[clang] [llvm] [X86][AsmParser] Fix MS inline asm label mismatch with offset operator (PR #199552)

[via cfe-commits]

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@@ -2317,8 +2317,12 @@ bool X86AsmParser::ParseIntelInlineAsmIdentifier(
     if (!IsParsingOffsetOperator)
       InstInfo->AsmRewrites->emplace_back(AOK_Label, Loc, Identifier.size(),
                                           InternalName);
-    else
-      Identifier = InternalName;
+    else {
+      // When parsing the offset operator, we need to prepend
+      // PrivateLabelPrefix to match the AOK_Label rewrite at label definition.
+      StringRef Prefix = getContext().getAsmInfo().getPrivateLabelPrefix();
+      Identifier = getContext().getOrCreateSymbol(Twine(Prefix) + InternalName)->getName();
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sonyps5201314 wrote:

> getPrivateLabelPrefix should not be used. I'm creating a patch to remove it to finish a migration I started long ago.

Replace with `getInternalSymbolPrefix()`. This is consistent with the API used by the `AOK_Label` rewrite logic ([AsmParser.cpp:6291](https://github.com/llvm/llvm-project/blob/6bfca10b7a9da1b35717f16a820c8e837f87ea17/llvm/lib/MC/MCParser/AsmParser.cpp#L6291)).

https://github.com/llvm/llvm-project/pull/199552