[clang] Fix handling of asm string literals (PR #169803)

[Abhina Sree via cfe-commits]

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@@ -8120,7 +7838,13 @@ bool CheckFormatHandler::HandleInvalidConversionSpecifier(
     keepGoing = false;
   }
 
-  StringRef Specifier(csStart, csLen);
+  // The csStart points to a character that has already been converted to the
+  // exec charset, so we have to reverse the conversion to allow diagnostic
+  // message to match an expected value when using -verify option,
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abhina-sree wrote:

I believe this function is also only used in Objective-C related code and may not need the change

https://github.com/llvm/llvm-project/pull/169803