[llvm] [AMDGPU] Add VGPR MSB-affinity pass to reduce s_set_vgpr_msb on gfx1250 (PR #216909)

[Yuyang Zhang via llvm-commits]

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@@ -659,6 +662,20 @@ class SIMachineFunctionInfo final : public AMDGPUMachineFunctionInfo,
     return MaskForVGPRBlockOps.inBounds(RegisterBlock);
   }
 
+  // Desired VGPR MSB group (HW index >> 8) for a vreg, set by
+  // AMDGPUVGPRMSBAffinity and consumed by getRegAllocationHints below.
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yuyzhang512 wrote:

Done.

https://github.com/llvm/llvm-project/pull/216909