Re: [Qemu-devel] [PATCH v2 0/9] Improve TCG optimizer

[Blue Swirl]

On Fri, Sep 7, 2012 at 1:16 PM, Aurelien Jarno <address@hidden> 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?

>   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
>
>