
                                     Label* on_end_of_input,
                                     bool check_bounds = true,
                                     int characters = 1) = 0;
   virtual void PopCurrentPosition() = 0;
   virtual void PopRegister(int register_index) = 0;
-  virtual void PushBacktrack(Label* label) = 0;
-  virtual void PushCurrentPosition() = 0;
-  virtual void PushRegister(int register_index) = 0;
+  virtual void PushBacktrack(Label* label,
+                             StackCheckFlag check_stack_limit) = 0;
+  virtual void PushCurrentPosition(StackCheckFlag check_stack_limit) = 0;
+  virtual void PushRegister(int register_index,
+                            StackCheckFlag check_stack_limit) = 0;
   virtual void ReadCurrentPositionFromRegister(int reg) = 0;
   virtual void ReadStackPointerFromRegister(int reg) = 0;
   virtual void SetRegister(int register_index, int to) = 0;
   virtual void Succeed() = 0;
   virtual void WriteCurrentPositionToRegister(int reg, int cp_offset) = 0;
   virtual void WriteStackPointerToRegister(int reg) = 0;
 
  private:
 };
 
@@ skipping 34 matching lines @@
   ArraySlice GetBuffer(Vector<T> values);
  private:
   size_t byte_array_size_;
   Handle<ByteArray> current_byte_array_;
   int current_byte_array_free_offset_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_REGEXP_MACRO_ASSEMBLER_H_