Re: [Qemu-devel] [PATCH 0/6] Implement constant folding and copy propagation in TCG

[Aurelien Jarno]

On Fri, May 20, 2011 at 09:35:08PM +0200, Aurelien Jarno wrote:
> On Fri, May 20, 2011 at 04:39:27PM +0400, Kirill Batuzov wrote:
> > This series implements some basic machine-independent optimizations.  They
> > simplify code and allow liveness analysis do it's work better.
> > 
> > Suppose we have following ARM code:
> > 
> >  movw    r12, #0xb6db
> >  movt    r12, #0xdb6d
> > 
> > In TCG before optimizations we'll have:
> > 
> >  movi_i32 tmp8,$0xb6db
> >  mov_i32 r12,tmp8
> >  mov_i32 tmp8,r12
> >  ext16u_i32 tmp8,tmp8
> >  movi_i32 tmp9,$0xdb6d0000
> >  or_i32 tmp8,tmp8,tmp9
> >  mov_i32 r12,tmp8
> > 
> > And after optimizations we'll have this:
> > 
> >  movi_i32 r12,$0xdb6db6db
> > 
> > Here are performance evaluation results on SPEC CPU2000 integer tests in
> > user-mode emulation on x86_64 host.  There were 5 runs of each test on
> > reference data set.  The tables below show runtime in seconds for all these
> > runs.
> 
> How are the tests done? Are they done with linux-user, or running the
> executables in qemu-system-xxx?
> 

Another point I forgot, the current TCG code already does a very simple
copy and constant propagation, so it might be a good idea to end the
series with cleanup this code. There is no point in doing such
optimisation twice, and it is most probably taking a non negligible 
time. This way you can provide benchmarks on the whole set.

-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net