Re: RISC-V -- are we ready for more, and what do we need to do it?

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Hi,

On Monday, 2021-10-04 13:03:27 -0400, Matthew Miller wrote:

> But beyond that: What other things might be limits? Are there key bits of
> the distro which don't build yet?

Fwiw, I learned just yesterday that apparently to stay on the cheap side
they underspecified RISC-V FPU to omit some IEEE 754 optional behaviour
that would preserve and propagate a quiet NaN's payload in floating
point calculations. It may or may not (optionally) be supported on
a given RISC-V architecture.

That is a feature LibreOffice Calc makes heavy use of to transport error
information in doubles, where without those payload details it would
result in just a general NaN error for illegal FP operation.

Some other software may also use NaN payloads (R is mentioned in the
IEEE 754 .pdf on NaNs
https://grouper.ieee.org/groups/msc/ANSI_IEEE-Std-754-2019/background/nan-propagation.pdf
("Known and possible uses of NaN payloads"), and JavaScript NaN-boxing
for type of data).

Further pointers in
https://bugs.documentfoundation.org/show_bug.cgi?id=152943

  Eike

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