[PATCH] Mark inputs being ZERO as unlikely __mul in powerpc

[Siddhesh Poyarekar]

On 20 February 2013 23:16, Ryan Arnold <rsa@us.ibm.com> wrote:
> Do you mean that there were no branch hints generated from the
> 'unlikely' call?
>
> Which platform (--with-cpu value) did you test this on?

I tried this on a P730 --with-cpu=power7.  I did not hand-check the
generated code.  I simply used a sha1sum of the entire library to
check if the code was the same.  When I said the code was identical, I
had a typo in my configure line which led to the use of generic code
instead of the power4+ code, because of which the resulting libraries
were identical.

> I wouldn't be surprised if the code gen was different between Power[4|5|
> 6] and Power7.  Power7 has different characteristics regarding branch
> hints and the compiler may chose to exclude the explicit hints on that
> platform (since they often negatively impact performance vs. what the
> machine can predict itself).  I'd be interested to see if there's a code
> gen difference between power6 and power7.

OK, I'll check --with-cpu=power6 also before I check in.

Thanks,
Siddhesh


-- 
http://siddhesh.in