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Re: GCC for SPARC Systems


On Fri, 10 Mar 2006, Andrew Pinski wrote:

>
> On Mar 10, 2006, at 3:34 PM, Alexey Starovoytov wrote:
>
> > Few major infrastructure features needs to be done first.
>
> Like?  Please give examples.  If link time optimizations,
> that is already starting to be worked on.

I doesn't look that my opinion here worth even 1 cent,
but here are few things:

 - inter-proc (link time) opt
   I think LLVM is a better approach.

 - 2nd link time opt
   not re-optimization like above, but asm code optimizations.
   Looks like LLVM is targeting that as well. Check -xlinkopt flag and BIT

 - profile driven opt
   Great progress in 4.1. I'm very interested to see how you can match
   it with link time opts.

 - value profiling
   doesn't look anything is done

 - openmp
   I think it needs to be fully platform dependent, but anyway.
   Certainly would be interesting to compare with Sun's approach.

 - struct reorg opts
   very intersting item on gcc's todo list

 - loop opts
   Not sure what exactly is being done, but what I can see in 4.0 and 4.1
   needs to be improved. Try -xloopinfo for verbosity.

 - prefetch
   It rather hurts performance when I tried it. Check -xprefetch* flags

 - struct type aliasing
   Great progress in 4.1, but still much behind Sun. Check -xalias_level flag

 - auto parallelization
   doesn't look anything is being done here. Check -xautopar

 - -ffast-math
   just compare it with Sun's -fsimple=2

 - optimized inline assembler

All of the above is done by sun compiler and gcc4ss (except openmp).
A lot of other things are coming.

Also I don't want to start "tree vs orc" flame, but it seems that Sun's IR
is better suited for the above opts. Ok. Ok. It's not.

Alex.

>
> -- Pinski
>
>



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