java exception

Mon Jun 27 08:13:00 GMT 2005

Thank you very much! But since gen_reg_rtx doesn't generate rtx for a 
specific register, how can the unwind functions know which register to 
store the reference to _Unwind_RaiseException?
cheers
yang
At 15:31 24/06/2005 -0400, you wrote:
>Yang Chang wrote:
>>>I am trying to understand the GCJ implementation of Java exception 
>>mechanism. Currently, I am aware of that the GCJ compiler uses the return 
>>value of a "gen_reg_rtx(ptr_mode);" (in function 
>>"get_exception_pointer") to represent something which holds a reference 
>>to an _Unwind_Exception struct and such a reference is passed to function 
>>_Unwind_RaiseException in libjava. However, I couldn't figure out how the 
>>two things map each other. I mean, how the _Unwind_RaiseException or some 
>>other lower level functions assign the aforementioned reference to what 
>>that rtx represents? and what that rtx really represents?
>>>The code you are looking at is used when generating an exception 
>_handler_. When the unwind mechanism gives control to the handler, the 
>exception object that was thrown needs to be passed to it somehow. 
>get_exception_pointer yields an RTL expression (in this case a REG, ie a 
>register) where a pointer to the _Unwind_Exception will be found. The 
>_Unwind_Exception will be put in that register by the unwinder before it 
>jumps into the handler. You'll want to look in gcc/unwind* and 
>libjava/exception.cc for the code for the unwinder itself.
>>Bryce