On Fri, Jan 31, 2020 at 12:53 AM Vitor Guidi <vitor.gu...@usp.br> wrote:
>
> Hi.
>
> This patch adds a new optimization to avoid the redundant calculation
> tanh(x)/sinh(x) by replacing it for 1.0/cosh(x), for all cases where x is a
> double, a long double or a float.
>
> There should be no need for numerical stability testing, since the division
> of the two functions only adds numerical noise. The correctness of the
> operation is justified by the definition of tanh(x) = sinh(x)/cosh(x). If
> you think it is wise to write a test, please let me know.
>
> As far as testing goes, I ran a check-gcc test under Ubuntu 19.04 by adding
> the test in tanhbysinh.c and found no issues.
OK for GCC 11, please either attach patches or avoid quoting them.
> Best regards,
>
> Vitor.
>
> in gcc/ChangeLog:
> 2020-08-28 Vitor Guidi <vitor.gu...@usp.br>
>
> * match.pd: New substitution rule for tanh(x)/sinh(x) ->
> 1.0/cosh(x).
>
> in gcc/testsuite/ChangeLog:
> 2020-08-28 Vitor Guidi <vitor.gu...@usp.br>
>
> * gcc.dg/tanhbysinh.c (new): Verify if simplification is applied.
Just use :New testcase, without any function designation.
>
> > diff --git gcc/match.pd gcc/match.pd
> > index 5fee394e7af..3933fcaf9fa 100644
> > --- gcc/match.pd
> > +++ gcc/match.pd
> > @@ -5069,6 +5069,11 @@ DEFINE_INT_AND_FLOAT_ROUND_FN (RINT)
> > (rdiv (SINH:s @0) (COSH:s @0))
> > (TANH @0))
> >
> > + /* Simplify tanh (x) / sinh (x) -> 1.0 / cosh (x). */
> > + (simplify
> > + (rdiv (TANH @0) (SINH @0))
> > + (rdiv {build_one_cst (type);} (COSH @0)))
> > +
> > /* Simplify cos(x) / sin(x) -> 1 / tan(x). */
> > (simplify
> > (rdiv (COS:s @0) (SIN:s @0))
> > diff --git gcc/testsuite/gcc.dg/tanhbysinh.c
> gcc/testsuite/gcc.dg/tanhbysinh.c
> > new file mode 100644
> > index 00000000000..fde72c2f93b
> > --- /dev/null
> > +++ gcc/testsuite/gcc.dg/tanhbysinh.c
> > @@ -0,0 +1,40 @@
> > +/* { dg-do compile } */
> > +/* { dg-options "-Ofast -fdump-tree-optimized" } */
> > +
> > +extern float sinhf (float);
> > +extern float tanhf (float);
> > +extern double sinh (double);
> > +extern double tanh (double);
> > +extern long double sinhl (long double);
> > +extern long double tanhl (long double);
> > +
> > +double __attribute__ ((noinline))
> > +tanhbysinh_ (double x)
> > +{
> > + return tanh (x) / sinh (x);
> > +}
> > +
> > +float __attribute__ ((noinline))
> > +tanhbysinhf_ (float x)
> > +{
> > + return tanhf (x) / sinhf (x);
> > +}
> > +
> > +long double __attribute__ ((noinline))
> > +tanhbysinhl_ (long double x)
> > +{
> > + return tanhl (x) / sinhl (x);
> > +}
> > +
> > +
> > +/* There must be no calls to sinh or atanh */
> > +/* There must be calls to cosh */
> > +/* {dg-final { scan-tree-dump-not "sinh " "optimized" } } */
> > +/* {dg-final { scan-tree-dump-not "tanh " "optimized" }} */
> > +/* {dg-final { scan-tree-dump-not "sinhf " "optimized" } } */
> > +/* {dg-final { scan-tree-dump-not "tanhf " "optimized" }} */
> > +/* {dg-final { scan-tree-dump-not "sinhl " "optimized" } } */
> > +/* {dg-final { scan-tree-dump-not "tanhl " "optimized" }} */
> > +/* { dg-final { scan-tree-dump "cosh " "optimized" } } */
> > +/* { dg-final { scan-tree-dump "coshf " "optimized" } } */
> > +/* { dg-final { scan-tree-dump "coshl " "optimized" } } */
> > \ No newline at end of file
