[Utils] Use StringRef::ends_with (NFC) (#135934)

Author: kazutakahirata

llvm/lib/Transforms/Utils/SimplifyLibCalls.cpp

@@ -1936,7 +1936,7 @@ static Value *optimizeDoubleFP(CallInst *CI, IRBuilderBase &B,
   bool IsIntrinsic = CalleeFn->isIntrinsic();
   if (!IsIntrinsic) {
     StringRef CallerName = CI->getFunction()->getName();
-    if (!CallerName.empty() && CallerName.back() == 'f' &&
+    if (CallerName.ends_with('f') &&
         CallerName.size() == (CalleeName.size() + 1) &&
         CallerName.starts_with(CalleeName))
       return nullptr;