[llvm] [BOLT][merge-fdata] Fix basic sample profile aggregation without LBR info (PR #118481)

[Paschalis Mpeis via llvm-commits]

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@@ -297,6 +298,25 @@ void mergeLegacyProfiles(const SmallVectorImpl<std::string> &Filenames) {
               "cannot mix profile collected in BOLT and non-BOLT deployments");
         BoltedCollection = false;
       }
+      // Check if the string "no_lbr" is in the first line
+      size_t FirstNewline = Buf.find('\n');
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paschalis-mpeis wrote:

nit: please capitalize var name to `CheckNoLBRPos`.

Also a nice way to settle this would be to simply add a test that covers this BAT mode case?
Could use split-file to tidy things up as well.


https://github.com/llvm/llvm-project/pull/118481