[libre-riscv-dev] [isa-dev] Re: FP transcendentals (trigonometry, root/exp/log) proposal

[lkcl]

On Sunday, September 15, 2019 at 1:41:53 PM UTC+8, Jacob Lifshay wrote:
> Note that Vulkan and RISC-V conformance are at different levels of the software/hardware stack: Vulkan requires API-level conformance whereas RISC-V requires ISA-level conformance, the Vulkan driver is free to translate as needed or even implement some features entirely in software, not everything needs to be implemented in hardware.

Very important point, thank you for raising it.

For the *hardware* instructions - and this includes FDIV which is *already* in RV - an OpenGL Khronos Compliant system would be performance-uncompetitive under normal market forces.

Put in the bluntest and clearest terms: complying with RISCV Standards actually *destroys* the chances of a product's competitive commercial adoption in the OpenCL market!

Software compliance with Khronos, the issue is moot, because (a) software can adapt and (b) nobody expects software to have the same performance as hardware.

It is therefore *only* the instructions that happen to be in IEEE754, *and* hapoen to be in OpenCL *and* happen to have non IEEE754 accuracy requirements in OpenCL *and* there are market forces that compel vendors to want to compete on hardware acceleration....

... and those are actually quite important despite the long list of happenings, FDIV, SIN, COS, and several others.

L.