Re: [Valgrind-developers] replacing --vex-iropt-precise-memory-exns=no|yes by --vex-iropt-register-updates=minimal|atmemaccess|exact

[Philippe W. <phi...@sk...>]

On Wed, 2012-08-08 at 17:22 +0200, Josef Weidendorfer wrote:
> BTW, I think "allregs-at-sb-exits" is a misnomer, as all other
> modes also update "all regs at sb exit". I would go for
> "only-at-sb-exits".
allregs-only-at-sb-exits ?
(as --vex-irop-register-updates=only-at-sb-exits seems also somewhat
misleading as some registers are updated in the middle of sb,
even with this mode).
In any case, it looks not possible to summarise precisely
in a few words when/which registers are updated
(e.g. helper calls also imply some registers to be updated).


> The difference of -15% in instructions and -35% in branches must
> be the effect of chaining introduced with 3.8.0. It is
> unclear to me why this does not result in any performance
> improvement.
I consider more and more performance measurement of Valgrind
as a not understandable magic.
There are too many factors which are uncontrolled.
(cpu frequency scaling was off during the measurements I guess) ?

Philippe