[llvm] [AMDGPU] Fix LSR cost comparator that regressed GFX9+ occupancy (PR #204344)

[Yuyang Zhang via llvm-commits]

yuyzhang512 wrote:

Gentle ping. The branch is up to date with main and premerge is green.

I believe I have addressed the feedback so far:

- @rampitec — added `lsr-cost-model-occupancy.ll`. On gfx950: 260 VGPRs / occupancy 1 before, 244 VGPRs / occupancy 2 after.
- @arsenm — test shrunk to 375 lines with named values, attributes restored, and the `isNumRegsMajorCostOfLSR` comment dropped.

@arsenm @rampitec @michaelselehov — I would appreciate any guidance on what this still needs.


https://github.com/llvm/llvm-project/pull/204344