[llvm] [IR][Instructions] Add `CallBase::getCalledFunctionName` helper (PR #127038)

[Nikita Popov via llvm-commits]

================
@@ -41,11 +41,10 @@ class VFDatabase {
   /// a vector Function ABI.
   static void getVFABIMappings(const CallInst &CI,
                                SmallVectorImpl<VFInfo> &Mappings) {
-    if (!CI.getCalledFunction())
+    const auto ScalarName = CI.getCalledFunctionName();
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nikic wrote:

```suggestion
    std::optional<StringRef> ScalarName = CI.getCalledFunctionName();
```

https://github.com/llvm/llvm-project/pull/127038