Re: [semi PATCH] ARM/Thumb branches out of range for MI thunks

["Zack Weinberg" <zack at codesourcery dot com>]

Richard Earnshaw <rearnsha@arm.com> writes:

> Yes.  Output the Thunk in ARM code (seriously, this is one of those cases 
> where you get better code density in ARM state than you can in Thumb).  
> But to do that, the C++ front end needs fixing so that we can get hold of 
> the thunk properly in the back end and control how it outputs the thunk 
> definition.
>
> I've posted on this before.

I've read old postings of yours that I can find -

http://gcc.gnu.org/ml/gcc/2002-06/msg01598.html
http://gcc.gnu.org/ml/gcc-patches/2002-07/msg00769.html
http://gcc.gnu.org/ml/gcc-patches/2003-07/msg01703.html

It sounds like the problem is that "this is a thunk" is a concept only
visible within the C++ front end, whereas it needs to be language-
independent.  That ought to be a feasible change to make, if we can
agree on what "this is a thunk" means.

I am not sure if the present state of thunk generation is better or
worse than it was at the time you posted these messages.

What is the cost of an arm/thumb mode switch, compared to the extra
cycles required to execute a purely Thumb thunk?

zw