Add README.md for berkeley-softfloat-3 library

[Nadime Barhoumi (nadime15)]

GitHub did not render README.txt or README.html, so this adds a README.md.

[github-actions]

Test Results

2 099 tests  ±0   2 099 ✅ ±0   17m 59s ⏱️ +3s
    1 suites ±0       0 💤 ±0 
    1 files   ±0       0 ❌ ±0 

Results for commit 9dede26. ± Comparison against base commit 94a4fa0.

[Tim Hutt (Timmmm)]

I dunno, this seems a little unnecessary and it also means this directory isn't just a straight copy of the upstream code. I guess it doesn't matter too much.

[Nadime Barhoumi (nadime15)]

The README.md is actually part of the berkeley-softfloat-3 repository.

I recommend that you have a look at https://github.com/riscv/sail-riscv/tree/master/dependencies/softfloat/berkeley-softfloat-3 and see how its rendered now.

[Nadime Barhoumi (nadime15)]

Btw. the code that we have right now is not a straight copy. 99% of the code is the same but some files are different including (at least) one folder name that was changed from (Linux-RISCV64-GCC to Linux-RISCV-GCC) including the files in the folder.

[Tim Hutt (Timmmm)]

Ah ok fair enough. I thought I updated it so that it was a whole ago but I must have not actually made that PR.

[Jordan Carlin (jordancarlin)]

This is fine for now. Might make more sense to just update the whole directory to get it back in line with upstream (or the Spike version) and bring in the bfloat16 additions.

[Nadime Barhoumi (nadime15)]

Jordan Carlin (@jordancarlin) Yes, I am working on it

[Prashanth Mundkur (pmundkur)]

A Spike install creates a softfloat include directory and libsoftfloat.so library; we could use that at the expense of adding a build dependency. That's an alternative to bringing in the whole directory and then tracking upstream fixes. Either option sounds good to me. Spike's softfloat has more updates than the github ucb-bar version, so the former (Spike's) might be preferable (to ucb-bar).

[Nadime Barhoumi (nadime15)]

To be honest, I would prefer not to merge the softfloat version from Spike and stick with berkeley-softfloat-3. Its harder to maintain the library otherwise, and we would have to keep track of changes within Spikes codebase. As far as I can tell the berkeley repository has everything we need for now.

Its true that Spike has broader support (they even support direct bfloat16 arithmetic for some reason, which the upstream Berkeley version currently does not), but there is no reason Spike couldnt push those changes upstream. In fact, some of the people maintaining Spike also maintain the Berkeley library.

[Nadime Barhoumi (nadime15)]

See ucb-bar/berkeley-softfloat-3#24 (comment) and ucb-bar/berkeley-softfloat-3#26