[Libclc-dev] NVPTX-backend and libclc arithmetic functions

[Jeroen Ketema]

Hi Christoph,

> In libclc many arithmetic functions like pow, rsqrt are lowered to
> corresponding llvm intrinsics. These are not handled correctly by the
> NVPTX backend.

The standard llvm intrinsics do not guarantee the precision required by
the OpenCL standard, so they should be replaced eventually. Or, only
used for the native_ functions from the OpenCL library; in which case
the backend should support them.

> Where should this be fixed? NVPTX-Backend or libclc?

libclc and there are two possible solutions:

* Either completely hand-rolled versions are introduced in libclc, see
  e.g. Aaron’s patch from yesterday.
* nvptx specific intrinsics should be used that do have the correct
  precision (if such intrinsics exist)

Jeroen

> Or is this expected to work and I am just not using it correctly?
> 
> Christoph Gerum
> 
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