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Re: [RFC][PATCH 0/2] aarch64: Add optimized ASIMD versions of sinf/cosf

On Tue, 13 Jun 2017, Szabolcs Nagy wrote:

> the c implementation is generic
> (sometimes the instruction scheduling is suboptimal and
> i found that union based bithacks don't always give good
> code but those are issues we can work on the gcc side)

Indeed, I've told powerpc people trying to add powerpc-specific versions 
of those union-based macros to do the optimization on the compiler side.  
Exactly the same applies to AArch64 - there are lots of copies of 
fdlibm-based code and similar union-based code in different projects, 
making compilers optimize better will help more than just glibc.

> one issue is fma vs non-fma code, i haven't solved that
> yet, but it will probably work either way (since we use
> double prec), if it makes a difference i will add ifdef
> code path for the two cases (might affect the fast arg
> reduction)

We already have __FP_FAST_FMA conditionals in glibc; having more such 
conditionals (where relevant) is fine.

Joseph S. Myers

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