Update Sail pseudo code

[nadime15]

The Sail (pseudo)code needs to be updated. The code looks mostly fine, but there are a few things that are incorrect. I know this is pseudocode, but since the actual implementation is quite similar, I think it would be better to use the actual code wherever possible and keep the pseudocode as close to the implementation as possible.

For example:

• sext_or_truncate_to_sew does not exist. The model uses get_scalar(rs1, SEW), see model/extensions/V/vext_utils_insts.sail.
• match suffix { "vv" => ..., "vx" => ... } uses a suffix variable that is never defined.
• let (result, mask) = init_masked_result(...) followed by result[i] = ... does not work because let bindings are immutable.
• ...

Here is the latest code:

https://github.com/riscv/sail-riscv/pull/1886/changes

Any thoughts on this Andrew Waterman (@aswaterman) Prashanth Mundkur (@pmundkur)?

[pmundkur]

I agree, I think it would be good to use actual Sail code from the Sail PR for this extension, since it at least compiles with the Sail compiler. In the long term, it would be good to automate the splicing in of Sail code into the manual, but that is a different discussion and workflow.