[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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@@ -467,6 +484,47 @@ bool MergeFunctions::runOnModule(Module &M) {
   return Changed;
 }
 
+bool MergeFunctions::runOnFunctions(std::set<Function *> &F) {
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SLTozer wrote:

It'd be good if this could be de-duplicated with `MergeFunctions::runOnModule` - the implementation looks to be identical, apart from iterating over a `std::set<Function *>` rather than a `Module`, and not having the `collectUsedGlobalVariables` step at the start (it's not immediately clear to me if this step would be meaningful in the `runOnFunctions` case.

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