[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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@@ -409,24 +428,36 @@ static bool isEligibleForMerging(Function &F) {
          !hasDistinctMetadataIntrinsic(F);
 }
 
-bool MergeFunctions::runOnModule(Module &M) {
+template <typename FuncContainer>
+bool MergeFunctions::runOnModule(FuncContainer &M) {
   bool Changed = false;
 
-  SmallVector<GlobalValue *, 4> UsedV;
-  collectUsedGlobalVariables(M, UsedV, /*CompilerUsed=*/false);
-  collectUsedGlobalVariables(M, UsedV, /*CompilerUsed=*/true);
-  Used.insert(UsedV.begin(), UsedV.end());
+  if constexpr (std::is_same<FuncContainer, Module>::value) {
+    SmallVector<GlobalValue *, 4> UsedV;
+    collectUsedGlobalVariables(M, UsedV, /*CompilerUsed=*/false);
+    collectUsedGlobalVariables(M, UsedV, /*CompilerUsed=*/true);
+    Used.insert(UsedV.begin(), UsedV.end());
+  }
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SLTozer wrote:

Since this runs at the top of the function and is only being used for the module case, which is only called from `run`, this could be moved into `run` before the call to `runOnModule`.

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