* Irregexp: Handle backtrack past look-ahead.

src/regexp-macro-assembler-ia32.cc

 // 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 314 matching lines @@
     __ sub(edi, Operand(esi));
   } else {
     ASSERT(mode_ == UC16);
     // Save registers before calling C function.
     __ push(esi);
     __ push(edi);
     __ push(backtrack_stackpointer());
     __ push(ebx);
     const int four_arguments = 4;
     FrameAlign(four_arguments, ecx);
-    // Put arguments into allocated stack area.
+    // Put arguments into allocated stack area, last argument highest on stack.
+    // Parameters are
+    //   UC16** buffer - really the String** of the input string
+    //   int byte_offset1 - byte offset from *buffer of start of capture
+    //   int byte_offset2 - byte offset from *buffer of current position
+    //   size_t byte_length - length of capture in bytes(!)
+
+    // Set byte_length.
     __ mov(Operand(esp, 3 * kPointerSize), ebx);
+    // Set byte_offset2.
+    // Found by adding negative string-end offset of current position (edi)
+    // to String** offset of end of string.
     __ mov(ecx, Operand(ebp, kInputEndOffset));
     __ add(edi, Operand(ecx));
     __ mov(Operand(esp, 2 * kPointerSize), edi);
+    // Set byte_offset1.
+    // Start of capture, where eax already holds string-end negative offset.
     __ add(eax, Operand(ecx));
     __ mov(Operand(esp, 1 * kPointerSize), eax);
+    // Set buffer. Original String** parameter to regexp code.
     __ mov(eax, Operand(ebp, kInputBuffer));
     __ mov(Operand(esp, 0 * kPointerSize), eax);
+
     Address function_address = FUNCTION_ADDR(&CaseInsensitiveCompareUC16);
     CallCFunction(function_address, four_arguments);
     // Pop original values before reacting on result value.
     __ pop(ebx);
     __ pop(backtrack_stackpointer());
     __ pop(edi);
     __ pop(esi);
 
     // Check if function returned non-zero for success or zero for failure.
     __ or_(eax, Operand(eax));
@@ skipping 585 matching lines @@
                                                               int cp_offset) {
   if (cp_offset == 0) {
     __ mov(register_location(reg), edi);
   } else {
     __ lea(eax, Operand(edi, cp_offset * char_size()));
     __ mov(register_location(reg), eax);
   }
 }
 
 
-void RegExpMacroAssemblerIA32::ClearRegister(int reg) {
+void RegExpMacroAssemblerIA32::ClearRegisters(int reg_from, int reg_to) {
+  ASSERT(reg_from <= reg_to);
   __ mov(eax, Operand(ebp, kInputStartMinusOne));
-  __ mov(register_location(reg), eax);
+  for (int reg = reg_from; reg <= reg_to; reg++) {
+    __ mov(register_location(reg), eax);
+  }
 }
 
 
 void RegExpMacroAssemblerIA32::WriteStackPointerToRegister(int reg) {
   __ mov(register_location(reg), backtrack_stackpointer());
 }
 
 
 // Private methods:
 
@@ skipping 18 matching lines @@
   void* stack_top = RegExpStack::stack_top();
 
   int result = matcher_func(input,
                             start_offset,
                             end_offset,
                             output,
                             at_start_val,
                             stack_top);
 
   if (result < 0 && !Top::has_pending_exception()) {
-    // We detected a stack overflow in RegExp code, but haven't created
-    // the exception yet.
+    // We detected a stack overflow (on the backtrack stack) in RegExp code,
+    // but haven't created the exception yet.
     Top::StackOverflow();
   }
   return (result < 0) ? EXCEPTION : (result ? SUCCESS : FAILURE);
 }
 
 
 int RegExpMacroAssemblerIA32::CaseInsensitiveCompareUC16(uc16** buffer,
                                                          int byte_offset1,
                                                          int byte_offset2,
                                                          size_t byte_length) {
@@ skipping 161 matching lines @@
     __ j(above, &no_stack_overflow);
 
     SafeCall(&stack_overflow_label_);
 
     __ bind(&no_stack_overflow);
   }
 }
 
 
 void RegExpMacroAssemblerIA32::FrameAlign(int num_arguments, Register scratch) {
+  // TODO(lrn): Since we no longer use the system stack arbitrarily, we
+  // know the current stack alignment - esp points to the last regexp register.
+  // We can do this simpler then.
   int frameAlignment = OS::ActivationFrameAlignment();
   if (frameAlignment != 0) {
     // Make stack end at alignment and make room for num_arguments words
     // and the original value of esp.
     __ mov(scratch, esp);
     __ sub(Operand(esp), Immediate((num_arguments + 1) * kPointerSize));
     ASSERT(IsPowerOf2(frameAlignment));
     __ and_(esp, -frameAlignment);
     __ mov(Operand(esp, num_arguments * kPointerSize), scratch);
   } else {
@@ skipping 40 matching lines @@
 
 
 void RegExpMacroAssemblerIA32::LoadConstantBufferAddress(Register reg,
                                                          ArraySlice* buffer) {
   __ mov(reg, buffer->array());
   __ add(Operand(reg), Immediate(buffer->base_offset()));
 }
 
 #undef __
 }}  // namespace v8::internal