1716311 - (wasm-multiprecision) [exploration] Multiprecision arithmetic / carry propagation - sketches, explorations

Status: RESOLVED WONTFIX

(Core :: JavaScript: WebAssembly, task, P3)

Description

[Lars T Hansen [:lth]]

There have been some discussions about multiprecision arithmetic primitives. Of these, the only hard cases are those that deal with add-with-carry and subtract-with-borrow, as we wish to keep the carry flag in the flags register as much as possible. I'll attach some sketches I've made to address the issue in Ion / Baldr.

Comment 1

[Lars T Hansen [:lth]]

Attachment: WIP: Bug 1716311 - Sketches for carry-aware instructions

Comment 2

[Lars T Hansen [:lth]]

Attachment: r.js

Simple test case for a simple example instruction. The latest patch actually generates working code on ARM64.

Comment 3

[Lars T Hansen [:lth]]

The very latest patch has a very large comment block discussing various optimization strategies (none of them implemented).

Comment 4

[Lars T Hansen [:lth]]

Attachment: r.js

Comment 5

[Lars T Hansen [:lth]]

Not currently working on this. Note comment 3 - there's information in the patch about how we might go about implementing this if it comes to that.

Comment 6

[Ryan Hunt [:rhunt]]

The CG has voted to go with the approach in bug 1949081 instead. This is still useful for some implementation ideas.