Irregexp: Added derived knowledge of whether we are at the start of input.

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 618 matching lines @@
   // Entry code:
   __ bind(&entry_label_);
   // Start new stack frame.
   __ push(ebp);
   __ mov(ebp, esp);
   // Save callee-save registers.  Order here should correspond to order of
   // kBackup_ebx etc.
   __ push(esi);
   __ push(edi);
   __ push(ebx);  // Callee-save on MacOS.
-  __ push(Immediate(0));  // Make room for input start minus one
+  __ push(Immediate(0));  // Make room for "input start - 1" constant.
 
   // Check if we have space on the stack for registers.
   Label retry_stack_check;
   Label stack_limit_hit;
   Label stack_ok;
 
   __ bind(&retry_stack_check);
   ExternalReference stack_guard_limit =
       ExternalReference::address_of_stack_guard_limit();
   __ mov(ecx, esp);
@@ skipping 593 matching lines @@
 
 
 void RegExpMacroAssemblerIA32::LoadConstantBufferAddress(Register reg,
                                                          ArraySlice* buffer) {
   __ mov(reg, buffer->array());
   __ add(Operand(reg), Immediate(buffer->base_offset()));
 }
 
 #undef __
 }}  // namespace v8::internal