[cxx-mem-model] disallow load data races (1 of some)

[Michael Matz]

Hi,

On Thu, 31 Mar 2011, Jeff Law wrote:

> Without trip count estimates the speculative read can introduce a 
> performance regression.

Like any other transformation.  So what are you trying to say?  That 
therefore introducing a mode in GCC disallowing any speculative reads 
(even if they happen to improve performance!?) is a bright idea?

I sure hope not.

The right way to deal with performance concerns is to model them and (try 
to) avoid them.  Not to introduce random restrictions onto a (timing 
independend) as-if model.

So, please let's leave out any disguising arguments about performance in 
connection with the cxx mem-model, shall we?  It has different goals 
AFAIU, and if it has to resort to performance for showing its usefulness 
it's bound to fail already.


Ciao,
Michael.