[llvm] [AMDGPU] Allocate AVRegClass last (PR #146606)

[Matt Arsenault via llvm-commits]

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@@ -936,14 +940,15 @@ class VRegClassBase<int numRegs, list<ValueType> regTypes, dag regList> :
 
   // Requires n v_mov_b32 to copy
   let CopyCost = numRegs;
-  let AllocationPriority = !sub(numRegs, 1);
+  defvar SizePrioriity = !if(!le(numRegs, 14), !sub(numRegs, 1), !if(!le(numRegs, 16), 14, 15));
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arsenm wrote:

Comment on this logic 

https://github.com/llvm/llvm-project/pull/146606