splitting add instructions

[Paulo J. Matos]

On 19/07/11 16:06, DJ Delorie wrote:
>> What's the point of the second define insn? The first insn seems to
>> take us from expansion to asm generation so I can't see where the
>> second one will come into play except in an expansion after reload
>> but that doesn't happen, right?
>
> IIRC it has to do with optimizing away compare instructions.  Which
> pattern you need depends on whether the flags will get used by a
> conditional branch or not.
>

So, this seems to have to do with the post-reload comparison 
optimization pass Richard mentioned. But I am still confused as to how 
GCC matches them. Is *_flags any special name GCC loops for (doubtful)?

-- 
PMatos