[EXTERNAL] Fix v_mov_b16_t16 index in folding pass

[justinrosner]

Motivation

This is a pulldown from an upstream change (llvm/llvm-project#161764) that provides a fix for functional failures in the MIGraphX CI on Navi3X.

Technical Details

With true16 mode, v_mov_b16_t16 is added as a new foldable copy inst, but the src operand is in a different index. This change fixes a bug in the folding pass so that we are using the correct index.

Test Plan

• Run failing MIGraphX CI (test_group_query_attention_decode_small)
• Add a new rocMLIR unit test to catch this

Test Result

• Failing MIGraphX CI (test_group_query_attention_decode_small)

Submission Checklist

• Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.

[justinrosner]

Once the changes on upstream are finalized, I'll create two separate commits that I'll merge in: 1 for the external changes and 1 for rocMLIR changes

[justinrosner]

The Tune selected rocMLIR configs stage of the CI is continuously timing out for Navi3x. E.g., https://ml-ci-internal.amd.com/job/MLIR/job/mlir/job/PR-2011/8/pipeline-overview/. I've kicked off a local run of the same tuningRunner commands to ensure that this passes.

[justinrosner]

The Tune selected rocMLIR configs stage of the CI is continuously timing out for Navi3x. E.g., https://ml-ci-internal.amd.com/job/MLIR/job/mlir/job/PR-2011/8/pipeline-overview/. I've kicked off a local run of the same tuningRunner commands to ensure that this passes.

I tried running the 'problematic' tuningRunner using both develop and this branch, and they both take multiple hours (i.e., not going to finish in the time allotted by the CI). All other CI jobs pass: https://ml-ci-internal.amd.com/job/MLIR/job/mlir/job/PR-2011/10/pipeline-overview/. Given that the tuningRunner jobs pass locally on Navi3x, this seems safe to merge.