On Sat, Sep 8, 2012 at 9:12 AM, Aurelien Jarno <aurel...@aurel32.net> wrote: > On Sat, Sep 08, 2012 at 09:06:52AM +0000, Blue Swirl wrote: >> On Sat, Sep 8, 2012 at 9:01 AM, Aurelien Jarno <aurel...@aurel32.net> wrote: >> > On Sat, Sep 08, 2012 at 08:18:50AM +0000, Blue Swirl wrote: >> >> On Fri, Sep 7, 2012 at 1:16 PM, Aurelien Jarno <aurel...@aurel32.net> >> >> wrote: >> >> > This patch series improves the TCG optimizer, based on patterns found >> >> > while executing various guest. The brcond ad setcond constant folding >> >> > are useful especially useful when they are used to avoid some argument >> >> > values (e.g. division by 0), and thus can be optimized when this >> >> > argument >> >> > is a constant. >> >> > >> >> > This bring around 0.5% improvement on openssl like benchmarks. >> >> > >> >> > >> >> > Modifications between V1 and V2 following feedback I got: >> >> > - In the first patch, account for the liveness analysis time and >> >> > optimizing pass time separately >> >> > - Fixed swith/break in patch 7 to correctly throw an error >> >> > - Added patch 9 to make the code more readable >> >> > Other patches are unmodified. >> >> > >> >> > >> >> > Aurelien Jarno (9): >> >> > tcg: improve profiler >> >> > tcg/optimize: split expression simplification >> >> > tcg/optimize: simplify or/xor r, a, 0 cases >> >> > tcg/optimize: simplify and r, a, 0 cases >> >> > tcg/optimize: simplify shift/rot r, 0, a => movi r, 0 cases >> >> >> >> Aren't the above or/and/shift/rot simplifications (and also for >> >> example OR with 0xfffffffff and XOR register by itself) already >> >> handled by tcg/tcg-op.h? >> > >> > They are handled there when the values are known at decode time. It is >> > not the case when the value are propagated in the TB. >> > >> > For example, this is optimized in tcg/tcg-op.h: >> > ori t0, t1, 0 >> > >> > This is not optimized in tcg/tcg-op.h: >> > movi t2, 0 >> > or t0, t1, t2 >> >> I see. Does the optimizer pass then make the tcg/tcg-op.h optimization >> redundant, could we do the optimizations only in optimizer? > > Technically yes. In practice it's a good idea to keep simple > optimizations in tcg/tcg-op.h, as they cost less in CPU time than when > done later.
OK. Could there be further optimizations based on tcg/tcg-op.h, for example case OR reg, 0xffffffff -> mov reg, 0xffffffff could be rechecked? > > On the other hand, we can remove such optimizations done in some > TCG backends as they won't see this kind of ops anymore. > >> > >> >> > tcg/optimize: swap brcond/setcond arguments when possible >> >> > tcg/optimize: add constant folding for setcond >> >> > tcg/optimize: add constant folding for brcond >> >> > tcg/optimize: fix if/else/break coding style >> >> >> >> Otherwise a very nice series. >> >> >> >> > >> >> > tcg/optimize.c | 179 >> >> > +++++++++++++++++++++++++++++++++++++++++++++++++++----- >> >> > tcg/tcg.c | 12 +++- >> >> > tcg/tcg.h | 1 + >> >> > 3 files changed, 175 insertions(+), 17 deletions(-) >> >> > >> >> > -- >> >> > 1.7.10.4 >> >> > >> >> > >> >> >> >> >> > >> > -- >> > Aurelien Jarno GPG: 1024D/F1BCDB73 >> > aurel...@aurel32.net http://www.aurel32.net >> > > -- > Aurelien Jarno GPG: 1024D/F1BCDB73 > aurel...@aurel32.net http://www.aurel32.net
