[Libclc-dev] fast_length and fast_normalize

Jeroen Ketema j.ketema at imperial.ac.uk
Tue Mar 11 17:21:23 PDT 2014


On 11 Mar 2014, at 23:14, Tom Stellard <tom at stellard.net> wrote:

> On Tue, Mar 11, 2014 at 07:05:16PM +0000, Jeroen Ketema wrote:
>> Hi all,
>> I was wondering: Would it make sense to provide implementations of fast_length and fast_normailze even though currently no implementations of half_sqrt and half_rsqrt are provided by libclc?
> Can fast_length and fast_normalize be implemented correctly without
> half_sqrt and half_rsqrt?

The OpenCL specification says that the result should be equal to something that involves half_sqrt and half_rsqrt, respectively. So, it seems to make most sense to use the definitions given by OpenCL directly.

> Are there llvm intrinsics that we could
> use for half_sqrt and half_rsqrt?

The nvptx back-end has the sqrt.approx and rsqrt.approx intrinsics, but it’s not clear to me whether these have enough precision. Also this isn’t a solution for the r600 back-end.


> -Tom
>> Thanks,
>> Jeroen
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