[llvm] [Codegen] (NFC) Faster algorithm for MachineBlockPlacement (PR #91843)

[via llvm-commits]

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@@ -3119,6 +3159,8 @@ bool MachineBlockPlacement::maybeTailDuplicateBlock(
         // Handle the filter set
         if (BlockFilter) {
           BlockFilter->remove(RemBB);
+          if (*PrevUnplacedBlockInFilterIt == RemBB)
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weiguozhi wrote:

RemBB is already deleted from BlockFilter, you'll never find it again.

https://github.com/llvm/llvm-project/pull/91843