[llvm] [MergeFunctions] Add support to run the pass over a set of function pointers (PR #111045)

[Stephen Tozer via llvm-commits]

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@@ -297,17 +300,31 @@ class MergeFunctions {
   // dangling iterators into FnTree. The invariant that preserves this is that
   // there is exactly one mapping F -> FN for each FunctionNode FN in FnTree.
   DenseMap<AssertingVH<Function>, FnTreeType::iterator> FNodesInTree;
+
+  /// Deleted-New functions mapping
+  std::map<Function *, Function *> DelToNewMap;
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SLTozer wrote:

This (and probably other maps here) could be a `DenseMap` instead, unless there's a reason this needs `std::map`. I think it could also be a returned value from `runOnFunctions` rather than a member, but that's mostly subjective.

https://github.com/llvm/llvm-project/pull/111045