Hello, What's the status of live range shrink in GCC

[Vladimir Makarov]

On 12-09-10 6:05 AM, Bin.Cheng wrote:
> Hi,
> I digged into gcc mail archive and found there are several threads
> discussing about live range shrink, like:
As I know Ghassan preferred to work on Open64 that time in AMD and never 
touched GCC.
> and
> http://gcc.gnu.org/ml/gcc-patches/2009-01/msg00188.html
>
> In these messages many people showed interests in LRS, in or out of
> sched1 pass. I am curious about the status now and have following
> questions:
> 1. Does sched-pressure patch Vlad worked is the LRS we mentioned in the message?
No, the pressure-sensitive insn scheduler is not LRS.  It mostly does 
not increase the register pressure when it is already high. There is 
other more comprehensive pressure-sensitive heuristic implemented by 
Richard Sandiford.  I think it is better to ask Rcihard the same 
question about his heuristic.
> 2. If the answer is no, are there still someone want to do this in
> sched1? Or as Vlad once mentioned that we should implement LRS in
> another pass along with register re-materialization?
It is still on my list of possible projects although I am busy with LRA 
project now and don't know when I can start it.  I know how to decrease 
register pressure through rematerialization but I did not figured out 
yet how to do LRS and how to combine them.
> 3. What's the status/expectation of LRS now?
I don't think there is any status of LRS.  I only can say that 
introduction of IRA made this project more doable for implementation.  
Before its implementation accurate register pressure estimation just was 
not possible.
> I didn't follow the message on this topic before, so please forgive if
> I have missed some important updates about this.
>
>