[llvm] [VPlan][UTC] Number VPlan passes' instances in printing/filtering (PR #211424)

[Florian Hahn via llvm-commits]

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@@ -57,11 +57,18 @@ struct VPlanTransforms {
   static decltype(auto) runPass(StringRef PassName, PassTy &&Pass, VPlan &Plan,
                                 ArgsTy &&...Args) {
 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+    static DenseMap<std::pair<Function *, StringRef /* Pass */>, unsigned>
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fhahn wrote:

Should this be keyed by the vplan instead of the function, we could optimize multiple plans per function (not really relevant for the unit test, but may be for debugging)?

I think this static map may get accessed in parallel when doing ThinLTO, but if we guard this behind the printing flag, it should not cause issues in practice.

Otherwise, `LLVM_THREAD_LOCAL` may be needed like used in `PrettyStackTrace.cpp` etc

https://github.com/llvm/llvm-project/pull/211424