need to focus on java performance?

[David Daney]

Andrew Haley wrote:
> David Daney writes:
>  > Bryce McKinlay wrote:
>  > > David Daney wrote:
>  > >> The calling method's address is in the standard location (as 
>  > >> specified by the ABI), we know how to find the class given this 
>  > >> information. 
>  > >
>  > > Finding the method's address is easy enough, but what about the 
>  > > address of the atable entry containing the pointer to the method?
>  > Isn't the atable part the the calling method's class?  The stack trace 
>  > infrastructure allows you to find the class of a method given an IP that 
>  > is contained by the method.
> 
> Mmm, but it's quite expensive.  It would be nice not to do unwinding
> in the class initialization path.
> 

If you structured the little trampoline code properly, you would not 
have to use the full DWARF unwinder.  You only have to go back one 
level.  GCC even has a built-in that allows you to do this 
(__builtin_return_address(0)).  Now looking up the class given this 
might still be slow, but you don't need a complete stacktrace.

David Daney.