[llvm] [AMDGPU] Add option to bias SGPR allocation to reduce read hazards (PR #129869)

[Carl Ritson via llvm-commits]

perlfu wrote:

* Rebase
* Fold analysis into getRegAllocationHints

To clear up any confusion, `getRegAllocationHints` in MRI is what creates the base order returned by TRI `getRegAllocationHints`.
Essentially the MRI methods setup static hints, and the TRI `getRegAllocationHints` provides dynamic adjustments to order during allocation.
`PriorityAdvisor` is informing the order live intervals are selected for assignment, not the order physical registers are considered when allocating for a given register.

We could envision moving `getRegAllocationHints` to some kind of Analysis and Advisor infrastructure.
Although the results of that advisor would be more than advise, but an absolute list of register to allocate from.
Again, such a change is adjunct to this patch.



https://github.com/llvm/llvm-project/pull/129869