[llvm] [NFC] RuntimeLibcalls: Prefix the impls with 'Impl_' and use an enum class (PR #153850)

[Daniel Paoliello via llvm-commits]

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@@ -157,7 +157,7 @@ class RuntimeLibcallImpl {
 
   const Record *getDef() const { return TheDef; }
 
-  StringRef getName() const { return TheDef->getName(); }
+  Twine getName() const { return Twine("Impl_") + TheDef->getName(); }
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dpaoliello wrote:

Fair enough, I'll go with `lci_` for `LibCallImpl`

https://github.com/llvm/llvm-project/pull/153850