Re: Code generation problem with optimizations enabled

[Jamie Prescott <jpresss@yahoo.com>]

----- Original Message ----
> From: Jim Wilson <wilson@codesourcery.com>
> To: Jamie Prescott <jpresss@yahoo.com>
> Cc: Paolo Bonzini <bonzini@gnu.org>; gcc@gcc.gnu.org
> Sent: Wednesday, May 13, 2009 6:15:07 PM
> Subject: Re: Code generation problem with optimizations enabled
> 
> Jamie Prescott wrote:
> > Thank you Paolo, I'll take a look at it.
> > Is there a reason why the fcmp insn was dropped with such implementation?
> 
> The code that optimizes away redundant cc0 compares is in final.c, in 
> final_scan_insn().  It is about line 2310 in my tree, near the comment "Check 
> for redundant test and compare instructions".  Try stepping through that code to 
> see what is going on.  Maybe you are setting cc_status.value1 but not 
> cc_status.value2?
> 
> In any case, as Paolo mentioned, you are better off not using cc0.  cc0 should 
> only be used if you have no other choice.  And even then, you still probably 
> shouldn't use it.  Every couple of years someone tries to eliminate the cc0 
> code, and eventually someone will succeed.

Thanks for the insight. But anyway, I took the path Paolo told me using CCmode and
now it's working nicely.


- Jamie