[llvm] Make 'UnrollMaxUpperBound' to be overridable by target. (PR #76029)

[via llvm-commits]

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@@ -560,6 +560,13 @@ class TargetTransformInfo {
     // (set to UINT_MAX to disable). This does not apply in cases where the
     // loop is being fully unrolled.
     unsigned MaxCount;
+    /// Set the maximum upper bound of trip count. Considering a loop with 'pragma 
+    /// unroll' specified but without 'full' or 'n' field, it depends on the 
+    /// UnrollMaxUpperBound option if the loop trip is unknown. However, the 
+    /// default value is 8 for this option which might not suitable for certain
+    /// target. Allowing the MaxUpperBound to be overrided by a target gives more
+    /// flexiblity on such cases. By default, MaxUpperBound uses UnrollMaxUpperBound
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boxu-zhang wrote:

Comments update, can you please review it again and merge if it's OK? 

https://github.com/llvm/llvm-project/pull/76029