Re: Can I use -Ofast without libmvec

[Steve Ellcey <sellcey@cavium.com>]

On Thu, 2018-03-22 at 11:42 -0700, H.J. Lu wrote:
> On Thu, Mar 22, 2018 at 11:08 AM, Steve Ellcey <sellcey@cavium.com>
> wrote:
> > 
> > I have a question about the math vector library routines in
> > libmvec.
> > If I compile a program on x86 with -Ofast, something like:
> > 
> > void foo(double * __restrict x, double * __restrict y, double *
> > __restrict z)
> > {
> >         for (int i = 0; i < 1000; i++) x[i] = sin(y[i]);
> > }
> > 
> > I get a call to the vector sin routine _ZGVbN2v_sin.  That is fine, but
> > is there some way to compile with -Ofast and not use the libmvec vector
> > routines?  I have tried -fopenmp, -fopenmp-simd, -fno-openmp, and -fno-
> > openmp-simd and I always get a call to _ZGVbN2v_sin.  Is there anyway
> > to stop the use of the vectorized calls (without turning off -Ofast)?
> Have you tried -lm?

It isn't a question of not working.  Everything works and links and
runs, but I would just like to know if there is any way to compile my
program in such a way that GCC does not generate calls to the libmvect
routines.

I am doing some performance analysis and would like to know how much
(or little) having these vectorized routines help in various
benchmarks.

Steve Ellcey