[llvm] [LoopUnroll] Allow runtime unroll with remainder for uniform trip count in convergent loops (PR #192819)

[Luo Yuanke via llvm-commits]

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@@ -1371,9 +1396,8 @@ tryToUnrollLoop(Loop *L, DominatorTree &DT, LoopInfo *LI, ScalarEvolution &SE,
   // to do the first few instructions before we hit the unrolled loop
   // is unsafe -- it adds a control-flow dependency to the convergent
   // operation.  Therefore restrict remainder loop (try unrolling without).
-  //
-  // TODO: This is somewhat conservative; we could allow the remainder if the
-  // trip count is uniform.
+  // This is already accounted for in UCE.ConvergenceAllowsRuntime, which
+  // also considers whether the trip count is uniform across all threads.
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LuoYuanke wrote:

I move the comments about uniformity to the code place where UCE.ConvergenceAllowsRuntime is initialized.

https://github.com/llvm/llvm-project/pull/192819