[NFC][Cloning] Remove now unused CollectDebugInfoForCloning

Summary:
This function is no longer used, let's remove it from the header and
impl.

Test Plan:
ninja check-llvm-unit

stack-info: PR: #129152, branch: users/artempyanykh/fast-coro-upstream-part2-take2/10

Author: artempyanykh

llvm/include/llvm/Transforms/Utils/Cloning.h

@@ -230,20 +230,6 @@ void CloneAndPruneFunctionInto(Function *NewFunc, const Function *OldFunc,
                                const char *NameSuffix = "",
                                ClonedCodeInfo *CodeInfo = nullptr);
 
-/// Collect debug information such as types, compile units, and other
-/// subprograms that are reachable from \p F and can be considered global for
-/// the purposes of cloning (and hence not needing to be cloned).
-///
-/// What debug information should be processed depends on \p Changes: when
-/// cloning into the same module we process \p F's subprogram and instructions;
-/// when into a cloned module, neither of those.
-///
-/// Returns DISubprogram of the cloned function when cloning into the same
-/// module or nullptr otherwise.
-DISubprogram *CollectDebugInfoForCloning(const Function &F,
-                                         CloneFunctionChangeType Changes,
-                                         DebugInfoFinder &DIFinder);
-
 /// This class captures the data input to the InlineFunction call, and records
 /// the auxiliary results produced by it.
 class InlineFunctionInfo {

llvm/lib/Transforms/Utils/CloneFunction.cpp

@@ -168,27 +168,6 @@ void llvm::CloneFunctionAttributesInto(Function *NewFunc,
                          OldAttrs.getRetAttrs(), NewArgAttrs));
 }
 
-DISubprogram *llvm::CollectDebugInfoForCloning(const Function &F,
-                                               CloneFunctionChangeType Changes,
-                                               DebugInfoFinder &DIFinder) {
-  // CloneModule takes care of cloning debug info for ClonedModule. Cloning into
-  // DifferentModule is taken care of separately in ClonedFunctionInto as part
-  // of llvm.dbg.cu update.
-  if (Changes >= CloneFunctionChangeType::DifferentModule)
-    return nullptr;
-
-  DISubprogram *SPClonedWithinModule = nullptr;
-  if (Changes < CloneFunctionChangeType::DifferentModule) {
-    SPClonedWithinModule = F.getSubprogram();
-  }
-  if (SPClonedWithinModule)
-    DIFinder.processSubprogram(SPClonedWithinModule);
-
-  collectDebugInfoFromInstructions(F, DIFinder);
-
-  return SPClonedWithinModule;
-}
-
 void llvm::CloneFunctionMetadataInto(Function &NewFunc, const Function &OldFunc,
                                      ValueToValueMapTy &VMap,
                                      RemapFlags RemapFlag,