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

[William Junda Huang via llvm-commits]

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@@ -3158,9 +3158,9 @@ bool MachineBlockPlacement::maybeTailDuplicateBlock(
 
         // Handle the filter set
         if (BlockFilter) {
-          BlockFilter->remove(RemBB);
           if (*PrevUnplacedBlockInFilterIt == RemBB)
             PrevUnplacedBlockInFilterIt++;
+          BlockFilter->remove(RemBB);
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huangjd wrote:

It looks like PrevUnplacedBlockInFilterIt does not need to be modified at all because it does not increment automatically in buildChain()

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