[llvm] [NFC][AMDGPU] Rename some variable names to follow convention better (PR #213827)

[Tim Gymnich via llvm-commits]

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@@ -580,9 +580,9 @@ class SIMachineFunctionInfo final : public AMDGPUMachineFunctionInfo,
   WWMSpillsMap WWMSpills;
 
   // Before allocation, the VGPR registers are partitioned into two distinct
-  // sets, the first one for WWM-values and the second set for non-WWM values.
+  // sets, the first one for WWM values and the second set for per-lane values.
   // The latter set should be reserved during WWM-regalloc.
-  BitVector NonWWMRegMask;
+  BitVector PerlaneVGPRMask;
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tgymnich wrote:

```suggestion
  BitVector PerLaneVGPRMask;
```

https://github.com/llvm/llvm-project/pull/213827