[VectorDistribute] Zero dimensional vectors causing distribution failure in VectorDistribute

[Max191]

A new change in mlir (llvm/llvm-project@1004865#diff-51a55079ee1ee8936812c5be30869c89451372a0c675ff80ff739998c494e806L750) introduces zero dimensional vector transfers, which causes VectorDistribute to break later on. The change is reverted for now, but we need to fix the bug to reapply the patch.

Repro

The following gist contains an executable benchmark and a compile command for reproducing the failure:

https://gist.github.com/Max191/8a110c7eb192377c5f0665a14382f2b6

• Checkout https://github.com/Max191/iree/tree/zero-d-vecdist
• run the command at the top of the above gist file: iree-compile test.mlir --compile-from=executable-sources --iree-hal-target-backends=rocm --iree-hip-target=gfx942 --iree-input-demote-f64-to-f32 -o /tmp/z.vmfb

Pass Repro

The gist also includes a smaller pass reproducer of just the VectorDistribute pass that fails:

• run iree-opt --pass-pipeline="builtin.module(func.func(iree-llvmgpu-vector-distribute))" pass_repro.mlir