[M3devel] barrier labels?

[Tony Hosking]

I extracted that usage from what C++ was doing for exception labels.  The point is to make sure that flow analysis knows that the exception handler label targets are important "non-local" label targets.  I do remember that DECL_NONLOCAL was *not* the right thing to do (that is used for proper non-local outer-scope goto targets for nested functions) and I remember the SP hacks being used with that (they need to recover from targeting from an inner-scope function and clean up the stack accordingly).  I suggest poking around in what the C++ exception handling now does with table-driven exception targets.

On 11 Jul 2010, at 07:46, Jay K wrote:

> 
> Tony, six years ago you introduce what is now:
> 
> 
> http://modula3.elegosoft.com/cgi-bin/cvsweb.cgi/cm3/m3-sys/m3cc/gcc/gcc/m3cg/parse.c.diff?r1=1.5;r2=1.6
> 
> 
> static void
> m3cg_set_label (void)
> {
> ...
>   if (barrier)
>     {
> ...
>       {
>         rtx list = DECL_STRUCT_FUNCTION (current_function_decl)->x_nonlocal_goto_handler_labels;
>         DECL_STRUCT_FUNCTION (current_function_decl)->x_nonlocal_goto_handler_labels
>           = gen_rtx_EXPR_LIST (VOIDmode, r, list);
>       }
> ...
> 
> 
> I'm not sure what to do here for gcc 4.5.
>   The data has moved around and isn't available this early. I suppose we could hang some information on and
>     deal with it later in compilation.
> 
> 
> DECL_NONLOCAL(l) = true; seems promising, but it caused very bad code to be produced (incorrect, not inefficient).
> I didn't look into why. The bad code was changing the stack pointer where it should leave it alone.
> 
> 
> gcc-4.5 is working for me now (cm3 built with it can built itself), at least with -O1, AMD64_DARWIN.
> And Juno/mentor/tetris work without optimization, I'll test optimized later.
> Next I'll test -O2, -O3, m3-sys/m3tests.
> 
> 
> Do we have good exception handling tests?
> I know that cm3 uses exceptions, like, looking for cm3.cfg.
> 
> 
> I'll poke around more..
> 
> 
>  - Jay
>