[llvm] [AMDGPU][NFC] Minor source cleanups in SIInsertWaitcnts (PR #181095)

[via llvm-commits]

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@@ -2972,7 +2973,7 @@ bool WaitcntBrackets::mergeAsyncMarks(ArrayRef<MergeInfo> MergeInfos,
   // pending async operations at this checkpoint" and acts as the identity
   // element for max() during merging. We pad at the beginning since the marks
   // need to be aligned in most-recent order.
-  CounterValueArray ZeroMark{};
+  constexpr CounterValueArray ZeroMark{};
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vporpo wrote:

My original comment in https://github.com/llvm/llvm-project/pull/180467 clearly states that this should be a `static constexp` but you keep pushing back without providing a good justification. There is never a good reason that I am aware of for dropping `static` in such cases. If you know of any please share it here.

Also please refrain from expressing comments like "This is a really really minor corner case that does not justify the time that has already been spent thinking about it". Such comments are not helping with resolving code issues.

https://github.com/llvm/llvm-project/pull/181095