[llvm] [AMDGPU] Create an AMDGPUIfConverter pass (PR #106415)

[Juan Manuel Martinez Caamaño via llvm-commits]

jmmartinez wrote:

I've started an alternative implementation in https://github.com/llvm/llvm-project/compare/main...jmmartinez:llvm-project:amd/if-cvt-v2

I'm starting to submit the patches separately.

These new series of patches consists of 3 parts:

1. Make StructurizeCFG maintain branch weight metadata (e.g. that comes from the [[likely/unlikely]] user annotations)
2. Make mustRetainExeczBranch use a cost model based on BranchProbability and the TargetSchedmodel
3. Implement a demote s_cbranch_scc into vcmp pass (but this transfromation could be placed elsewhere).

https://github.com/llvm/llvm-project/pull/106415