Math trig intrinsics and compiler options

[gustav trede]

2009/7/15 Christian Thalinger <Christian.Thalinger at sun.com>

> gustav trede wrote:
> > Hello,
> >
> > Azeem Jiva told me an easy way to improve trig performance.
> > Changing the intrinsics to use an existing but faster path gives me a
> > boost of roughly 40% for the Math cos and sin on solaris x64.
> >
> >
> > library_call.cpp
> >
> > bool LibraryCallKit::inline_math_
> > native(vmIntrinsics::ID id) {
> >   switch (id) {
> >
> >    case vmIntrinsics::_dcos: return Matcher::has_match_rule(Op_CosD) ?
> > runtime_math(OptoRuntime::Math_D_D_Type(), CAST_FROM_FN_PTR(address,
> > SharedRuntime::dcos), "COS") : false;
> >    case vmIntrinsics::_dsin: return Matcher::has_match_rule(Op_SinD) ?
> > runtime_math(OptoRuntime::Math_D_D_Type(), CAST_FROM_FN_PTR(address,
> > SharedRuntime::dsin), "SIN") : false;
> >    case vmIntrinsics::_dtan: return Matcher::has_match_rule(Op_TanD) ?
> > runtime_math(OptoRuntime::Math_D_D_Type(), CAST_FROM_FN_PTR(address,
> > SharedRuntime::dtan), "TAN") : false;
> >    case vmIntrinsics::_dlog:   return Matcher::has_match_rule(Op_LogD) ?
> > runtime_math(OptoRuntime::Math_D_D_Type(), CAST_FROM_FN_PTR(address,
> > SharedRuntime::dlog), "LOG") : false;
> >    case vmIntrinsics::_dlog10: return Matcher::has_match_rule(Op_Log10D)
> > ? runtime_math(OptoRuntime::Math_D_D_Type(), CAST_FROM_FN_PTR(address,
> > SharedRuntime::dlog10), "LOG10") : false;
> >
> >
> > Is there any potential problem with such a patch  ?
>
> I'm not sure I understand this "patch".  Why should the code above be
> faster than the current code in HotSpot, which tries to inline the
> trigonometric functions?  Maybe the speedup you're seeing is because of
> the missing fast/slow path check and you are always using the slow path
> because of rounding?  Just a guess...
>
> -- Christian
>

Thats how i interpret the difference too, and correct me if im wrong  but
the rounding is only needed for the strictmath to get its platform
independent exact results and not for Math ?.

when testing with the input ranges that matches the different code paths
(PI/4 , 3PI/4, 2^19*(pi/2)) with 1 minute runtime per test i get consistent
improvement of roughly (40%, 100%, 32% ) for Math.sin  and similar for cos.


-- 
regards
 gustav trede
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