[CNCF LFX Proposal] WasmEdge Support for the Wide Arithmetic Proposal

### CNCF Project

WasmEdge Runtime

### Term

2026 Term 3 (Sep-Nov)

### Program Name

Support for the Wide Arithmetic Proposal

### Program Description

## Description

Add support for the WebAssembly Wide Arithmetic proposal to WasmEdge by implementing the `i64.add128`, `i64.sub128`, `i64.mul_wide_s`, and `i64.mul_wide_u` instructions. These instructions enable efficient 128-bit addition and subtraction, as well as signed and unsigned 64×64-bit widening multiplication.

Since this is not a large proposal, the mentee must implement it in all execution modes, including interpreter, JIT, and AOT.

## Expected Outcome

1. WasmEdge must be able to correctly parse, validate, and execute all four Wide Arithmetic instructions while preserving the semantics defined by the proposal.
2. The implementation must pass the corresponding WebAssembly specification tests and provide consistent behavior across the interpreter, AOT compiler, and JIT engine.
3. The document must be completed within the WasmEdge/docs repository.

### Technologies

C++, WebAssembly, LLVM

### Skills same as Technologies?

- [x] Yes, the required skills are the same as the technologies listed above.

### Required/Desirable Skills

_No response_

### Mentors

Hung-Ying Tai | @hydai | hydai@secondstate.io | hydaitw
Yi-Ying He | @q82419 | yiying@secondstate.io | q82419

### Upstream Issue URL

https://github.com/WasmEdge/WasmEdge/issues/5153

### Application Prerequisites

- [x] Resume
- [ ] Cover Letter
- [ ] School Enrollment Verification
- [ ] Participation Permission from school or employer
- [ ] Coding Challenge
- [x] Custom Prerequisite (fill in details below)

### Coding Challenge URL

_No response_

### Custom Prerequisite Name

Pre-test report

### Custom Prerequisite Description

Please check this link: https://hyd.ai/lfx-wasmedge-pretests/2026-lfx-term-3-5153.html. Follow the format defined inside to create a complete report.

### Custom Prerequisite — File Upload

- [x] Yes — completion of this task requires the mentee to submit a file.

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**LFX program:** [CNCF - WasmEdge Runtime: Support for the Wide Arithmetic Proposal (2026 Term 3)](https://mentorship.lfx.linuxfoundation.org/project/14d8a870-ed14-4a49-8b8c-8ac50c4605cc)

Start by reading the linked upstream WasmEdge issue #5153 and the linked pre-test instructions, which explain the required report. The proposal calls for parsing, validating, and executing four Wide Arithmetic instructions in interpreter, JIT, and AOT modes. Done means the specification tests pass and behavior is consistent across all three modes; the completed document must also be in the WasmEdge/docs repository.

Written by the indexing model from the issue text.