[llvm] Allow .alt_entry symbols to pass the .cfi nesting check (PR #82268)

[Fangrui Song via llvm-commits]

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@@ -1950,7 +1951,9 @@ bool AsmParser::parseStatement(ParseStatementInfo &Info,
       Lex();
     }
 
-    if (MAI.hasSubsectionsViaSymbols() && CFIStartProcLoc && Sym->isExternal())
+    if (MAI.hasSubsectionsViaSymbols() && CFIStartProcLoc &&
+        Sym->isExternal() &&
+        (!isa<MCSymbolMachO>(Sym) || !cast<MCSymbolMachO>(Sym)->isAltEntry()))
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MaskRay wrote:

Since only `MCAsmInfoDarwin` sets `hasSubsectionsViaSymbols`. The `isa<MCSymbolMachO>(Sym)` check is unneeded.

https://github.com/llvm/llvm-project/pull/82268