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Re: libm support for ARMv7 and VSQRT?
On 20/03/17 14:54, Sebastian Huber wrote:
>
>
> On 20/03/17 14:31, Richard Earnshaw (lists) wrote:
>> On 20/03/17 06:52, Sebastian Huber wrote:
>>> Hello,
>>>
>>> there is some ARM-specific libm support for ARMv8:
>>>
>>> https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;a=tree;f=newlib/libm/machine/arm;h=5457f11619b2d67e8f56f352afb404c06a12c2bb;hb=HEAD
>>>
>>>
>>>
>>> The VFPv2+ supports a VSQRT instruction. Would it make sense to use it
>>> for the sqrt() implementation, similar to
>>>
>>> https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;a=blob;f=newlib/libm/machine/aarch64/e_sqrt.c;h=e4b7554ac1811bf04f726da198b913c0c30595ca;hb=HEAD
>>>
>>>
>>> https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;a=blob;f=newlib/libm/machine/aarch64/ef_sqrt.c;h=19fec952517769ad3851efef3b11dc6c02fb7582;hb=HEAD
>>>
>>>
>>>
>>> ?
>>>
>> I'm sure a patch would be welcome :-)
>
> The ARMv7-AR reference manual is quite verbose if it comes to the
> floating-point square root implementation of VSQRT. Is it IEEE 754
> compatible?
>
It will be the same as for AArch64, but with options for default NaNs
and flush to zero; but you don't need to worry about either of those, I
think.
R.