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

lkcl luke.leighton at gmail.com
Sun Sep 8 15:56:00 BST 2019


Transcendental opcodes in ARM's MALI ISA include

E8 - fatan_pt2
F0 - frcp (reciprocal)
F2 - frsqrt (inverse square root, 1/sqrt(x))
F3 - fsqrt (square root)
F4 - fexp2 (2^x)
F5 - flog2
F6 - fsin
F7 - fcos
F9 - fatan_pt1

pt1 stands for "pi times 1" and pt2 should br obvious.

NVIDIA CUDA transcendentals


Further internal documentation is hard to find.



sin, cos, exp, log, rcp, rsqrt, all in FP16/32/64.

Intesestingly no tan, atan, arc or hypot.

If these are standard opcodes in commercial GPUs, requesting specific and individual quantitative analysis is puzzling in the extreme. Their inclusion is so obviously critical for commercial success in the field of 3D and HPC that it is the equivalent of asking for quantitative analysis of "integer add" or "mul" for a DSP.


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