[llvm] [SampleProfile] Fix bug where remapper returns empty string and crashing Sample Profile loader (PR #71479)

[William Junda Huang via llvm-commits]

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@@ -1788,8 +1788,11 @@ void SampleProfileReaderItaniumRemapper::applyRemapping(LLVMContext &Ctx) {
 
 std::optional<StringRef>
 SampleProfileReaderItaniumRemapper::lookUpNameInProfile(StringRef Fname) {
-  if (auto Key = Remappings->lookup(Fname))
-    return NameMap.lookup(Key);
+  if (auto Key = Remappings->lookup(Fname)) {
+    StringRef Result = NameMap.lookup(Key);
+    if (!Result.empty())
+      return Result;
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huangjd wrote:

The comment in the header file should be clear enough that it returns a remapped name Only if a remapped symbol is found. The problem is the function's API design  is bad (mixing both empty string and null to represent non-existent value). This should be addressed somewhere else. 

https://github.com/llvm/llvm-project/pull/71479